Adsorption Chiller Research Articles

Waste-Derived carbon porous materials for enhanced performance in adsorption chillers: A Step toward a circular economy

Waste-Derived carbon porous materials for enhanced performance in adsorption chillers: A Step toward a circular economy

Modeling of bed-to-wall heat transfer coefficient in fluidized adsorption bed by gene expression programming approach

Adsorption cooling and desalination methods with adsorption chillers (AC) are promising in energy technologies. However, the low-performance coefficient and bulkiness of traditional packed-bed ACs, primarily due to the high voidage of the sorbent beds leading to low heat transfer coefficients, pose significant challenges. Despite numerous attempts, a practical solution to this problem is yet to be found.In response to this challenge, we propose a novel approach: a fluidized adsorbent bed instead of the traditional packed bed. We also introduce gene expression programming (GEP) as an innovative artificial intelligence (AI) method for modeling the bed-to-wall heat transfer coefficient in the adsorption bed. Our study includes calculations and model validation for a heat transfer adsorption bed reactor designed for low-pressure adsorption processes. The fluidizing agent of the adsorbent bed was water vapor generated in the evaporator. Silica gel was used as the parent adsorption material in our tests. The heat transfer coefficient was successfully validated and determined through experiments and estimated using the formulated (b-t-wHTc) meta-model. The data evaluated by the model aligns well with the experimental results. Our calculations demonstrate that the GEP-based model accurately predicts the heat transfer coefficient and is suitable for analyzing the fluidized adsorption bed reactor.The outlined studies serve as a benchmark for subsequent simulations of the intensified heat transfer adsorption bed reactor, as they are integral to project No. 2018/29/B/ST8/00442, titled “Research on sorption process intensification methods in modified construction of adsorbent beds,” supported by the National Science Center in Poland.

Systematic screening and evaluation for an optimal adsorbent in a facade-integrated adsorption-based solar cooling system for high-rise buildings

Solar-powered adsorption chillers are a climate-friendly solution for building cooling, but costs and space requirements limit their widespread adoption. Recently developed adsorption cooling facade systems (ACFS) save installation space and further reduce CO2 emissions. The performance of ACFS depends on the implemented adsorbent. To achieve low costs and high performance of ACFS, this study systematically screened and scored adsorbents using the analytic hierarchy process (AHP) method, focusing on price, stability, driving temperature and adsorption capacity. This method narrowed down 293 adsorbents to top 10 scored adsorbents including 4 silica gels, 4 active carbons and 2 molecular sieves. The adsorbent-specific performance is evaluated by numerical simulation, revealing silica gel Type A++, Type 2560, Siogel and molecular sieve AQSOA-FAM-Z02 have peak adsorber temperatures 1.5–9.3 °C lower and increase solar cooling efficiency (SCE) by 25–27 % compared to reference adsorbent Zeolite 13X. A sensitivity analysis of the Dubinin-Astakhov equation shows increasing E and decreasing V leads to an only minor adsorber temperature decrease and minor system efficiency increase. Lower temperatures and higher capacity cannot guarantee better system performance. This underscores that improving system performance cannot be achieved solely through adsorbent optimization but requires system optimization in parallel.

Experimental studies of activated carbon/graphite composite adsorbent for improved performance of packed and coated bed adsorption cooling system

In this study, composite adsorbents are developed by using various compositions of activated carbon (AC)/polyvinyl alcohol (PVA) with graphite powder (GP). The optimal adsorption material chosen for the adsorption cooling system (ACS) is found to be composite A, which comprises 93 % AC, 5 % graphite powder, and 2 % PVA. This selection is made based on the physical characterization of the composite materials by BET, FESEM, adsorption capacity, desorption capacity and thermal conductivity tests. The specific cooling power (SCP), coefficient of performance (COP), and exergetic COP of the adsorption chiller are experimentally evaluated. By maintaining the optimal desorption and condenser temperatures (Tdes = 70 °C and Tcon = 35 °C), the maximum COP, SCP and exergetic COP of the system are found to be 0.582, 206 W/kg and 0.19 for packed bed and 0.738, 261.37 W/kg and 0.25 for coated bed, when the adsorption temperature (Tads) = 30 °C and evaporation temperature (Teva) = 25 °C. The Freundlich isotherms exhibit a better correlation with the vapour pressure of methanol. The samples exhibited no deformations after 17 adsorption/desorption cycles, confirming the durability of the activated carbon. The more uniform coating thickness and smooth surface structure could ensure long-term stability and performance of the adsorbent.

