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![Schematic diagram (a) and photograph (b) [7] of fin-tube heat exchanger. Characteristic dimensions: D -HEX diameter, d -tube diameter, fh -fin height, fw -fin width, fs -fin spacing.](publication/334258289/figure/fig1/AS:777309086826496@1562336336491/Schematic-diagram-a-and-photograph-b-7-of-fin-tube-heat-exchanger-Characteristic.png)
Schematic diagram (a) and photograph (b) [7] of fin-tube heat exchanger. Characteristic dimensions: D -HEX diameter, d -tube diameter, fh -fin height, fw -fin width, fs -fin spacing.
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![Fig. 1. Schematic diagram (a) and photograph (b) [7] of fin-tube heat...](publication/334258289/figure/fig1/AS:777309086826496@1562336336491/Schematic-diagram-a-and-photograph-b-7-of-fin-tube-heat-exchanger-Characteristic_Q320.jpg)
Important parameters used for adsorption chillers, e.g. cooling capacity, coefficient of performance, are strictly dependent on heat and mass transfer conditions between adsorbent mass and the cooling/heating medium. With the aim of energy efficiency increasing it is essential to reduce heat transfer resistance. Different bed configurations and hea...
Contexts in source publication
Context 1
... heat exchangers are simple constructions based on straight tube with perpendicular fins. Finned tube can be used as single straight line (Fig. 1a) connected in parallel, shaped into coil with finned straight elements or u-tube with fins (Fig. 1b). Fins may have circular or rectangular shape. Fin-tube HEX can be adapted do adsorption bed by filling space between fins with loose grains of adsorbent and covering with mesh in case of keeping adsorbent grains in place. Also it is ...
Context 2
... heat exchangers are simple constructions based on straight tube with perpendicular fins. Finned tube can be used as single straight line (Fig. 1a) connected in parallel, shaped into coil with finned straight elements or u-tube with fins (Fig. 1b). Fins may have circular or rectangular shape. Fin-tube HEX can be adapted do adsorption bed by filling space between fins with loose grains of adsorbent and covering with mesh in case of keeping adsorbent grains in place. Also it is possible to cover heat exchanger surface with coating made from adsorbent grains and binder. Poyelle et ...
Context 3
... applied in such type of HEX may have different geometry. The comprehensive analysis of typical geometric parameters (Fig. 1) influence on chiller performance was conducted [10,11]. Rectangular and circular fins were compared for various fin spacing (3,6,9,12 mm) and height (15-70 mm). Increasing fin height require supplying more heat for regeneration, but it was indicated that at the same time COP value rises. The cooling capacity increment exceeds higher ...
Citations
... The desorption process of adsorbents is endothermic, while the adsorption process is exothermic. The enthalpy of adsorption differs among various adsorbents, meaning that the selection of adsorbents greatly influences the system's thermal efficiency [39,40]. According to the above literature, 13X zeolite is the most widely used material in adsorption CCES systems and has obtained considerable thermodynamic properties. ...
In recent years, energy storage technology has developed rapidly with the aim to promote the development of renewable energy sources and establish a green and sustainable energy structure. A novel compressed CO2 energy storage system based on Gua2SO4 adsorption is proposed in this study. Gua2SO4 has low sorption enthalpy and mild physical conditions in the adsorbent and desorption process, which are very beneficial for reducing the design difficulty of low‐pressure gas storage devices and improving the system performance. The energy and exergy analysis models are conducted after establishing several assumptions. The round trip efficiency, energy density, CO2 capture unit volume and liquid CO2 tank volume are 68.8%, 12.6 kWh/m³, 44,208 m³ and 19,235 m³ under design conditions, respectively. In addition, according to the exergy analysis, the liquefaction unit and compression unit have the highest exergy destructions. The monotonic increase in high‐pressure cooler end temperature difference and ambient temperature will cause the system efficiency to show a trend of first increasing and then decreasing. The liquid CO2 tank temperature and throttling pressure have a trade‐off relationship on system performance. It should be noted that when the throttling pressure is below a certain value and the liquid CO2 tank temperature is above a certain value, the system efficiency will sharply decrease. Moreover, increasing compressor and turbine efficiency has a conducive effect on improving system efficiency while the growth of heat exchanger pinch temperature and pressure loss rate have a negative influence to that.
