Adsorption Refrigeration System Research Articles

Monte Carlo simulation of an ammonia adsorption refrigeration system based on calcium chloride impregnated nanoporous carbon.

We use Monte Carlo simulations to investigate the effect of incorporating calcium chloride salt into nanoporous carbon on the performance of an ammonia-carbon adsorption refrigeration system. Simulations of ideal carbon slit-pores with pore sizes of 1, 2, and 3nm, each containing calcium chloride with ion densities of 0.0, 0.25, and 0.5nm-3, were carried out at temperatures between 0 and 30 °C and ammonia pressures up to 15.0 bar. The results reveal that ideal 1nm pores are able to achieve a good refrigeration performance using waste heat below 100 °C to drive the process, but adding salt to these pores increases the waste heat temperature required beyond 100 °C. However, ideal 2nm pores require the addition of 0.25nm-3 salt to achieve a similar performance, while the 3nm pores were unable to achieve a satisfactory refrigeration performance. Considering that real nanoporous carbons usually feature a variety of specific adsorption sites and non-ideal geometries that should have a similar impact to adding salt, these results indicate that nanoporous carbons with pores in the range of 1-2nm are likely to hold the most promise for adsorption refrigeration applications and that the addition of salt may not always be helpful.

Experimental study of the optimal mixing ratio of metallic additives for improving the performance of the solar activated carbon-methanol adsorption refrigeration system

An activated carbon–methanol system can run on low heat (70–100°C). Methanol is dependable and works well with activated carbon because of several benefits, including an appropriate latent heat of evaporation, a low freezing point, and negligible copper corrosion and steel at temperatures below 100 °C. An experimental study of the thermal performance by increasing the adsorption bed thermal conductivity was conducted. Using0 10 % 20 and %30 % of metallic copper powder with activated carbon to improve the bed thermal conductivity. A sample is prepared with 20 % copper powder to find out the improvement of heat transfer characteristics to the cooling effect. The temperature gradient has been tested with two flow rates to examine the coolant performance and increase. Solar energy can be effectively utilized based on low-grade temperature consumption in such systems. This work aims to make an experimental investigation of the thermal performance of an activated carbon-methanol adsorption refrigeration system to study the effect of the enhanced thermal conductivity of the adsorbing bed. Using 0 %, 10 %, 20 %, 30 % of metallic copper powder with activated carbon to enhance the thermal conductivity of the bed, providing a significant improvement in the system efficiency, specific cooling power (SCP), and coefficient of performance of adsorption cooling. It is found that copper filing with a mass concentration of 20 % are appeared the optimal ratio metallic additive to enhance the thermal performance of the system. Moreover, the effect of the hot water flow rate is studied. Results indicated that the addition of 20 % metallic copper filings to the activated carbon lowered the evaporator temperature to reach -5 and -10 °C for heating water flow rates 3 and 2 LPM, respectively. Also, the addition of copper filing enhances the cycle COP of the system by 49 % and 46 % at hot water flow rates of 2and 3 LPM, respectively. The highest cycle COP of the current system reached was 0.92 for the condition 20 % additives at 3 LPM hot water flow rate. Owning the feature of great solar energy availability and the long daily sunny hours, solar-powered adsorption cooling systems have promising potential applications in Egypt. A mathematical model of the system performance is also studied.

Experimental and theoretical analysis of the solar adsorption refrigeration system under south Iraq climate condition

This study investigates the performance of a solar adsorption refrigeration system utilizing activated carbon and methanol as the adsorbent/adsorbate combination in the context of the climate conditions in southern Iraq. The primary aim is to develop an efficient and environmentally friendly refrigeration technology that can operate off-grid, particularly in regions with limited access to electricity. Through a combination of experimental trials and theoretical analysis, the research explores the impact of factors such as solar radiation intensity, collector design, and operational parameters on system efficiency. The findings reveal that the tubular form of the collector/adsorber enhances system performance by simplifying maintenance and reducing the risk of leaks. Additionally, the study demonstrates the system's capability to cool water significantly, showcasing its potential for practical applications. The key contribution of this research lies in its innovative approach to solar refrigeration technology, offering a sustainable solution for cooling needs in challenging environments. The solar-driven refrigerator achieves a COP of 0.38 (ambient 30 °C) using 5.5 kg of carbon and 0.24 kg of methanol. Collector efficiency reaches 43 % under peak sun (847 W/m2), with a theoretical maximum of 51 % (1000 W/m2). The refrigerator cools 1 L of water from 30 °C to −0.6 °C, demonstrating its potential for sustainable refrigeration and reduced reliance on fossil fuels. These findings contribute to advancing solar-driven refrigeration and reducing reliance on fossil fuels. To counteract climate change, this work lays out a practical road towards sustainable refrigeration.