Dynamics of water adsorption on SAPO-34: Comparison of three adsorbent bed configurations of adsorption chillers

Intensification of the adsorption dynamics is a strategic way to make adsorption chillers and heat pumps more competitive with conventional vapour compression systems. This can be achieved by consolidating the adsorbent bed with a heat exchanger to enhance heat transfer. This work investigates the dynamics of water adsorption on a commercial adsorbent SAPO-34 for three bed configurations, namely, a reference bed consisting of a monolayer of loose beads located on an aluminium plate, and two consolidated beds – a monolayer of beads glued to the plate, and a homogeneous coating of the plate prepared with binder. The morphology and texture of the prepared beds were studied by optical and scanning electron microscope techniques as well as by low temperature nitrogen adsorption. Six binders involved, both organic (hydroxyethyl cellulose, polyvinylpyrrolidone, polyaniline) and inorganic (heat-conductive compound CPTD, bentonite clay, colloidal silica sol), produced varying effects. It was found that the most preferred configuration involves SAPO beads glued to the plate with bentonite for which the heat transfer was enhanced by a factor of 1.2–1.7 while maintaining sufficient mass transfer. The effective heat transfer coefficient was measured for the most promising binders and selected configurations, and varied between 120 and 248 W/(m2 K). The heat transfer acceleration permitted the specific cooling power (at a conversion of 0.8) to increase from 2.7 kW/kg for loose beads of 0.8–0.9 mm size to 3.5 kW/kg for the same beads bound with bentonite. Thus, gluing pre-made commercial adsorbent beads with heat-exchanger with suitable binders presents a simple and promising method to enhance the adsorption dynamics, resulting in a more compact design of adsorption chillers.

Experimental and numerical studies on moisture adsorption/desorption characteristics across the circular fin tube desiccant coated heat exchanger

To improve the energy transfer abilities, enhance the quality of air, and curtail the growth of microorganisms, the desiccant coated heat exchangers are a capable substitute compared to conventional heat exchangers due to their capability of decoupling the sensible and latent loads and utilizing low-grade thermal energy. The concept of desiccant coated heat exchangers (DCHE) can be employed in various heat exchange/transport systems like heat pumps, atmospheric water harvesters, adsorption chillers, and air conditioners. Thus, in this research work, a circular fin tube desiccant coated heat exchanger (DCCHE) has been proposed and designed and a dynamic numerical model is established for simulating the combined heat and mass transport occurring across the adsorption/desorption process of a DCCHE employing finite element approach. The moisture and temperature distribution and flow of fluid are considered in the transient numerical model covering several domains such as water flow, air flow, and the coated desiccant. The desiccant material utilized in the current analysis is silica gel. The validation study showed good agreement, and the maximum error between the experimental result and simulated model for the humidity ratio of air and temperature of outlet air were observed to be ± 8 % and ± 7 %, respectively. A parametric analysis is carried out to assess the effect of varying the different input parameters on DCCHE’s performance. The field emission scanning electron microscopy results concluded that a uniform coating is formed on the circular fin surface. The experimental examination on the sorption kinetics of the silica gel showed that the moisture uptake capability was 0.34 g/g. Moreover, the proposed circular fin tube desiccant coated heat exchanger has been compared with the conventional plate type fin tube DCHE to assess its performance in terms of thermal coefficient of performance and specific dehumidification energy.