... • choice of modern sorption materials [6]; • improved heat transfer in the sorbent [9]; • improved heat transfer at the interface between the sorbent and the heat exchanger [6,10,11]; • use of internal heat recovery [4,12]; • selection of the optimum duration of the half-cycle [13]; • use of an appropriate number of beds [12]; • fluidisation of the adsorbent bed [14]. ...
... The most important component responsible for heat exchange is the one in which the heating/cooling water flows in the heat exchanger. Its design can greatly affect the performance of the entire unit [10]. ...
... This type of flow is known as natural (or mixed) convection. The influence of buoyancy forces on the share of free and forced convection in the flow determines the mutual ratio of the Grashof and Reynolds numbers (10) Gr ...
Adsorption systems are alternatives to compressor cooling systems. Apart from many advantages, these systems are characterized by low COP and SCP parameters. One of the most promising options to improve the performance of adsorption chillers is the replacement of the stationary bed with a fluidized one. A fluidized bed significantly increases the heat and mass transfer within the bed, enables better contact between gas and solid phases, and results in the proper mixing of adsorbent particles. This paper presents the possibility of using fluidized beds in adsorption chillers. This paper shows the results of CFD numerical modelling of the operation of a fluidized bed for an adsorption chiller and simulations of the bed temperature profiles during the adsorption and desorption processes of sorbent in a fluidized bed. This article presents an analysis of CFD simulation results for the optimal angle of heat exchangers.
... It can also be defined differently as a change in the concentration of the adsorbate on the surface of the sorption material (adsorbent) [34]. This phenomenon occurs due to the adhesion of the adsorbate to the surface of the adsorbent [35]. The extent of adsorption, i.e., the amount of adsorbate adsorbed, depends on the properties that characterise the sorbent material, which primarily include the size with pore volume and the specific surface area of the adsorbent. ...
Adsorption cooling technology is a promising alternative to replace conventional solutions. However, adsorption chillers still need to be improved in terms of performance parameters. One of the most important factors affecting their efficiency is the characteristics of the adsorbent, which should have the highest adsorption capacity and enable efficient heat transport in the bed. The objective of this paper is to present current developments in the field of composite sorbents with silica gel matrix as modern and very promising materials and then perform a detailed analysis of them. The paper summarises the methods of synthesis of composite sorbents and the current knowledge concerning these materials. The analysis focuses on a comparison of the available data, particular taking into account the types of matrixes, so that the analysis provides a clear and qualitative basis for further research. As a result of exploring the state of the art, this subject is found to be insufficiently described; therefore, these materials are comprehensively analysed in terms of their properties and the impact of their use on the COP (coefficient of performance) and SCP (specific cooling power) of adsorption chillers. Based on the analysis of the literature, the most promising directions for further research are also indicated.
... • Redesigning the adsorption beds [30][31][32][33]. ...
Recently, there have been several endeavours to enhance the performance of the adsorption systems for cooling cum desalination by developing new materials and adsorbent bed designs. Therefore, this article contributes to the field by computationally studying the utilisation of state-of-the-art MOF 801 adsorbent packed into the emerging copper-foamed adsorbent bed heat exchanger and benchmarking its performance against that utilising silica gel baseline adsorbent. A multi-objective global optimisation aimed simultaneously at the best coefficient of performance, specific cooling power, and clean water productivity was undertaken. The optimisation was built
on the insights from a broad parametric study for the geometric and operating conditions. Given the novelty of the adsorbent MOF-801 and bed design combination, a one-dimensional model was developed to imitate the heat transfer in the adsorbent bed and coupled with a previously validated empirical lumped analytical model for the adsorption system using the MATLAB platform. Using copper foam significantly enhanced the effective thermal performance of the adsorbent bed, improving the overall system performance under different operating condi-
tions. Furthermore, the clean water productivity of the MOF-801-based system outperformed that of the SG- based system by 38%, as the former yielded 29.7 m3/(ton.day), while the latter 21.5 m3/(ton.day). Besides, the MOF-801-based system showed specific cooling power of 830.8 W/kg compared to 611.5 W/kg for the silica gel-based system. However, the cooling capacity per unit volume determined the systems’ form factor, and the
coefficient of performance was respectively higher by 9.6% and 20.2% for the silica gel-based system than those of the MOF-801-based system, stemming from the low packing density of MOF-801.
... Parametric analysis studied a two-stage adsorption chiller using reheat demonstrating the effect of the overall thermal conductance and adsorbent mass on system performance [13][14][15]. Bed and heat exchanger configurations to reduce heat-transfer resistance and improve performance were reviewed for a single-stage and a multistage adsorption chiller [16][17][18]. Finally, Ahmad, R.M. Rezk and Raya. ...
