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Abstract

In this paper, a detailed parametric study on a dual-mode silica gel–water adsorption chiller is performed. This advanced 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. In this paper, the effect of chilled-water inlet temperature, heat transfer fluid flow rates and adsorption–desorption cycle time effect on cooling capacity and COP of the dual-mode chiller is performed. Simulation results show that both cooling capacity and COP values increase with the increase of chilled water inlet temperature with driving source temperature at 50 and 80°C in three-stage mode, and single-stage multi-bed mode, respectively. However, the delivered chilled-water temperature increases with chilled-water inlet temperature in both modes.

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... To overcome this problem, the dual-mode adsorption cooling cycle has the ability to utilize effectively a wide range of driven heat source temperatures between 40 and 95°C. Saha et al. [81] examined a double-staged, non-regenerative adsorption, four-bed, and silica gel-water adsorption chiller driven by 55°C solar/waste heat at a cooling temperature of 30°C to produce 3.2 kW with a COP of 0.36. To utilize waste/solar heat at near environment temperature, Hamamoto et al. [82] investigated numerically the performance of a two-stage adsorption chiller. ...
... Hot water flow rate [54,120,122,172] High hot water flow rate produces high cooling power with low COP. [81] CC and COP increase as the hot water flow rate increases. Cooling water flow rates [81] CC and COP increase with increasing the cooling water flow rate. ...
... [81] CC and COP increase as the hot water flow rate increases. Cooling water flow rates [81] CC and COP increase with increasing the cooling water flow rate. Chilled water flow rate [81,120,125] CC and COP improved by increasing the chilled water flow rate. ...
... The performance enhancement is achieved through the creation of intermediate pressure stages between the condenser and evaporator for adsorbate exchange between the adsorbent beds of a cooling system. The multi-stage strategy can be classified into two types, viz., conventional, and two-stage, depending on the heating/cooling of various beds involved in the Saha et al. [23] studied the effect of a three-stage strategy on a 6-bed system and found it to be capable of operating with a low regeneration temperature of 50 • C. Alam et al. [24] implemented two kinds of two-stage strategies on a 4-bed system and observed the reheat two-stage strategy yielding better cooling performances at lower regeneration temperatures. ...
... The lack of improvement in the chiller performance through the two-stage strategy is mainly due to the nonequalization of bed pressures caused by a constricted mass flow through the mass recovery valve, as described in Appendix C. A suitable mass recovery valve design enabling pressure equalization can be suitable for implementing the two-stage operation under extreme conditions. Various researchers [23,27] have attempted to model the adsorbate mass transfer operation, assuming a constant intermediate pressure throughout the process. Mitra et al. [25] have used a varying pressure approach during adsorbate exchange between the beds, such that the rate of adsorbate desorbed from the lower stage equals that of the rate adsorbed in the upper stage. ...
Article
Along with the measures to improve the design of the adsorption cooling systems, the operating strategy selection plays an equally important role in their performance enhancement. Though several strategies such as heat recovery, mass recovery, multi-staging, etc., have been reported in the literature, their implementation in the more popular small-scale two-bed systems has not been given due attention. The present study highlights the performance enhancement of a two-bed single-stage silica gel-water adsorption cooling system through novel interventions in the operating cycle. A facility has been developed for testing a 10 kW water-cooled adsorption chiller. Passive heat recovery and two-stage operational strategies have been proposed for the enhancement of performance and operational envelopes through modifications in the chiller’s valves sequencing. An improvement of 23-42% in coefficient of performance (COP) is observed with an optimized passive heat recovery strategy, while maintaining the water level in the hot water tank. Two kinds of two-stage operations viz., conventional two-stage and reheat two-stage, show potential for performance improvement under extreme conditions, resulting in an operational envelope enhancement up to 56%. A theoretical approach based on the thermodynamic analysis of adsorbent limits has been presented to assess the maximum desorption temperature limits.
... To lower the driven temperature (<70 • C), Multi-bed design systems [30][31][32] and multi-stage design systems [33][34][35] were proposed. Saha et al. [36] performed a parametric investigation on dual-mode, multi-stage and multi-bed regenerative adsorption chiller working at low-temperature solar thermal sources. Results displayed that the COP of the multi-stage machine was around 0.2 for low thermal sources between 40 and 60 • C . ...
... This is mainly because increasing heat source temperature causes an increase in the LiBr concentration and then the adsorption process happens at lower generation pressure for higher hot water temperatures. Furthermore, the COP of 0.39 at the low hot water inlet temperature of 50 • C indicates that the integrated system is very promising compared to other sorption systems proposed to work under low-grade thermal source temperatures [36][37][38]. Fig. 7 shows the effect of the intermediate pressure on the system COP and cooling capacity at the hot water inlet temperature of 65 • C. It reveals that the system COP increases with the pressure to its optimum value and then it decreases. An increase in the intermediate pressure means the adsorption pressure increases in the AD sub-cycle, which leads to more refrigerant adsorbed by the adsorbent in the adsorber. ...
Article
The integrated adsorption-absorption system is a novel technology to convert low-temperature waste thermal energy into useful cooling, which substantially improves energy utilization efficiency and lowers environmental pollution. This novel system incorporates the adsorption cycle into the absorption cycle so that the generation/adsorption pressure can be adjusted to enhance the system performance at low-temperature heat sources. In this paper, the thermal characteristics of the integrated system are theoretically evaluated. The optimization of the key parameters (e.g. cycle time, switching time, intermediate pressure and solution concentration) are conducted to achieve the best system performance. Furthermore, different configurations of the integrated system and the effect of the heating and cooling flow arrangements on the system performance are also investigated. The results showed that the coefficient of performance of the proposed system was as high as 0.4 at a heat source temperature of 50 °C. As the heat source temperature increased from 50 to 85 °C, an optimal intermediate (generation/adsorption) pressure varied gently from 2.36 to 2.16 kPa while the optimal solution concentration increased from 52.4 to 65% to achieve the best system coefficient of performance. The results also showed that the maximum specific cooling power is 193.7 W/kg when the heating and cooling water flow arrangement are both in parallel. In contrast, the lowest specific cooling power is 157.9 W/kg for both heating and cooling water flow arrangements in series. When compared the two different configurations, the cooling capacity and coefficient of performance of the configuration with absorption-cycle as the bottom cycle and adsorption-cycle as the top cycle were about 5 and 15% higher, respectively than those of the configuration with adsorption-cycle as the bottom cycle and absorption-cycle as the top cycle.
... This chiller proved to be a major breakthrough because of its COP and cooling capacity values of 0.51 and 10.76 kW. A few years ago, a three stage silica gelwater adsorption prototype shown in Fig. 22 was reported by Saha et al. [132]. In 2009 in China, SJTU successfully developed adsorption refrigeration of 10-200 kW which employed heat and mass recovery process driven by a heat source of 65°C. ...
... Three-stage silica gel-water adsorption chiller[132]. (a) Schematic diagram and (b) photo. ...
Article
Adsorption refrigeration technology has established enhanced significance in last three decades, due to its noiseless, non-corrosive and environment friendly operation by the utilization of low grade heat sources, especially solar energy. A plethora of adsorption cooling systems had been developed but still these cooling systems are not ready to compete with the traditional vapor compression cooling systems. This paper aims to provide fundamental knowledge on the adsorption systems and presents a comprehensive literature review of the past efforts in the field of their solar energy utilization. This paper also presents a brief of various related researches conducted in India. A survey of developments in the market trends is also presented in this paper. It shows that a number of attempts have been made by various companies to enhance the performance of adsorption refrigeration systems and maintain their presence in market but limitations regarding their technical and economic aspects seem difficult to overcome. Nevertheless, adsorption cooling systems driven by solar energy not only lowers down the daily electricity consumption but also reduces the global warming potential due to its environment friendly nature.
