Adsorption Refrigeration System Research Articles

Integration of evacuated solar collectors with an adsorptive ice maker for hot climate region

This research study compares the steady-state and dynamic behaviour of a solar-powered activated carbon-35 (AC35)/methanol-based vapour adsorption refrigeration system for production of ice at hot climate region. Thermodynamic comparisons are made with the coefficient of performance (COP), system COP (SCOP), specific refrigeration capacity (SRC) and critical parameters such as cycle time and ice production rate are quantified. Further, the sustainability of the proposed ice maker has proven by integrating economic and environmental perceptions. The minimum solar flux required to ensure continuous ice production was found 800 W/m2. Moreover, the maximum ice production rate and COP were decreased by 32.36% and 37.63% respectively when the system was operated under real ambient conditions. The proposed solar adsorptive ice maker achieved maximum SRC of 61.6 g m−2 during April month and reduced the CO2 emissions by 12.82 ton annually.

Unjuk Kerja Evaporator Pada Mesin Pendingin Dengan Siklus Adsorpsi Menggunakan Energi Surya

Energy needs in Indonesia continue to increase every year. The largest use ofenergy is in the industrial sector, where its needs reach 42.12% of the totalnational energy needs. To save energy, energy saving measures are needed in theindustrial sector so that the increase in energy demand can be restrained. So weconducted research on the performance of the evaporator in a refrigerationmachine with an adsorption cycle using solar energy. The purpose of this studywas to determine the working process of the evaporator with activated carbonrefrigeration and to determine the efficiency of the evaporator in the activatedcarbon pair adsorption refrigeration system. This research was conducted byobserving and recording the evaporator temperature of the refrigeration machineevery hour. The results of the research in three days of testing, namely, on the firstday the highest evaporator temperature increase was at 16.00 o'clock, which was33.2oC and the lowest evaporator temperature was at 07.00 o'clock, which was 25.1 oC. On the second day, the highest increase in evaporator temperature was at 16.00, which was 32.2oC and the lowest evaporator temperature was at 07.00, which was 23.8 oC. On the third day, the highest increase in evaporator temperature was at 36.4 oC and the lowest evaporator temperature was at 06.00,which was 24.5 oC.Kata kunci: Adsorption, evaporator, temperature

Optimization and experimental analysis of a solar powered adsorption refrigeration system using selective adsorbent/adsorbate pairs

Adsorption-based cooling system is a cost-effective method of heat conversion. It has the potential to dramatically enhance energy efficiency while also lowering pollutant levels. For this purpose, a solar-powered vapor adsorption refrigeration system (VAdRS) using activated carbon–methanol and zeolite–water as the working pair has been designed and experimentally evaluated. The aim of this experiment was to evaluate the coefficient of performance (COP) and specific cooling power (SCP) of a solar cooling unit by utilizing the optimum minimum and maximum mass concentration ratios. The novel solar-assisted adsorption refrigeration system optimization technique is used in this research to evaluate the optimal performance of the solar-powered VAdRS under various operating scenarios. The experiment was conducted at the optimum minimum and maximum mass concentration ratios of 0.1 and 0.2, respectively. The experimental results show that the activated carbon–methanol adsorption system produces a higher COP value than the zeolite–water adsorption system of 0.49–0.64 and 0.64–0.67 at constant evaporator and condenser temperature, respectively. It also showed that the higher SCP value was revealed in the zeolite–water-based adsorption cooling system as 207.5–217.4 kJ/kg. It was revealed that AC–methanol could be used to operate better in low-generating-temperature conditions. On the other hand, the zeolite–water adsorption system can be used at higher generating temperatures.

Heat Recovery for Adsorption Refrigeration System via Pinch Technology

Heat Recovery for Adsorption Refrigeration System via Pinch Technology

Mixture optimization of synthesized zeolites 4A and 13X for solar adsorption refrigeration application