4E evaluation and optimization of a hybrid CCHP system integrated PEM fuel cell and adsorption chiller

In order to promote the sustainable development of green energy, this study developed a hybrid combined cooling, heating and power system primarily consisting of proton exchange membrane fuel cells and an adsorption chiller. The system is designed to provide both power generation and heating, while also offering cooling capabilities. Initially, the models of the proton exchange membrane fuel cell stack and adsorption chiller were rigorously validated against experimental data, showcasing remarkable consistency with discrepancies below 3.5 %. Subsequently, the investigation delved into the influence of operational parameters for the proton exchange membrane fuel cell stack and adsorption chiller on various performance. These metrics encompassed energy efficiency, exergy efficiency, annual costs, and annual greenhouse gas reduction. Finally, the NSGA-II optimization algorithm was employed to perform multi-objective optimization on the system. The outcomes demonstrated that, in comparison to the initial configuration, the optimized system achieved a 22.51 % reduction in annual greenhouse gas emissions, while simultaneously enhancing energy efficiency by 14.72 %, exergy efficiency by 0.34 %, cooling power by 3.14 %, and heating power by 42.63 %. Moreover, the annual cost experienced a substantial decrease of 69.86 %.

A case study on optimizing industrial air conditioning with thermal solar energy in Egypt

This study investigates the feasibility of implementing a solar-assisted adsorption chiller in an industrial building at the Oriental Weavers International factory located in 10th of Ramadan City, Cairo, Egypt. The objective is to replace an inefficient split air conditioning system currently used to cool the Jacquard units during carpet manufacturing. The research begins by analyzing the performance of the existing cooling system to establish a baseline. It then explores the potential energy savings achievable by replacing the current system with a solar-assisted adsorption chiller. The existing oversized boiler will serve as an auxiliary heater for the new system. TRNSYS simulation tools are employed to model the building, simulate its thermal performance, and develop a solar-assisted cooling system. A parametric analysis investigates the impact of varying collector area and hot/cold-water storage tank volumes on key energy performance indicators. This analysis aims to determine the optimal component sizes needed for efficient system operation. Results indicate that a collector area of 90 m2 offers the optimal balance between performance and cost. There are minimal benefits to increasing the collector area beyond 100 m2. Larger hot water storage tanks demonstrate reduced outlet temperatures, reaching a maximum solar fraction at a capacity of 4 m³. The impact of cold-water storage tank volume on the system is minimal. The economic assessment reveals a payback period of 7.6 years, an Internal Rate of Return (IRR) of 14.3 %, and a Return on Investment (ROI) of 34.5 % over a 10-year period, indicating the financial viability of the proposed system. Furthermore, the solar-assisted adsorption chiller system has the potential for substantial environmental benefits. The system has the capacity to reduce CO2 emissions by up to 7200 metric tons. This highlights not only the technical feasibility of the system but also its economic and environmental advantages.

Novel solid oxide fuel cell system integrating adsorption cooling, heating, and carbon dioxide fertilization for greenhouse tomato production

Fuel cells have been widely used for power sources in the power plant, building, and transportation sectors, while few attempts have been made to use fuel cells for agriculture. Heating costs make up a high proportion of agricultural operating costs, and fossil fuels are the primary fuels used, which affects agricultural income according to changes in international oil prices. This study proposes a novel solid oxide fuel cell(SOFC) system integrates adsorption cooling, heating, and carbon dioxide fertilization for greenhouse tomato production. To confirm the superiority of the proposed system (Case 3) in terms of efficiency, its energy consumption is compared with that of the reference systems (cases 1 and 2). Case 1 uses only the air-cooled scroll chiller while Cases 2 and 3 utilize both the air-cooled scroll chiller and the adsorption chiller as a heating and cooling device for the horticulture. In order to reduce the energy consumption for the horticulture thermal management, electrical and thermal energy required for the adsorption chiller are supplied by the SOFC. Case 3 supplied SOFC exhaust gas to fertilize carbon dioxide in horticulture for photosynthesis of the tomato. To determine the heating and cooling loads for horticulture, horticulture energy modeling has been developed based on target temperature, weather data, and tomato evapotranspiration using TRNSYS®. The total power consumption in Case 3 is reduced by up to 12 % during the heating season compared to Case 1, but it increases by up to 6.2 % during the cooling season. For Case 2, there is a savings of 9.8 % during the heating season but an increase of up to 4.1 % during the cooling season compared to Case 1. The study contributes to reduction of the energy consumption for the greenhouse crops production. This finally results in the significant reduction of the carbon emission and the enhancement of the economics in agricultural field.

