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Performance evaluation of a zeolite–water adsorption chiller with entropy analysis of thermodynamic insight
Abstract
This paper presents an environment-friendly adsorption chiller using Zeolite FAM Z01-water pair as opposed to the conventional silica gel and water pair. The adsorbent, zeolite, is thinly coated onto the surfaces of fin-tube heat exchanger for faster rates of heat and mass transfer. Another feature of the adsorption chiller is the use of a lever-countered weighted valve which can be open or closed by the pressure difference between the reactors and the condenser or evaporator. Experiments are conducted to evaluate the performance of zeolite-based chiller in terms of total heat input, cooling capacity, and coefficient of performance (COP) with respect to heat source temperature and adsorption/desorption cycle time where an optimal operational zone can be determined: (i) hot water inlet temperatures range from 65 °C to 85 °C, (ii) adsorption/desorption cycle times of 200-300 s at optimum cooling and COP, Entropy analyses have been conducted to understand the irreversibility contributed by both the desorption and adsorption beds at assorted hot water inlet temperatures and cycle time.
... In comparison to the systems employing conventional pairs such as silica gel-water [32], activated carbon-methanol [33], zeolite-water [34], etc., the SCP values of these composite-R32 systems are observed to be lower. This can be attributed to the relatively lower latent heat of evaporation of R32 (304.8 kJ/kg) in comparison to that of water (2485.0 ...
... However, in comparison to the activated carbon-R134a pair based system described in [35] with an SCP value of around 37.5 W/kg under similar operating conditions (computed from the specific cooling energy (30 kW/kg) and cycle time duration (800 s), the composites are seen to have higher values as shown in Table 7. The VCP values of the conventional adsorption pairs computed from the respective adsorbent apparent density and SCP values in the literature [32][33][34] are observed to be over 100 kW/m 3 , which can be mainly attributed to their higher SCP values over the composite-R32 pairs considered in the present study. In comparison with the conventional adsorption pairs [32][33][34], the composite-R32 pairs are seen to offer relatively lower COP values. ...
... The VCP values of the conventional adsorption pairs computed from the respective adsorbent apparent density and SCP values in the literature [32][33][34] are observed to be over 100 kW/m 3 , which can be mainly attributed to their higher SCP values over the composite-R32 pairs considered in the present study. In comparison with the conventional adsorption pairs [32][33][34], the composite-R32 pairs are seen to offer relatively lower COP values. This can be attributed to the lower SCP values of the composites in comparison to that of the conventional adsorption pairs as well as the higher specific heat capacity of R32 at higher temperatures (>70 • C) over water, methanol, etc. ...
To further the research on R32 refrigerant-based adsorption cooling applications, Maxsorb-III activated carbon composites synthesized with the additives of H25 Graphene nanoplatelets (GNP), 1-Hexyl-3-methylimidazolium bis(trifluormethylsulfonyl)imide ([HMIM][Tf2N]) ionic liquid with polyvinyl alcohol (PVA) are studied for cooling performance evaluation. Their respective kinetic characteristics and heat of adsorption assessments are carried out for this purpose in the present study. The adsorption kinetics characteristics are studied using gravimetrically for the composite samples. A first-order kinetics model is seen to fit their kinetic uptakes with regression coefficients ≥ 0.97. The heat of adsorption estimates of the composites for varying uptakes and temperatures are numerically evaluated, incorporating the non-ideal behavior of the refrigerant. An approach for a holistic comparison of the cooling performances of the composites containing their respective heat and mass transfer characteristics for compact heat exchanger designs is further proposed. While the composite with the highest Maxsorb-III mass fraction yields the highest specific and volumetric cooling powers, the composite with the highest thermal conductivity requires the lowest heat exchanger area with a slightly larger adsorbent volume of around 12.1% over the former. A second law thermodynamic analysis is further carried out to evaluate the composite performances for cooling applications.
... The adsorption/desorption beds were found to be the main contributors of irreversibility. Li et al. [11] presented an entropy analysis on a zeolite-water adsorption cooling cycle. The specific entropy generation with respect to the cooling capacity was found to be reduced by increasing the cycle time. ...
... adsorption/desorption beds have to be switched periodically, and states of the system vary with time in each cycle. Figure 7.12 shows the schematic of an adsorption chiller, while Fig. 7.13 portrays the profiles of water temperatures leaving each component of a zeolite-water adsorption chiller [11]. The inlet temperatures for the hot water, cooling water and chilled water are 65°C, 27°C, and 12°C, respectively, while the cycle time and switching The water temperatures leaving the adsorption/desorption beds change significantly at the beginning of each cycle and become steady afterwards. ...
... The reason is that during the switching period, hot water is circulating in the bed that is still cold while cooling water is supplied to the bed that is at a high temperature. Due to a large potential for adsorption/desorption, evaporation and condensation rates are also promoted at the beginning of each cycle, and, as a Water temperature profile for a zeolite-water adsorption chiller at hot water temperature of 65°C and cycle time of 250 s [11] result, the temperatures of chilled water and cooling water also fluctuate markedly at the beginning of each cycle. Figure 7.14 shows the instantaneous entropy generation rates of different components as well as the whole system for the zeolite-water system with a cycle time of 200 s [11]. ...
To improve the energy efficiencies of cooling cycles, it is important to identify the key sources of internal dissipative losses, thus pinpointing the major inefficient components that require optimization. This chapter conducts a second-law analysis on different cooling systems, including a mechanical vapour compression chiller, an absorption chiller, an adsorption chiller, and an indirect evaporative cooler. Based on thermodynamic states of these systems, the entropy generation rates of each component are calculated which revealed that the compressor, the regenerative heat exchangers and the reactor beds account for the most dissipative losses in mechanical chillers, absorption and adsorption chillers. The exergy efficiency of mechanical chillers can be improved by promoting the heat transfer in the evaporators and the condensers. The system-level entropy generation rates are normalized with respect to the cooling capacities to allow a direct comparison of different systems. The indirect evaporative cooler is found to perform most efficiently among the compared cooling cycles, while the adsorption chiller incurs the most internal dissipations due to poor heat transfer in its porous adsorbents.
... Most of the demand is met by Vapor Compression Refrigeration Cycle(VCRS) which consumes much energy with negative effects on the environment. The improvements for VCRS also reached their peaks [1]. An alternative to this cycle can be thermally driven cycles powered by low temperature waste heat or renewable sources e.g. ...
... Askalany et al. Li et al. [1] worked with an adsorption chiller with FAM-01 zeolite-water pair to analyze the entropy of the system. Their evaluation indicated that the cyclic average entropy generation rate increases with increasing hot water temperature and reduces with decreasing cycle time. ...
... Zeolites also serve as great adsorbents in gas treatment facilities, capturing contaminations [97] like nickel (Ni) [141], arsenic (As) [142], zinc (Zn), copper (Cu) [143], and lead (Pb) [111,144]. Zeolites are also used as a bed material in adsorption refrigerators [145][146][147], because they are sorption materials characterized by excellent sorption properties: high adsorption capacity, molecular shape selectivity, and a very large surface area. A synthesized zeolite may be characterized by superior properties compared to a commercial zeolite, making it a more appealing choice for gas separation fly ashderived zeolites As for the more specific use of zeolites synthesized from FA, they can also be used in adsorption systems for CO 2 [138,139]. ...
... Zeolites also serve as great adsorbents in gas treatment facilities, capturing contaminations [97] like nickel (Ni) [141], arsenic (As) [142], zinc (Zn), copper (Cu) [143], and lead (Pb) [111,144]. Zeolites are also used as a bed material in adsorption refrigerators [145][146][147], because they are sorption materials characterized by excellent sorption properties: high adsorption capacity, molecular shape selectivity, and a very large surface area. A synthesized zeolite may be characterized by superior properties compared to a commercial zeolite, making it a more appealing choice for gas separation applications. ...
The synthesis and utilization of zeolites derived from fly ash (FA) gained significant attention years ago due to their potential to address environmental challenges and promote sustainable practices subscribing to the circular economy concept. This paper highlights the recent findings regarding the synthesis and utilization of zeolites derived from FA. It begins with a discussion about the recent challenges regarding industrial waste management and statistics regarding its availability on the global market with a special insight into the situation in Poland. The characteristics of FA obtained from various fuels were presented and the main differences were highlighted. Then, different methods used for the synthesis of zeolites from FA were discussed in small and pilot scales taking into consideration the main challenges and problems. The analytical methods used in porous materials synthesis verification and properties determination were described. The sorption properties of FA-derived zeolites were presented and discussed. Finally, the paper emphasizes the potential applications of fly ash-derived zeolites in different fields. Their importance as sustainable alternatives to conventional materials in industry, construction, agriculture, power, medicine, and other industrial sectors was analyzed.
... The entropy value is used to measure the discrete degree of decision-making attributes. The greater the discrete degree, the greater the impact on the comprehensive evaluation; therefore, a larger weight should be given [25,28]. The The cities of Shanghai, Shenzhen, and Guangzhou were developing rapidly, and the cities accumulated a lot of wealth. ...
... The entropy value is used to measure the discrete degree of decision-making attributes. The greater the discrete degree, the greater the impact on the comprehensive evaluation; therefore, a larger weight should be given [25,28]. The coefficient of variation method means that the attribute with the greater difference in attribute value has a greater influence on the order of the decision-making scheme. ...
From 2000 to 2020, storm surges occurred 397 times in China, resulting in direct economic losses of up to CNY 220.64 billion. Storm surges not only threaten safety but also cause property damage; hence, it is necessary to assess the changes in vulnerability to storm surges in order to understand how to reduce said vulnerability. Fifteen coastal cities of four types were chosen, with different levels of urban development, rapid expansion of impervious surface, high extent of agricultural land, and high fishery output value. Viewing vulnerability through the dimensions of exposure, sensitivity, and adaptability, a GIS and RS were used to evaluate and assess the vulnerability in 15 coastal cities in China over the past 30 years. The results indicated that the vulnerability of these 15 Chinese cities presented the characteristics of a continuous downward trend from 1990 to 2020, and the average rate of reduction in vulnerability over the 10 years from 2005 to 2015 was the highest, at 2.23%. The areas of high vulnerability shifted from the southern region to the northern region. The vulnerabilities in the southern region, with Shanghai, Shenzhen, and Dongguan, changed significantly, to 3.30%, 3.20%, and 3.45%, respectively. An important factor in determining vulnerability reductions is a city’s ability to adapt to storm surges. Coastal cities can improve their adaptability to storm surge disasters through general public budget expenditure, investment in fixed assets, GDP, and medical and health services, thereby alleviating their vulnerability. Due to China’s frequent storm surge disasters during the 2005–2015 period, government departments have strengthened the investment of relevant resources in adaptive indicators, ultimately causing the cities’ vulnerability to rapidly decrease during this period.
... It was observed that treatment with distilled water and acidic solution purification may re-establish silica gel adsorption, although silica gel is necessarily spilled out of absorbers. The adsorption of ethanol and carbon dioxide on different metallic frameworks showed an increase in the effect of cooling (El-Sharkawy et al., 2014;Li et al., 2014;Mohamadinejad et al., 2000;Pal et al., 2016;Rezk et al., 2013;Saha et al., 2015). Tretiak and Abdallah (2009) examined the sorption and desorption of clay-CaCl2 desiccant composition by varying the inlet air temperatures (23 0 C to 36 0 C) and the relative humidity (42% to 66%) throughout the sorption process and inlet air temperature (50 o C to 57 o C) during the desorption process. ...
... Liquid desiccant dehumidifying setup integrated with Solar evacuated tube collectors(Bhowmik et al., 2021).Different types of desiccants, namely molecular sieves (silica gel), zeolite(3A,4A,5A,13X), and adsorbents from activated carbon found to be popular choices(Al-Ansari, 2001;Ayinla et al., 2019;Czarna-Juszkiewicz et al., 2020;El-Sharkawy et al., 2014;Li et al., 2014;Myat et al., 2013;Ochedi et al., 2020;Rodriguez-Reinoso and Silvestre-Albero, 2016)(Ahmed et al., 2020). Composite MOF'S (metal-organic frame works)(Solovyeva et al., 2018) and Composite Desiccants significantly attracted researchers recently ...