This study is the second part of the theoretical study of “Modeling and Simulation of a Two-Stage Air-Cooled Adsorption Chiller with Heat Recovery”, which is based on developing a theoretical model for a two-stage adsorption chiller with an activated carbon/methanol pair. The following models were conducted numerically using MATLAB. The model was based on 10th order differential equations; six of them were used to predict bed, evaporator and condenser temperatures, while the other four equations were used to calculate adsorption isotherm and adsorption kinetics. In this second part, bed heat exchangers and evaporator and condenser heat exchangers are studied by varying the parametric design of a chiller. This includes but is not limited to activated carbon mass inside a single bed, overall heat transfer coefficient for the bed and evaporator and the mass flow rates of all components comprising the chiller. The optimum values increased the COP from 0.35 to 0.4, while the cooling capacity was slightly changed. The COP is 95% of a Carnot cycle working at hot water temperatures as low as 60 °C, and 90% at hot water temperatures as high as 90 °C. It was found that the simulation model results for the two-stage air-cooled chiller agreed well with the experimental data in terms of cooling capacity (6.7 kW for the model against 6.14 kW for the experimental result at 30 °C cooling water temperature). The model optimized the adsorption/desorption time, switching time and heat recovery time to maximize both cooling capacity and COP. Moreover, the model is used to study the effect of activated carbon mass, size of beds and mass flow rates of cooling, heating, chiller and condenser on both cooling capacity and COP.
... The study was conducted for HTF temperatures in the range of 45-55 • C, which allows us to analyze the investigated exchanger in the context of its application in an adsorption bed. Other ways to increase heat transfer in the bed are the use of heat pipes and modification of the bed by using coating, bonding techniques, and additives [10,[13][14][15][16][17][18][19]. Nevertheless, the solutions proposed often involve an increase in the heat transfer surface area, which, beside the power of the exchanger, is the most important parameter that characterizes it. ...
... On this basis, it should be concluded that the optimum solution is to use the same medium for bed heating and bed cooling because this avoids unnecessary increase in the liquid capacity of the system. bonding techniques, and additives [10,[13][14][15][16][17][18][19]. Nevertheless, the solutions proposed often involve an increase in the heat transfer surface area, which, beside the power of the exchanger, is the most important parameter that characterizes it. ...
In the face of increasing demands with regard to the share of renewable energy sources in the energy mix, adsorption chillers are becoming a potentially important part of the energy transition. A key component of this type of equipment is the heat exchanger in the adsorption bed, the design of which affects both heat and mass transfer. This study includes an analysis of the geometry and materials used to manufacture such heat exchangers. The geometry analysis is mainly based on the evaluation of the impact of the different dimensions of the exchanger components on heat and mass transfer in the bed. The second part of the study focuses on material-related issues where the main emphasis is on the analysis of the thermal inertia of the exchanger. The paper analyses the latest research on the design of exchangers in adsorption beds, mainly from 2015–2021. Currently, the commonly used SCP and COP coefficients and various test conditions do not provide sufficient information for comparative analysis of adsorption bed heat exchangers, so the authors propose to introduce a new index for the evaluation of heat exchangers in terms of the effect of the design parameters on the energy efficiency of an adsorption chiller.
... An optimize design of the adsorber unit is a key factor for improving performance of adsorption heat transformers. At the moment, adsorbers of commercial heat pumps and chillers are mainly based on granular beds or coated heat exchangers [13][14][15][16]. Granular beds of adsorbent materials represent the first technology adopted in adsorption heat pumps and during the years has been joined by coatings and others technologies in order to improve heat and mass transfer [17,18]. ...
Adsorbent materials made of hybrid, inorganic/organic, microfibers can be easily produced by electrospinning. Due to the presence of a polymeric component, microfibers coatings and textiles are intended for adsorption heat transformers driven by low-temperature heat sources. In this work, two different systems, SAPO-34 and silica gel microfibers with an adsorbing particles concentration of 68 wt%, have been electrospun using polymethylmethacrylate (PMMA) as polymeric carrier. The thermal stability of hybrid microfibers coatings were characterized by thermogravimetric analysis in the temperature range 25–500 °C while water sorption properties were evaluated measuring isobars at 10 mbar and 40 mbar by vacuum thermogravimetry. The mechanical properties of hybrid microfibers were measured by a specially developed micro-tensile tester. Adsorption measures demonstrated that PMMA/SAPO-34 and PMMA/silica gel microfibers maintained all water sorption characteristics of the original adsorbent materials and that PMMA did not occlude the adsorbents porosity. PMMA resulted an ideal component for its thermal stability, good affinity with the adsorbent phases and mechanical resistance. From this point of view, the addition of SAPO-34 powder has been shown to improve the tensile strength of PMMA/SAPO-34 fabrics compared to pure PMMA microfibers.