... The three-bed mass recovery chiller comprises with three sorption elements (adsorber/desorber heat exchangers), a condenser, an evaporator, and metalic tubes for hot, cooling and chilled water flows as shown in Figure 1. The design criteria of the three-bed mass recovery chiller are almost similar to that of the three-bed chiller without mass recovery which is proposed and developed by Saha et al. [10] and [11]. ...
... Resultantly, T ADRS, ch, out also increases to decrease Q c, DCS, loss and Q c . Therefore, when the inlet air temperature increases from 28 • C to 35 • C, T ADRS, ch, in increases from 19.96 • C to 23.60 • C and T ADRS, ch, out increases from 16.61 • C to 18.62 • C. Meanwhile, Q c, ADRS increases from 2542.2 W to 3066.6 W and Q c increases from 2008.8 W to 2619.4 W. As the inlet air temperature is regulated within 28-35 • C, Q h changes little, ranging from 7266 W to 7630 W. Because of the significantly improved Q c, ADRS and Q c , the COP ADRS increases from 0.423 to 0.504 and the COP increases from 0.319 to 0.418. ...
... To this day, the adsorption refrigeration on solar cooling application has been widely studied both experimentally and numerically. A three-stage adsorption chiller proposed Shah et al. [81] can decrease its driving temperature to about 50 • C, which facilitate the application of adsorption cooling in DC WHR. In addition, due to the characteristics of the year-round uninterrupted operation and high waste heat output in DC, DC can maintain steady, high-temperature waste heat supply, and thus has more promising application for adsorption cooling [45]. ...
Article
Full-text available
Data centers (DCs) uninterruptedly run 24/24 h, 365 days per year with much huge operating scale, and have the characteristics of high operation safety requirement, high heat flux density, high energy consumption and high carbon emission. They are influential energy consumers and carbon emitters in building or even global energy sectors (around 3% of global energy consumption), who are also significant waste heat producer (e.g., waste heat from year-round uninterrupted operation of IT equipment and cooling system). Huge energy consumption has increased the burden on the global energy industry, while carbon and direct waste heat emissions have also caused great damages to the outdoor environment. Thus, it is critical to improve the energy efficiency in DCs and to realize the energy conservations and environmental deterioration alleviation. Waste heat recovery technology is considered as a promising approach to improve energy efficiency, achieve energy and energy cost savings, and mitigate environmental impacts (caused by both carbon emission and waste heat discharge) at the same time. This article conducts a comprehensive review on recovering waste heat from all kind of sources (e.g., exhaust air, circulating water, and coolants) in DCs for various energy uses (e.g., heating supply, district heating supplement, cooling and electricity productions, and industrial/agricultural production process) and different application scenarios (e.g., office buildings, comprehensive energy community and residential buildings), while the future research and development proposals for DC waste heat recoveries are given through technical, energy, environmental and economic analysis.
... The upper cycle used AC-R134a adsorbent pair while the bottom cycle used the AC-R507A adsorbent pair. They found that the proposed cycle can produce a cooling effect at − 10 • C. Saha et al. [26,27] investigated different operation modes for a two-stage 4-bed adsorption cycle powered by a low-temperature heat source. The used heat source was between 40 and 95 • C. ...
... Untuk mencapai nilai unjuk kerja yang lebih baik, sebagian besar sistim pendinginan adsorpsi yang lebih maju telah dilakukan penelitian lanjutan baik yang dilakukan secara penelitian laboratorium maupun dalam bentuk pemodelan simulasi (Rogala, 2017;Saha et al., 2006;. Penelitian tentang unjuk kerja juga sudah dilaksanakan pada sistem pendinginan adsorpsi pemanasan ulang dua tingkat dengan menggunakan empat penukar kalor yang dapat memanfaatkan sumber panas 50-90 C dalam operasionalnya (Alam dkk., 2003;Bahrehmand & Bahrami, 2021;Tong dkk., 2000). ...
Article
Full-text available
The adsorption refrigeration system is a cooling system that offers several benefits, including being environmentally friendly due to the very small amount of global warming effect given, the lack of potential for ozone depletion, the low energy consumption of its operation, the low heat source used in its operation and good for reducing gas emissions on earth. This paper describes a combined reheating adsorption refrigeration system with three heat exchangers, as well as operating modes. The operation of the adsorption refrigeration system with combined reheating is schematically described with operational modes and diagrams. This adsorption cooling system is made up of three heat exchangers (H), one evaporator, and one condenser. The combination cycle is intended for heat exchanger systems that operate in a reheat cycle (H1 and H2) and a non-reheating cycle (H3). This paper also discusses system cycle time optimization. Research to get the optimum value of cycle time in this system is still rarely done and therefore optimization of cycle time is carried out on the system to get the best performance. The PSO (particle swarm optimization) program is paired with the MATLAB program to simulate the performance of the system under discussion while also enhancing its performance. The goal of this work is to use simulation to determine the optimal system performance versus the overall cycle time, which includes adsorption/desorption time, pre-cooling and pre-heating time as well as mass recovery time. Getting the best value for the entire cycle time is made possible by fusing the simulation of the system's process performance with performance optimization. As a results, the greatest increase in the optimization results' performance value occurs at a heat source temperature of 55ºC with a longer time to achieve optimal performance.
... To utilize energy at heat source temperatures as low as 50 • C, multi-stage and multi-bed cycles can be applied. Saha et al. [11] analyzed the performance of a double-stage and four-bed silica gel-water adsorption chiller driven by a 55 • C heat source, and the thermal coefficient of performance (COP th ) reached 0.36. Wang et al. [12] compared the experimental and simulation results for a four-bed adsorption system under an inlet hot water temperature of 65/75 • C, and the COP th was reported to be 0.25/0.33. ...
Article
To extract as much energy as possible from a low-grade heat source in the range of 50–95 °C, a hybrid adsorption refrigeration system using desiccant coated heat exchangers is proposed and investigated in this study. This hybrid system can be operated in three working modes to satisfy various demands for cooling capacity output forms and system performance. Models of the adsorption refrigeration system and desiccant coated heat exchangers are integrated to match the two separate systems and evaluate the system performance. The results indicate that 24 °C is the optimal chilled water temperature to establish circulation between the two systems. Mode 1 exhibits the best cooling capacity output, which is 24% and 32% higher than that of Mode 2 and Mode 3, respectively. Mode 2 ranks first in exergetic efficiency with a heat source of 50 °C and reaches a maximum thermal coefficient of performance (COPth) of 11.09% and 0.998, respectively. Mode 3 provides the highest exergetic efficiency at a heat source of 55–95 °C and a cold-water supply. Finally, the performance of the hybrid system is compared with that of a traditional adsorption system to verify the improved efficiency and wider operable heat source range of the proposed system. The hybrid system can operate effectively with a heat source range of 50–95 °C, while the traditional system cannot work below 65 °C. The COPth of Mode 2 is superior to that of the traditional system, and the heat source of 50–65 °C results in a better COPth of Mode 1, while the traditional mode shows higher COPth than that of Mode 3 at a heat source of 65–95 °C. The three modes outperform than the traditional mode in terms of exergetic efficiency. The proposed hybrid system can thus effectively exploit a low-grade heat source with high efficiency, providing a promising solution for efficient energy utilization.
