Absorption Refrigeration System Research Articles

Design, analysis, and operation optimisation of a shipborne absorption refrigeration–ice thermal storage system based on waste-heat utilization

The integration of waste-driven absorption refrigeration technology into marine applications is recognized as a promising low-carbon solution. Nonetheless, its practical application does not inherently outperform electric compression technology, primarily due to the absorption system’s inherent thermal inertia and limited adjustability. This characteristic renders the system less responsive to the dynamic refrigeration requirements typically encountered on board vessels. In this study, a shipborne ammonia absorption refrigeration–ice storage system is proposed to balance the cooling load between supply and demand. To evaluate the efficiency of the integrated system for ice storage and cooling during ship sailing, key operational variables including refrigeration temperature, cooling water temperature, and generation temperature are analyzed to assess the thermal cycle performance of the system. A typical shipping route is considered for cooling operation optimisation of the absorption refrigeration–ice storage system. This paper explores four typical cooling-supply strategies and determines the operation modes for the ice storage period and the cooling period based on considerations of energy consumption, energy utilization, and economic factors. The final optimisation results indicate that the combined system has significant advantages based on energy consumption and operation cost. In comparison to compression and absorption refrigeration systems, the proposed system exhibits 52.4% and 8.31% reductions in energy consumption, respectively. Additionally, the operation costs are decreased by 12.27% and 27.41%, respectively, and the life cycle costs are lowered by 11.51% and 32.35%, respectively. The findings of this combined system can provide a technical reference for the design and operation of a ship waste-heat refrigeration system.

Screening HFC/HFO and ionic liquid for absorption refrigeration at the atomic scale by the prediction model of machine learning

Absorption refrigeration is a highly effective method for utilizing renewable energy, as it can be driven by low-grade heat sources such as industrial waste heat, solar energy, and geothermal energy. The development of new working pairs, particularly hydrofluorocarbon/hydrofluoroolefin refrigerants combined with ionic liquids, has been pivotal in enhancing the cooling efficiency of absorption refrigeration systems. These systems rely on the solubility difference between the generator and absorber, making solubility a crucial factor in determining their efficiency. In this context, we have established an advanced solubility estimation model. This model employs the Attention E(n)-equivariant Graph Neural Network (AEGNN) applied to disconnected graphs, enabling comprehensive learning from both topological and Euclidean structural information. Our atomic-scale model demonstrates significantly higher accuracy than traditional group contribution methods, with an average absolute deviation of 0.003 mol/mol from experimental data. Moreover, it encompasses a much broader range of working pairs. Through extensive screening, we have identified working pairs with high estimated solubility differences. Compared to the high-efficiency working pair identified in the literature, the best-screened working pairs exhibit an improvement in solubility differences by more than 0.3 mol/mol under common operating conditions.

Effect of salt on the performance of ammonia absorption refrigeration cycle: A simulation study

To overcome the drawbacks associated with conventional binary mixtures (NH3-H2O and H2O-LiBr) in the vapor absorption refrigeration system (VARS), salt is added to the NH3-H2O mixture. The present simulation study analyzes the influence of adding LiBr and LiNO3 salts within a salt mass fraction range of 0 to 35% on the coefficient of performance (COP) of the NH3-H2O cycle. The simulations are conducted using Aspen Plus software. Furthermore, the influence of generator temperature on the COP and evaporator capacity of the ternary NH3-H2O-LiBr and NH3-H2O-LiNO3 cycles are also studied. The simulation results demonstrate that adding LiBr and LiNO3 salts improves the COP and reduces the initial temperature requirement in the generator of the VARS. Specifically, the NH3-H2O-LiBr cycle achieves the highest COP of 0.645 at an NH3 mass fraction of 55% and a LiBr mass fraction of 25%. This represents an 8.81% improvement compared to the COP of the NH3-H2O cycle. Similarly, the NH3-H2O-LiNO3 cycle exhibits the peak COP of 0.603 with the same NH3 mass fraction and LiNO3 mass fraction of 20%, which is 2.2% greater than the COP of the NH3-H2O cycle. Under similar operating conditions, the COP of the NH3-H2O-LiBr cycle is greater than that of the NH3-H2O-LiNO3 cycle.