Operating characteristics of an adsorption chiller with heat and mass recovery scheme for low-grade heat source

Waste heat recovery from data center is regarded as one of the most promising application of adsorption refrigeration in the future. To better understanding of the system, the operating characteristics, including temperature, pressure and heat exchange capacity, of the adsorption chiller for such low-grade heat source should be revealed. Unfortunately, they have not been detailedly reported yet. In this paper, lab experiments on a silica gel-water adsorption chiller prototype with heat and mass recovery scheme are implemented. The results show that this chiller can achieve 3.17 kW of average cooling power and 0.482 of coefficient of performance under the conditions of 60 °C hot water inlet temperature, 30 °C cooling water inlet temperature and 22 °C chilled water inlet temperature. The temperature and pressure characteristics reveal that adsorbent bed desorption phase results in the worsening of the deviation from ideal cycle when compared to its adsorption phase. Hence, the heat and mass transfer performance of bed in desorption phase is prioritized to be enhanced. The analysis on heat exchange capacity indicates that mass recovery operation is more beneficial to the adsorption reaction. The optimal heat recovery time is found to be 24 s while the heat recovery efficiency is 0.711.

Experimental evaluation of Adsorption Heat for Water vapour/Silica gel pair for chiller application

Isosteric adsorption heat is crucial in assessing adsorption cycle performance. Typically, adsorption heat is indirectly estimated from the isotherm equation fitted to the experimental uptake data. This indirect method is susceptible to the accuracy and choice of isotherm equation. Consistency of this indirect method with actual adsorption heat measurements is rarely examined. Present work addresses this research gap by simultaneously measuring adsorption uptake and heat. This is achieved by incorporating heat flux sensors within an existing constant volume variable pressure (CVVP) setup. The measurements are carried out for water vapour/RD-silica gel pair with temperature and pressure ranging from 298 to 363 K and 0.15 kPa to 6.3 kPa respectively. Two popular isotherms viz. Dubinin–Astakhov (D–A) and Tóth isotherm equation are used to estimate the indirect adsorption heat. Both isotherm equations show a good fit with the experimental uptake (< 5% deviation). Interestingly, indirect adsorption heat estimated using Tóth isotherm fails to predict (∼15% deviation) the uptake dependent adsorption heat trend shown by calorimetric data, whereas D–A isotherm agrees well (<5% deviation). Therefore, the present work forms fundamental basis for identifying suitable isotherm equation, which is consistent with experimental adsorption uptake as well as heat data. Subsequently, a comparison of theoretical coefficient of performance (COP) for water vapour/RD-silica gel adsorption chiller is undertaken, based on indirect adsorption heat values available in the literature. The comparison reveals that COP prediction is sensitive to adsorption heat. This further emphasizes the necessity for experimentally measuring adsorption heat.