Abstract In a way to overcome challenges with global warming, the use of fossil fuels in producing environmentally friendly energy towards reducing the ozone layer depletion and greenhouse gas emissions by participating countries is of interest. The adsorption refrigeration system has the advantages of a long lifespan and its environmental friendliness; however, its major disadvantage is the low coefficient of performance, which is a function of adsorbent–adsorbate, with zeolite–water as the most common adsorbent–adsorbate working pair. Zeolites 4A and 13X are the most used zeolite classes due to their higher selectivity for separating mixtures of CO2/N2 and CO2/CH4/N2 and their high-water adsorption capability, respectively. In this study, for the first time, the synthesis of zeolites 4A and 13X from natural sources (Kankara kaolin) and the mixture optimization for solar adsorption refrigeration application were considered. Raw Kankara kaolin, beneficiated Kankara kaolin, calcined Kankara kaolin and synthesized zeolites 4A and 13X were characterized using X-ray fluorescence, while the synthesized zeolites 4A and 13X were characterized using X-ray diffraction. Using the mixture simplex lattice design of experiment, mixtures of zeolites 4A and 13X were developed and characterized using Brunauer, Emmett and Teller analysis to obtain their pore size, specific surface area and pore volume. The statistical analysis produced the mathematical models of the response that were significant for pore size and specific surface area. The analysis proposed an optimal solution of 75 wt% zeolite 4A and 25 wt% zeolite 13X, which gave a desirability of 0.944.

Parametric study of reflectivity transmittance of materials for potential solar adsorption refrigeration system

Abstract One of the most promising alternative energy sources has been recognized as solar energy. Solar energy may be utilized for electricity, solar thermal and power generation directly or indirectly. Sun adsorbing refrigeration systems require adsorbing qualities, which can be produced by concentrated solar energy collectors. Previous research has found that the collector components’ reflectivity transmittance is one of the characteristics that have a substantial impact on the performance of a solar adsorption refrigeration system. For the first time, the solar insolation of Reflectech mirror, a new solar concentration material was compared parametrically with three popular solar concentration materials (metallic film, aluminium film and polymer film) that have been used for solar adsorption application. The optimized simulation results revealed that employing Reflectech film in the design of the solar adsorption refrigerating system has the ability to reflect the maximum solar insolation of 144.5 W/m2 in comparison with metallic film with 119.75 W/m2, aluminium film with 100 W/m2 and polymer film with 68.67 W/m2. Thereby, implying that the Reflectech film has the potential of producing the highest system coefficient of performance than the other materials is under research for all periods under study.

A comprehensive thermodynamic analysis and performance evaluation of a transcritical ejector expansion CO2 adsorption refrigeration system integrated with thermoelectric sub-cooler

A detailed performance evaluation of modified transcritical CO2 adsorption refrigeration systems integrated with an ejector and a thermoelectric sub-cooler is carried out using simplified thermodynamic models. The simultaneous effect of subcooling and the lift produced by the ejector on system COP and the specific cooling effect (SCE) is expounded. It is observed that the proposed system yields an identical COP with that of heat and mass recovery systems with reduced design and operational complexity. However, the heat and mass recovery systems clubbed with ejector and thermoelectric sub-cooler yield the best system performance with a maximum increment of 126% in COP. The gas cooler pressure and subcooling temperature strongly affect the entrainment ratio; however, COP and SCE strongly depend on gas cooler pressure, evaporator and generator temperatures. The maximum COP attained (i.e., 0.353) using the novel adsorbent (M-AC C-500) in the modified system can be used as a benchmark.

Experimental Investigation of silica-gel based composite adsorbent for adsorption refrigeration system

Two novel composite adsorbents have been developed with porous home silica-gel to enhance the performance of the adsorption refrigeration system. The two types of thermal conductivity enhancers (TCEs) namely graphite and copper powder with a polymeric binder polyvinyl alcohol (PVA) are used to develop the high-performance composite adsorbents. The thermal stability, crystallinity and morphology of prepared composite adsorbents are analyzed. The porous properties such as specific surface area, pore volume and pore size distribution, and the thermophysical properties such as specific heat, thermal conductivity and thermal diffusivity are also investigated. A maximum specific surface area of 417 m2/g and pore volume of 0.3648 cm3/g is observed for a composite of 80% silica-gel + 10% graphite + 10% PVA. The copper-based composite adsorbents show lower specific heat values as compared to the graphite-based composite adsorbents. The thermal conductivity and diffusivity of composite adsorbents are significantly increased with the increased percentage of TCEs. A maximum thermal conductivity of 0.5 W/m K and diffusivity of 0.34 × 10-6 m2/s is observed for graphite-based composite adsorbent with a composition of 50% silica-gel + 40% graphite powder + 10% PVA. This is 4.23 times and 2.12 times greater than the thermal conductivity and thermal diffusivity of the silica-gel respectively. Similarly, a maximum thermal conductivity of 0.433 W/m K and diffusivity of 0.214 × 10-6 m2/s are observed for copper-based composite adsorbent with the same composition of TCE. This is 3.66 times and 33% greater than the thermal conductivity and diffusivity of the silica-gel respectively. The developed composite adsorbents show improved thermal and physical properties as compared to the conventional silica-gel.