Optimization of Triple Effect Vapour Absorption Refrigeration System: A Statistical Approach

Abstract The present manuscript optimized the First and Second Law performance of the triple effect vapour absorption refrigeration systems (TE-VARS) using statistical techniques like Taguchi, Taguchi-based GRA, and RSM-based GRA methods, which provide the most accurate and optimized results. Liquified pertrolium gas (LPG) and Compressed natural gas (CNG) are considered as the source of energy to operate TE-VARS, as the system requires significantly higher generator temperature. Also, volume flow rate of these gases along with the annual operating cost to drive the system have been presented. A thermodynamic model was first formulated using EES software for the computation of the coefficient of performance (COP) and exergetic efficiency (ECOP). The most influential parameters like temperature in the main generator, concentration and pressure at different components are studied and determined using ANOVA and Taguchi methods. The optimum parameters were determined based on the mean effect plot of S/N ratios for COP and ECOP. It has been found that the maximum COP and ECOP were calculated to be 1.915 and 0.15, respectively under the Taguchi method. Furthermore, Taguchi-GRA was used for the simultaneous optimization of the operating parameters and performance of the system. It is observed that the absorber temperature is the most influential parameter for affecting COP and ECOP. Moreover, a RSM-based GRA method was also applied and developed regression models that yield most optimum COP and ECOP as 1.963 and 0.1606, respectively. Comparison shows that the RSM-based GRA method provide the most optimum conditions, which is one of the key finding of the present study. Also, rate of exergy destruction at each component of TE-VARS has been plotted under optimized operating conditions. The optimum volume flow rate for LPG and CNG comes out to be 0.057 and 0.177 m3/s, while the minimum operating cost (yearly) are 299.827$ and 183.293$, respectively.

Utilization of Geothermal Fluid as a Heat Source for Absorption Refrigeration System for Food Preservation – A Case of Bwanda and Gwisho Hotsprings

Zambia has significant geothermal resources with over 86 hotsprings identified. Installation of a 250kW off-grid pilot binary-cycle power plant is currently underway at the Bwanda and Gwisho goethermal site. It is estimated that there is 90,000 herd of cattle in the villages around the pilot power plant. Little milk from these herds of cattle reaches the market due to scarce collection points with cooling facilities. This study assesses the applicability of utilizing exhaust geothermal fluid from a binary-cycle geothermal power plant for powering an absorption refrigeration system (ARS) for storing food, specifically milk. Two absorption systems; Lithium Bromide-water and the ammonia-water ARS are compared. The COPs, energy input and mass flowrates required to produce various cooling loads (40kW – 160kW) are compared. The results show that the exhaust geothermal fluid energy (504kW) is sufficient for powering both ARSs for storing milk to its suitable storage temperature of 4oC. The results also show that the Lithium Bromide-water system is more suitable for this application, because it produces a higher maximum COP (0.76) compared to the ammonia-water system’s maximum COP (0.64), it produces a higher maximum cooling capacity (380kW) compared to the ammonia-water systems maximum capacity (216kW). It requires lower input mass flowrate and pump work at all cooling capacities (40kW – 160kW). Therefore, a Lithium Bromide-water absorption chiller for storing the amounts of milk currently collected in the study area is designed. Optimized design specifications are provided.

Simulation of the heat exchange processes of an absorber and a generator with NH3/LiNO3

A mathematical model is the representation, through equations, of the phenomenon that you want to model. In the context of control systems, models are used to analyze and design control systems. A system is dynamic when its variables change depending on another variable, which is generally time. In this article, an absorption refrigeration system is considered, a model and simulation of it is carried out and the results are compared with the available experimental data, where the existence and uniqueness of the solution in a certain space of finite smoothness is demonstrated, and the certain properties of the solution to the problem.