... However, the relatively large system size, low coefficient of performance (COP) due to the low adsorption performance, and high initial cost are technical hurdles that currently hinder wide-spread application of the system. Many studies have been conducted to overcome these technical hurdles, by using different adsorption bed configuration i.e. double beds [7,8], three beds [9], four beds [10] and multi-stage and multiple beds [11,12], optimizing the operation strategy of advanced adsorption cycles [13][14][15][16], and improving the heat exchangers [17,18]. And, also, the system performance can be improved by utilizing new adsorbents materials that could have the ability to adsorb a larger amount of adsorbate [19][20][21][22][23][24]. ...
Article
Most previous studies on adsorption chillers were conducted using the same adsorption and desorption times. Instead, this study analyzed various adsorption/desorption time allocations, and systematically examined the effect of cycle time allocation on system performance. The results provide physical insights for 3-bed adsorption chillers. The effect of hot water temperature and cycle time on the optimum adsorption/desorption time ratio was also examined. Setting the proper adsorption and desorption times was much more important for smaller cycle times. The highest degradation in COP (coefficient of performance) found was 36 % at 300 s of cycle time, compared with the conventional 1:1 ratio. When the temperature of the heat source is low, the ratio of adsorption/desorption time was not significantly affected, however, for higher performance at high temperature, a longer adsorption time than desorption time was required.
... Habib et al.[12] used the experimental data of a solar system installed in Durgapur, India, to investigate numerically the feasibility of a dual mode adsorption chiller in this location. Simulations of the dual mode adsorption chiller proposed by Saha et al.[18] were performed, concluding that it can be driven throughout the year using solar energy; 10 months at the singlestage four-bed mode and 2 months at the double-stage mode, when the regeneration temperature is below 60 • C. Alam et al.[19] numerically studied a two-bed conventional adsorption chiller driven by compound parabolic concentrator collectors for the climatic conditions of Tokyo, Japan. The system did not contain thermal storage and the chiller is directly driven by the solar field. ...
Article
Adsorption cooling systems (ACS) may contribute towards a sustainable way of satisfying the increasing cooling demand, as they utilize solar thermal energy and employ non-ozone-depleting substances. Apart from the intrinsic ACS performance, the successfulness of its operation depends on its integration within the entire thermal system (solar collectors, thermal storage and building), which is not straight-forward due to thermal inertia effects and its inherent cyclic operation. Numerical simulations can contribute in understanding the system behavior, its adequate dimensioning and the implementation of optimized control strategies. A computational model was developed, capable of performing conjugate, dynamic simulations of the entire thermal system. The influence of the control criteria is investigated and quantified through three simulation phases, conducted for various solar collectors areas and storage volumes. Higher solar fraction is achieved for lower auxiliary heater activation temperature and lower temperature difference activation of the solar pump. Subsequently, simulations with variable cycle duration were performed, using optimized cycle duration according to the instantaneous operating temperatures. This approach reduces significantly the auxiliary consumption or satisfies the demand with less solar collectors. The potential CO2 emissions avoidance is calculated between 28.1–90.7% with respect to four scenarios of electricity-driven systems of different performance and CO2 emission intensity.
... Researchers have investigated various strategies to increase the thermodynamic performance of adsorption cooling systems. Some of them are (i) different scheme of adsorption beds i.e. double beds [26,27], three beds [28][29][30][31], four beds [32,33] and multi-stage & multiple beds [34,35], (ii) Heat and mass recovery schemes [36,37] (iii) improving heat exchanger design [38,39] (iv) optimized operating conditions [26,40,41]. However, the system performance can be improved by utilizing such adsorbents that could have the ability to adsorb a larger amount of adsorbate. ...
... Researchers have investigated various strategies to increase the thermodynamic performance of adsorption cooling systems. Some of them are (i) different scheme of adsorption beds i.e. double beds [26,27], three beds [28][29][30][31], four beds [32,33] and multi-stage & multiple beds [34,35], (ii) Heat and mass recovery schemes [36,37] (iii) improving heat exchanger design [38,39] (iv) optimized operating conditions [26,40,41]. However, the system performance can be improved by utilizing such adsorbents that could have the ability to adsorb a larger amount of adsorbate. ...
Article
Adsorption cooling is getting huge attention from last few years due to environment-friendly and thermally-driven technology. Many systems designs based on various adsorbent-adsorbate pairs are investigated worldwide to develop a cost-effective and high-performance system. Until now, performance of the systems is lower as compared to conventional compressor-based systems. Performance of the adsorption systems mainly depends on adsorption equilibrium, adsorption kinetics, isosteric heat of adsorption, and thermo- physical/chemical properties of assorted adsorbent-refrigerant pairs. Thereby, the present study aims to review and compare the physical properties (surface area, pore volume/size etc.) of adsorbents and adsorption equilibrium (adsorption isotherm) by various types of adsorbent-adsorbate pairs available in the literature. Amount of adsorbate adsorbed per unit mass of adsorbent has been critically reviewed and compared accordingly. Highest adsorption uptake was attributed in case of R-32 adsorption onto phenol resin-based activated carbon i.e. 2.23 kg/kg (excess adsorption) and 2.34 kg/kg (absolute adsorption) at 30°C and 1670 kPa. Activated carbon of type Maxsorb-III being highly microporous possesses high surface area and shows good adsorption uptakes for most of the adsorbates including ethanol, methanol R-134a, CO2, R-507A and n-butane. In addition, fundamentals, principle and features of adsorption cooling systems are discussed. Adsorption equilibrium models used to express the adsorption mechanics of adsorbent-adsorbate pairs are explored, and the models’ parameters are collectively listed and discussed. The review is useful to prioritize available adsorbent-adsorbate pairs for adsorption based heat transformation applications. The study is useful for researchers working for the development of adsorbent materials for various applications and conditions.
... As it was mentioned before, many studies which have been performed to increase the COP of the adsorption heat pumps can be found in literature. Among those studies, the system of Saha et al., (2001) and Hamamoto et al., (2005) is remarkable. They worked on an advanced two stages adsorption heat pump cycle and improved the thermal wave process by employing two additional adsorbers in cycle. ...
Conference Paper
Full-text available
Adsorption heat pumps have considerably sparked attentions in recent years. The present paper covers the working principle of adsorption heat pumps, recent studies on advanced cycles, developments in adsorbent-adsorbate pairs and design of adsorbent beds. The requirements for the adsorbent-adsorbate pairs in order to be employed in the adsorption heat pumps are described. The adsorption heat pumps are compared with the vapor compression and absorption heat pumps. The problems and troubles of adsorption heat pumps are classified and researches to overcome the difficulties are discussed. INTRODUCTION Heating and cooling systems are widely used in industrial and comfort applications. Nowadays, the share of the energy for heating and cooling purposes in total energy consumption increases. Due to the economical benefits resulting from high COP values, mechanical heat pump systems become convenient devices for heating and cooling purposes. However, in the past two decades, it is found out that the mechanical heat pumps and traditional refrigeration systems play an important role in the depletion of the ozone layer and global warming. For the protection of the ozone layer, refrigeration technology should continue developing refrigeration systems without ecological damages. Chlorofluorocarbons and hydrochlorofluorocarbons have been prohibited for the protection of ozone layer considering new environmental regulations which have been accepted first in Montreal in 1988 and in Kyoto in 1998. According to the new regulations, the conventional vapor compression systems are currently worked by using hydrofluorocarbons as refrigerant. However, the use of these new refrigerants has also been restricted due to limitation of the emission of some greenhouse gases (CO 2 , CH 4 , N 2 O, Hydrofluorocarbons, PFC, and SF 6) in Kyoto protocol. The greenhouse gases might be banned in the next decades (Ülkü, 1986; Ülkü, 1987; Meunier, 2002; Wongsuwan et al., 2001). Due to the limitation of conventional energy sources, beside the definition of traditional efficiency or performance of devices, the primary energy efficiency must also be considered. Since the mechanical heat pumps work by electrical power, the primary energy efficiency of the mechanical heat pumps will be less than their COP. Recent researches on heat pumps are mostly focused on developing more environmental friendly new systems that have high primary energy efficiency and are able to employ various kinds of energies from the solar energy to waste heat. Adsorption heat pumps that have advantage of being environmental friendly, provide heating and cooling effects by employing thermal energy sources such as solar and geothermal energies or waste heat of the industrial processes. Another important advantage of this type of heat pumps is the ability of thermal energy storage. In this paper, the adsorption heat pumps are reviewed in details.