The present article regards a systematic review of adsorption cooling systems assisted by solar, ultrasound, and microwave energy sources. Numerical and experimental studies are included in this work, while the emphasis is given to the presentation of the mathematical formulation techniques. Due to the exceptional capability of utilizing low-grade energy, the adsorption cooling system attracted researchers amid increasing demand for cooling applications, decreasing the consumption of rapidly lasting fossil fuels. A significant quantity of energy is available as waste heat from industry, power stations, solar radiation, etc. The critical review is done on adsorption cooling systems to enhance the existing system's efficiency, which contributes to the reduction of pollution and global warming. Moreover, the efficient system is expected to have low adsorption and desorption time. This review presents different types of desiccants and various integrated techniques available to enhance the effectiveness of the adsorption-based cooling system, including ultrasound, microwaves, solar energy, etc. The present study critically reviews different modeling techniques of integrated adsorption cooling systems, using recent advancements in power techniques like microwave energy and ultrasound.
... Every adsorption pair forms a particular shape [20,21] of adsorption isotherm. Several researchers investigated the adsorption isotherms of different adsorption pairs, namely, watersilica gel [22][23][24][25][26][27], waterzeolites [28][29][30][31][32], ethanol -Maxsorb III [33][34][35][36], ethanol -MIL 101Cr [37], CO 2 -Maxsorb III [38,39], R134a -Maxsorb III [40] and so on. The scientists utilize various isotherm models [41][42][43][44][45][46][47] to fit the experimental isotherm data. ...
... Solving Eqs. (31), (36) gives, ∂w ∂t ...
The dynamic uptake of adsorbate onto the porous adsorbent plays a crucial role in determining the performance of the adsorption-based cooling system. Therefore, it is imperative to know the kinetics parameters of an adsorbate – adsorbent pair to design a system to be operated at variable working conditions. The kinetics models of adsorption, used to simulate the adsorption rate of different pairs, are derived and presented in this paper. Besides, the limitations and advantages of the models are also mentioned. Moreover, the dynamic performance of different adsorption pairs is analyzed, and the values of kinetics parameters, determined through experimental procedures and fitting of kinetics models, are also summarized. It is opined that during the initial unsaturated condition of adsorption, the semi-infinite model can be preferred to determine the diffusion time constant. The modification of different models, e.g., Langmuir and linear driving force models, can significantly overcome the drawbacks of the models, as shown by several researchers. However, research may be carried out to investigate different models' fitting errors from a statistical perspective. Furthermore, to evaluate the dynamic performance of different adsorbates, a lot of research needs to be done, specifically, on the adsorption of the newly developed environment-friendly refrigerants, onto the promising composite adsorbents possessing high thermal conductivity and significantly improved adsorption uptakes.
... Saha et al. [2] presented a numerical analysis for the performance evaluation of a silica-gel water AD system to estimate the influences of operating conditions on AD system performance. In addition, various adsorbents were developed as adsorption agents in the AD system to enhance the system performance [15][16][17][18][19][20][21][22][23][24][25][26]. The performance evaluation studies of the AD system were conducted with FAM-Z01, which is manufactured based on zeolite material [15][16][17][18]. ...
... In addition, various adsorbents were developed as adsorption agents in the AD system to enhance the system performance [15][16][17][18][19][20][21][22][23][24][25][26]. The performance evaluation studies of the AD system were conducted with FAM-Z01, which is manufactured based on zeolite material [15][16][17][18]. The FAM-Z01 has an S-shape isotherm graph, and the adsorption and desorption rates may exhibit sudden jumps at certain relative pressure values. ...
In this study, the performance evaluation of an adsorption chiller (AD) system with three different adsorbents—silica-gel, aluminum fumarate, and FAM-Z01—was conducted to investigate the effects of adsorption isotherms and physical properties on the system’s performance. In addition, the performance evaluation of the AD system for a low inlet hot-water temperature of 60 °C was performed to estimate the performance of the system when operated by low quality waste heat or sustainable energy sources. For the simulation work, a two-bed type AD system is considered, and silica-gel, metal organic frameworks (MOFs), and ferro-aluminophosphate (FAPO, FAM-Z01) were employed as adsorbents. The simulation results were well matched with the laboratory-scale experimental results and the maximum coefficient of performance (COP) difference was 7%. The cooling capacity and COP of the AD system were investigated at different operating conditions to discuss the influences of the adsorbents on the system performance. Through this study, the excellence of the adsorbent, which has an S-shaped isotherm graph, was presented. In addition, the influences of the physical properties of the adsorbent were also discussed with reference to the system performance. Among the three different adsorbents employed in the AD system, the FAM-Z01 shows the best performance at inlet hot water temperature of 60 °C, which can be obtained from waste heat or sustainable energy, where the cooling capacity and COP were 5.13 kW and 0.47, respectively.
... The energy and mass balance equations for each component of the chiller is based on lumped heat capacity model, and the temperature changes are simulated with respect to time only. Once the outlet temperatures of various heat exchangers are known under steady state condition, the performance parameters such as the specific cooling power (SCP) and the COP are calculated for various operating conditions of an adsorption chiller [31][32][33]. The schematic diagram of adsorption-desorption process in pressure-temperature-uptake co-ordinate system. ...
... This calculation (i) considers 80% conversion of adsorption and desorption stages, (ii) neglects the duration of isosteric stages (switching time is 30 s according to manufacturer-data [46]), (iii) also neglects the thermal mass capacities for each component of adsorption chiller as well as heat transfer interactions between the working fluids and the beds (both for adsorption and desorption cases). Furthermore, as compared with zeolite FAM Z01 + water assisted adsorption chiller [33,47], the parent MOF-801 (Zr) delivers the nearly similar SCP and COP. By tailoring the hydrophobic length with methyl-functional group, the hydrophobicity of the parent MOF-801 (Zr) is enhanced in the lower pressure region, and therefore higher COP (>0.6) and SCP (>0.7 kW/kg) are obtained. ...
The use of environmentally friendly adsorption assisted thermal storage and chiller is hindered by their bulky sizes and poor performances, which are mainly due to the limited characteristics of solid adsorbents and their poor interactions with water. Therefore, this article presents the parent and CH3 ligand MOF-801 (Zr) adsorbents and their synthesization procedures with surface characterization. Later, the water uptakes on these two MOFs are measured under dynamic and equilibrium conditions for the temperatures of 25 oC to 80 oC. Employing experimentally confirmed water uptake and kinetics data of MOFs + water systems, the energetic performances of an adsorption chiller are calculated in terms of the specific cooling power (SCP) and the coefficient of performance (COP). Hence, the methyl functional group enhances the thermal stability of the parent MOF-801 structures with water uptake/offtake rates i.e. kinetics. Under chiller operating conditions, the SCP and the COP of CH3 ligand MOF-801 (Zr) are found 40% and 30% higher as compared with the parent MOF-801(Zr). Methyl-functional ligand in MOF-801 (Zr) shows promising results for cooling application.
... As one of the important applications of adsorption phenomenon, adsorption refrigeration cycle is very similar to adsorption separation cycle. Many papers [23][24][25][26][27] have calculated the entropy generation in the process of adsorption refrigeration, with calculation method similar to Myat et al. [21]. But there is a difference between the adsorption refrigeration cycle and the adsorption separation cycle, mainly because the adsorption refrigeration cycle is single component adsorption and the cycle configuration between them is quite different. ...
... As the process develops, the thermodynamic forces that drive the process will continue to decrease and the irreversible losses will also decrease. Similar conclusions can be drawn from the literature [26][27][28]. Therefore, reducing the irreversible loss of the TSA cycle can be started from matching the different grade heat sources with the adsorption bed of different temperature during the TSA cycle. ...
Carbon capture by adsorption is supposed to be an effective method to reduce CO2 emissions, among which Temperature Swing Adsorption (TSA) can utilize low-grade thermal energy even from renewable energy source. At present, TSA technology still has several challenges to be practical application, such as intensive energy-consumption and low energy-efficiency. Thermodynamics could be a powerful method to explore the energy conversion mechanism of TSA, among which entropy analysis could further provide a clear picture on the irreversible loss, even with a possible strategy of energy-efficient improvement. Based on the theory of non-equilibrium thermodynamics, the entropy analysis of TSA cycle is conducted, using the Computational Fluid Dynamics (CFD) method. The physical model and conservation equations are established and calculation methods for entropy generation are presented as well. The entropy generation of each process in cycle is analyzed, and the influence from the main parameters of desorption process is presented with optimization analysis. Finally, the performance of the cycle with regeneration is compared with that of the cycle without regeneration, and the method of reducing the entropy generation is obtained as well. This paper provides possible directions of performance improvement of TSA cycle with regards on energy utilization efficiency and the reduction of irreversible loss.
... The highest source temperature is required for zeolite/water pair, which is about 250−300 • C [28]. According to Anyanwu et al. [29], using zeolite/water pair provides an optimum source temperature of 200 • C. On the other hand, the driving temperature for AC/methanol pair is 120 • C [30]. Using silica gel/water pair, this temperature is roughly between 50 • C and 100 • C, Critoph [31] reported that this pair can be regenerated at a relatively low temperature (below 100 • C and typically about 85 • C). ...
... 29: Temperature profiles of the solar adsorption air conditioning system components for the cycle time of 700 s. ...
Worldwide, a multitude of the industrial processes utilizes fossil fuel to supply heat and power. However, the present stock of the fossil fuel is ultimately finite and will deplete in a few decades. On the other hand, the emissions of the fossil fuel combustion process share with a vast role in the environmental problems such as global warming and air pollution. Reducing this dependence on such energy sources becomes important in refrigeration and air conditioning field as it represents one of the most energy consumption industries. Locally in Egypt, the demand for the electricity has been growing at an average rate around seven present (7 %) annually over the last ten years, since the early 2000s. Remarkably, the conventional refrigeration system has another environmental problem representing in its ozone depletion potential. Therefore, providing an alternative refrigeration technology in attenuation of these effects will be valuable. Solar adsorption chillers are technologically promising especially in the developing countries and remote areas because the system can be driven by solar energy without involving electricity. The adsorption
refrigeration systems have a great share in reducing the environmental crises by using a low-grade solar energy thus reducing the carbon footprint so, reducing the global warming potential. Therefore, it is technologically possible and socially feasible in the areas where electricity is not enough but solar energy is rather easy to obtain.
Adsorption refrigeration systems are regarded as one of promising clean technologies
since it uses low-grade heat sources, such as solar, geothermal, biomass as well
as process/waste heat. The present study provides a dynamic modeling of two-bed
adsorption chiller using both RD silica gel/water and SWS-1L/water as working
pairs. Herein, a mathematical model has been developed using MATLAB software.
Also, the mathematical model was validated with the experimental data from the
literature. The analysis is based on the following conditions; (i) the cycle time of
0 s to 900 s, (ii) hot water inlet temperature of 55�C to 95�C, (iii) cooling water
inlet temperature of 25�C to 40�C and (iv) chilled water inlet temperature of 10C to 22�C. Simulation results indicate that the coefficient of performance increases
monotonically with the adsorption/desorption cycle time whereas the system cooling
capacity increases gradually until reaches an optimum adsorption/desorption cycle
time and then reduces. RD silica gel/water and SWS-1L/water pairs provide a higher
system cooling capacity of 16 kW and 4.18 kW, respectively at the hot, cooling and
chilled water inlet temperature of 95�C, 30�C and 14�C, respectively. Interestingly, it
was found that the system cooling capacity increases gradually from 6 kW to 16 kW
as the heat source temperatures varies from 55�C to 95�C for RD silica gel/water pair.
The half cycle times are �fixed to 350 s and 280 s for both pairs, respectively which
selected based on optimum time which gives maximum cooling capacity, whereas the
switching time is set to 30 s for both working pairs.
Moreover, enhancing of the adsorption chiller performance plays an important role
not only on the energy savings but also in the environmental pollution reduction.
The present work aims to improve the system cooling capacity of an adsorption
chiller working with a silica gel/water pair by an allocation of the optimum cycle
time at di�erent operating conditions. A prediction of the optimum cycle time for
a wide range of hot (55�C to 95�C), cooling (25�C to 40�C) and chilled (10C to 22�C) water inlet temperatures. Then, correlations for the optimum cycle time
as well as system performance characteristics such as system cooling capacity and
COP were derived in terms of the system operating temperatures. The optimum
and conventional chiller performance are compared at different operating conditions.
Enhancement ratio of the system cooling capacity was tripled as the cooling water
inlet temperature increased from 25�C to 40�C at constant hot and chilled water inlet temperatures of 85�C and 14�C, respectively. Mapping the assorted operating
temperatures with an adsorption/desorption cycle time of 0 s to 500 s, provides a
superior maximum cooling capacity of 21.4 kW at the optimum cycle time of 389 s for
hot, cooling and chilled water inlet temperatures of 95�C, 25�C and 22C, respectively.