Utilizing waste heat from data centers with adsorptive heat transformation – Heat exchanger design and choice of adsorbent

The electricity and water consumption of data centers is growing on a global scale. A shift towards liquid cooled racks in combination with thermally driven cooling can help to reduce the electricity and water demand associated with the necessary heat rejection. To quantify the potential of adsorptive heat transformation devices in reducing the electricity and water demand, the prediction of thermal efficiency, heat flow rates and energy efficiency ratio is required. To this end, a numerical model is newly developed using basic adsorption heat exchanger theory. This model can predict the necessary performance indicators with respect to temperatures and volume flow rates, heat exchanger design and adsorbent. The full performance map of a market-available adsorption chiller (71 points) and own measurements are used for calibration and rigorous validation of the model. An average deviation (experiment vs. calculation) of 8.3 % in terms of thermal efficiency and 7.2 % in terms of heat flow rates is achieved, indicating a very good agreement for a wide range of temperatures. At a moderate liquid cooled rack outlet temperature of 50 °C, a heat rejection temperature of 26 °C and a cold aisle inlet temperature of 18 °C the cooling power of the silica gel reference chiller of 5.3 kW can be increased by 59 % to 8.5 kW at a partial energy efficiency ratio (pumps and control, no fans) of > 20 by assuming MIL-100(Fe) as adsorbent on a flat-tube lamella heat exchanger. The model can be used in subsequent annual system simulations to quantify the savings in electrical power and water consumption, which strongly depend on the ambient conditions.

Dual-template synthesis of SFO-type aluminophosphate with enhanced water-sorption-driven cooling performance

Water-based adsorption chillers (ADC) driven by low-grade thermal energy are environment-friendly alternatives to the traditional compression ones to realize the net zero carbon target. Aluminophosphates molecular sieve (AlPOs) is an excellent material for water-based adsorption applications. However, AlPOs suffers from relatively high cost attributed to the extensive use of expensive structure direct agents (SDAs). This study employed a dual-template method, using cheap organic amine as a dual-template, to synthesize low-cost and excellent adsorbent AlPOs with SFO topology (AlPO-SFO). AlPO-SFO synthesized with dual templates shows high crystallinity, large micropore volume, excellent water uptake, and low regeneration temperature. AlPO-SFO guided by 4-dimethylaminopyridine (4-DMAPy) and diethanolamine (DEOA) molar composition of 0.4 and 0.1 exhibits large microporous volume (0.30 ml g−1), high water uptake (0.26 g g−1 at P/P0 = 0.25) and low regeneration temperature (65 °C). Importantly, this AlPO-SFO exhibits a high coefficient of performance (COP) of 0.89 for cooling at a low driven temperature of 64 °C. The additive amine providing alkaline medium ensures the practical synthesis of AlPO-SFO when expensive 4-DMAPy decreases, endowing the 42 % reduction of the raw material cost. The results provide a cheaper synthesis route of AlPO-SFO, which is conducive to its large-scale production as a distinguished adsorbent for adsorption chillers.

Experimental studies on the impact of adsorbent particle size on the adsorption chiller performance

Adsorption chiller dynamics and its effect on the performance are greatly influenced by the adsorbent particle size because they govern both the micro (intra-particle) and macro (inter-particle) heat and mass transfer resistances within the adsorber bed. The net effect of adsorbent particle size and shape on the overall cooling system performance is addressed here. Initial CFD analysis of columnar adsorber bed with silica gel + water as the working pair, assuming uniform spherical adsorbent, showed increased uptake capacity with smaller sized (0.23 mm radius) particles over bigger sized (0.8 mm radius) ones despite smaller vapor penetration depth of the former. Subsequently, the effect of adsorbent particle size and shape on the overall cooling system performance is investigated experimentally in a single-stage one-bed mode for RD 2060 (0.8 mm radius) and RD 3070 (0.23 mm radius) silica gel specimens. Though the smaller size of RD 3070 is favourable for the adsorption kinetics at the particle level, its non-spherical shape and highly non-uniform size distribution resulted in significantly lower permeability and thermal diffusivity of the packed adsorber bed, thus hindering the cyclic steady state throughput. For the same operating conditions, RD 2060 and RD 3070 yield a cooling capacity (CC) of 107 W and 22 W, respectively. Further, the coefficient of performance (COP) drops by 73% in the case of RD 3070. The present study indicates that the adsorber bed design must consider both the adsorbent size and shape, in addition to other system operational parameters to enhance performance indicators.