... 17Continuously working dual-bed adsorption chiller the solar absorption cooling system by simply replacing the absorption chiller with the adsorption chiller. The most common adsorption chillers used are the single-stage or multistage silica gel/water chillers[40][41][42][43][44][45][46]. ...
Chapter
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With the rapid development of urbanization, the energy consumption problem has attracted more and more attention. Solar energy, a kind of inexhaustible renewable energy, has played an important role in the energy sector. Solar energy can be used through the solar thermal transformation process and solar photovoltaic process. Then, the heat and electricity gained by those two processes can be used for many urban building applications, such as heating, cooling, hot water, and power supply. In this chapter, a detailed introduction on solar heating and cooling and domestic hot water applications for urban buildings is presented, which includes the integration of solar collectors with buildings, solar domestic hot water, space heating, and cooling applications for buildings and building-integrated photovoltaics.
... 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). ...
Conference Paper
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.
... The silica gel-water adsorption cooling system can be driven by low temperature heat source in range from 60 to 95 °C [15]. So, the simulation will be run at some variation of hot water input temperatures. ...
Article
Full-text available
The adsorption technology is becoming the more expected solution by today’s researchers for fix the energy and environmental issues. The main part of the cooling system adsorption is adsorbent and adsorbate. One of the most widely used adsorbents in research of adsorption technology is silica gel. A new silica gel-water adsorption chiller design was developed that composed of two sorption chambers with compact fin tube heat exchangers as adsorber, condenser, and evaporator. Energy, mass, and momentum conservation equations of the adsorption systems have been used for the CFD two and three dimensional models. The geometry of simulation is simply made within silica gel layer between two fins. The simulation is also implemented using a finite volume method through the CFD software Fluent. User defined functions are given to modify the energy, mass, and momentum conservation equations. The simulation of adsorption process is adjusted at unsteady condition. Adsorption and desorption processes are simulated with room temperature for cooling water inlet at temperature 305.15 °K, hot water inlet at temperature 353.15 °K, mass flow rate cooling water inlet at 0.3 kg/s and pressure 32 KPa. For the whole adsorbent bed area, the result shows that the highest absolute adsorption rate at the outer surface, while the lowest rate is at the center. After adsorption was finished, the condition is reversed. The highest absolute adsorption rate is achieved at center, while the lowest rate is achieved at the outer surface.
... Lavan [13] investigated the probability of the absorption refrigeration system driven by the exhaust gas of trucks. Saha et al., [14] presented a doublestage adsorption refrigeration cycle with four beds driven by a low temperature heat source. Sumathy and Li [15], Y.K. Tan [16][17][18] and Z.F. ...
Article
Selection of a proper adsorbent-refrigerant working pairs plays a crucial role in the effective performance of an adsorption refrigeration system. In practice composite adsorbents intensify the adsorption and desorption rates when compared to physical and chemical adsorption working pairs. Hence in this work, an evaluative overview of composite adsorbent-refrigeration working pairs is epitomized in comparison with the physical and chemical working pairs. In addition to this, authors also summarized performance characteristics of different composite working pairs. Authors hope that this work will provide a paradigm in selecting best suitable adsorbent-refrigerant working pair for the practical application.
... It consists of four adsorber/desorber beds, namely bed 1, bed 2, bed 3 and bed 4, one evaporator, one condenser and an expansion valve. Saha et al. (2006b) proposed the working principle of the singleeffect two-stage adsorption cooling system to use low temperature (<70°C) industrial waste heat/solar heat for producing the continuous cooling effect. The working principle of the single-effect two-stage cooling system is similar to that of the single-stage cooling system. ...
Article
The CO2 adsorption pressure concentration isotherms of indigenous coconut shell based activated carbon are measured using Sievert's type experimental setup. The thermodynamic properties viz. isosteric heat of adsorption at surface loading, Gibbs free energy, entropy and specific heat capacity are estimated using measured adsorption isotherms data. These measured adsorption isotherms data and thermodynamic properties are used for the thermodynamic analysis of single-stage and single-effect two-stage adsorption cooling system. The performance of the adsorption cooling cycle in terms of the maximum theoretical specific cooling effect and coefficient of performance at different driving heat source temperatures (80 °C for single-stage and 65 °C for single-effect two-stage) and evaporator temperatures (0, 5, 10 and 15 °C) is estimated. The maximum values of specific cooling effect and coefficient of performance are obtained as 9.26 kJ kg⁻¹ and 0.06 for single-stage and 8.85 kJ kg⁻¹ and 0.04 for single-effect two-stage cooling system respectively.
... It was indicated that cooling power, COP and SCP could reach 42.8 kW, 0.51 and 125.0 W/kg, respectively. To further lower the driven temperature, Saha et al. [22] investigated a three-stage silica-gel/water sorption chiller which could supply cooling power with the lowest heat source temperature of 50°C. To further improve the performance of sorption chiller, novel silica gel/CaCl 2 composite sorbent was developed and investigated. ...
Article
In order to further realize efficient utilization of low grade heat, an innovative cascading cycle for power and refrigeration cogeneration is proposed. Pumpless Organic Rankine Cycle (ORC) acts as the first stage, and the refrigerant R245fa is selected as the working fluid. Sorption refrigeration cycle serves as the second stage in which silica-gel/LiCl composite sorbent is developed for the improved sorption characteristic. The concerning experimental system is established, and different hot water inlet temperatures from 75 °C to 95 °C are adopted to investigate the cogeneration performance. It is indicated that the highest power and refrigeration output are able to reach 232 W and 4.94 kW, respectively under the condition of 95 °C hot water inlet temperature, 25 °C cooling water temperature and 10 °C chilled water outlet temperature. For different working conditions, the total energy and exergy efficiency of the cascading system range from 0.236 to 0.277 and 0.101 to 0.132, respectively. For cascading system the exergy efficiency of heat utilization ranges from 30.1% to 41.8%, which is 144% and 60% higher than that of pumpless ORC and sorption chiller when the hot water inlet temperature is 95 °C.
... In order to better demonstrate the application of T-Q diagram for adsorption refrigeration cycle, a relatively complex adsorption refrigeration system should be chosen. Consequently, a multi-stage heat recovery adsorption refrigeration system (Saha et al., 2006) whose heat recovery configuration has more potential to be optimized was selected as the object of study, except that the working pair was replaced with the refrigerant ammonia and the novel adsorbent of consolidated activated carbon (AC) combined with expanded natural graphite treated with sulfuric acid (ENG-TSA) . This working pair of consolidated AC/ENG-TSA-ammonia is suitable for both freezing and air-conditioning working conditions and can bear heating source temperatures higher than . ...