Further results can be achieved by applying the concept of the optimum cycle time allocation, the system cooling capacity enhancement ratio can be reached to 15.6%
at hot, cooling and chilled water inlet temperatures of 95�C, 40�C and 10.
Additionally, the performance indicators comparisons are conducted for various cycle times of 900 s, 700 s and the adaptive cycle time under the Egyptian climate conditions using RD silica gel/water pair. Then, temperature profi�les of the solar storage tank, adsorber, desorber, evaporator and condenser are forecasted. Simulation results show that the maximum cyclic cooling capacity of the system reaches about 14.6 kW, 14 kW and 12.8 kW for cycle time operation of 900 s, 700 s and using the adaptive cycle time, respectively. In deep, a higher cycle time duration considers as an essential parameter in optimizing the solar adsorption chillers, which achieves a higher system performance. Moreover, using the solar adsorption chiller with a cycle time of 900 s, 700 s and for the adaptive variable cycle time was achieved an electrical consumption saving by about 34.2%, 32.9% and 30.4%, respectively. Finally, A CFD simulation study is performed to investigate the effect of using different heat exchanger con�figurations on the adsorption parameters.
... It is not only necessary to comprehensively consider the enhancement of heat transfer but also to find ways to reduce irreversible loss and power consumption in the heat transfer process. Therefore, many researchers have proposed new evaluation indexes based on the second law of thermodynamics, such as the entransy dissipation extremum principles (EDEP) [27][28][29], the exergy destruction minimization principle (EDMP) [30][31][32][33], the entropy generation minimization principle (EGMP) [34][35][36][37], etc. The EDMP, proposed by Liu et al. [30], can not only evaluate irreversible loss in the heat transfer process but also describe the flow loss caused by the fluid flow process. ...
In this study, the effects of fin tip thickness and fin root thickness of integral rolled spiral finned tube bundles on flow resistance, heat transfer performance and heat transfer and flow exergy destruction were investigated via mathematical simulation. The correlations between heat transfer and flow resistance performance were fitted with dimensionless numbers. The optimized parameters with performance evaluation criteria (PEC) as the objective were obtained using methods involving computational fluid dynamics and machine learning. The results show the effects of fin tip thickness and fin root thickness on the Nusselt number (Nu), Euler number (Eu), PEC, heat transfer exergy destruction (ExT) and flow exergy destruction (ExP) as obtained via mathematical simulation. A new mathematical correlation is proposed for predicting the Nu and Eu of integral rolled spiral finned tube bundles. Among the four optimization models tested, the random forest regression algorithm was the most accurate algorithm for PEC prediction models. In the studied range, the optimal parameters were a fin tip thickness of 2 mm and a fin root thickness of 3.5 mm. Compared with the initial parameters, when the Reynolds number was 20,380, the PEC increased by 2.53%, the ExP increased by 2.37% and the ExT decreased by 7.96%.
... Their testing module as a refrigerator could provide a solar COP of 0.136 and 0.159 in cold and hot climates, respectively. A prototype adsorption cooling system using natural zeolite-water was investigated by Solmus et al. [13,14]. The experimental results showed the average COP and SCP were 0.25 and 6.4 W/kg, respectively at the heat source temperature of 150°C. ...
Performance of an adsorption cooling system driven by solar thermal energy was studied under different climatic conditions. The effects of solar collector area, collector slope, hot water temperature and flow rate on the system performance were investigated using the real-time weather data of two cities: Perth, Australia (a representative city in the southern hemisphere) and Amman, Jordan (a representative city in the northern hemisphere). The simulation results showed that the two cities had similar solar radiation during the summer period and that the solar adsorption chiller could reliably provide cooling at a reasonably high system COP. For residential cooling with a total CPC (Compound Parabolic Collector) solar collector area of 36.22 m2, the average system COP was 0.491 for Perth weather conditions and 0.467 for Amman weather conditions, respectively while the cooling capacity was 10.3 kW for Perth and 8.46 kW for Amman, respectively at peak times. Optimum performance occurred when the system run with the CPC collector slope of around 30°, the solar water storage tank volume of 1.4 m3, inlet hot water temperature of 80 °C, and a hot water flow rate of 0.33 kg/s. An economic analysis was further investigated and the results showed that the solar driven adsorption cooling system could reduce the electricity consumption for Perth and Amman cities by 34% and 28%, respectively in comparison to a conventional vapour compression cooling system.
... For example, SAPO-34, usually be used as a catalyst for menthol to olefin reaction, has been investigated for more than two decades as a promising water adsorbent 30,31 . Several years ago, the company of Mitsubishi Plastics from Japan developed three types of aluminophosphates (namely AQSOA-Z01, AQSOA-Z02 and AQSOA-Z05), representing a considerable advancement for ADC applications owing to their outstanding performances of high water uptake and low regeneration temperature (< 90°C) [32][33][34] . The attractive performances of lab-scale and commercial-scale ADCs using AQSOA-Z02 have been demonstrated 35,36 . ...
Thermally driven water-based sorption refrigeration is considered a promising strategy to realize near-zero-carbon cooling applications by addressing the urgent global climate challenge caused by conventional chlorofluorocarbon (CFC) refrigerants. However, developing cost-effective and high-performance water-sorption porous materials driven by low-temperature thermal energy is still a significant challenge. Here, we propose a zeolite-like aluminophosphate with SFO topology (EMM-8) for water-sorption-driven refrigeration. The EMM-8 is characterized by 12-membered ring channels with large accessible pore volume and exhibits high water uptake of 0.28 g·g⁻¹ at P/P0 = 0.2, low-temperature regeneration of 65 °C, fast adsorption kinetics, remarkable hydrothermal stability, and scalable fabrication. Importantly, the water-sorption-based chiller with EMM-8 shows the potential of achieving a record coefficient of performance (COP) of 0.85 at an ultralow-driven temperature of 63 °C. The working performance makes EMM-8 a practical alternative to realize high-efficient ultra-low-temperature-driven refrigeration.
... The adsorption isotherm of the adsorbent is an important factor affecting the performance of the ADCS [64,[66][67][68]. Therefore, modeling the adsorption isotherm in ADCS with zeolite as adsorbent is key in designing and predicting their performance. ...
Adsorption desalination is an emerging desalination technology with low energy consumption, which is based on the principle of desalination by using the adsorption and desorption properties of solids with porous properties on water vapor. Compared with the traditional distillation and membrane methods, adsorption desalination can use renewable energy sources such as solar energy, geothermal energy, or industrial low-grade waste heat as the driving heat source, and thus has the excellent characteristics of being green and pollution-free. However, as a newly developed desalination technology, there is relatively little theoretical and experimental research on adsorption desalination, and it is still at the stage of small-scale experiments. This paper firstly introduces the adsorption theory and circulation process to clarify the key elements of this desalination method. Further, based on the available results, the related researches are analyzed and summarized according to the critical elements of the adsorption desalination system, i.e., preparation of adsorbents, optimization of system configuration, cyclic operating conditions, and combination systems. Finally, the future directions to be focused on for future research prediction are discussed, which will be useful for related studies in this field.
... Since the bed regeneration process is more complete, due to better thermal conditions corresponding to higher hot water inlet temperatures THin, the refrigeration circulation increases with the increase in the amount of desorbed refrigerant and the equilibrium uptake of water vapor is higher for the thorough regenerated bed. Such conditions improve the cooling capacity CC [66,[69][70][71]. On the other hand, as CC improves, the heating power HP of the AdC also increases, leading for THin higher than 356 K to the decrease in COP (Fig. 14). ...
Adsorption cooling and desalination technologies have recently received more attention. Adsorption chillers, using eco-friendly refrigerants, provide promising abilities for low-grade waste heat recovery and utilization, especially renewable and waste heat of the near ambient temperature. However, due to the low coefficient of performance (COP) and cooling capacity (CC) of the chillers, they have not been widely commercialized. Although operating in combined heating and cooling (HC) systems, adsorption chillers allow more efficient conversion and management of low-grade sources of thermal energy, their operation is still not sufficiently recognized, and the improvement of their performance is still a challenging task. The paper introduces an artificial intelligence (AI) approach for the optimization study of a two-bed adsorption chiller operating in an existing combined HC system, driven by low-temperature heat from cogeneration. Artificial neural networks are employed to develop a model that allows estimating the behavior of the chiller. Two crucial energy efficiency and performance indicators of the adsorption chiller, i.e., CC and the COP, are examined during the study for different operating sceneries and a wide range of operating conditions. Thus this work provides useful guidance for the operating conditions of the adsorption chiller integrated into the HC system. For the considered range of input parameters, the highest CC and COP are equal to 12.7 and 0.65 kW, respectively. The developed model, based on the neurocomputing approach, constitutes an easy-to-use and powerful optimization tool for the adsorption chiller operating in the complex HC system.
... For example, SAPO-34, usually be used as a catalyst for menthol to ole n (MTO) reaction, has been investigated for more than two decades as a promising water adsorbent 30,31 . Several years ago, the company of Mitsubishi Plastics from Japan developed two types of aluminophosphates (namely AQSOA-Z01 and AQSOA-Z02), representing a considerable advancement for ADC applications owing to their outstanding performances of high water uptake and low regeneration temperature (< 90 °C) [32][33][34] . ...
Thermally driven water-based sorption refrigeration is considered a promising strategy to realize near-zero-carbon cooling applications by addressing the urgent global climate challenge caused by conventional chlorofluorocarbon (CFC) refrigerants. However, developing cost-effective and high-performance water-sorption porous materials driven by low-temperature thermal energy is still a significant challenge. Here, we propose a low-cost zeolite-like aluminophosphate with SFO topology (EMM-8) for water-sorption-driven refrigeration. The EMM-8 is characterized by 12-membered ring channels with large accessible pore volume and exhibits high water uptake of 0.36 g·g ⁻¹ , low-temperature regeneration of 65 °C, fast adsorption kinetics, remarkable hydrothermal stability, and scalable fabrication. Importantly, the water-sorption-based chiller with EMM-8 shows the potential of achieving a record coefficient of performance (COP) of 0.85 at an ultralow-driven temperature of 63 °C. The extraordinary working performance makes EMM-8 a practical alternative to realize high-efficient ultra-low-temperature-driven refrigeration.
... Furthermore, Warsinger et al. [26] summarized six representative desalination approaches where second law efficiency and entropy generation analysis were used to characterize the performance of desalination systems. Li et al. [27] presented the entropy analysis to understand the irreversibility contributions from the thermal compressor during adsorption and desorption periods with respect to the driving heat source temperature and cycle time. For zeolite FAM Z01 + water system, they found an optimal operational zone at the hot water inlet temperatures of 65 o C to 85 o C with cycle times ranging from 200 to 300 s. ...
This article presents the entropy flow and generation of an adsorption assisted heat transformation (A-HT) system. Hence the Gibbs analogy and the thermodynamic property fields of adsorbents + water systems are employed to formulate the entropy balance of adsorption beds. Later, the experimentally confirmed isotherms, kinetics and bed heat exchanger data are applied for computing the energetic performances of adsorption system in terms of entropy flow and generation, from which one can calculate (i) the system-performances with respect to heating and cooling capacities, specific water production and the overall efficiency and (ii) dissipations from each component of A-HT systems. The temperature entropy-flow (T-Sf) maps show close loops for the evaporator, the condenser and the beds indicating the stored energy under batch operating conditions of A-HT cycle. It is observed that the entropy generation (Sg) are mainly contributed by various processes such as mass and heat transfer, de-superheating and flushing of heat transfer fluids. The highest entropy generation occurs in the adsorption bed during desorption period, and the least Si is found in the evaporator. The proposed temperature-entropy maps can be applied to design each component of bed heat exchanger with minimum entropy generation. It is found that the entropy flow and generation depend on the periods of batch operation, the heating source temperature, and the quality of porous adsorbents.
... So, to intensify the heat and mass transfer characteristics, the design and optimization of the beds are investigated by numerous researchers. The main deficiencies of the adsorber reactors are usually divided into, poor contact between the metal surface and solid surface [101], the thickness of the adsorbent layer [102], the thermal contact resistance between the bed and adsorbents and the adsorbents' thermal conductivity [103,104]. Accordingly, Rezk et al. [103] have studied the effect of the contact resistance on the performance of the adsorption chiller, finding that the contact resistance accounted for 25% of the overall heat transfer resistance. ...