Design of adsorption chillers under rolling conditions in naval applications: Experimental and numerical approaches

International shipping is one of the major contributors to the overall greenhouse gases emissions and therefore its decarbonization is a key priority worldwide. Among the possible energy efficiency measures, the use of waste heat for cooling through adsorption chillers has gained significant attention. However, the proper integration of such kind of chillers on board needs to consider the effect of the rolling movement of the ship. In the present work, two different sorption modules (i.e the couple of adsorber + evaporator/condenser) are experimentally tested in horizonal position and at different inclinations, considering permanent tilting or continuous moving. The results were subsequently used for the implementation in a dynamic simulation model and the design of the chiller for application on passengers’ vessels. Results showed that operation under constant inclination of 30° resulted in a reduction of the cooling energy supplied by 22.5 % for the module with zeolite and by 55.8 % for the module with silica gel. The highest specific cooling energy (SCE) is 0.26 kWh/kg for the zeolite module and 0.18 kWh/kg for the silica gel module. The main issues underlined under tilted operation is the progressive reduction of the water level in the evaporator, which causes incorrect operation of capillary-driven evaporation. Accordingly, the increase of water level in the evaporator was suggested as mitigation strategy. It was however found out that the issue is only relevant if prolonged operation in a tilted condition is foreseen, but not under typical rolling operation with continuous movement.

Performance investigation on dual bed adsorption chiller integrated with a partially covered N-PVT collector

The theoretical performance investigation of the adsorption chiller system integrated with a partially covered N-PVT Collector is mathematically modeled and presented in the paper. The study employs a MATLAB-Simulink integrated interface, and the silica gel-water combination serves as the working pair. The average weather conditions of Shiv Nadar Institute of Eminence for the month of May are taken into account the study. The investigation shows that solar energy integrated with an adsorption cooling system could efficiently provide a cooling effect. The results suggested that, due to the direct integration of the PVT with the chiller system, the influence of cycle operation is significant at the minimum and maximum solar radiation times. An optimization research for the optimal number of collectors for silica gel regeneration revealed that using N = 5 collectors results in an outlet hot water temperature range of 110 0C. During operation, the maximum adsorption capacity of 0.21 kg of water/Kg desiccant is obtained, for providing an adequate cooling effect. The system achieved a specific cooling power of between 50 and 200 W/kg during the process, and a coefficient of performance between 0.15 and 0.23.

AutoML‐based predictive framework for predictive analysis in adsorption cooling and desalination systems

AbstractAdsorption cooling and desalination systems have a distinct advantage over other systems that use low‐grade waste heat near ambient temperature. Since improving their performance, including reliability and failure prediction, is challenging, developing an efficient diagnostic system is of great practical significance. The paper introduces artificial intelligence (AI) and an automated machine learning approach (AutoML) in a real‐life application for a computational diagnostic system of existing adsorption cooling and desalination facilities. A total of 1769 simulated data points containing data indicating a failure status are applied to develop a comprehensive AI‐based Diagnostic (AID) system covering a wide range of 42 input parameters. The paper introduces a conditional monitoring system for adsorption cooling and desalination systems. The novelty of the presented study mainly consists of two aspects. First, the intelligent system predicts the health or failure states of various components in a complex three‐bed adsorption chiller installation using the extensive input data sets of 42 different operating parameters. The developed AID expert tool, based on selecting the best from 42 models generated by the DataRobot platform, was validated on the complex, existing three‐bed adsorption chiller. The AID system correctly identified healthy and failure states in various installation components. The developed expert system is very efficient (AUC = 0.988, RMSE = 0.20, LogLoss = 0.14) in predicting emergency states. The proposed method constitutes a quick and easy technique for failure prediction and represents a complementary tool compared to the other condition monitoring methods.