Experimental studies on solar assisted activated carbon based adsorption refrigeration system

The refrigeration and air conditioning has become an integral part of today’s life in both domestic and industrial sector and is continuously growing beyond one’s imagination resulted in the price rise of fossil fuels and negative environmental impact due to the existing cooling technologies which works mainly on vapour compression principles using traditional refrigerants. This results in the emission of harmful gases which in turn causes global warming and ozone layer depletion. This has made to find the refrigeration system which is reliable, pollution free, environmental friendly and economical. In this context heat operated systems such as adsorption refrigerators run by low heat source temperatures from solar or waste heat energy are gaining significant importance for cold production. The cooling systems run by vapour adsorption principles are favourable in terms of eco-friendliness and reliability but the coefficient of performance (COP) that can be achieved is low and hence are not able to compete with the vapour compression systems which is due to the lack of technological development. Hence the research activities are still ongoing in this area to solve the environmental, technical and economic issues. The literature indicates that the adsorption refrigeration system’s performance depends upon the working pair used such as silica gel-water, activated carbon-ammonia, zeolite-water etc. and driving temperature. It is also observed that in India, research related to adsorption refrigeration is rare. Hence in the present work using activated carbon and methanol as the working pair, experimental studies are carried out on a solar assisted double bed adsorption refrigeration system to evaluate the performance under different working conditions. Results show that the lowest cool down temperature noticed in the evaporator under no load condition is 2 °C for the operated cycle time and the values of COP obtained were in the range of 0.1–0.3 for different operating parameters studied. The adsorption system is viable to produce cold even with low temperature source of heat.

Thermodynamic Analysis of Two Bed Adsorption Refrigeration System Driven by Solar Energy

Thermodynamic Analysis of Two Bed Adsorption Refrigeration System Driven by Solar Energy

Performance Testing and Analysis of Silica Gel-Water Adsorption Refrigerator

In recent years, adsorption refrigeration technology has attracted wide attention from experts and scholars at home and abroad due to its environmental friendliness and energy saving advantages. In order to study the effectiveness of adsorption refrigeration technology to recover low-grade energy, a silica gel-water adsorption refrigeration system was proposed, which can effectively utilize low-grade energy such as industrial waste heat. The structure and composition of the system are introduced. The operation performance of the unit is tested under different working conditions by orthogonal experimental method, and the experimental results are analyzed. The effects of hot water temperature and flow, chilled water temperature and flow on the refrigeration capacity and COP value of the system are obtained. The experimental results show that under the low-temperature heat source of 55-75°C, the cooling capacity of the system can reach 5.3-12 and the COP value can reach 0.36-0.56. Under the same hot water temperature difference, the cooling capacity and COP value of the system increase rapidly under the condition of changing the hot water temperature at low temperature, indicating that increasing the heat source temperature at low temperature has a greater impact on the system performance. Through the analysis of primary and secondary effects, it is concluded that the inlet temperature of hot water is the main factor affecting the refrigeration capacity and COP value of the system.

TRNSYS 16: A veritable solar modelling and programming simulation tool used in the design of a continuous solar powered adsorption refrigeration system

Project feasibility gave rise to the need for simulation. Simulation of a project leads to reduction in production cost, which ensures the success of the proposed project. Also, it provides initial design data for the experimental project. Thus, the design analysis and variables used for project simulation must be designed properly, revised, tested, and re-tested to guarantee how accurate the experimental design is. Hence, solar adsorption refrigeration system was designed, simulated and constructed using zeolite 4A/13X blend and water. The models were simulated using TRNSYS 16.0 simulation tool. From the result, it was observed that the collector area increases with increase in the system COP from month to month. The highest system COP of 1.53 was obtained in the month of April while the least was 0.4 for July due to frequent rainfall. Also, a much high COP was obtained for dry season while lower COP was gotten for harmattan season. Key words: TRNSYS, adsorption refrigeration, solar cooling, solar adsorption, adsorbent, solar concentrating collectors.