Thermodynamic analysis for new solutions of data center cooling with adsorption refrigeration and heat pipe

This study investigated the potential of integrating separate heat pipe and adsorption refrigeration systems as a data center efficient cooling system. Compared to water-cooled data centers, this approach demonstrates improved heat transfer efficiency and reduced energy consumption. The effectiveness of heat transfer in this approach is illustrated by applying exergy and entranspy theories. By conducting numerical simulations across five representative Chinese cities with different climates, both Power Usage Effectiveness (PUE) and key cooling system performance indicators are assessed. The analysis reveals that all cities can achieve a PUE below 1.095, realized a 65.87 % and 13.60 % reduction in cooling system energy consumption and entransy dissipation, respectively. Data centers using mechanical chiller cooling cause a high energy consumption. This paper indicates the benefits of integrating heat pipe and adsorption refrigeration systems in reducing energy consumption and optimizing overall data center performance.

Demonstration of long-term cyclic sorption of ammonia in modified expanded graphite-calcium chloride composites for practical applications

The long-term viability of the ammonia‑calcium chloride (NH3−CaCl2) pair in commercial adsorption refrigeration systems faces challenges due to the disintegration of calcium chloride (CaCl2) during multiple ammonia sorption cycles. To address this issue, we conducted a comprehensive study, starting from lab-scale investigations to experiments with full-scale commercial refrigeration systems. We prepared three calcium chloride–expanded graphite (CaCl2:EG/4:1) composite samples (labelled B1, B2, and B3) with varying water content (20–45% by weight), and also used a conventional CaCl2-activated carbon-white cement composite (CaCl2:AC:WC/16:4:1, sample A). The composites were coated over fin tubes wrapped around with wire mesh for this purpose. These composites were tested for structural integrity over 300 continuous cycles in a customized constant-volume single fin-tube adsorption/desorption bed. While all samples initially exhibited similar sorption capacity ∆χof≈0.6−0.7kgNH3/kgCaCl2, sample A experienced a significant deterioration of approximately 60% in capacity within 300 cycles due to agglomeration and volumetric expansion. In contrast, the EG-based samples demonstrated remarkable stability, with B3 maintaining ∆χ≈0.57kgNH3/kgCaCl2 even after 800 cycles. We applied B3 in a 2 TR adsorption refrigerator that uses biomass as fuel to demonstrate <15% cooling power attenuation even after prolonged operation over 800 cycles in practical scenarios. We believe these engineering interventions are necessary to encourage the broader adoption of ammonia-based adsorption refrigeration systems, which are a sustainable choice due to their zero global warming and ozone depletion potentials.

Development and experimental study of a compact silica gel-water adsorption chiller for waste heat driven cooling in data centers

In recent years, data centers have experienced rapid construction, leading to a significant surge in energy consumption, and cooling systems have emerged as prominent energy consumers of data centers. Among the cooling technologies, liquid cooling allows higher cooling circuit temperatures and provides potential for heat recovery. As a thermally driven cooling technology, adsorption refrigeration systems offer an alternative way to compression refrigeration systems by utilizing low-grade waste heat from liquid-cooled circuits to produce chilled water for air-cooled components. In this study, a compact silica gel-water adsorption chiller is developed for a small modular data center and experimentally investigated under extremely low driving temperatures. Under the typical summer conditions with the hot/cooling/chilled water inlet temperatures of 50 °C/30 °C/23 °C, the adsorption chiller achieves the cooling power of 4.9 kW and the COP of 0.50. When the cooling water inlet temperature changes from 32 °C to 24 °C, both the cooling power and COP show significant improvements, from 3.04 kW to 10.50 kW and from 0.44 to 0.66, respectively. Moreover, the increase of the hot water inlet temperature from 48 °C to 56 °C can enhance the cooling power to some extent, while the chilled water inlet temperature has little influence on the performance. The experimental results demonstrate the feasibility and performance of the developed adsorption chiller in data center waste heat driven cooling. Besides, potential adsorbents and possible optimization strategies are presented for performance improvement based on adsorption potential method.