Enhancing indoor thermal comfort and sustainability: A solar-driven desiccant cooling and adsorption chiller system with environmental impact assessment

Addressing indoor thermal comfort in buildings located in hot and humid climates is a persistent challenge, demanding innovative cooling solutions that are both efficient and environmentally responsible. This paper introduces a new integration of a Phase Change Material (PCM)-based solar desiccant cooling system with an adsorption chiller, a setup designed to enhance indoor thermal comfort conditions while utilizing renewable energy sources. This research simultaneously leverages the heating and cooling capacities of the adsorption chiller, leading to an efficient system performance. The TRNSYS software is used to evaluate the system's behavior in a typical house with moderate cooling demand and characterized by high relative humidity. Two types of solar collectors, the evacuated tube and Wavy Direct Absorption Solar Collectors (WDASC), are evaluated to supply the required thermal energy, providing a comprehensive assessment of the system’s efficiency under different configurations. Additionally, the study conducts a comprehensive Life Cycle Assessment (LCA) to quantify the Global Warming Potential (GWP) of the systems. The results confirm the proposed system's capability to maintain indoor thermal comfort within acceptable Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) ranges. The evacuated tube collector showed marginally better performance (average PMV: 0.018, average PPD: 6.7 %) compared to the WDASC (average PMV: 0.075, average PPD: 7.3 %). Additionally, the evacuated tube collector demonstrates superior energy (75.68 %) and exergy (10.82 %) efficiencies compared to the WDASC. The system utilizing the evacuated tube collector surpasses the WDASC configuration, achieving a higher Coefficient of Performance (COP) of 0.47 compared to 0.41, and emitting lower GWP values of 0.0194 kg-CO2 per kWh of cooling capacity compared to 0.0201 kg-CO2. An analysis of Embodied Energy reveals that the adsorption chiller is the most significant contributor to lifecycle energy consumption, with a quicker Energy Payback Time (EPBT) for the evacuated tube system (2.75 years) compared to the WDASC system (3.94 years). This research thus contributes a highly efficient, sustainable, and environmentally friendly solution to the challenge of cooling in buildings, setting a new standard for future green building practices.

The Effect of Nozzle Configuration on Adsorption-Chiller Performance

Broadly defined climate protection is a powerful incentive in the search for environmentally friendly refrigeration technologies. Adsorption chillers are considered to be one such technology; however, their main disadvantages include a low cooling capacity, a low energy efficiency ratio (EER), and cyclic operation. Thus, a great deal of effort is being put into improving adsorption-chiller performance. In this paper, the influence of the spray angle, the number of nozzles, and the water flow rate through the nozzles on adsorption-chiller performance was investigated. Adsorption-chiller performance was investigated mainly in terms of the cooling capacity (CC), the energy efficiency ratio (EER), and the specific cooling power (SCP). The results indicated that the chiller’s cooling capacity increased from about 210 W to 316 W and that the EER increased from 0.110 to 0.167 when the spray angle of the nozzles was increased from 90° to 120°. It was also reported that increasing the flow rate of water through the nozzles did not improve the average cooling capacity or the other performance parameters but resulted in more stable operation of the chiller. Additionally, using six nozzles instead of three improved the average cooling capacity and EER tenfold.

Computer-aided molecular refrigerant design for adsorption chillers based on classical density functional theory and PC-SAFT

Adsorption chillers are a promising technology for sustainable cooling. The performance of adsorption chillers is highly influenced by the selection of the refrigerant. Still, systematic selection of refrigerants is challenging because evaluating adsorption properties requires significant experimental or simulation efforts. Thus, refrigerant design options are often limited.Here, we propose a systematic refrigerant design method for adsorption chillers assessing refrigerants based on their process performance. Our method quantifies adsorption isotherms by 1-dimensional classical density functional theory (DFT) based on the PC-SAFT equation of state. The method is used to screen over 1800 refrigerants based on their coefficient of performance (COP). We identify refrigerants with higher COPs than commonly used refrigerants and highlight the advantage of a process-based objective function over material-based heuristic selection criteria. Finally, we advance from screening to computer-aided molecular design of the refrigerant, leveraging the efficiency of the DFT model to explore the molecular design space systematically.