Article
The method of temperature–heat (T–Q) diagram analysis was proposed in this article. In T–Q diagram, the area between two process curves along the temperature axis represents the irreversibility degree of heat transfer, which has the same dimension with entransy dissipation. T–Q diagram can be used to optimize the heat exchange configuration and the heat exchanger network of adsorption refrigeration systems. The proposed T–Q diagram and traditional energy, exergy and entropy analyses were adopted to a multi-stage heat recovery adsorption refrigeration system. Results show that the optimal heat recovery schemes determined through T–Q diagram and cycle entropy production analyses are identical, while T–Q diagram is more intuitional since the analysis procedure is done graphically. T–Q diagram can also be applied to analyze experiment related results of process temperatures, and is capable of giving an estimation of the performance improvement for heat recovery cycle.
... In order to consider the application of similar methods to adsorption refrigeration, a relatively complex adsorption chiller should be chosen. As a result, a multi-stage heat regenerative adsorption chiller (Saha et al., 2006) whose heat regeneration configuration has more potential to be optimized was selected as the object of study, except that the working pair is replaced with the refrigerant ammonia and the novel adsorbent of consolidated activated carbon (AC) combined with expanded natural graphite treated with sulfuric acid (ENG-ICR 2015, August 16 -22 -Yokohama, Japan ID:425 TSA) . This working pair of consolidated AC/ENG-TSA-ammonia is suitable for both freezing and air-conditioning working conditions and can bear heating source temperatures higher than 120 °C, which is the suggested upper limit of working temperature region for silica gel. ...
Conference Paper
The method of temperature–heat (T–Q) diagram analysis was proposed in this paper. In T–Q diagram, the area between two process curves along the temperature axis represents the irreversibility degree in the heat transfer process, which has the same dimension with entransy dissipation. The diagram can be used to optimize the heat exchange configuration and the heat exchanger network of an adsorption refrigeration system. The proposed T–Q diagram and the traditional COP, exergy and entropy analysis were adopted to a multi-stage heat regenerative adsorption chiller under different heat regeneration schemes. The results show that the optimal scheme determined through T–Q diagram and cycle entropy production analysis are identical, while T–Q diagram is more intuitional since the analysis is done graphically. If consider a complete heat regeneration between two adsorption beds, the performance of the multi-stage chiller with different heat regeneration schemes should be almost the same.
... Advanced cycles were studied to enhance adsorption chiller performance. B.B.Saha [4][5][6] designed a dualmodel, multi-stage, multi-bed, silica gel-water adsorption chiller which can utilize effectively low temperature solar or waste heat sources. The performance of a two-stage adsorption chiller with different mass allocation between upper and bottom beds had been investigated numerically [7]. ...
Article
Full-text available
Adsorption refrigeration has attracted considerable efforts over the past few decades. Adsorption refrigeration is considered as green refrigeration technology, which is driven by low grade heat source. Intensified efforts were promoted to improve the adsorption chiller performance in recent years. Two stages with different adsorbents adsorption chiller working principle and test were proposed in this paper. The novel adsorption chiller contains 4 pieces adsorbers and evaporator and condenser. Zeolite and actived carbon were applied for adsorbents in the two-stage cycle and two adsorbers were packed with zeolite and other adsorbers with actived carbon. The two-stage cycle can be operated effectively with 50°C, even with 45°C. Coefficient of performance (COP) and volumetric cooling power (VCP) of two-stage adsorption chiller with different operation conditions were investigated in this paper. The results showed that VCP increases firstly and then decreases with increasing the elapsed time and the maximum of VCP with driving heat source temperature of 50°C and cooling water temperature of 30°C and chilled water temperature of 15°C was about 0.2 kW/L. The COP with driving heat source temperature of 45°C was much higher than that of 50°C.
... Multistage adsorption refrigeration cycle is used to utilize low generation temperature sources 45­60˚C, heat sink temperature of 30˚C and evaporative temperature of 7˚C (Saha et al, 2006 and Hamamoto et al, 2005). These operating temperatures are not suitable for simple two­bed adsorption refrigeration cycle operation (Khan et al, 2008). ...
Chapter
Full-text available
The global demand for commercial and domestic refrigeration and air conditioning systems has dramatically increased; currently it takes around third of the total worldwide energy consumption. Mechanical vapour compression refrigeration systems use refrigerants with adverse environmental effects. Sorption refrigeration systems offer the potential for better alternative to the mechanical vapour compression systems, if their technology can be improved to overcome current limitations. Sorption refrigeration systems are driven using low grade energy, solar energy and waste heat, and can operate with environmentally friendly refrigerants and non corrosive materials. This chapter presents a comprehensive review for adsorption cooling systems, including adsorption principles, refrigerants used, range of adsorbent materials, working pairs, various bed designs, operating conditions, development techniques and their applications.
Article
The escalating demand for computational power and data storage has led to a substantial increase in the number and scale of data centers (DCs) worldwide. Due to characteristics of high heat flux and reliable operational security, there is an urgent need for innovative solutions to solve the problem of DC cooling and waste heat recovery. Direct liquid cooling technology is one of the most promising energy-saving cooling technologies due to its advantages of high cooling efficiency, low noise, and reduction of hot spots. Waste heat recovery is also one of the effective ways to improve energy efficiency and reduce carbon emissions due to higher coolant temperature. This study provides a comprehensive review of direct liquid cooling and waste heat recovery technologies for DCs that have been published in high level journals in recent years. Herein, the primary innovation and contribution of this review paper is its comprehensive coverage of advanced/emerging cooling technologies for DCs including immersion cooling and spray cooling, and its broad overview of global trends in performance, energy consumption, power density, and PUE of related systems. In addition, this review addresses the issue of heat recovery and reuse in DCs with an overview of common waste heat recovery technologies such as heating, district heating networks, cooling supply and organic Rankine cycle (ORC) are summarized and then compared and analyzed their application scenarios, advantages and disadvantages. Through the comprehensive review of cutting-edge technologies and methodologies for direct liquid cooling and waste heat recovery, this review aims to provide a thorough understanding of current landscape and future direction of sustainable and high-performance DC solutions.
Article
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.
Article
Low-grade heat sources at 70 °C exist widely in the nature and industrial fields, which require to be exploited effectively for supplying cooling capacity. Recently, a hybrid adsorption refrigeration system using desiccant coated heat exchangers was proposed to improve the energy efficiency of the adsorption system under low-grade heat sources and achieve multi-mode cooling outputs. In essence, this hybrid system aims to improve the evaporation temperature of the adsorption system by incorporating a terminal which decouples the sensible and latent heat load. In order to validate its feasibility and high efficiency, a 3-kW hybrid system is designed and constructed for the first time, and its performance is tested preliminarily at a 70 °C heat source. The transient characteristics is analyzed and the parametric influence on the system performance is discussed. Experimental results indicate that the hybrid system can be effectively driven by a low-grade heat source at 70 °C with a 30 °C coolant. The effects of the inlet air temperature and relative humidity on the system performance are both positive. A moderate air flow rate (wind speed ∼ 1.2 m/s) is suggested to obtain a promising system performance. The cooling capacity and coefficient of performance can reach 3.95 kW and 0.539, respectively. The performance of the hybrid system is also compared with published studies. Results show that the hybrid system possesses a high efficiency in extracting 70 °C heat sources and satisfies the demand for cooling and dehumidification, which is expected to provide a reference for efficient energy utilization.