Performance evaluation of a high-efficient hybrid adsorption refrigeration system for ultralow-grade heat utilization

50–80 °C heat sources are abundant in renewable energy areas and industrial processes. However, they are difficult to be effectively used due to their ultralow grade. In order to solve this problem, this paper presents a high-efficient hybrid adsorption refrigeration system combing with desiccant coated heat exchangers. In this study, the performance of the hybrid system is experimentally investigated and parametric effects are fully discussed. Results indicate that the hybrid system operates efficiently across a wide heat source range of 50–80 °C. A high-temperature hot water facilitates the cooling production of the hybrid system, while a low-temperature hot water is more beneficial to the COP promotion. Also, a lower cooling water temperature, higher air temperature, higher relative humidity and longer switch time can enhance system performance. The optimal cooling capacity is quantified as 4579 W when powered by 80 °C hot water and the COP reaches its maximum of 0.673 under a heat source temperature of 50 °C. Comparison results show that compared with present systems, the hybrid system has greater adaptability as well as higher efficiency in utilizing 50–80 °C ultralow-grade heat sources, and can satisfy the simultaneous demand for cooling and dehumidification, which offers a promising way to high-efficient energy utilization and sustainable development.

Solar adsorption refrigeration system: Comparison between equilibrium, universal and transient model

Three models of different level of complexity are detailed in order to predict the cold production of a solar cooling device. The transient model consists on a heat and mass transfer model of the absorber, coupled with a solar collector model which conceives the ambient temperature as variable along the day and comprehends the evolution of the solar radiation throughout the day according the locations of the prototype to be analyzed in addition to the ideal models of the condenser and evaporator. The Equilibrium and Universal Model are both lumped models in which the spacial distributions of the variables and the heat and mass transfer resistance in the system are disregarded. The advantages and disadvantages of each model are discussed.The results of the models are compared with experimental data obtained from four methanol/activated-carbon adsorption refrigerator prototypes. The cold generated is underestimated 12%–20% by the transient model, while it is overestimated 22%–46% by the equilibrium model and 53%–66% by the universal model. Even when the transient model allows some improvements, is a useful tool to analyze the impact that different variables of a solar adsorption refrigeration system have in the generation of cold. The simpler models can be used for preliminary design and feasibility studies of solar adsorption refrigeration devices (SARS) whose results can be extrapolated on the premise of its overestimation of cold generation approximately given by this work.

Performance Assessment of Silica Gel-Water Solar Adsorption Refrigeration System in Egypt

Performance Assessment of Silica Gel-Water Solar Adsorption Refrigeration System in Egypt

Effect of refrigerant absorbent combinations in the corrosion resistance of copper as structural material in absorption refrigeration systems (ARS)

ABSTRACT The present research was focused on analyzing the corrosion resistance of copper in the presence of refrigerant-absorbent combinations such as lithium bromide (LiBr), lithium nitrate (LiNO3) and calcium chloride (CaCl2), used in Adsorption Refrigeration Systems (ARS). Electrochemical techniques such as open circuit potential, electrochemical impedance spectroscopy, electrochemical noise analyses and potentiodynamic polarisation curves were applied to study the test solution combination effect on the corrosion rate of copper as a structural material in ARS. OCP analyses reveal that the E corr shifted based on the temperature and test solution. Meanwhile, when the copper was immersed in LiBr/H2O + CaCl2 at 80°C, the corrosion current density (I corr) was lower (0.003 mA/cm2). Also, The R p estimated from EIS shows an increase at 80°C. Micrographs of the copper surface immersed in LiBr/H2O and LiBr + CaCl2 observed cracks and pits. But also, when the corrosion product layer was removed, a less heterogeneous surface was revealed.