This paper thoroughly reviews the integration of absorption, adsorption and desiccant cooling technologies into vapor compression cooling/refrigeration systems. Different configurations of hybrid absorption-compression cooling systems have been collectively listed and studied based on energetic, exergetic, economic and environmental analysis. Several reviewed studies revealed that such systems could diminish the electricity consumption by 45-88% in comparison with conventional compression systems. Besides, various arrangements of hybrid adsorption-compression cooling systems have been intensively investigated using cascade, partially integrated and fully integrated systems. These layouts of integrated adsorption-compression cooling systems focus on escalating the performance of vapor compression cooling systems by dwindling their condensation temperatures. Surveys showed that using adsorption cooling systems with oversized capacity could result in increasing the performance until approaching freezing limits, while downscaled adsorption cooling systems could worsen the system performance as a result of increasing the intermediate condensation temperature. The amalgamation of vapor compression systems with both solid and liquid desiccant cooling cycles has also been reported and compared with different regeneration schemes; for instance, electric energy, solar energy and heat rejected from the assisted vapor compression cooling systems. Considerable studies confirmed that using multi-stage solid desiccant cooling systems compared with single-stage solid desiccant cooling systems can be operated at lower regeneration temperatures. Also by introducing integrated liquid desiccant-vapor compression systems, cooling can be attained with a dehumidification process that cools the supply air lesser than its dew point with an energy provision of 30-80%. This work is beneficial for researchers involved in the field of multi-integrated cooling systems.
... The influencing factors are associated with the heat transfer due to the number of cascades and the temperature differences are discussed. Entropy analysis [52] was applied to understand the irreversibility of both the desorption and adsorption beds. It was found that the average entropy production increased with the increase of the hot water temperature and the adsorption/desorption cycle time. ...
Owing to its high porosity and high surface area, zeolite has a good adsorption effect on liquid adsorbates such as water, ammonia, organic liquids and gas adsorbates such as volatile organic compounds, hydrocarbons, etc. A large amount of heat is released during the adsorption period when the zeolite adsorbs these gases and liquids. The energy storage, the heat and mass transfer performance of zeolite adsorption is influenced by the selection of adsorbent and adsorbate as well as the design of zeolite bed. In this paper, the mechanism of zeolite adsorption is discussed, and equations that describe the adsorption isotherm and the heat and mass transfer of adsorbate on zeolite are reviewed. From the view of system aspect, the factors (such as the structural design of zeolite bed, the mass flow rate of adsorbate, the operating temperature, and the cycle time) that will affect the heat storage and transfer in adsorption are concluded. In terms of adsorbent/adsorbate, the properties of modified zeolites and zeolite composites are presented, and the reaction behavior of different zeolites and adsorbates is discussed. As for the application of zeolite adsorption system in the energy storage and heat transfer field, zeolite-based heat exchanger (HX), energy storage system (ESS), dehumidifier, energy absorption system (EAS), volatile organic compounds (VOCs) removal system and hydrocarbon (HC) trap are reported. Research results demonstrate that the zeolite adsorption system is promising no matter used alone or in combination with other equipment in energy-saving and environmentally friendly fields.
... In general, a good adsorbent should be characterized by: high thermal conductivity and low specific heat [11], it has to be non-toxic and non-corrosive [12]. High durability [13] and similar adsorption properties over time, with relatively small price and high water uptake at low temperature [14] are also crucial. In case of adsorbate, it should be characterized by a relatively low evaporation temperature, high evaporation heat and high latent heat value per unit of volume. ...
The article presents experimental results of the metal-based and carbon nanotube additives influence on sorption kinetics of a silica-gel-based adsorption bed in an adsorption chiller. The purpose of the doping is to improve the efficiency of sorption processes within the bed by use of metallic and non-metallic additives characterized by higher thermal diffusivity than basic adsorption material. The higher the thermal conductivity of the bed, the faster the sorption processes take place, which directly translates into greater efficiency of the refrigerator. In this study, sorption kinetics of pure silica gel sorbent doped with a given amount of aluminum (Al) and copper (Cu) powders and carbon nanotubes (CNT) were analyzed. The tests were performed on DVS Dynamic Gravimetric Vapor Sorption System apparatus used for dynamic vapor sorption measurements. A decrease in the amount of adsorbed water was observed with an increase in the mass share of the additives in the performed studies. Experimental results show that, CNTs seems to be the most promising additive as the sorption process time was reduced with the smallest decrease in water uptake. Any significant reduction of adsorption time was noted in case of the Al addition. Whereas, in case of Cu doping, delamination of the mixture was observed.
... Such significant changes are attributed to a high fraction of energy cost From the design point of view, the energy efficiency of the adsorption chiller can be improved by enhancing heat transfer in the adsorbent beds [9], conducting internal heat and mass recovery [10,11] and optimizing the system configuration [12]. The COP can also be improved during operation by increasing the regeneration temperature, reducing the cooling water temperature, and optimizing the cycle time [13]. Figure 9.4d shows the cost of the indirect evaporative cooler under different COPs. ...
The levelized cost of cooling accounts for the costs of cooling systems throughout their life cycle and is an effective measurement of the economic viability of cooling cycles. This chapter presents a life-cycle economic analysis of different cooling cycles. Economic and thermodynamic performance data are firstly collected from open literature. The cost of cooling over the plant lifetime is then calculated considering different energy sources. Results revealed that the mechanical chiller and the indirect evaporative cooler are the most cost-effective under the regular scenario, while heat-driven processes like absorption and adsorption cooling cycles are expensive due to high thermal energy costs. Costs of thermally driven cycles can be reduced if low-cost thermal energy sources are available, and under such situations, the absorption chiller can become a viable option. The cooling costs are also strongly impacted by interest rate, annual operation hour, and energy efficiency. Therefore, optimal design, selection, and energy efficiency are key to sustaining low capital and operating costs. The derived results offer a robust and convenient basis for selecting cooling systems in real applications.
... Based on classical thermodynamics, some existing studies established the entropy balance for each component inside the adsorption-based energy systems (such as adsorption chillers and gas storage systems) [21,22]. Some researchers considered the adsorption system as a closed thermodynamic system which just exchanges heat with its surroundings, and the entropy generation was obtained using the entropy flux of each process [23,24]. ...
... The mathematical model of the adsorption chiller used in this study is based on models that include thermal capacities of the various components [32,33], and the adsorbent (zeolite) has modelled only considering the interactions with the adsorbate. Each machine's component has been considered as homogeneous, its properties have been assumed as constant and the heat transfer has been accounted for through a global coefficient considering the thermal conductivities and the convective coefficients inside the bed. ...
In this study, a novel trigeneration system is conceived to produce heat and electricity and to provide cooling for the health treatments and touristic facilities of a spa, based on the natural hot water and solar sources. The power generation components, individually considered, are commercially available ones, but their novel combination and the complex power flow management represented a challenge. The proposed system is composed of a low‐temperature driven adsorption chiller, thermally activated by a low enthalpy geothermal source, and by hybrid photovoltaic/thermal panels. In this way, multiple objectives are achieved: produce electricity and thermal energy by renewable sources; optimise the use of different renewable sources (geothermal and solar); use the energy available for free from a geothermal source also during summer (otherwise wasted) to produce a cooling effect, and in so doing, avoiding the huge electricity consumption of conventional air conditioning units in summer; reduce the temperature of the fluids released to the environment (in a natural reserve); reduce the CO2 emissions by 45% with respect to the present configuration, limiting the global warming. The mathematical models were experimentally validated using a pilot plant built on purpose, and the performance of the whole system was analysed and discussed.
... For example, SAPO-34, usually be used as a catalyst for menthol to olefin reaction, has been investigated for more than two decades as a promising water adsorbent 30,31 . Several years ago, the company of Mitsubishi Plastics from Japan developed three types of aluminophosphates (namely AQSOA-Z01, AQSOA-Z02 and AQSOA-Z05), representing a considerable advancement for ADC applications owing to their outstanding performances of high water uptake and low regeneration temperature (< 90°C) [32][33][34] . The attractive performances of lab-scale and commercial-scale ADCs using AQSOA-Z02 have been demonstrated 35,36 . ...
Aluminophosphate molecular sieves are recognized as very promising materials for catalysis, adsorption, and separation. This study presented an attempt to synthesize LTA-type AlPO4 and AlGaPO4 molecular sieves by an ionothermal method. The influences of the relevant synthesis parameters and various template removal methods were discussed. The optimum growth temperature, doses of ILs, and crystallization time were suggested. The two-step calcination method was recommended since the intact crystalline structure and microporosity of LTA-type AlPO4 were retained after template removal. Perfect cubic AlPO4-LTA molecular sieves were successfully prepared with an excellent micropore volume of 0.33 ml/g and water uptake of 0.38 g/g at P/P0 = 0.20. Moreover, an LTA-type AlGaPO4 molecular sieve was also successfully synthesized by an ionothermal method with partial Ga doping. Evident changes in morphology were found and could be ascribed to various crystal plane orientations. Ga-doped crystals subjected to template removal and water soaking showed worse thermal and hydrothermal stability. The microporosity and water sorption capacity of AlGaPO4-LTA also decreased greatly due to its sharply reduced stability and collapsed structure. After Ga doping, however, the materials became more hydrophilic, with slightly higher water uptake at low relative pressure. The materials also showed greater acidity strength at both Brønsted and Lewis acid sites.
... Adsorption cooling system uses adsorbents such as silica gel to adsorb and desorb a water vapor by changing temperature or pressure. Notable works have been done on temperature swing adsorption cooling systems [8][9][10][11][12][13][14][15][16][17], and pressure swing adsorption cooling is still developing [18,19]. We proposed pressure swing adsorption cycle (PSAD) that can utilize low-pressure steam (2-5 bar) for regeneration using thermal vapor compressor (TVC). ...
Over the last century, fresh water and cooling demand have been increased tremendously due to improved living standard, industrial and economic development. The conventional air-conditioning and refrigeration processes consume 15% of total global electricity and it is expected to increase any fold due to harsh weather conditions. In terms of fresh water supplies, the current 38 billion m3 per year desalination capacity is projected to increase to 54 billion m3 per year by 2030, 40% more compared to 2016. The current business as usual trend of cooling and desalination is not sustainable due to high energy consumption and CO2 emissions.
In contrast, the adsorption (AD) cycle operate at low-grade waste heat or renewable energy and produce fresh water and cooling simultaneously. The major bottleneck of conventional thermally driven AD cycle is its large foot print and capital cost due to complex packed bed arrangements. We proposed pressure swing adsorption cycle (PSAD) that can utilize low-pressure steam (2-5 bar) for regeneration using thermal vapor compressor (TVC). The proposed system has best thermodynamic synergy with CCGT plants where low-pressure bleed steam can be utilized more efficiently to produce cooling and water. In this paper, a preliminary experimental investigation on PSAD has been presented. It is successfully demonstrated that 2 bar primary steam can regenerate silica gel at less then 0.5 kPa through TVC with compression ratio 3-4 and entrainment ratio around 1-1.5. The discharge steam can be re-utilized to operate the desalination cycle, maximizing the bleed steam exergy. The proposed system will not only reduce footprint but also CAPEX and OPEX due to simple design and operation.
... zeolite-water/-ethanol [15][16][17][18][19][20][21]; activated carbon (AC)-ethanol/-methanol/-R32/-R134a/-R410A/-R404A/-R152a/-CO 2 [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41]; MOFethanol/-water/-CO 2 [42][43][44][45]; ACF-ethanol/-methanol/-R32/-CO 2 [41,[46][47][48][49]. ...
Adsorption cooling systems powered by low-grade thermal or renewable energy are considered as a potential alternative to the vapor compression systems. To improve the performance and compactness of the system, this study focuses on the synthesis and characterization of activated carbon (AC) composite employing graphene nanoplatelets (GNPs) namely H-grade and C-grade, and polyvinyl alcohol. The influence of GNPs on the porous properties, thermal conductivity, and ethanol adsorption characteristics of composites have been experimentally investigated. Porous properties results show that the studied composites possess high surface area and pore volume with microporous nature. The C-grade contained composite shows the higher porous properties compared to H-grade, however, thermal conductivity for the later one is the highest. The highest thermal conductivity is found to be 1.55 W m −1 K −1 for H-grade (40 wt%) contained composite which is 23.5 times higher than that of powder AC. Ethanol adsorption characteristics on studied composites are conducted gravimetrically at adsorption temperatures 30-70 °C. Experimental data are also fitted with Tóth and Dubinin-Astakhov (D-A) isotherm models within ± 5% RMSD and found 23% improvement of effective volumetric uptake for H25 (20 wt %) composite compared to parent AC. The instantaneous ethanol adsorption uptake onto composites has also been presented for adsorption temperature 30 °C and evaporator pressure at 1.8 kPa.