Article
In rural regions, freshly harvested fruits and vegetables cannot be precooled in time, resulting in enormous economic losses. In this paper, a novel solar-driven compression-assisted desorption chemisorption refrigeration/cold energy storage system for refrigerated warehouses is proposed. Compression-assisted desorption allows flexible adjustment of the desorption temperature of composite sorbent to actively adapt to the instable solar hot water temperature. The desorption reaction can increase compressor suction pressure, which helps to reduce power consumption and improve the coefficient of performance (COP). The chemisorption energy storage module completes its regeneration by day and releases cold energy to refrigerated warehouse at night. This module can change the refrigerating temperature depending on the type of fruits and vegetables, superior to the phase change cold storage technology. Therefore, the system can effectively overcome the problems caused by the instability and intermittency of solar energy. According to the performance test results of the reactor, the COP is 5.5 at a hot water temperature of 90 °C, an evaporating temperature of −10 °C and a condensing temperature of 40 °C, which is higher than the 2.6 of the R404A vapor-compression system. Additionally, its refrigerating capacity can be changed by adjusting the number of reactors operating inside the sorption bed, ranging from 1.52 kW to 5.21 kW. Analysis results indicate that the system can efficiently and consistently meet the precooling needs of freshly harvested fruits and vegetables during the picking season. The payback period is less than one year, considering the economic benefits it brings. Ultimately, the novel system is suitable for refrigerated warehouses in sunny rural regions.
Article
Full-text available
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.
Article
In the traditional adsorption cooling system, there are two main problems. One is its low coefficient of performance (COP). The other one is that it usually only can be used for cooling. A multifunctional adsorption system with CaCl2 and matrix is proposed to improve COP. Additionally, it can produce a cooling effect and electricity simultaneously. The authors compared twenty organics performance for the organic Rankine cycle firstly. Then they tested the adsorption cooling performance using different thermal transfer fluids. The results show that the COP, SCP (specific cooling power) can reach 0.23, 451.9 W/kg, respectively, and the overall exergy efficiency of the integrated system can rise from 0.14 to 0.25 due to the power generation of the organic and NH3 expansion power generation, when the waste heat source temperature, refrigeration temperature, and the cooling water temperature are about 103.2 °C, -16.1 °C, and 29.5 °C in the water system.
Chapter
This chapter reviews the latest research and advancements in solar cooling technologies. In addition, it includes a discussion of the energetic, economic, and environmental indicators used to evaluate and compare different cooling options. Conventional vapor compression refrigeration systems driven by photovoltaic solar systems are gaining increased attention due to their maturity, modularity, and ease of installation. Solar thermal absorption and adsorption systems are slowly moving from demonstration to the market as well. Using solar desiccant cooling systems to dehumidify the air and improve its thermal comfort is economical, environmentally friendly, and easily achieved. Several combined ejector cooling systems can be utilized to improve their performance or create new functions. Hybrid solar cooling systems with various configurations are advancing and improving system efficiency and performance. Reviewed literature has revealed the great potential of solar energy to provide cooling with low energy consumption and reduced environmental impacts.
Article
This article presents a new effective utilization way of low-grade solar energy to produce cooling power with a novel integrated adsorption-absorption cooling system under climate conditions in Australia. In the integrated cooling system, the solution generation happens in the intermediate pressure, which is associated with the heat source temperature and can be adjusted according to the solution concentration and generation temperature. Two different solar system layouts with and without hot water storage tank are investigated. In the system without storage tank no cooling energy is generated at the beginning and ending cycle time and it reaches the maximum value of 16 kW around noon. While the maximum cooling capacity, 15 kW, is produced in the late afternoon between 14 h and 16 h along with higher cooling capacity at the beginning and ending cycle time in the system with storage tank. It is found that the average daily cooling capacity improve by 15% with better coefficient of performance by installing storage tank for a wide range of collecting area. Furthermore, the average daily coefficient of performance remains slightly stable at around 0.37 with expanding the solar collecting area. Results obtained from the economic analysis disclose that the lifecycle cost is minimised for the financially viable collector area of 34 m². Moreover, the payback period of 10.46 years for the optimum collecting area indicates the high profitability of the solar energy application in the proposed cooling system in a 25-year project investment lifetime. The performance comparison among various solar systems indicates that the average daily specific cooling powers are as high as 106 and 121 Wkg⁻¹ in the 1st and 2nd layouts respectively, which are achieved considerably greater than other systems operating at low driving hot water temperature of 60 °C. The low heat temperature required to run the proposed cooling system and the advantage of high solar radiation availability in Australia proves the high potentiality for operating the proposed system in most warm months.
Chapter
Adsorption heat pumps are thermally driven heat pumps that compress low-temperature, low-pressure vapor to high temperature and pressure through adsorption, which is the formation of a reversible bond between adsorbate molecules and a solid adsorbent, and subsequent desorption. While all adsorption heat pumps share this thermally driven compression process, many different heat pump cycles have been studied. Modifications to the basic, single-bed adsorption heat pump cycle allow for continuous cooling or heating, improved COP, better matching of thermal energy resources to the cycle temperature requirements, and operation with extremely low-temperature driving heat. In this chapter, the single-bed adsorption heat pump cycle is presented in detail, and cycles that modify the cycle capabilities are discussed, along with their advantages and drawbacks. The chapter concludes by quantitatively comparing the performance of three of these cycle configurations for a common adsorbent and refrigerant.
Book
Solid chemisorption technology is an effective form of energy conversion for recovering low-grade thermal energy, but limited thermal conductivity and agglomeration phenomena greatly limit its performance. Over the past 20 years, researchers have explored the use of thermal conductive porous matrix to improve heat and mass transfer performance. Their efforts have yielded composite sorption technology, which is now extensively being used in refrigeration, heat pumps, energy storage, and de-NOx applications. This book reviews the latest technological advances regarding composite solid sorbents. Various development methods are introduced and compared, kinetic models are presented, and different cycles are analyzed. Given its scope, the book will benefit experts involved in developing novel materials and cycles for energy conversion, as well as engineers working to develop effective commercialized energy conversion systems based on solid sorption technology
Chapter
Composite sorbents in single-stage refrigeration cycle, two-stage freezing cycle, semi-open solar-driven sorption air-to-water cycle, NH3 sorption cycle, NOx converting cycle and solid sorption heat pipe cycle for refrigeration, eliminating NOx emission, water production and heat transfer are summarized in this chapter, which promote the relative commercial utilization in energy conversion fields.
Article
Adsorption chillers powered by the low-grade thermal energy or renewable solar energy for cooling have gained growing research interests due to their environmental friendliness and low electricity consumption. The cascaded adsorption chillers consisting of the high-temperature stage and low-temperature stage exhibit a higher coefficient of performance for cooling than the single-stage adsorption chillers. Searching for high-performing working pairs in advanced cascaded adsorption chillers is essential to improve their cooling performance. In this work, three water-stable metal organic frameworks including UiO-66, DUT-67 and NU-1000 were chosen as adsorbents with water as working fluid. Their cooling performance of the four-bed cascaded adsorption chillers was tested by a dynamic adsorption cooling model under different desorption temperatures. It was demonstrated that DUT-67-water working pair for the low-temperature stage and DUT-67-water working pair for the high-temperature stage in cascaded adsorption chillers can achieve the highest coefficient of performance for cooling of 1.43 and a circulating cooling capacity of 2.6×10⁴ kJ. Moreover, the operation conditions of the cascaded adsorption chiller based on DUT-67 (high-temperature stage)/DUT-67 (low-temperature stage) have been optimized. It was revealed that the hot water inlet temperature of 373 K, the hot and heat recovery water mass flow rate of 0.5 kg/s, the chilled water mass flow rate of 1 kg/s, the adsorbent for the low-temperature stage and the high-temperature stage mass ratio of 1, and the cycle time of 1600 s were beneficial for the coefficient of performance for cooling and circulating cooling capacity of the cascaded adsorption chiller based on DUT-67/DUT-67.