Performance prediction of adsorbent in an adsorption refrigeration system based on variable temperature and constant pressure experiment and dynamic model

• A method was designed to predict the performance of MOFs in adsorption refrigeration system using a small amount of MOFs. • The addition of calcium chloride increases the range of suitable cooling conditions for MIL-101(Cr). • The screening time of MOFs in adsorption refrigeration system is shortened. In order to study the performance of metal organic framework materials (MOFs) in adsorption refrigeration systems, the current research method is to test the equilibrium adsorption characteristics of the materials, estimate the adsorption refrigeration conditions of the materials, and then prepare a large amount of them and fill them into the adsorption bed for testing. However, the above methods affect the authenticity evaluation of materials due to the adsorption refrigeration experimental device. In addition, the preparation time of MOFs materials is generally long, and the time cost of verifying materials is high. Therefore, the purpose of this paper is to shorten the prediction time of material performance of adsorption refrigeration system. The large temperature jump method is used to carry out the dynamic adsorption and desorption experiments of three kinds of adsorbents at variable temperature and constant pressure. The dynamic adsorption and desorption model is established and combined with the experimental results to calibrate and verify the combination of heat and mass transfer coefficients of adsorbents. Finally, the performance coefficient of the adsorbent under different conditions is predicted, and the suitable refrigeration operating range is determined. The results show that the addition of calcium chloride increases the range of suitable cooling conditions for MIL-101(Cr). When the desorption temperature is 90°C, the minimum evaporation temperatures of MIL-101 (Cr) and MIL-101 (Cr)/CaCl 2 -20% are 12 °C and 5°C, and the maximum adsorption temperatures are 31 °C and 38°C, respectively.

Performance study of adsorption refrigeration system with composite adsorbent

As an effective way to improve the performance of heat and mass transfer, Composite adsorbent used in adsorption refrigeration has attracted increasing research attention. The aim of the research is to reveal composite theory of silica gel composite adsorbent and to understand adsorption refrigeration system mechanism running by above composite adsorbent. Coarse porous silica gel with different particle diameters was selected as the matrix of composite adsorbent and calcium chloride was selected as additive. The results showed that composite adsorbent's thermal conductivity and adsorption capacity increased significantly compared with pure silica gel. The thermal conductivity could be increased by 58.2%, and the adsorption capacity could be increased by 4–10 times. Finally, the adsorption refrigeration system using silica gel-calcium chloride composite adsorbent was studied. A two-bed adsorption refrigeration cycle running by above composite adsorbent was adopted. The experimental results showed that the optimal values of system cooling capacity and COP were not at the same time. The system cooling capacity reached its maximum at 1500 s and the system COP reached its maximum at 1200 s. The best heat recovery time was 20 s. The SCP of the system was up to 288.1 W kg−1, which could reduce the volume of the adsorption refrigeration system effectively.

Controlled Strategy for the Cooling Effect of the Solar-Driven Constant-Temperature Solid Sorption System

Cooling and refrigeration based on solid sorption is an attractive technology especially when it is powered by solar energy. The development of the Continuously-Operated Solar-driven Adsorption Refrigeration (CO-SAR) system has offered a method to overcome the problem of the intermittent production of cold. In this study, the ability of the CO-SAR system to control the production of cooling effect under different operating schemes is studied. The studied CO-SAR system uses activated carbon and methanol solid sorption pair. The governing mathematical relations are introduced to solve the coupling behavior of heat and mass transfer inside the adsorption reactor and the integrated solar collector. Furthermore, the feasibility of controlled cold production of the CO-SAR system is investigated. Three different cooling strategies of the CO-SAR system operating mode are demonstrated. In the first operating scheme, the refrigerant flow valve is fully opened and the produced cooling effect is self-controlled by the process of refrigerant adsorption. Moreover, a refrigerant fixed mass flow rate is allowed to flow towards the evaporator in the second controlled operating schedule. The third controlled operating strategy of the CO-SAR system demonstrated in this work represents a more practical and realistic working scheme. It is found out that the CO-SAR system is superior to the traditional intermittent solar-operated single-bed adsorption cooling system because it has the potential to be controlled. In other words, the CO-SAR system has the capability of managing the desired output cooling effect, the required cooling starting time, the duration of the cooling effect, as well as the required cooling ending time. The continuity in cold production and the steady temperature of the cold delivered are noteworthy, especially. This potential makes the system, more reliable, more dependable, and better in functionality than the conventional intermittent solar-operated single-bed adsorption cooling system.

Performance Analysis of an Adsorption Refrigeration System Working on Activated Carbon/Methanol Pair Using Finned Tube Type Adsorber Bed

Adsorption refrigeration, being a unique and eco-friendly technology, has gained popularity over conventional refrigeration systems. The present study is aimed at developing an annular finned tube adsorber model which serves as a thermal compressor in adsorption refrigeration systems. The mathematical model is addressed numerically using finite difference discretization method and explicit scheme was used for the solution. The generalized model has been simulated for activated carbon–methanol working pair. The system has an optimum cycle time of 1800s. It was found to have a highest refrigeration capacity of 260.66 kJ/kg at a regeneration temperature of 393 K and evaporator temperature of 283 K. The highest COP (Coefficient of Performance) achieved by the system is 0.3706 at a regeneration temperature of 353 K and evaporator temperature of 283 K. A highest SCP (Specific Cooling Power) of 144.8 W/kg was obtained at an evaporator temperature of 283 K and regeneration temperature of 393 K.