... It is expected to possess the essential characteristics for sorption cycles such as high affinity to water vapor, lower regeneration temperature (< 85 °C) and the ability to sustain uptake process at relatively higher adsorption temperature. Subsequently, many studies have investigated the characteristics of FAM-Z01, such as the effects of cooling temperature, mass and heat recovery time (Qian et al. 2013;Li et al. 2014;Myat et al. 2013). However, the isotherm shape was also shown to be controlled mainly by the amount of the substituted metal as revealed for MeAlPO-5, MeAlPO-11 and MeAlPO-31 (Kornatowski 2005). ...
With a characteristic of S-shape isotherms for water vapor adsorption, aluminophosphate molecular sieve with AFI type (AlPO-5) has been considered as an up-and-coming adsorbent for the utilization in the adsorption cooling and heating (ACH) system. In order to improve its adsorption performance, iron doped AlPO-5 (FeAPO-5) with variable Fe loading was synthesized by microwave hydrothermal method. The effects of the iron doping content on the structure and adsorption performance were systematically investigated. The analysis results of X-ray diffraction (XRD), UV–visible spectroscopy (UV–Vis-DR) and scanning electron microscopy (SEM) showed that the iron ion was incorporated into aluminophosphate molecular sieves with a typical AFI structure as that of AlPO-5 through the isomorphous substitution. As the iron content of FeAlPO-5s increased, the isolated FeIII decreased, while oligonuclear FeIII and nanosized FeIII increased, besides, the static adsorption curves showed that the adsorption capacity of FeAlPO-5 increased first and then decrease. After iron modifying, the crystallinity and morphology of crystals was improved, and the adsorption performance increased from 0.185 g/g (AlPO-5A) to 0.235 g/g (FeAlPO-5), while the desorption performance of FeAlPO-5 (95.69 kJ/mol) was close to that of AlPO-5A (81.59 kJ/mol).
... Another important aspect of the isosteric heat of adsorption is in the process or cycle simulations of adsorption related systems. The energetics involved in such systems are often modelled using the isosteric heat as a key parameter, be it lumped model [29][30][31][32][33] or multi-scale distributed models [34][35][36][37] and subsequently, the second law analyses [38][39][40]. ...
... In addition to the inexpensive activated carbon adsorbent, attention has also directed at water. The research on water as an adsorbate has also been in-depth, including study on the silica gel/ water pair [13,14] and the zeolite/water pair [15][16][17]. Additionally, some novel composite adsorption working pairs have emerged recently. ...
The current work demonstrates a novel prototype of a solar adsorption refrigeration system with enhanced mass transfer based on an ideal basic solid adsorption refrigeration cycle with activated carbon-methanol as the working pair. The working principle of the hypothesis was analysed, and the coefficient of performance (COP) was used to assess the system's performance. A solar simulator consisting of a halogen lamp light resource array was adopted to provide a light source for heating. Different comparative tests under different input radiation energy conditions were carried out to prove the hypothesis that a lower condensing pressure can be realized by using an enhanced mass transfer method and is good for increasing the amount of desorption. The variations of the adsorbent bed temperature, system pressure and ice production were analysed. The maximum COP and maximum ice-making capacity of the enhanced mass transfer adsorption refrigeration system were 0.142 and 7 kg, respectively. The average COP of the novel system showed an improvement of 35.9% compared with the average COP of the natural mass transfer adsorption refrigeration system when the input radiation energy was not less than 14.7 MJ during a refrigeration cycle.
Purpose
With the global economic slowdown in 2023, most universities in the central and western regions of China may face the problem of shortage of government financial funding, which is directly related to the development of science and technology of the universities. With the support of the local government, most of the ordinary universities have shifted attention to the transfer and transformation of intellectual property based on school-enterprise cooperation, hoping to seek more commercialization income as an extra source of income. Therefore, this paper aimed to study the current situation of university intellectual property, i.e. the reserve and distribution of transferable patents, discipline distribution of patents, and regional cooperation of university patents.
Design/methodology/approach
A patent database of 10 key universities in Henan Province of China from 2012 to 2021 was established. The evaluation indicator model by the Entropy method was conducted to reveal the interaction mechanism between quantity indicators, quality indicators, and value indicators. Based on the data analysis, the development direction of the discipline construction and school-enterprise cooperation for local universities was clear.
Findings
The findings indicated that the number of patent applications from ten key universities in Henan Province has been increasing rapidly over the years. The trend for authorized invention patents has remained relatively stable. Compared with the patent applications and authorizations, the growth of transferable patents was notably slow. The significance of strategic layout of dominant disciplines and related high-value patents was not appreciated enough by Chinese government and universities. There was a large difference of dominant disciplines between 10 key universities, and the patent level of each university was directly proportional to the number of dominant disciplines. The university patent level heavily relied on the researchers' contributions and the distribution mechanism of scientific research resources within the university. Guangdong Province and the Yangtze River Delta of China, being economically developed regions, exhibited the most active engagement in patent technology cooperation. Conversely, the central and western regions displayed relatively lower participation in high-value patent research and development.
Research limitations/implications
This study can provide a unique perspective to understand and solve the financial bottleneck problem of ordinary universities in the central and western regions of China. The discipline construction and school-enterprise cooperation are just one of the existing schemes, but it still cannot solve the financial problems faced by local universities in China towards the government.
Practical implications
The findings of this study can serve as a foundation for further investigation into policies aimed at improving the financial problems of ordinary universities in the central and western regions of China.
Originality/value
As an important attempt, the study tried to focus the financial problem of universities in the central and western regions of China based on the evaluation of the current situation of university intellectual property. This research findings are of great value in finding optimal layout between university patents, disciplines and school-enterprise cooperation.
A two-bed adsorption refrigeration cycle (ARC) with a new proposed modified mass recovery process is investigated (modeled, optimized and compared with ARC cycle with conventional mass recovery process) here. This proposed modified mass recovery process increases the system cooling capacity and cycle exergy efficiency. These achievements reached by opening the connecting valve between two beds during mass recovery process as usual, but continuing cooling of adsorption bed by water even during mass recovery process. Thus, the refrigerant vapor moved from desorber to adsorber bed in this situation by two effects, the higher pressure of refrigerant vapor in desorber bed and also due to higher effect of adsorption process for cooling of this bed by water. Furthermore, at the end of the proposed modified mass recovery process, the equilibrium pressure of beds was closer to the evaporator pressure than that for ARC with conventional mass recovery process. Thus, the new switched adsorption bed could connect to evaporator even during pre-cooling process. This makes connecting time period of evaporator and adsorber longer than that for ARC with the conventional mass recovery process. The above effects increased the amount of refrigerant vapor adsorbed in the adsorption bed which increased ARC cooling capacity as well. Finally to study the effects of various design variables, a two bed ARC with the proposed modified mass recovery cycle is modeled and optimized for a specific cooling capacity by considering coefficient of performance and exergy destruction as two objective functions. Results for a system with 14 kW (4 refrigeration tons) cooling capacity showed 0.555, 0.284 and 1719.6 kJ for optimum values of coefficient of performance (COP, with 0.9% increase), exergy efficiency (14% increase) and total exergy destruction (16.2% decrease), respectively in comparison with those for ARC with the conventional mass recovery process.
To further the deployment of adsorption cooling systems for various applications, the cooling potential assessment of novel activated carbon-based pairs with R32 refrigerant is carried out in this work. The compositions of Maxsorb-III activated carbon with H25 Graphene nanoplatelets (GNP), 1-Hexyl-3-methylimidazolium bis(trifluormethylsulfonyl)imide ([HMIM][Tf2N]) ionic liquid, and polyvinyl alcohol (PVA), that have yielded the highest volumetric cooling energy (80:0:10:10) and thermal conductivity (40:40:10:10) respectively are considered for performance evaluation. The present study focuses on the under-explored aspect of heat exchanger optimization for HFC-based adsorbents through numerical analysis of two finned tube heat exchanger design configurations, viz., annular and longitudinal. A computationally less expensive numerical modeling is adopted, enabled by a scaling analysis. The impact of fin aspect ratios is analyzed for the composites with both the finned tube design configurations, and the significance of the adsorbent's thermal conductivity in realizing compact lightweight heat exchangers is highlighted. Further, an impact assessment of the adsorbent's orientation within the heat exchanger is presented for its anisotropic thermal conductivity characteristics. While it is observed that the annular fin configuration yields higher cooling performance for the composition 80:0:10:10, the longitudinal fin configuration yields a higher coefficient of performance for the composition 40:40:10:10 with a minimal decrement in the volumetric cooling power (<4.9%) over the annular fin configuration. The higher thermal conductivity of the composition 40:40:10:10 is seen to yield savings in the heat exchanger mass of up to 40.9% over that of the composition 80:0:10:10, for the same cooling capacity. The results indicate that present working pairs offer better cooling capacities and compact designs over other HFC-based studies in the literature.
Adsorption desalination is prescribed as a promising and eco-friendly solution for mitigating water scarcity, owing to its utilization of low-grade thermal waste and zero liquid brine discharge. The keystones that regulate the performance of the adsorption desalination system (ADS) include nature of adsorbents, system design, and operating conditions. The present study aims to provide a state of the art review on the keystones of ADS. Metal-organic frameworks (MOFs) hold remarkable adsorption capacity and tunable structure. However, hydrothermal instability, high cost, and complex synthesizing procedures are the potential challenges that need to be addressed. The technological advancements in ADS have been classified into: (i) Conventional Approach, (ii) Heat and Mass Recovery Approaches, (iii) Hybridization Approaches, (iv) and Adsorbent Substituting Approach. The study provides critical insight and compares the performance of each approach based on specific daily water production (SDWP), specific cooling power (SCP), and coefficient of performance (COP). The conventional ADS produce SDWP of 4.7 m3/ton/d, however producing zero and/or minimal SCP while using payable energy of 1.50 kWh/m3. In heat/mass recovery approaches, pressure equalization-valve delay schemes and master–slave configuration provide ∼ 5 % additional water adsorption/desorption on/from silica-gel and reduce ∼ 50 % thermal heating load, respectively. Evaporator-condenser amalgamation emphasizes the evaporator temperature of 30–42 °C leading towards ∼ 69 % higher SDWP with zero SCP. Dual stage, multi evaporators/condensers scheme is found supportive in cogenerating feature of ADS thereby improvising COP to ∼ 0.87. In hybridization approach, ejector integrated ADS produces SDWP of 80 m3/ton and COP of 2.22 using payable energy of 0.92 kWh/m3, however, needs experimental validation. In the adsorbent substituting approach, CPO-27(Ni), Emim-Ac/Syloid 72FP, and composite adsorbent manifest the SDWP to higher levels. The operating conditions are sensitive and need to optimize depending on the configuration of ADS. Possible future research directions may include efficient designing/ sizing of evaporators/ condensers, minimizing the heat and mass transfer resistances in adsorber/desorber reactor, optimize the thickness of the adsorbent layer in heat exchangers, and investigating wide range of adsorbent classes that can be driven with very low regeneration temperature.
This study focuses on a comprehensive study of MOFs (metal-organic frameworks) plus water systems for adsorption desalination applications. The paper first deals with the modification of parent MOFs such as aluminium fumarate, MOF-801 (Zr) and UiO-66 (Zr) employing MOFs functionalization, alkali ion doping and impregnation of zeolites, and secondly, we focus on their characterizations for understanding both structural and thermal stabilities. Later, water adsorption on these parents and modified MOFs are investigated for a wide range of pressure (0 < P/Ps < 1.0) and temperature (30 to 80 °C). Based on experimentally confirmed isotherms, kinetics and MOFs characteristics data, the performance factors such as SDWP (specific daily water production) and PR (performance ratio) are evaluated for various regeneration temperature (55 to 80 °C) and cycle time (100 to 1000 s). Furthermore, the water adsorption characteristics are applied to calculate the entropy flow and generation for each component of AD system. The SDWP is also calculated from the concepts of temperature – entropy diagram. It is found that both OH-UiO-66 (Zr) and 5%Li-Al-FumMOFs provide promising SDWP (> 34 m³ /tonne of MOFs/day) and 5%Li-Al-Fum shows minimum entropy generation.