Article
Since the energy and environment issues, adsorption refrigeration technology has raised the great attention and interest by worldwide researchers and scholars, because it can efficiently use low-grade heat and its refrigerants are natural. Among the numerous working pairs of adsorption refrigeration, silica gel-water is most suitable for massive applications in solar and waste heat field, as its developed technology and low driving temperature. In this paper, application analysis of adsorption refrigeration system for solar and data center waste heat utilization and economic evaluation, based on investment of main components, operation cost and payback period, is done. For the study of solar cooling application, a validated mathematical model of silica gel-water adsorption chiller is used. For very low temperature waste heat (up to 60 °C) recovery of data center, feasibility of silica gel-water adsorption chiller has been analyzed by previous experimental study. Through the investigation, payback period of solar cooling application using adsorption chiller is too long to get any economic benefit, based on the real weather conditions of Shanghai. Data center waste heat recovery by adsorption chiller has very short payback period and this application has greater economic potential and brighter prospect in the future than solar cooling application.
Article
A numerical analysis was conducted to examine the effect of a coating technique on adsorption cooling system (ACS) performance compared to a fully-filled grain configuration. The main interest was the effect of coating thickness, binder and cycle time for adsorption cooling applications. Validation of the numerical model was confirmed by comparison with experiment. The coating configuration resulted in a larger interfacial area to open space and also a shorter length of vapor flow path compared to the fully-filled configuration, which enhanced the vapor flow and resulted in higher performance. The optimal coating thickness was found to be 0.2–0.5 mm. A short cycle time was enough for the coating configuration, which improved system performance. For example, at coating thickness t = 0.2 mm, a 34.17% enhancement in specific cooling power (SCP) was achieved with a shorter cycle time of 480 s rather than 840 s, with the penalty of 9.87% decrease in coefficient of performance (COP). The coating technique with reduced cycle time is a good design approach for adsorption cooling systems. The binder had a negative effect on system performance, but the coating technique had clear advantages compared to the fully-filled configuration, and there was no other way of binding the adsorbent particles together. Thus, it is recommended that the binder content be kept as small as it can be.
Article
The half-cycle time effect on the performance of a solar single-stage dual-bed adsorption chiller, in Athens, Greece, in July, is investigated. The adsorption chiller coupled with the solar system is simulated, in real time, during the day for a) constant and b) adjusted half-cycle times and the system performance is monitored. In the former case, the half-cycle time is fixed, while in the latter one is dynamically adjusted according to the varying solar radiation intensity. Using a wide range of constant half-cycle times it is found that the maximum daily cooling capacity is obtained at some constant half-cycle time, which is larger than the optimum one of a single adsorption cycle. Similarly, using a wide range of adjusted half-cycle times, the one, providing the maximum cooling capacity is defined. The analysis is performed in a systematic manner through a proposed algebraic expression. It is found that the dynamically optimized adjusted half-cycle time operation mode provides about 12% higher daily and monthly cooling capacities than the corresponding maximum constant ones. This significant increase has been also confirmed for various incident solar radiation intensities.
Article
Compared to adsorption chiller, adsorption air-conditioner can get significant benefit of less cost and complexity when it directly provides chilled air for air-conditioning. Hence, adsorption air-conditioner is suitable for residential solar cooling application. A 3 kW adsorption air-conditioner using silica gel-water working pair is designed and manufactured and its performance is fully tested under different conditions. The experimental results show that cooling power and COP can reach 3.98 kW and 0.632, respectively, without obvious periodic fluctuation of chilled air outlet temperature and relative humidity. Smaller hot water flow rate can help to reduce unmatching between heating and cooling operation of adsorption bed. Optimal half cycle time of this adsorption air-conditioner is found to be 750 s. COP of adsorption air-conditioner is generally larger than that of adsorption chiller which provides chilled water because of higher evaporation temperature. Besides, cooling water outlet temperature can reach 39.9 °C which can meet the requirement of domestic hot water use. So that adsorption air-conditioner can be used for cooling and heating cogeneration in a residential solar cooling application and achieve good performance.
Article
The amount of low-temperature heat generated in industrial processes is high, but recycling is limited due to low grade and low recycling efficiency, which is one of the reasons for low energy efficiency. It implies that there is a great potential for low-temperature heat recovery and utilization. This article provided a detailed review of recent advances in the development of low-temperature thermal upgrades, power generation, refrigeration, and thermal energy storage. The detailed description will be given from the aspects of system structure improvement, work medium improvement, and thermodynamic and economic performance evaluation. It also pointed out the development bottlenecks and future development trends of various technologies. The low-temperature heat combined utilization technology can recover waste heat in an all-round and effective manner, and has great development prospects.
Article
Sorption is used for absorption/adsorption heat pumps (sorption refrigeration) and sorption for thermal energy storage (TES). This paper is the first review where the research on both applications is shown together. Sorption has advanced very much due to the immense amount of research carried out around heat pumping and solar refrigeration. Moreover, sorption and thermochemical heat storage attracted considerable attention recently since this technology offers various opportunities in the design of renewable and sustainable energy systems. The paper presents the operation principle of the technology and the materials used or in research are listed and compared. Absorption heat pumping and refrigeration research is today more focussed in the decrease of unit costs and increase of energy efficiency, adsorption is focussed in finding more efficient working pairs, and storage is testing the first prototypes and designing new ones with different or enhanced storage materials and new reactor concepts to optimize energy output.
Article
Full-text available
This article presents analytical investigation results on the performance of dual-mode multi-bed adsorption cooling systems using silica gel-water pair. This novel adsorption chiller utilizes effectively low-temperature solar or waste heat sources of temperature between 40 and 85°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 85°C. The second operation mode will be to work as an advanced two-stage adsorption chiller where the available driving source temperature is very low (below 60°C). In the present work, a simulation study of a dualmode, four-bed silica gel-water adsorption chiller is undertaken. For a driving source temperature above 60°C, the chiller functions as a single stage four-bed adsorption chiller. However, the chiller works as a two stage four-bed adsorption chiller when the driving source temperature falls within the range from 40°C to 60°C. With a cooling water temperature of 30°C. It has been found that this dual mode adsorption chiller is capable to provide cooling throughout the year via measuring the coefficient of performance and the cooling capacity of the system.
Article
A silica gel-water adsorption chiller driven by low-grade heat is developed. System configuration without any vacuum valves includes two sorption chambers, a 4-valve hot/cooling water coupled circuit and a 4-valve chilled water circuit. Each sorption chamber is composed of one adsorber, one condenser and one evaporator. The design of this chiller, especially the design of modular adsorber, is suitable for low-cost industrial production. Efficient and reliable heat and mass recovery processes are also adopted. This chiller is tested under different conditions and it features the periodic variations of temperatures and cooling power. Through the experimental study, the optimal cooling time, mass recovery time and heat recovery time are 720 s, 40 s and 24 s, respectively. Besides, the obtained cooling power, COP and SCP are 42.8 kW, 0.51 and 125.0 W kg(-1), respectively, under typical conditions of 86/30/11 degrees C hot water inlet/cooling water inlet/chilled water outlet temperatures, respectively.