Dynamic variation of bed parameters and time optimisation of solar adsorption refrigeration system based on CFD simulation

One major reason for the limited application of adsorption refrigeration systems is their lower refrigeration efficiency and performance compared to other alternatives. Additionally, there is limited research focused on optimizing the system performance over time. This paper presents a numerically validated thermodynamic model to analyse the effect of adsorption time on the performance efficiency enhancement of a solar adsorption refrigeration system. The adsorption rate model proposed by Sokoda and Suzuki has been used to evaluate the adsorption and desorption characteristics of water vapor on silica gel and the solar collector system has been fitted to a heat flow density equation based on measured concentrated solar heating. The water vapor adsorption capacity on silica gel as a function of temperature and pressure in the adsorption bed has been numerically evaluated during the four stages of the cooling cycle, namely adsorption, preheating, desorption, and cooling. The coefficient of performance and specific cooling power have been utilized as the major performance indicators, in the context of the influence of adsorption time on the refrigeration performance of the system. The simulation results revealed that, although increasing the adsorption time increased the system's cooling capacity, it also prolonged the cycle time and adversely affected the dynamics of preheating and desorption processes (due to increased solar input). As a result of the numerical simulation, an optimum value of adsorption time has been predicted to be 71 min corresponding to a coefficient of performance equal to 0.476 and a specific cooling power equal to 28.6 W/kg.

Dynamic simulation and exergy-economic assessment of solar thermal refrigeration systems in different climates

In this paper, the performance of solar-thermal cooling systems for air conditioning application is investigated in different climates of Iran. Diverse climate types are considered which makes the results applicable to other countries. Available commercial refrigeration cycles that are capable of integration with solar-thermal collector systems including the closed liquid absorption cycle, closed solid adsorption cycle, and desiccant cycle are studied. First, a solar and climatic map is proposed and the representative cities have been selected for each climate. Then, the climate parameters related to each region are extracted to create an hourly database. Also, the cooling load of a reference building is modeled based on the climate database, each refrigeration cycle is simulated using thermodynamic equations, and the dynamic model is generalized daily for the hot season in each city. In the last step, each cooling system is examined using an exergy-economic analysis, and technical and economic indicators are compared. The results show that the most suitable solar-thermal refrigeration cycle that can be installed in the central plateau and semi-arid areas of Iran is the closed-cycle liquid absorption system. The annual average exergy-economic factor and the annual solar fraction in this cycle are 0.7578 and 0.57, respectively. In the southern coastal areas, due to the high humidity and air temperature in summer, the solid desiccant refrigeration system with an exergy-economic factor of 0.6978 and a solar fraction of 0.2416 is preferred. The suitable solar-thermal refrigeration cycle in the cold and mountainous regions of Iran is a solid adsorption system with a silica gel absorber. The annual solar fraction and average annual exergy-economic factor in this cycle are 0.5158 and 0.7394. Also, in northern moderate regions, the solid adsorption refrigeration system with an average annual exergy-economic factor of 0.409 and average exergy efficiency of 0.12 is comparatively beneficial.

Dynamic simulation and exergy analysis of adsorption chiller powered by low-grade waste heat from a fuel-cell system: Effect of multibed configuration and time constant

Energy usage for space cooling and air conditioning has been rapidly growing in recent years and is expected to increase further owing to global warming and climate change. Adsorption chillers can provide an eco-friendly solution to space cooling because they utilize low-grade thermal energy such as waste hot water produced by the primary power-generation unit. In this study, dynamic analysis of a fuel-cell-system-driven adsorption refrigeration system was performed to expedite the optimal multibed configuration and its operating conditions. The scope of the study was extended to investigate maximizing the waste heat utilization achieved via exergy analysis of multibed configurations. The adsorption-to-desorption time ratio was integrated into the physical configuration of the adsorption chiller, and a new variable was introduced as a “time constant” that controls the cycle time and, under ideal conditions, equates the heating requirements of different bed configurations. Dynamic simulations for different bed configurations were conducted to evaluate the performance, specific cooling capacity, and unutilized exergy in the outlet waste stream. Under the operating conditions of 25 °C and 80 °C cold water and hot water temperatures, respectively, the five-bed configuration with a time ratio of 0.25 proved to be optimal, resulting in increases of 45.8%, 10.2%, and 15.1% in the specific cooling capacity, performance, and exergy efficiency, respectively, compared with those of the conventional two-bed configuration. The four-bed configuration yields very similar results, but with a slightly lower specific cooling capacity.