Triple effect absorption refrigeration systems for the deep recovery of low grade waste heat

With regard to energy conservation, low grade waste heat recovery technology is attracting significant interest. The absorption refrigeration can significantly utilize waste heat. The current researches have devoted little attention to the recovery of waste heat at lower temperature. This paper presents three triple effect absorption refrigeration systems for the deep recovery of low grade waste heat, which can make use of more waste heat as low as 60 °C. The involvement of absorption heat transformer cycle enables the proposed systems to exploit waste heat at lower temperature. The models of three systems are established using EES software. Energy, exergy and economic analysis of three systems are conducted. The results indicate that the best of three systems can achieve a coefficiency of performance of 0.178 and the maximum exergy efficiency is 0.190. The triple effect absorption refrigeration systems not only generate more cold energy, but also demonstrate better economic performance than the previous cascade absorption refrigeration system. Except for the first system, the other two systems achieve reductions of 8.7% and 15.2% in the cost of unit cold energy respectively. This paper provides three novel approaches for producing high grade cool energy from lower temperature of waste heat.

Thermodynamic and Optimization Comparison of a Solar-Powered Compressor-Assisted Combined Absorption Refrigeration and Power Systems

Thermodynamic and Optimization Comparison of a Solar-Powered Compressor-Assisted Combined Absorption Refrigeration and Power Systems

Compression-assisted absorption refrigeration cycle employing organic working pairs for ultra-low grade heat recovery

Solar absorption refrigeration technology is considered an ideal alternative to energy-intensive refrigerated warehouses due to its decarbonization and environmental friendliness. However, it faces challenges in competing with vapor compression refrigeration, such as high driving heat source temperature (>100 °C) and a long payback period. In this paper, we address these challenges by focusing on cycle structure and working pair, and propose a compression-assisted absorption refrigeration cycle (CARC) using R32/dimethylacetamide (DMAC) as working pair. The aim is to significantly reduce driving heat source temperature by adjusting absorption pressure utilizing an auxiliary compressor, enabling the cycle to be connected to low-cost and efficient non-concentrating solar collectors, thereby effectively shortening its payback period. This cycle includes two operating modes: CARC mode powered by solar energy during the daytime and vapor compression refrigeration cycle mode driven by off-peak electricity at night, ensuring 24-hour cooling capacity for refrigerated warehouses. The results indicate that this cycle can flexibly utilize 60∼80 °C solar hot water easily obtained as driving heat source and its evaporation temperature decreases to -20 °C. To assess its performance benefits, a compression-assisted absorption refrigeration system is developed and implemented. By utilizing the limited roof area of a refrigerated warehouse, it can achieve an 18.2 % reduction in electricity consumption and a 24.2 % reduction in carbon emissions compared to the vapor compression one annually. Additionally, during peak electricity demand periods in summer, the system exhibits significant energy-saving effects, and its payback period is about 4.2 years. Ultimately, this cycle provides a viable solution for energy-saving and emission reduction in refrigerated warehouses.

Experimental research of a novel binary solution for diffusion absorption cooling systems

AbstractThe diffusion absorption refrigeration (DAR) systems are driven by heat and utilize a binary solution along with an inert gas as the working fluid. In commercial applications, the choice of binary solutions operating with an auxiliary gas is typically limited to ammonia‐water or water‐lithium bromide combinations. The focus of this study is to explore the viability of using tetrafluoropropene (R‐1234yf, an HFO refrigerant) as the refrigerant, dimethylacetamide (DMAC) as the absorbent, and helium as the auxiliary gas. As the thermodynamic properties of this specific binary solution are yet to be studied, experimental investigations are conducted to obtain these properties. The results allow the establishment of the pressure‐temperature and concentration relationships and determine the mixture‘s enthalpy for various temperatures. Subsequently, both numerical and experimental analyses of the diffusion absorption system are performed. The experimental findings show that, under certain concentrations of the components and with appropriate heat input, temperatures in the evaporator reached below 0 °C. However, the system exhibits low coefficient of performance values, high generation temperatures, and overall inefficiency, suggesting that this particular binary solution may not be well‐suited for diffusion absorption cooling systems.