Adsorption refrigeration technology is being increasingly investigated over the past few decades as a sustainable technology option for meeting the fast-growing cooling needs for refrigeration and air-conditioning. What is attractive about adsorption technology is the opportunity to use low grade thermal energy such as solar heat and industrial waste heat. The present study is an attempt to provide readers a comprehensive update on status and challenges of adsorption refrigeration. The effects of working parameters like evaporator temperature, condenser temperature, regeneration temperature, cycle time, and inter-stage pressure on coefficient of performance and specific cooling power are covered with an objective to include experimental as well as theoretical research work reported thus far. Research work consolidated in this study includes the integrated cycles of adsorption cooling, adsorber design with extended surfaces, multi-stage and/or multi-bed scheme, and heat and/or mass recovery scheme either in combination or individually for thermal performance enhancement. Furthermore, work on a state of the art of various commercially available adsorption chillers highlighting their cooling capacity, working temperature range, novelties, and applications are reported in detail. This review also reveals an opportunity for research in optimizing the mechanism, design, orientation of the heat exchangers, functioning, and customizing the vapour adsorption refrigeration system for widespread applications in various sectors like automobiles and agriculture. Authors present this study with an expectation to provide beginners a quick review in the area of adsorption cooling technology.
This study provides an in-depth analysis of the sequence of procedures required to evaluate the performance of adsorption desalination (AD) using functional adsorbent material zeolites (i.e., FAM-Z series with AFI and CHA types). The applicability of zeolite as an adsorbent for the AD cycle was also demonstrated by comparing it with the performance of AD using silica gel. The adsorption isotherm of the adsorbent, which is the most important parameter in the performance and design of the AD cycle, is recognized as a crucial parameter that significantly affects the AD performance. The thermophysical properties of the FAM-Z series were analyzed using argon adsorption and desorption isotherms at 87 K, followed by water vapor adsorption isotherms. Modified Do–Do and hybrid Langmuir–Sips isotherm models were proposed and are suitable for the anomalous stepwise isotherms of the FAM-Z series and the mesoporous adsorption characteristics of silica gel. The performance of the AD cycle was assessed in terms of the specific daily water production, specific cooling capacity, coefficient of performance, and performance ratio with respect to chilled and hot water temperatures and cycle times using a mathematical model of the AD cycle validated through a comparison with experimental data. AFI-type zeolites showed the applicability of residential (FAM-Z01) and district cooling (FAM-Z05), which have a low regeneration temperature of 55 ℃ owing to an unusual isotherm (i.e., sigmoid adsorption isotherm). In addition, FAM-Z05 exhibited considerable potential as an adsorbent for AD cycles driven by extremely low-grade heat sources (<55 ℃) found in industrial plants and solar energy.
As adsorption refrigeration systems are powered by waste heat from automobile/industries and run by environment-friendly refrigerants, they have very promising cooling technology compared to vapor compression and absorption cooling systems. But due to large size, less performance and high installation cost, adsorption cooling systems have not yet been commercially popular. Literature review shows the physical adsorbent has poor adsorption capacity as compared to the chemical adsorbent. However, the salt swelling and agglomeration are the phenomenal challenges associated with chemical adsorption systems leading to reduction in the heat and mass transfer performances. To overcome the demerits of the physical and the chemical adsorbents, composite adsorbent systems have been developed to harness the potentiality of the adsorption capacity and increase the heat and mass transfer performances of adsorbent. In the present work the performance of different adsorption refrigeration system working on physical and chemical adsorbent has been discussed and compared on the basis of COP (Coefficient of Performance) and SCP (Specific cooling Power). A detailed comparative analysis has been provided between different composite adsorbents developed by using Silica-gel, Activated Carbon, Expanded Natural Graphite and Zeolite as a parent material. The performance of different composite adsorbents has been compared on the basis of thermal conductivity and adsorption capacity (of water, methanol, ethanol and CO2). Also, a novel composite adsorbent using polymeric binder (silica-gel and expanded natural graphite bound with polyvinyl alcohol) has been proposed and their physical properties are also discussed. In addition to this, three different methods of composite adsorbent materials preparation using silica-gel, activated carbon, zeolite with expanded natural graphite have been discussed. It is observed from the present study that the composite adsorbent of Metal Organic Frameworks shows better heat and mass transfer properties as compared to the conventional adsorbent. It is also observed that the performance of the adsorption refrigeration system can be improved significantly by developing high-performance composite adsorbents.
Adsorption cycles have been gaining significant interest in waste-heat recovery and renewable energy utilization. Adsorption isotherm data and the equilibrium cycle analysis are crucial steps in evaluating a typical adsorbent + adsorbate pair. In this paper, the performance of Maxsorb III + R245fa and spherical activated carbon, SAC-2 + R245fa were studied for adsorption cooling and adsorption heat transformer (AHT) cycles. Adsorption isotherms of these pairs were measured using the constant-volume-variable-pressure apparatus for temperatures ranging from 30 °C to 60 °C, and fitted with the Dubinin–Astakhov (D–A) and the Tóth isotherm model. An improved equilibrium model was developed, accounting the effects of thermal masses. The specific cooling energy (SCE) and the coefficient of performance (COP) of the adsorption cooling cycle were evaluated for various thermal mass to adsorbent mass ratios. It is observed that SAC-2 + R245fa pair offers better SCEs (20 kJ kg⁻¹and 160 kJ kg⁻¹ at 60°C and 90°C, respectively) when compared to that of Maxsorb III + R245fa. The impact of thermal mass is found to be significant for all regeneration temperatures for Maxsorb III + R245fa while the deterioration of COP in SAC-2 + R245fa is notable for high regeneration temperatures (> 75°C). When employed in the AHT cycle, Maxsorb III offers a slightly higher useful heat while SAC-2 provides a better Quh/QQR albeit by a small margin. The Quh/QQR values for both studied pairs are more than 0.6 for all regeneration temperatures for the heat extraction at 120°C.
The electricity-driven vapor-compression air-conditioning system registers around 3–10% second law efficiency under tropical climates due to the coupling between sensible and latent cooling loads. Desiccant coated heat exchangers (DCHEs) are the next-generation technologies that can improve the efficiency of the air-conditioning process by decoupling sensible and latent loads. Existing literature on DCHEs is primarily directed towards material development and performance evaluation from the first law of thermodynamics standpoint. However, to have an insight into the operation of DCHEs concerning its process irreversibility, performing the second law of thermodynamics analysis is necessary. This analysis will pinpoint the causes of irreversibility in the DCHE system and evaluate the useful work destroyed during its cyclic operation. In this paper, we have developed a general steady-state thermodynamic framework to study the performance of DCHEs from a combined first and second law perspective. Experiments were carried out to obtain the thermodynamic state properties of air, water, and desiccant that are necessary to perform energy and exergy analyses. Further, fundamental parametric studies were conducted to understand the influence of different desiccant type, varying operating parameters, and ambient conditions. Key results revealed that the regeneration process contributed to significant entropy generation rates and by reducing the hot water temperature by 10 °C, the second law efficiency illustrates improvement of almost two times. Additionally, by selecting to coat the heat exchanger with a composite polymer material instead of silica gel, the second law efficiency of DCHEs is enhanced by around 2.6 times. Lastly, a hybrid air-conditioning system comprising vapor-compression chiller and DCHE records 50% savings in energy consumption and yields two-times higher second law efficiency.
Evaluation of the comprehensive performance of different heat transfer technologies and selection the best enhanced surface to meet the requirements are of great significance for efficient energy recovery. In this paper, based on the previous research results from our group, a rapid multi-criterion comprehensive evaluation method of enhanced heat transfer surfaces was first proposed; it realizes the rapid evaluation of heat transfer performance under the condition of equal flow rate, equal pressure drop and equal pump power constraints. Three baselines divide evaluation plot into six zones, namely zone 1 (non-energy-saving zone), zone 2 (relative energy-saving zone), zone 3 (value-added energy-saving zone), zone 4 (ideal energy-saving zone), zone 5 (pure energy-saving zone), and zone 6 (simple energy-saving zone). A simplified evaluation plot was then developed to overcome the dependence on the correlations of the reference surface. Next, the prediction results of the evaluation plot under the condition of variable minimum flow cross-section area, variable total heat transfer area, variable equivalent diameter, and variable tube bundle arrangement were compared with the traditional method to verify the applicability and accuracy of the evaluation plot. Finally, numerical simulations and engineering application of typical heat transfer surfaces were conducted to compare the energy-saving effectiveness of different enhanced surfaces and to analyze the effect of geometry and operation parameters on comprehensive performance. The results showed that the evaluation chart established in this paper can be successfully applied to the comprehensive comparison of multiple evaluation criteria and has a high prediction accuracy. Compared with the common evaluation methods, this method has excellent practicability and visualization, and contributes to the rapid development of new enhanced surfaces and efficient utilization of energy.
The world is facing the ever‐worsening issues of global warming. The results show that the physical‐/chemical‐adsorbent water can improve the adsorption capacity of 1.22 kg/kg. If water is used as the adsorbate, the adsorbent has a serious issue of corrosion. So, methanol is utilized. However, methanol just can be heated by low‐temperature heat, because methanol will be broken down in above 140°C adsorption system. The multifunction adsorption system can produce one cold effect output and two power generation outputs. The results show that the silica gel/LiCl‐methanol multifunction adsorption system has a higher cooling exergy efficiency of 0.25 and a higher total system exergy efficiency of 0.87 compared with that of the silica gel‐water system. Performance stability of the compound adsorbent‐water is studied. The multifunction adsorption system can produce one cooling output and two generation outputs. The cooling exergy efficiency of the silica gel/LiCl‐methanol is high, as well as the total exergy efficiency of the silica gel/LiCl‐methanol.
The adsorption–desorption behavior of a fin-tube heat exchanger coated with Functional Adsorbent Material Zeolite (FAM-Z01) was investigated to experimentally determine the influence of the temperature of the hot water circulating in the heat exchanger and cycle time on adsorption-desorption behavior and heat flow. It was found that dehumidification performance increased significantly as the water temperature increased from 50 to 60°C and to a lesser degree from 60 to 70°C, in the temperature range in which the performance control step switches from regeneration to adsorption. Heat-flow analysis revealed that in the regeneration region the heat exchanger did not effectively use its heat supply, and preheating of the regeneration air was shown to improve the regeneration performance. Coefficient of performance COPth, which indicate the cooling efficiency, and COPlat, which indicate the dehumidifying efficiency, were significantly improved at a hot-water temperature of 50–60°C. Thus, preheating of air was shown to be quite effective in improving dehumidifying performance at the lower range of hot-water temperatures.
This article presents the synthetization and characterisation of fam (formic acid modulated) Al Fum (aluminium fumarate) MOFs. The parent Al Fum MOFs are modulated with 5 ml, 10 ml and 15 ml of formic acid for comparison purposes. The characteristics of newly developed fam Al Fum are presented by TEM and PXRD analyses. N2 volumetric adsorption is performed to evaluate the porous properties of fam Al Fum. It is found that Al Fum particles start to elongate with the addition of formic acid and the synthesis duration is greatly reduced. An increase in micro pores distribution is observed for 10 ml of formic acid added to the parent Al Fum MOFs. Water adsorption isotherms and kinetics are measured by a gravimetric analyser. It is found that fam Al Fum MOFs improve the water vapour uptake rates as compared with the parent Al Fum. The addition of 10 ml formic acid into Al Fum MOF shows the best performances in terms of uptake-offtake difference (Δq), which is 12.5% higher than that of the parent Al Fum MOF. The isosteric heat of adsorption is also calculated. The improved isotherms and kinetics results indicate fam Al Fum as potential adsorbent for heat transmission applications.
The history of adsorption cycles and the basic cycle are briefly described. The major refrigerants used are water, methanol, and ammonia. ‘Physical’ adsorbents include zeolites, active carbons, silica gels, and salts in mesoporous silica or alumina. Means of improving heat and mass transfer in both low (water, methanol) and high (ammonia) pressure systems are discussed. These include the use of conventional adsorbents that have been consolidated and more novel materials and approaches. There are a range of new thermodynamic cycles under development which have the varying goals of either using low temperature driving heat or maximizing the energy efficiency when using high temperature heat. In all machines there is a design compromise to be made between compactness (related to capital cost) and energy efficiency.
This paper investigates the performance of a solar-assisted adsorption (AD) cycle which produces two useful effects, namely cooling and desalination, with only a low-temperature heat input such as thermal energy from solar collectors. Heat sources varying from 65 to 80°C can be obtained from 215-m-super-2 flat plate-type solar collectors to regenerate the proposed silica gel--water-based AD cycle. In this paper, both mathematical modelling and experimental results from the AD cycle operation are discussed, in terms of two key parameters, namely specific daily water production (SDWP) and specific cooling capacity (SCC). The experimental results show that the AD cycle is capable of producing chilled water at 7 to 10°C with varying SCC range of 25--35 Rton/tonne of silica gel. Simultaneously, the AD cycle produces a SDWP of 3--5 m-super-3 per tonne of silica gel per day, rendering it as a dual-effect machine that has an overall conversion or performance ratio of 0.8--1.1. Copyright The Author 2009. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org, Oxford University Press.