Performance analysis of adsorption refrigeration using a composite adsorbent with improved heat and mass transfer

Adsorption refrigeration is a typical environmental protection and energy-saving waste heat utilization refrigeration technology. However, improving the heat and mass transfer performance of adsorption beds is crucial to the wide-spread applications of adsorption refrigeration systems. In this paper, three types of composite adsorbents are proposed: adsorbents with improved heat transfer, improved mass transfer, and simultaneously improved heat and mass transfer. Both characteristics of adsorption and heat transfer are tested and compared. Based on the experimental results, the use of these three types of composite adsorbents in the adsorption refrigeration system is further examined. The results indicate that the silica gel (SG)/MIL-100/CF (SGMC) composite outputs the highest cooling capacity and exhibits a coefficient of performance (COP) comparable to that of a composite adsorbent with improved mass transfer. The cooling capacity and COP of the proposed SGMC system compared with those of the traditional SG–water system increase by 22% and 12.8%, respectively, and the refrigeration cycle time is shortened by 16.7%. Based on the optimal SGMC system, the impact of operation parameters is further investigated, and optimum parameters are selected to enhance the overall system performance.

Performance of Solar Adsorption Cooling System Using Methanol and Activated Carbon as a Working Pair

The need for renewable energy sources is higher than ever due to rising global warming, climate change, and ozone depletion. For refrigeration and air conditioning applications, adsorption refrigeration systems are viable alternatives cooling techniques. This study is a topic and part of the M.Sc. thesis. A field solar-powered ice maker unit was created, studied, tested, and evaluated on the 13th and 30th of May, 2022. Activated carbon and methanol pair was used to set up a refrigeration system in Baghdad (Al Dora). Experimental tests were carried out outdoors to determine the coefficient of performance COP and specific cooling power SCP of the system. The results showed that the lowest temperature obtained at the evaporative surface was (4 oC) and (3 oC) for the 13th and 30th of May, respectively, at the opening time of the valve between the evaporator and the generator at 9 pm. In addition, the amounts of methanol condensate were (0.340 kg) and (0.344 kg) for the 13th and 30th of May, respectively, while the maximum cycle coefficient of performance (COP) and specific cooling power SCP are about 0.57 and 0.14 kW/kga.c , respectively

Study of Dynamic Sorption in Adsorption Refrigeration Cycle

This paper shows the characteristics of temperature and adsorbed (water vapor) mass rate distribution in the adsorber unit which is the key part to any adsorption refrigeration system. The temperature profiles of adsorption/desorption phases (Dynamic Sorption) are measured experimentally under the operating conditions of 90oC hot water temperature, 30oC cooling water temperature, 35oC adsorption temperature and cycle time of 40 min. Based on the temperature profiles, The mass transfer equations for the annulus adsorbent bed are solved to obtain the distribution of adsorption velocity and adsorbate concentration using non-equilibriummodel. The relation between the adsorption velocity with time is investigated during the process of adsorption. The practical cycles of adsorption and desorption were stated dependent on the variables obtained from the experiment and equations calculations.The results show that the adsorption velocity is diminished after a period of 20 min. The maximum value of the adsorbed water vapor concentration on silica gel is 0.12 kg water/kg adsorbent (adsorption phase) and the minimum value of the water content into silica gel is 0.04 kg water/kg adsorbent (desorption phase) producing a dynamic sorption of kg water/kg adsorbent.

Energy and exergy analyses of a hybrid adsorption refrigeration system for simultaneous production of cold water and dry air