CONCENTRATION OF NANO FLUID/BASE FLUID SUSPENSION ENHANCE SURFACE CHARGE WITH PH STABILITY FOR LOW TO MEDIUM TEMPERATURE PHASE CHANGE MATERIALS

Zeta potential and poly-dispersivity are used to characterize the samples that is obtained using absorption refrigeration system for low to medium temperature phase transition materials. Salicyclic acid, Benzanilide, Hydroquinone, Potassium thiocyanates, D-mannitol, Alunimium oxide, Iron oxide, and ZnO active concentration with base fluid, aspects including the influence of the PCMs property based on their phase transition mutual interaction are explored. In order to comprehend their behavior and improve their performance, functional materials synthesis and characterization depend heavily on the isoelectric point. Understanding the material surface charge role of the medium's pH stability to the many liquid-phase procedures involved in the synthesis of materials, since it conduct the processes like agglomeration, coagulation, peptization to form solid particles materials. Zeta potential measure, which commonly use concentration of volume fraction methods, electrophoretic migration techniques, are hence a valuable source of data.

Novel working fluid pair of methanol/betaine-urea for absorption refrigeration system driven by low-temperature heat sources

An absorption refrigeration system (ARS) designed for low-temperature heat sources like industrial waste heat, solar-heated water, or geothermal heat can offer substantial energy-saving benefits. This study explores a novel working fluid pair comprising methanol and betaine-urea (BE-UR), forming a deep eutectic solvent (DES) system. This design capitalizes on methanol's high enthalpy of vaporization, the low heat capacity of the working pair, and the appropriate intensity and strength of the hydrogen bonding network within the solution. The proposed fluid pair shows full solubility of BE-UR in methanol at a mole ratio of 1.81 to 1 (methanol to BE-UR), with an equilibrium vapor pressure dropping to 8.59 kPa at 303.15 K. Molecular dynamics simulations unveil a microscale solution structure, showcasing a hydrogen bond network and unbonded methanol in the concentrated working fluid pair. This configuration enhances the absorption process of methanol vapor in the ARS absorption unit. Aspen Plus simulations predict a coefficient of performance (COP) exceeding 0.85, comparable to H2O/LiBr in single effect-ARS and outperforming NH3/H2O in SE-ARS by approximately 30 %, while maintaining a lower cycle ratio of about 2.

EXERGOECONOMIC ANALYSIS OF A HYBRID SYSTEM OF WASTE INCINERATION AND ABSORPTION REFRIGERATION

The current global scenario presents a significant increase in energy demand for HVAC-R (Heating, Ventilation, Air Conditioning and Refrigeration) systems. Considering also that Brazil has the sixth most expensive energy in the world and that there is currently a greater scarcity of natural resources for energy generation, it is necessary to seek viable alternatives with lower energy consumption to the currently most used models, without any quality loss. On the other hand, absorption refrigeration and waste incineration systems can be lines of studies and research to be considered, considering that it is possible to reduce electrical energy consumption and also the environmental impacts that the usual compression refrigeration systems provide. . . In this context, one of the segments of Thermal Systems Engineering studied is the exergoeconomic analysis that comprises the concepts of Heat Transfer, Fluid Mechanics and Thermodynamics, based on the Second Law of Thermodynamics and which uses the notions of optimization and economic analysis. Therefore, this work aims to perform an exergoeconomic analysis of a hybrid system of waste incineration and absorption refrigeration, with the specific objective of developing an exergoeconomic model for the hybrid system. Absorption incinerator-refrigerator. This is an exploratory bibliographic research using an absorption refrigerator from the Center for Research and Development of Self-Sustainable Energy (NPDEAS) of the Federal University of Paraná, in which a model was made with a macroscopic approach of the mass and heat transfer phenomena of a absorption refrigeration cycle, applying the principles of conservation of mass and energy in steady state for each component of the cycle, that is, each component will be considered as a single control volume. It is expected that it will be possible to predict the behavior of the absorption refrigeration system and that it will be possible to develop a scientific analysis tool to design, control and optimize absorption refrigeration systems, using waste incineration. The highest exergy destroyed was verified in the desorber with about 0.9461 kW and through the exergoeconomic analysis of the incinerator, it was found that the cost rate associated with the product of the incineration gases was $ 39,926.31 per year.