Although energy has tended to lose it’s popularity due to the changing world supply of oil in recent years; if limited availability and depletion of the natural sources are considered; and since energy storage systems involves the collection and retention of the readily available energy for later use and facilitates the efficient utilization of the limited sources, necessity of research and development studies on it becomes clear. Among the storage modes thermel energy storage is attractive for the application related to waste heat, solar energy and Peak electricity.
Experimental measurements are made for a silica gel-water advanced adsorption refrigeration chiller (1.2-kW [4,095-Btu/h] cooling capacity) to evaluate its performance under different temperature and adsorption/desorption cycle time conditions. This paper describes the operating principle of the chiller, outlines the experimental hardware, and discusses results obtained by varying the cooling and hot water inlet temperatures and adsorption/desorption cycle times, as well as their agreement with the simulated results given by a lumped parameter model. The chiller performance is analyzed in terms of cooling capacity and coefficient of performance (COP). Excellent qualitative agreement was obtained between the experimental data and simulated results. The results showed the advanced three-stage cycle to be particularly well suited for operation with low-grade-temperature waste heat as the driving source, since it worked with small regenerating temperature lifts (heat source - heat sink temperature) of 10 to 30 K.
Experimental kinetics results of propane in Maxsorb III activated carbon is obtained at temperatures of 10°C and 30°C, and pressures up to 800kPa using a magnetic suspension balance. A multi-gradient linear driving force (LDF) approximation is used for adsorbate uptake as a function of time. The LDF mass-transfer-rate coefficients were thus determined. Using this approach, the experimentally derived LDF coefficients based on independently measured kinetic parameters for propane in the activated-carbon bed agree very well with experimental results. The computational efficiency is gained by adopting this extended LDF model.
This paper discusses the analysis of an adsorption (AD) chiller using system entropy generation as a thermodynamic framework for evaluating total dissipative losses that occurred in a batch-operated AD cycle. The study focuses on an adsorption cycle operating at heat source temperatures ranging from 60 to 85 °C, whilst the chilled water inlet temperature is fixed at 12.5 °C, – a temperature of chilled water deemed useful for dehumidification and cooling. The total entropy generation model examines the processes of key components of the AD chiller such as the heat and mass transfer, flushing and de-superheating of liquid refrigerant. The following key findings are observed: (i) The cycle entropy generation increases with the increase in the heat source temperature (10.8 to 46.2 W/K) and the largest share of entropy generation or rate of energy dissipation occurs at the adsorption process, (ii) the second highest energy rate dissipation is the desorption process, (iii) the remaining energy dissipation rates are the evaporation and condensation processes, respectively. Some of the noteworthy highlights from the study are the inevitable but significant dissipative losses found in switching processes of adsorption-desorption and vice versa, as well as the de-superheating of warm condensate that is refluxed at non-thermal equilibrium conditions from the condenser to the evaporator for the completion of the refrigeration cycle.
Adsorption refrigeration systems are commercially developed due to the need of replacing the conventional systems which utilise environmentally harmful refrigerants and consume high grade electrical power. This paper presents the key equations necessary for developing a novel empirical lumped analytical simulation model for commercial 450 kW two-bed silica gel/water adsorption chiller incorporating mass and heat recovery schemes. The adsorption chiller governing equations were solved using MATLAB (R) platform integrated with REFPROP (R) to determine the working fluids thermo-physical properties. The simulation model predicted the chiller performance within acceptable tolerance and hence it was used as an evaluation and optimisation tool. The simulation model was used for investigating the effect of changing fin spacing on chiller performance where changing fin spacing from its design value to minimum permissible value increased chiller cooling capacity by 3.0% but decreased the COP by 2.3%. Furthermore, the effect of generation temperature lift on chiller performance and the feasibility of using it as a load control tool will be discussed. Genetic Algorithm optimisation tool was used to determine the optimum cycle time corresponding to maximum cooling capacity, where using the new cycle time increased the chiller cooling capacity by 8.3%.
This article presents a thermodynamic framework for a lithium bromide – water absorption chiller, in which a transient model is developed to simulate the operation process. Local energy and mass balance within the main components like absorber, regenerator, condenser, evaporator and solution heat exchanger is respected to investigate the behavior of the chiller. Experimental correlations are used to predict heat transfer of the related working fluids. The cooling water is set to typical cooling tower conditions of tropical countries such as Singapore. The coefficient of performance (COP) is evaluated against a range of heat source temperatures from 75oC to 100oC. The results indicate the operation conditions of the chiller at its maximum COP is 95oC to 100oC.
In this study, a thermally driven adsorption cooling unit using natural zeolite–water as the adsorbent–refrigerant pair has been built and its performance investigated experimentally at various evaporator temperatures. The primary components of the cooling unit are a shell and tube adsorbent bed, an evaporator, a condenser, heating and cooling baths, measurement instruments and supplementary system components. The adsorbent bed is considered to enhance the bed’s heat and mass transfer characteristics; the bed consists of an inner vacuum tube filled with zeolite (zeolite tube) inserted into a larger tubular shell. Under the experimental conditions of 45 °C adsorption, 150 °C desorption, 30 °C condenser and 22.5 °C, 15 °C and 10 °C evaporator temperatures, the COP of the adsorption cooling unit is approximately 0.25 and the maximum average volumetric cooling power density (SCPv) and mass specific cooling power density per kg adsorbent (SCP) of the cooling unit are 5.2 kW/m3 and 7 W/kg, respectively.
This paper features the adsorption equilibria of refrigerants R134a, R290, R410a, and R507a on microporous activated carbon samples at temperatures between 278 K and 338 K with pressures up to 1.4 MPa. The adsorption isotherm data are obtained by utilizing the constant-volume–variable-pressure (CVVP) approach and analyzed using the Dubinin–Ashtakov (DA) model. The regressed adsorption parameters acquired by using this model produces isotherm curves that agree within 5 % of the experimental results. The concentration- and temperature-dependent enthalpies of adsorption of these pairs are evaluated and presented.
This paper presents a theoretical framework for the understanding of pressurized adsorption systems using the statistical rate methodology. Utilizing results from the statistical rate theory, basic thermodynamic variables including enthalpy (ha), entropy (sa) and the specific heat capacity (cpa) of the adsorbed phase are derived using the thermodynamic requirements of chemical equilibrium, Gibbs law, as well as Maxwell relations. A built-in constant (K) describes the adsorbed molecular partition function (q^s) and it captures the heterogeneous properties of the adsorbent + adsorbate pair at equilibrium states. Improved adsorbed-phase volume considerations were incorporated in the formulations of these variables where they could be utilized with relative ease for analyzing the energetic performances of any practical adsorption system. In this paper, we have demonstrated how derived thermodynamic quantities can bridge the information gap with respect to the states of adsorbed-phase, as well as resolving some theoretical inconsistencies that were found in previously derived quantities. Experimentally, the adsorption isotherms of Propane (refrigerant) on Activated Carbon Powder (Maxsorb III) for temperatures from 5°C to 75°C and pressures up to 8 bars are presented and they are used to illustrate the behaviors of the adsorbed-phase during uptakes, temperatures and pressure excursions or changes.
This paper describes the development of a simple hybrid desalination system of a Multi-Effect Distillation (MED) and an adsorption (AD) cycle operating at sub-atmospheric pressures and temperatures. By hybridizing the conventional MED with an AD cycle, there is a symbiotic enhancement of performances of both cycles. The performance enhancement is attributed to (i) the cascade of adsorbent’s regeneration temperature and this extended the usage of thermal energy emanating from the brine heater and (ii) the vapor extraction from the last MED stage by AD cycle which provides the effect of lowering saturation temperatures of all MED stages to the extent of 5 °C, resulting in scavenging of heat leaks into the MED stages from the ambient. The combined effects of the hybrid cycles increase the water production capacity of the desalination plant by nearly twofolds.In this paper, we demonstrate a hybrid cycle by simulating an 8-stage MED cycle which is coupled to an adsorption cycle for direct vapor extraction from the last MED stage. The sorption properties of silica gel is utilized (acting as a mechanical vapor compressor) to reduce the saturation temperatures of MED stages. The modeling utilizes the adsorption isotherms and kinetics of the adsorbent + adsorbate (silica-gel + water) pair along with the governing equations of mass, energy and concentration. For a 8-stage MED and AD cycles operating at assorted temperatures of 65–90 °C, the results show that the water production rate increases from 60% to twofolds when compared to the MED alone. The performance ratio (PR) and gain output ratio (GOR) also improve significantly.
Growing energy demand and global climate change are compelling reasons to look for effective utilisation of waste thermal energy and renewable energy resources. Fifteen percent of the electricity produced in the whole world is employed for refrigeration and air-conditioning processes of various kinds. Low-temperature heat operated environment-friendly adsorption cooling systems are emerging as viable alternatives to electricity-driven vapour compression refrigeration systems. Comparatively bigger sizes of adsorption based cooling units, due to their low specific cooling power, are preventing successful commercialization of the technology. Efforts are on to enhance the performance of adsorption systems through improvements in adsorbents properties, use of advanced cycles, etc. Recent application of nano-technology in the development of adsorbent material may be a big step forward towards making this technology competitive with available technologies in the market. This paper traces the evolution of the technology and analyses the obstacles to wide spread use of adsorption chillers.
In the present study, a dynamic model of the adsorption refrigeration cycle was established with the consideration of interfacial convective heat transfer within adsorbent particles. In the model, a concept and mathematical definition of a transient pressure process at the beginning of the traditionally considered isobaric adsorption process are introduced. The model was solved numerically and experimentally verified in terms of the adsorbent/adsorbate temperature development, system pressure variation, and dynamic adsorption/desorption amount. A temperature jump at the beginning of the adsorption process was experimentally identified and was successfully predicted in the numerical simulation with the introduction of a transient pressure process. Numerical results simulated with the newly introduced transient pressure process and the traditional constant pressure process were compared. The comparison shows that the introduced transient pressure process can significantly improve the accuracy of the presented model. In addition, a notable adsorbate migration phenomenon was discussed according to the abnormal temperature development in the processes of isosteric heating and cooling. The present model can be used for a valve-controlled and long cycle-time based ART and other systems with similar operating procedures.
This article presents the transient modeling and performance of waste heat driven pressurized adsorption chillers for refrigeration at subzero applications. This innovative adsorption chiller employs pitch-based activated carbon of type Maxsorb III (adsorbent) with refrigerant R134a as the adsorbent-adsorbate pair. It consists of an evaporator, a condenser and two adsorber/desorber beds, and it utilizes a low-grade heat source to power the batch-operated cycle. The ranges of heat source temperatures are between 55 to 90 degrees C whilst the cooling water temperature needed to reject heat is at 30 degrees C. A parametric analysis is presented in the study where the effects of inlet temperature, adsorption/desorption cycle time and switching time on the system performance are reported in terms of cooling capacity and coefficient of performance.
This article presents the performance analysis of a waste heat-driven adsorption cycle. With the implementation of adsorption–desorption phenomena, the cycle simultaneously produces cooling energy and high-grade potable water. A mathematical model is developed using isotherm characteristics of the adsorbent/adsorbate pair (silica gel and water), energy and mass balances for the each component of the cycle. The cycle is analyzed using key performance parameters namely (i) specific cooling power (SCP), (ii) specific daily water production (SDWP), (iii) the coefficient of performance (COP) and (iv) the overall conversion ratio (OCR). The numerical results of the adsorption cycle are validated using experimental data. The parametric analysis using different hot and chilled water temperatures are reported. At 85 °C hot water inlet temperature, the cycle generates 3.6 m3 of potable water and 23 Rton of cooling at the produced chilled water temperature of 10 °C.
AFI-type structure ferroaluminophosphate zeolite (FAPO-5) was examined as an AHP adsorbent. FAPO-5 with iron content of 2-8mol% (Functional Adsorbent Material-Zeolite 01; FAM-Z01) was selected for further testing. The water vapor adsorption isotherm of FAM-Z01 was S-shaped and highly dependent on temperature, and almost no hysteresis was observed with adsorption/desorption at 333 K and 348 K. No changes were observed in the properties of FAM-Z01 after 200,000 cycles of water vapor adsorption-desorption, indicating that FAM-Z01 is suitably durable for practical use. When the AHP was operated under conditions of TL/TM/TH= 283 K/303 K/333 K, the adsorption capacity of FAM-Z01 was 4 times that of silica gel.