Investigation of a high-efficient hybrid adsorption refrigeration system using desiccant coated heat exchangers

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.

Experimental study of single bed prototype adsorption refrigeration unit using waste heat energy

Adsorption refrigeration has more potential to become an attractive technology due to use of low-grade thermal energy and environmentally friendly refrigerants. Ammonia-activated charcoal pair based prototype of single bed adsorption cooling system was presented and tested. The most extreme measure of adsorption capacityof ammonia was found to be 0.22 kg/kg of activated charcoal, in shell and tube type adsorption bed respectively. This experimentation indicates that the cooling limit ranges from of 46.38 to 50.67 W, and thus the results show that it achieves a COP of0.0971 during a 62-minute total working cycle time under the condition of the temperature of hot fluid 120 °C, cooling fluid provided at the temperature of 30 °C, adsorption bed temperature of 40 °C and working pressure range up to 16 bar. The results have been represented by graphical relations. This unit of adsorption cooling is environment-friendly and has zero ozone depletion potential. The result indicated that the adsorption refrigeration system works effectively and is a better alternative to replacement for traditional refrigeration systems and the concept of a waste heat driven adsorption cooling system can be applied in the small cold storages.

Multi-mode integrated system of adsorption refrigeration using desiccant coated heat exchangers for ultra-low grade heat utilization

A traditional adsorption refrigeration system cannot run under ultra-low grade heat source temperatures. In order for ultra-low grade heat utilization, a multi-mode integrated system of adsorption refrigeration using desiccant coated heat exchangers (DCHEs) is proposed. The key point of this integrated system is the rise in evaporation temperature by the use of DCHEs, which contributes to lowing the driving temperature and enhancing the system performance. A mathematical model based on the first and second law of thermodynamics perspective is developed, and the performance investigation is conducted to understand the effect of different modes, driving and medium temperatures. The results reveal that Mode 1 has a wider working range, Mode 2 has better performance and Mode 3 can realize the cogeneration of chilled water and dehumidified air. Compared to a traditional system, the integrated system has obviously lower driving temperature and higher performance. The integrated system with Modes 1 and 2 can operate effectively at driving temperatures below 50 oC and its maximum COP and exergetic efficiency can reach around 0.8 and 0.21, respectively. For ultra-low grade heat utilization, the medium temperature has a greater effect on the COP and equal effect on the exergetic efficiency to driving temperature.

Energy performance analysis and optimization of a coupled adsorption and absorption cascade refrigeration system

An energy cascade utilization system is an advanced technology that recoveries waste heat energy efficiently. However, research on cascade systems by utilizing waste hot water with 60–100 °C is still considerably lacking in the literature. Specifically, this paper investigates the waste heat recovery performance of a multistage coupled absorption chiller (ABC)-adsorption chiller (ADC) cascade system. The proposed ABC-ADC cascade system is capable of producing potable water and three streams of chilled water under different temperature settings. Firstly, the experimental analysis is judiciously carried out on a four-bed two-evaporator ADC subsystem prototype. Key results reveal that the ADC’s maximum specific daily water production is 10.5 m3/day/ton. Subsequently, the ABC-ADC cascade system’s performance is experimentally analysed and optimized. The achievable maximum cooling coefficient of performance (COPc) is obtained to be 0.55. Additionally, a general method is proposed to optimize the subsystem’s cooling capacity combination of the ABC-ADC cascade system in search of an optimal COPc. The results indicate that the optimized COPc can further be enhanced by around 20%. The performance efficiency of an optimized ABC-ADC cascade system incorporating a microturbine system is then investigated. Compared to the experimental ABC-ADC cascade system, the optimized system’ total coefficient of performance is demonstrated to improve by 18%. The primary energy saving ratio is also promoted from 9.8% to 18%. Moreover, 68.92% of the gas turbine’s dissipated energy is able to be recovered by the optimized ABC-ADC system. As far as application is concerned, this cascade system has been demonstrated to be superior to standalone heat-driven chillers with great commercial potential for implementation in industries where low-grade waste heat is readily available.