Machine learning-based Nusselt number prediction for falling-film evaporators in absorption refrigeration systems

The evaporator serves as a pivotal component of an absorption refrigeration system (ARS), bolstered by improved wettability and mitigation of the irregular arrangement of the liquid film. The complexities of the evaporation heat transfer characteristics of falling films have led to numerous empirical correlations for falling-film Nusselt number (Nu) estimation, demanding substantial computational resources and experimental expenses and limiting their universal applicability. This study used machine learning to predict Nu of a falling-film evaporator. Artificial neural network (ANN) and random forest regression (RFR) models were used to predict heat transfer characteristics and establish a novel Nu correlation using an experimentally derived dataset. Correlations of falling-film Nu were established for six tube types using empirical data, ANN, and RFR predictions and then compared based on experimental falling-film Nu. The ANN and RFR provided high prediction performance within 10 % error and an R2 of 0.985 and 0.999, respectively. The Nu correlations derived from ANN and RFR demonstrated satisfactory agreement, typically within ±15 % error of experimental results lower than that of the empirical correlations. The optimized ANN and RFR demonstrates their promising ability to predict heat transfer characteristics and establish Nu correlations, thereby reducing the need for immense experimental efforts.

Economic optimization and thermodynamic analysis of a novel nuclear district cooling system

“Yanlong” pool-type low-temperature heating reactor (DHR-400) stands at a highly promising nuclear heating technology. However, its annual utilization duration faces constraints when exclusively employed for winter heating. To cope with this challenge, a novel nuclear district cooling system driven by DHR-400 is proposed for the first time in this paper. As the core component of the proposed nuclear district cooling system, single-effect double-lift LiBr-H2O absorption refrigeration system (SDARS) can significantly increase the temperature difference between the supply and return of the primary heating network (PHN), thereby reducing the transmission energy consumption. Despite the significant potential, the optimization design of SDARS has received limited attention. An optimization model for SDARS with the annual cost (AC) as the objective function is developed. Focusing on a real district cooling scenario in Xi'an High-tech Zone, the heat transfer areas of all process units and the operating parameters of all streams in SDARS are optimized. Results demonstrate that the optimal annual average coefficient of performance (AACOP) is improved by 10.63 % and AC is reduced by 5.44 % compared with the Benchmark case. The dynamic payback period for the combined heating and cooling system driven by DHR-400 is reduced by 5.53 years compared to the heating-only system.

Energetic performance of a solar driven absorption refrigeration system integrated with humidification dehumidification desalination system

Integrating cooling and desalination systems with a single heat source is a shortcut technique to meet the shortage of fresh water and energy as well as enhancing the efficiency of energy utilization. In this paper, the energetic performance of a double effect vapor absorption refrigeration system integrated with humidification-dehumidification desalination system has been optimized·H2O–LiCl achieves higher system primary energy ratio and needs lower heat source temperature by 5 °C and 11 °C at evaporation temperature of 10 °C and 4 °C, respectively as compared with H2O–LiBr. Therefore, a parametric study has been performed to get the optimum operating conditions for the integrated system using H2O–LiCl as working pair by varying generation, condensation, and evaporation temperatures. The optimum system conditions are generation, condensation, and evaporation temperatures of 103 °C, 103 °C and 7 °C, respectively. The corresponding system COP, GOR and EUF are 1.471, 2.391 and 3.863, respectively. Finally, the transient performance of the proposed integrated system assisted by solar energy has been evaluated for Marsa-Matrouh city in Egypt. The proposed integrated system could save 71.2 % of the input energy without solar assistance and 88.5 % with solar assistance as compared with separated systems.