Current adsorption refrigeration systems are limited by dehumidification methods and produce either cold water or cold dry air. The single cooling product greatly hinders their application into situations where multiple cooling outputs are needed. In order to address this issue, this paper introduces a hybrid adsorption refrigeration system using efficient desiccant coated heat exchangers to provide both cold water and dry air via the deep utilization of input heat sources. In this study, the performance of the hybrid system is experimentally investigated from a combined perspective of energy and exergy. Results show that the hybrid system can simultaneously output cold water and dry air with a heat source of 50–80 °C. A low-temperature cooling water is beneficial to system performance, while an optimum input hot water temperature exists. At a coolant-side temperature of 25 °C, the COP reaches its maximum of 0.238 under a heat source temperature of 60 °C, and the highest exergetic efficiency is quantified as 13.9% when powered by 50 °C hot water. Increasing inlet air temperature or relative humidity facilitates the COP improvement but has a negligible effect on the exergetic efficiency. In comparison with a traditional adsorption air conditioning system, the hybrid system has a wider range of input hot water temperatures and is more advantageous in terms of cooling exergy and exergetic efficiency. This hybrid system firstly enables adsorption refrigeration to export dual cooling products of cold water and dry air, which is expected to extend adsorption refrigeration into fully automatic industrial fields.

Simulation of the performance of continuous solar-powered adsorption refrigeration system for optimal use in Zaria, Nigeria

Cooling without electricity is the reason for solar adorption refrigeration systems. The epileptic power supply, especially in developing countries, makes solar refrigeration a very attractive option. This is coupled with the abundance of solar energy, making it a favourable alternative power source amongst other power mixes. This article introduces a solar adsorption refrigerator that continually generates cooling using solar energy as a standalone. Thus, this study aims to simulate and analyse the feasibility of refrigeration from a system that uses a blend of zeolite-based adsorbents and water (H2O) as adsorbate pairs via four solar concentrating collectors, two for adsorption and two for desorption using TRNSYS 16.0 simulation software. Unlike the conventional refrigeration system, the compressor was replaced with a solar concentrating collector while other components, such as the condenser, evaporator, and throttling valves, remained. The findings demonstrate that the technology delivered continuous cooling, and due to the comparatively intense beam radiation during the middle of the day, the cooling rate increased.

Performance Assessment of an Ice-Production Hybrid Solar CPV/T System Combining Both Adsorption and Vapor-Compression Refrigeration Systems

The technology of a hybrid solar concentration photovoltaic/thermal (CPV/T) system is an efficient way of converting solar energy to heat and electrical power, in which overall energy-extraction efficiency is at its highest. In this study, numerical dynamic simulation models were developed for a hybrid solar CPV/T system and an adsorption refrigeration system (ARS). Under the climatic conditions of Riyadh all year round, the electrical and thermal powers generated by the CPV/T system were used to estimate the ice production of both the vapor compression refrigeration system (VCS) and the ARS. The CPV/T system can provide a thermal energy of 37.6 kWh and electrical energy of 24.7 kWh a day on average over the year using a 12.5 m2 facing area of Fresnel lenses. The ARS employed an advanced approach which used Maxsorb III adsorbent packed in two aluminum foam beds. An optimum cycle time of the ARS was adapted for each month to match the variation in the thermal energy, while a variable-speed compressor was chosen for the VCS. Due to its higher coefficient of performance (COP), the proposed solar hybrid system can produce 494.4 kg of ice per day while sharing 84.5% of the VCS. The average solar COP over the year of the hybrid system can attain 0.875, which represents a promising value for a solar ice-production system.

Thermodynamic study of integrated proton exchange membrane fuel cell with vapour adsorption refrigeration system

With the rising usage of fossil fuels, there is an urgent need to develop new technologies specifically based on renewable energy sources to power the vehicles running on fuel. A fuel cell is an electrochemical cell that is used to convert the chemical energy of a fuel directly to electric power. Fuels cells possess advantages such as smaller size, high efficiency, silent operation, etc. However, there can be significant variations in the size and power output of the fuel cells depending upon the application. The focus of this paper is to estimate the performance of an integrated system comprising of Polymer Exchange Membrane Fuel cell (PEMFC) and vapour adsorption refrigeration system to produce electric output and cooling effect simultaneously. The adsorption system in this study is based on activated carbon and methanol combination. The effect of operating parameters such as the operating temperature, current density and evaporator temperature on the energy and exergy efficiency of the system is presented. The study shows a remarkable improvement in the performance of the integrated system compared to PEMFC alone. The results show that the system energy and exergy efficiency decrease as the current density value increases. Maximum system energy and exergy efficiency of 63.01% and 29.88% are achieved. In addition, a maximum energy efficiency of 65.39% was reported at an evaporator temperature of 5 °C and a current density of 0.8 A/cm2.