... -Modification of the adsorption/desorption cycle time; -Increasing the efficiency of heat exchange in the bed between exchanger and sorbent; -Increasing the sorbent regeneration temperature; -Changing the design of the bed exchanger; and -Using new adsorbents with higher sorption capacity [21]. ...
... SCP strongly depends on the cooling water temperature. It increases when a lower temperature is reached in the condenser [21,24,25]. ...
The intensive development of the world economy and the expected population growth mean that demand for cooling and water will continue to rise. The use of conventional technologies to meet this demand is associated with an enormous expenditure of electricity, which still comes mainly from non-renewable sources. With the increasing demand for energy, the increasing scarcity of drinking water, and the negative impact of humankind on the environment due to global warming and ozone depletion, intensive research has been carried out to find modern desalination technologies Most of the technologies use electricity for the process of desalination, and over 6% of the world’s electricity is generated from non-renewable sources, thus increasing the emissions of harmful pollutants into the atmosphere. One possibility to reduce emissions is the use of adsorption chillers with desalination function, which allow the production of cooling simultaneously with the process of water desalination. These systems can be powered by low-temperature waste heat from industrial processes or from renewable sources (solar panels) and require little electricity to operate. This paper presents options to improve their performance and increase the production of condensate in the process of desalination of saline water. Moreover, also presented are the results of tests carried out on a two-bed adsorption chiller with desalination function. The aim of the study was to determine the effect of cycle time on the cooling coefficient of performance (COP) and on the production of condensate from water desalination. The obtained results confirmed that increasing the adsorption and desorption cycle time leads to an increase in the COP value of the adsorption chiller, but the efficiency of the desalination process and condensate production decreases with increasing cycle time.
... Climate change caused, among other things, by greenhouse gas emissions from anthropogenic sources has led to an increase in the global average temperature. Its increase, in turn, intensifies the demand for cooling, which is most often generated in a way contributing indirectly to negative climate change [6]. In most cases, the chillers used today are compressor systems driven solely by electricity and using synthetic refrigerants [7]. ...
... Its simplified diagram is shown in Figure 2. The main components of the adsorption chiller are the adsorbent beds (3), the evaporator (5), the condenser (1) and the expansion valve, which is responsible for maintaining the correct pressure difference between the condenser and the evaporator during the condensate flow from the condenser to the evaporator. The system under consideration is also equipped with a distillate tank (2), a brine tank (4) and a deaerator (6). ...
Adsorption chillers with desalination functionality, being devices characterised by very low electricity consumption, provide an alternative to conventional sources of cooling and water. The option of desalinating water means that the use of a single device enables obtaining two useful products. Adsorption chillers are not widely used at present. due to their low performance characteristics; these are, however, constantly being improved. This paper presents a verification of the possibility of increasing the cooling coefficient of performance (COP) and specific cooling power (SCP) of a laboratory adsorption chiller by optimising the length of cycle times and using a copper additive to silica gel with a mass fraction of 15% to increase heat transport in the bed. The choice of copper among other considered additives was determined by the conclusions from the research on the sorption kinetics of various mixtures, price and availability, and a high thermal conductivity. The device was operated in a two-bed mode aimed at producing cooling. The adsorbate was distilled water. The results were compared with those obtained under similar conditions when the beds were only filled with silica gel. As a result of the testing, it was found that the use of the copper additive with the sorbent increased both the COP and SCP. The tests were performed for different cycle times, of 100, 200, 300 and 600 s. With increasing cycle time COP also increased. In contrast, the specific cooling power increased only up to a certain point, whereafter its value decreased.
... • Generation of continuous cooling effect, such as double-and multiple-bed systems, etc. (Rouf et al. 2020). • Development of low-grade heat sources-based adsorption systems (Stefanski et al. 2018). ...
... • Development of systems with minimum fabrication, operation and running cost (Stefanski et al. 2018). • Development of compact system with optimum size and minimum number of components (Faizan et al. 2020). ...
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.