Study and development of a technique for measuring concentration and mass flow rate for saline solutions

The purpose of this work is the design and construction of a non-invasive meter for concentration in saline solutions and the proposal of a low-cost mass flow meter for absorption refrigeration systems with LiBr/H2O. The proposed meter makes use of a capacitive sensor relating the electrical capacitance of the LiBr/H2O mixture to the mass fraction of LiBr in the solution. Thus, an experimental apparatus composed of a capacitive sensor with cylindrical geometry, high-frequency oscillators, and a temperature control system was built. Tests involving samples of the solution at concentrations from 50 to 64% LiBr were conducted to reproduce the typical operating conditions of the absorption chiller, establishing correlations between concentration, voltage, and temperature. The matches of these correlations between concentration and density were very good with maximum relative errors of less than 2.5%. The same procedure was performed for the density measurement, achieving a density, voltage, and temperature relationship with errors of less than 0.27%. For the determination of the volumetric flow rates, a turbine-type meter, equipped with a Hall effect sensor W1305347 and an Arduino microcontroller (MEDY FLOW), was adopted, which proved to be effective when dealing with the LiBr/H2O salt solution and good accuracy when compared to conventional meters, showing statistically proven relative errors of less than 4%. The results showed a satisfactory level of repeatability and accuracy with errors of 0.4% and 2.5%, for the range of operation evaluated.

Investigation of a Hybridized Cascade Trigeneration Cycle Combined with a District Heating and Air Conditioning System Using Vapour Absorption Refrigeration Cooling: Energy and Exergy Assessments

The insufficiency of energy supply and availability remains a significant global energy challenge. This work proposes a novel approach to addressing global energy challenges by testing the supercritical property and conversion of low-temperature thermal heat into useful energy. It introduces a combined-cascade steam-to-steam trigeneration cycle integrated with vapour absorption refrigeration (VAR) and district heating systems. Energetic and exergetic techniques were applied to assess irreversibility and exergetic destruction. At a gas turbine power of 26.1 MW, energy and exergy efficiencies of 76.68% and 37.71% were achieved, respectively, while producing 17.98 MW of electricity from the steam-to-steam driven cascaded topping and bottoming plants. The cascaded plant attained an energetic efficiency of 38.45% and an exergy efficiency of 56.19%. The overall cycle efficiencies were 85.05% (energy) and 77.99% (exergy). More than 50% of the plant’s lost energy came from the combustion chamber of the gas turbine. The trigeneration system incorporated a binary NH3–H2O VAR system, emphasizing its significance in low-temperature energy systems. The VAR system achieved a cycle exergetic efficiency of 92.25% at a cooling capacity of 2.07 MW, utilizing recovered waste heat at 88 °C for district hot water. The recovered heat minimizes overall exergy destruction, enhancing thermal plant performance.

Conceptual design and 4E analyses of a tetrageneration system in two different configurations based on poplar sawdust as a local woody biomass fuel

ABSTRACTIn this study, an innovative woody biomass‐fueled hybrid tetrageneration system composed of a single‐effect lithium bromide‐water absorption refrigeration system, a reverse osmosis desalination system, two organic Rankine cycle for the production of cooling, heating, power, and freshwater in two distinct configurations (configurations A and B), compared and discussed using energy, exergy, economic, and exergoeconomic analyses. The poplar sawdust used as a local woody biomass fuel was a by‐product of the Iran Wood and Paper Industries Company, located in northern Iran. The results revealed that the highest heating production and lowest exergy destruction were related to configuration B. The overall cost of configuration A was higher than that of configuration B. A detailed sensitivity analysis was also developed to study the effect of various factors on the thermodynamic and economic performance of the proposed configurations. By increasing the turbine inlet temperature of ORC1 from 625 to 692 K, the total sum unit costs of product of the system in configurations A and B decreased by 20 and 23 $ GJ−1, respectively (about 21%).

Utilizing an Artificial Intelligence Model to Estimate Performance Coefficients in Absorption Cooling Systems

Absorption cooling system is a cooling method used to transfer heat from one environment to another. In this system, the refrigeration cycle is based on a chemical reaction between two different fluids that absorb and expel heat. Generally, the absorption refrigeration system includes a refrigeration fluid and an absorbent heat absorbing fluid. Artificial intelligence is a field of science and engineering that aims to enable computer systems to have human-like intelligence. Artificial intelligence aims to enable computers to perform tasks such as data analysis, pattern recognition, learning, problem solving and decision making. In this study, the change of the inlet and outlet pressure values of the generator in the absorption cooling system and the prediction of the system performance (COP) value with the artificial intelligence model were studied.