In 1997, the International Association for the Properties of Water and Steam (IAPWS) adopted a new formulation for the thermodynamic proper-ties of water and steam for industrial use. This new formulation, called IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam (IAPWS-IF97), replaces the previous industrial formulation, IFC-67, that had formed the basis for power-plant calculations and other applications in energy engineering since the late 1960's. IAPWS-IF97 improves significantly both the accuracy and the speed of the calculation of the thermodynamic properties compared with IFC-67. The differences between IAPWS-IF97 and IFC-67 will require many users, particularly boiler and turbine manufacturers, to modify design and application codes. This paper summarizes the need and the requirements for such a new industrial formulation and gives the entire numerical information about the individual equations of IAPWS-IF97. Moreover, the scientific basis for the development of the equations is summarized and the achieved quality of IAPWS-IF97 is presented regarding the three criterions accuracy, consistency along region boundaries, and computation speed. For comparison, corresponding results for the previous standard IFC-67 are also presented.
The current thrust on the use of environmentally friendly technologies for cooling applications, inter alia, envisages the adoption of adsorption systems. Adsorption chillers are known to be `inefficient' due to their low coefficient of performance. Although the basic physics of heat and mass transfer in various components of the system is well understood, there is a lacuna in the quantification of irreversibilities. In this paper, a silica gel-water, two-bed, non-regenerative chiller is analysed. It is shown that the largest cycle-averaged rate of entropy generation is in the beds and that the least is in the condenser. The entropy generation rates in the beds are further studied, showing that the maximum contribution is made during the switching phase. In general, manufacturers' effort to maximize cooling capacity is shown to correspond to maximum entropy generation in the evaporator.
The reason why the performance of adsorptive refrigeration cycles is always less than that of the Carnot cycle corresponding to the same heat reservoir temperatures is analysed. This analysis is performed using the entropy production concept and introducing numbers of entropy production which are a direct measure for the efficiency degradation. The thermal entropy production due to the external thermal coupling of the isothermal heat reservoirs to the temperature varying adsorbers is important in all cases considered. It prevails for the basic uniform temperature cycle (about 95% of the total entropy production). For n-adsorber uniform temperature cycles, internal thermal entropy production (due to heat recovery between adsorbers) may reach 50% of the external thermal entropy production. The entropy production due to the refrigerant flow inside the unit does not depend on the process and is small (less than about 10%) in all cases. For thermal wave cycles, the origin of the entropy production depends highly on the cycle time. For very short cycle times, the external thermal entropy production is very small but an important internal thermal entropy production is observed in the adsorbers. For long cycle times, it is the opposite, the external thermal entropy production becomes very large while the internal thermal entropy production in the adsorbers does not increase.
A fundamental issue that remains to be solved when approaching the nanoscale is how the size induces transformation among different polymorphic structures. Understanding the size-induced transformation among the different polymorphic structures is essential for widespread use of nanostructured materials in technological applications. Herein, we report water adsorption and high-temperature solution calorimetry experiments on a set of samples of single-phase monoclinic zirconia with different surface areas. Essential to the success of the study has been the use of a new ternary water-in-oil/water liquid solvothermal method that allows the preparation of monoclinic zirconia nanoparticles with a broad range of (BET) Brunauer–Emmett–Teller surface area values. Thus, the surface enthalpy for anhydrous monoclinic zirconia is reported for the first time, while that for the hydrous surface is a significant improvement over the previously reported value. Combining these data with previously published surface enthalpy for nanocrystalline tetragonal zirconia, we have calculated the stability crossovers between monoclinic and tetragonal phases to take place at a particle size of 28 ± 6 nm for hydrous zirconia and 34 ± 5 nm for anhydrous zirconia. Below these particle sizes, tetragonal hydrous and anhydrous phases of zirconia become thermodynamically stable. These results are within the margin of the theoretical estimation and confirm the importance of the presence of water vapor on the transformation of nanostructured materials.
A compact silica gel-water adsorption chiller without vacuum valves was manufactured and experimentally studied. This chiller contains two adsorption/desorption chambers and one chilled water tank. Each adsorption/desorption chamber consists of one adsorber, one condenser and one evaporator. The chilled water tank is adopted to mitigate the variation of the chilled water outlet temperature. A mass recovery-like process, which is a heat recovery process between the two evaporators, was carried out in this chiller. A novel heat recovery process was also fulfilled after the mass recovery-like process to improve the coefficient of performance (COP). The cooling power and COP were 9.60 kW and 0.49 respectively when the average hot water inlet temperature, cooling water inlet temperature, and chilled water outlet temperature were 82.0, 31.6 and 12.3 °C, respectively.
The equilibrium adsorption capacity of water on a natural zeolite has been experimentally determined at different zeolite temperatures and water vapor pressures for use in an adsorption cooling system. The Dubinin-Astakhov adsorption equilibrium model is fitted to experimental data with an acceptable error limit. Separate correlations are obtained for adsorption and desorption processes as well as a single correlation to model both processes. The isosteric heat of adsorption of water on zeolite has been calculated using the Clausius-Clapeyron equation as a function of adsorption capacity. The cyclic adsorption capacity swing for different condenser, evaporator and adsorbent temperatures is compared with that for the following adsorbent-refrigerant pairs: activated carbon-methanol; silica gel-water; and, zeolite 13X-water. Experimental results show that the maximum adsorption capacity of natural zeolite is nearly 0.12 kgw/kgad for zeolite temperatures and water vapor pressures in the range 40-150 °C and 0.87-7.38 kPa.
As a consequence of the Kyoto Protocol and its predecessor, the Montreal Protocol, environmental considerations will play
an important role in the choice of a refrigeration or heat pump system. Accordingly, sorption technology is expected to develop
for cooling as well as for heat pump applications because it uses benign fluids. At the moment, liquid absorption technology
is the leading technology in that field; however, adsorption offers advantages that cannot be achieved by liquid absorption
technology. This article addresses the measures to reduce halocarbon emissions and the possibilities of adsorption technology.
Not only are the direct emissions taken into account but also the indirect ones due to energy consumption. Several cases that
show that adsorption cooling is very promising, from the global warming point of view, are considered in this article. They
are: waste heat adsorption chilling, natural gas adsorption chilling, trigeneration and natural gas reversible heat pump.
Adsorption air conditioning for automobiles is also discussed as a very challenging possibility for adsorption cooling.
We experimentally show that for the same heat exchanger inventory allocation, a four-bed adsorption chiller delivers a 12% higher ultimate cooling capacity than its two-bed counterpart. In addition it delivers a significantly improved quality of instantaneous cooling than a two-bed chiller at the same cooling capacity. The COP-enhancing feature of a passive heat recovery scheme that does not involve additional pumping action or valves is experimentally proven. It improves the COPs of a two-bed chiller and a four-bed chiller by as much as 38 and 25%, respectively, without any effect on their cooling capacities. The highest COPs achieved with a two-bed and four-bed chillers are 0.46±0.02 and 0.45±0.02, respectively. These are measured at a hot-water inlet temperature of 85 °C, cooling-water inlet temperature of 29.4 °C and chilled-water inlet temperature of 12.2 °C.
A multi-bed regenerative adsorption chiller design is proposed. The concept aims to extract the most enthalpy from the low-grade waste heat before it is purged into the drain. It is also able to minimise the chilled water temperature fluctuation so that downstream temperature smoothing device may be downsized or even eliminated in applications where tighter temperature control may be required. The design also avoids a master-and-slave configuration so that materials invested are not under-utilised. Because of the nature of low-grade waste heat utilization, the performance of adsorption chillers is measured in terms of the recovery efficiency, eta instead of the conventional COP. For the same waste heat source flowrate and inlet temperature, a four-bed chiller generates 70% more cooling capacity than a typical two-bed chiller. A six-bed chiller in turn generates 40% more than that of a four-bed chiller. Since the beds can be triggered into operation sequentially during start-up, the risk of ice formation in the evaporator during start-up is greatly reduced compared with that of a two-bed chiller.
Solid sorption short cycle heat pump (⩽10 kW) which uses physical adsorption and is of interest to the space and domestic application is designed and tested. This heat pump has a very short (12 min), nonintermittent, two adsorber heat recovery cycles with an active carbon fiber as a sorbent bed and ammonia as a working fluid. It has two energy sources: solar and gas flame. The system management consists only in actuating the special type valves to change the direction of the heating circuit and water valves to change the water cooling circuit.
Over the past few decades there have been considerable efforts to use adsorption (solid/vapor) for cooling and heat pump applications, but intensified efforts were initiated only since the imposition of international restrictions on the production and utilization of CFCs and HCFCs. In this paper, a dual-mode silica gel–water adsorption chiller design is outlined along with the performance evaluation of the innovative chiller. This adsorption chiller utilizes effectively low-temperature solar or waste heat sources of temperature between 40 and 95 °C. Two operation modes are possible for the advanced chiller. The first operation mode will be to work as a highly efficient conventional chiller where the driving source temperature is between 60 and 95 °C. The second operation mode will be to work as an advanced three-stage adsorption chiller where the available driving source temperature is very low (between 40 and 60 °C). With this very low driving source temperature in combination with a coolant at 30 °C, no other cycle except an advanced adsorption cycle with staged regeneration will be operational. The drawback of this operational mode is its poor efficiency in terms of cooling capacity and COP. Simulation results show that the optimum COP values are obtained at driving source temperatures between 50 and 55 °C in three-stage mode, and between 80 and 85 °C in single-stage, multi-bed mode.
Adsorption cycle is a practical and inexpensive method of desalinating the saline and brackish water to produce potable water for both industrial and residential applications. As compared with the commercial desalination methods, the adsorption technology has the unique advantages such as (i) the utilization of the low-temperature waste heat, (ii) low corrosion and fouling rates on the tube materials due to the low-temperature evaporation of saline water, (iii) and it has almost no major moving parts which renders inherently low maintenance cost. In addition, the adsorption cycle offers two important benefits that are not available to the existing desalination technologies; namely, (i) a two-prong phenomenal barrier to any “bio-contamination” during the water generation process as compared with existing methods and (ii) the reduction in global warming due to the utilization of low-temperature waste heat which otherwise would have been purged to the atmosphere. This paper describes an experimental investigation and the specific water yields from a four-bed adsorption desalination plant is presented with respect to major assorted coolant and feed conditions.
The theoretical efficiencies of a solid adsorption heat pump (using fixed bed heat exchangers are discussed as a function of the number of cascades. A systematic analysis of the heat and entropy flows in and out the heat pump are presented (Tables 1 and 2) in a case study. The impact of the number of cascades and of the temperature differences associated to the heat transfer are discussed using the usual efficiency concepts but also using the entropy generation number as introduced by Bejan [1].
We have investigated analytically the performance of the thermally driven, advanced three-stage adsorption chiller utilizing low-grade waste heat of 50°C and lower temperatures as the driving heat source, in combination with a heat sink (cooling water) of 30°C. The closed cycle chiller for use in air-conditioning utilizes the silica-gel-water adsorption system. A cycle-simulation program was constructed to analyze the influence of operating conditions (temperatures, flow rates and adsorption-desorption cycle times) on cooling output, COP and chiller efficiency (η = COP/Carnot COP). The main advantage of this chiller is that it is operational with smaller regenerating temperature lifts (ΔTregen = heat source-heat sink temperature) than other heat-driven chillers. By cycle simulation, it was shown that the three-stage chiller can be operated with heat sources of 50 and 40°C in combination with cooling sources of 39 and 30°C, respectively. The simulation results also show that for the chiller to operate effectively, heat sources of 50°C require cooling sources between 35 and 20°C (ΔTregen = 15 to about 30K), while heat sources of 40°C need cooling sources in the range of 28-20°C (ΔTregen = 12 to about 20 K).
A novel adsorption air conditioner is designed that supplies 8–12 °C chilled water for the fan coil in the locomotive operator cabin. Different from other two-bed adsorption cooling systems, this system has two adsorption/desorption chambers. One adsorber, one condenser and one evaporator are housed in one and the same adsorption/desorption chamber. There are no valves installed in the vacuum side. So, the reliability of the system is improved greatly. This machine uses zeolite and water as the working pairs. This system is driven by 350–450 °C exhaust gas generated by the internal combustion engine of the locomotive. The designed refrigerating power and COP (coefficient of performance) are 5 kW and 0.25, respectively, according to the requirements for the refrigeration output in the locomotive operator cabin and the waste heat provided by the engine. In this paper, a model for this system is described, and the simulation results are discussed. The model is validated in principle by limited experimental data. According to the calculation results, the refrigerating power of the machine is up to 10 kW with gas inlet temperature of 450 °C and