Article
This paper presents the modeling and successful operation of a miniaturized Pressurized Adsorption Chiller (PAC) which utilizes Propane as the adsorbate and activated carbon as the adsorbent. The Propane + Activated Carbon Pair has previously been found to be able to function under adverse conditions where low temperature refrigeration is required, placed at high ambient temperature locales. This work focuses on the modeling of the pressure equalization process, and the feasibility of the working pair. A maximum cooling load of 7W is tested for the various cycle times. Experimentally, it has been found to successfully provide cooling, albeit with a low COP (<0.5), typical of waste heat driven systems.
Article
The global demand for commercial and domestic refrigeration and air conditioning systems has dramatically increased; currently it takes around third of the total worldwide energy consumption. Mechanical vapour compression refrigeration systems use refrigerants with adverse environmental effects. Sorption refrigeration systems offer the potential for better alternative to the mechanical vapour compression systems, if their technology can be improved to overcome current limitations. Sorption refrigeration systems are driven using low grade energy, solar energy and waste heat, and can operate with environmentally friendly refrigerants and non corrosive materials. This chapter presents a comprehensive review for adsorption cooling systems, including adsorption principles, refrigerants used, adsorbent materials, working pairs, various bed designs, operating conditions, development techniques and their applications.
Chapter
The features of heat sources are given in this chapter, which include solar energy and waste heat. The characteristics and the performance of adsorption refrigeration systems driven by different heat sources are also discussed, including integrated solar adsorption refrigeration systems, separated solar adsorption refrigeration systems, systems driven by parabolic trough collectors, air conditioners for locomotives, and chillers for CCHP (cogeneration system for cooling, heat, and power) systems.
Article
This paper is the second part of a study on the use of adsorption refrigeration cycles driven by waste heat of near-ambient temperature. Experiments were conducted with several heat transfer fluid operating temperatures (hot, cooling, and chilled water), flow rates, and adsorption-desorption cycle times, and good qualitative agreement was obtained with the simulated results. Both experiments and simulation showed that the silica gel-water adsorption cycle is well suited to near-environmental-temperature heat sources and small regenerating temperature lifts, which help reduce the heat losses intrinsic to batched cycle operation. The chiller was operational with a hot water inlet temperature (Thot in) of 50°C (122°F), and the highest experimental values of the coefficient of performance (COP) (more than 0.4) were obtained with Thot in = 50°C (122°F) in combination with cooling water at 20°C (68°F).
Article
A thermally driven heat pump using a solid/vapor adsorption/desorption compression process in a vapor compression cycle is thermodynamically analyzed. The cycle utilizes a simple heat transfer fluid circulating loop for heating and cooling two solid adsorbent beds. This heat transfer fluid loop also serves to transmit heat recovered from the adsorbing bed being cooled to the desorbing bed being heated. This heat recovery process greatly improves the efficiency of the single stage solid/vapor adsorption process without the complication of a two stage cycle. During the heating and cooling processes a thermal wave profile travels through the beds. This paper uses a square wave representation for the true shape of the thermal wave. However, this square wave is assumed to stop short of the bed ends to account for realistic finite waveforms. The square wave model is integrated into a thermodynamic cycle which provides detailed information on the performance of the beds as well as the COP and the heating and cooling outputs of the heat pump system. Significant cycle design and operating parameters are varied to determine their effect on cycle performance.
Article
Four cases of cascading solid adsorbent cycles operating at a high regenerating temperature (275°C) are presented. One of these cycles is a double effect zeolite-water cycle, the three other cycles consists in a low temperature active carbon-methanol cycle boosted by a high temperature double effect zeolite-water cycle. The predicted performances as well as the components needed to operate the cycle and the heat management are presented. Cogeneration of chilled water (2°C) and either hot water (70°C) or steam (120°C); cogeneration of refrigeration (−10°C) and hot water (70°C) are very attractive. Production of refrigeration (−10°C) with a COP as high as 0.85 is also possible.
Article
The convective thermal wave is part of a patented cycle which uses heat transfer intensification to achieve both high efficiency and small size from a solid adsorption cycle. Such cycles normally suffer from low power density because of poor heat transfer through the adsorbent bed. Rather than attempting to heat the bed directly, it is possible to heat the refrigerant gas outside the bed and to circulate it through the bed in order to heat the sorbent. The high surface area of the grains leads to very effective heat transfer with only low levels of parasitic power needed for pumping. The new cycle presented here also utilises a packed bed of inert material to store heat between the adsorption and desorption phases of the cycle. The high degree of regeneration possible leads to good coefficients of performance (COPs). Thermodynamic modelling, based on measured heat transfer data, predicts a COP (for a specific carbon) of 0.90 when evaporating at 5°C and condensing at 40°C, with a generating temperature of 200°C and a modest system regenerator effectiveness of 0.8. Further improvement is possible. Experimental heat transfer measurements and cycle simulations are presented which show the potential of the concept to provide the basis of a gas-fired air conditioner in the range 10–100kW cooling. A research project to build a 10-kW water chiller is underway. The laboratory system, which should be operational by June 1997, is described.
Article
Fundamental experiments on the solar-powered adsorption cooling system were carried out with small-scale apparatus simulating ideally a practical unit by employing a combination of silica-gel and water vapor as an example of the adsorbent-adsorbate combinations. A simple model which takes into account both adsorption properties and apparatus characteristics is proposed to interpret experimental results quantitatively. Then the transitional behavior of heat and mass transfer in continuous adsorption-regeneration experiments was successfully interpreted by the model. The model proposed is not a complete one and is to considered as a first-step model for estimating operation with practical equipment.
Article
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.
Article
A lot of speculation exists on the possibilities of cascading cycles while very few experimental data are available. Herein, experiments on a cascading adsorptive heat pump are reported. The cascading cycle consits of a two adsorber zeolite—water high temperature stage and an intermittent active carbon—methanol low temperature stage. Driving heat is supplied by a boiler to zeolite adsorbers while active carbon adsorber is heated by heat recovered from zeolite adsorber under adsorption. Evaporators from both basic cycles operate at the same temperature and contibute to the evaporating load. Experimental cooling COP is found to be 1.06, much more than the COP of an intermittent cycle (≈0.5) and more than the COP of a two adsorber zeolite water cycle (≈0.75). Despite of the discontinuous operation of the cycle, evaporating rate is nearly constant (≈2.35 kW or 37W per kg of adsorbent). An analysis of the results shows that the components which limit the power of the unit are the evaporators and basically water evaporator. The COP of this cascading cycle is very sensitive to the evaporating temperature lift. If the temperature lift is higher than 45°C, a two adsorber zeolite water cycle has to be preffered. This cycle seems to be well adapted to air conditioning as long as the evaporation temperature lift is less than 45°C.
Article
A thermal wave adsorption heat pump cycle utilizes a simple heat transfer fluid loop for heating and cooling two solid adsorbent beds. This loop also serves to transmit heat recovered from the bed being cooled to the bed being heated. During these heating and cooling processes the so-called thermal wave (steep temperature front) travels through the bed. This paper uses a ramp wave model for the true shape of the thermal wave. The effect of the bed thickness on the waves is taken into account by assuming that the wave in the bed comes a little while after the wave in the fluid. This paper gives some examples for the pairs zeolite/ammonia and zeolite/methanol. The new model is also compared with the existing old models by Shelton.
Performance analysis of advanced adsorption cycle
  • B B Saha
Saha BB. Performance analysis of advanced adsorption cycle. PhD. thesis, Tokyo University of Agriculture and Technology, 1997.