Vapour Absorption Refrigeration System Research Articles

Multi-objective optimization of vapor absorption refrigeration system for the minimization of annual operating cost and exergy destruction

A low-grade energy source-driven thermal compressor-based vapor absorption refrigeration system is considered a better alternative for an electrically operated mechanical compressor-based conventional vapor compression refrigeration system. In this article, multi-objective optimization of a single-stage LiBr–H2O vapor absorption refrigeration system (VARS) and a modified VARS are explored by minimizing the total annual operating cost and exergy destruction of the system. Exergy destruction during the operation is inversely proportional to the total annual cost of the system. Multi-objective optimization can be implemented to optimize these conflicting objectives for both systems. The nonlinear multi-objective model based on the concept of exergy and economic performance are minimized using multi-objective genetic algorithm (MOGA), multi-objective particle swarm optimization (MOPSO), and multi-objective sanitized teaching learning-based optimization (MOs-TLBO) for both VARS and MVARS. The current study also compares the decision variables obtained for minimizing the total annual cost and exergy destruction in basic and modified VARS thermo-economic models. The comparative analysis suggests that MOGA, MOPSO, and MOs-TLBO can be successfully employed to achieve these objectives. MOGA determines minimum annual cost, whereas minimum exergy destruction is reported by MOPSO. On the other hand, when compared to the other two algorithms (MOGA and MOPSO), MOs-TLBO reports a minimum total annual cost of plant operation for the reported minimum exergy destruction by effectively tuning the operating temperature of the system components for both basic and modified VARS. The current study reports Pareto points, which offer an optimal annual cost and exergy destruction based on the requirements using multi-objective algorithms.

Technical challenges and opportunities for milk chilling unit based on vapor absorption refrigeration systems

Vapor absorption refrigeration systems are a heat driven technology and have been used for many years. This technology is used today in remote locations where electricity is not available. It has several applications like cold storage, milk chilling unit and district cooling. In this study problems associated with conventional VARS is being discussed. Beside this several other aspect like fluid and salt used for VARS is also discussed. The main focus is given on milk chilling unit along with the proposed solution. This study also includes design changes in VARS for milk chilling unit. The solution recommended for VARS is replacement of solution pump with bubble pump. A brief discussion on new proposed experimental setup has also being done to overcome the limitation of power supply in remote locations.

Monitoring and simulation of parabolic trough collector powered vapor absorption refrigeration system for rural cold storage

India is one of the largest contributors to the world?s agricultural products. The majority of people?s livelihood in India depends on agriculture and its allied sec-tors. According to an economics survey in the agricultural year of 2019-2020, India is estimated to have produced around 292 million tonnes of food grain. The share of agriculture in India?s GDP is 19.9%. Even though India is an active participant in global agricultural trade, the total agricultural product export is only 2.5%. Agricultural produce is easily perishable and the quality gets affected which will then affect their market value. To meet the future food demands, agricultural produce must be able to store for a longer amount of time for round the year availability. The traditional food storage practices cannot satisfy that condition. These perishables need a proper cold supply chain to increase the shelf life. In this paper performance of a parabolic trough collector integrated vapor absorption refrigeration system was developed and studied. Renewable integrated cold storage would open door to the sustainable energy future.

Towards Techno-Economics of Green Hydrogen as a Primary Combustion Fuel for Recreational Vehicle Vapor Absorption Refrigeration System

Towards Techno-Economics of Green Hydrogen as a Primary Combustion Fuel for Recreational Vehicle Vapor Absorption Refrigeration System

Study of cryogenic CO2 capture with solar-assisted VAR system

One of the major contributors to the rise in global warming potential (GWP) is the continuous accumulation of carbon dioxide (CO2) in the atmosphere. Carbon capture and storage (CCS) is a modern approach to capture CO2 from various industrial processes and store it efficiently for further use. In the cryogenic carbon capture method, CO2 is liquefied by condensation and separated from the CO2 contained gas. The CO2 capture by the cryogenic method can yield high purity CO2 and negligible secondary emissions. However, huge energy is required for the condensation process. In the present study, a low energy penalty method for a post-combustion carbon capture process by the application of the cryogenic technique is performed using process simulation. To reduce energy consumption, a solar integrated vapor absorption refrigeration (VAR) system is designed. The designed solar VAR system provides the required refrigeration cooling load for condensing CO2 in a flue gas stream. For this purpose, the flue gas mixture composed of CO2, N2, and water vapor with respective molar fractions of 15%, 75%, and 10% is considered. The mass flow rate of the flue gas considered is 673.4 kg/s at 1.1 bar and 40 °C. CO2 is separated by condensing the gas at a pressure of 40 bar and temperature of −28 °C. The heat energy required to operate the VAR is 83.3 MW at 75 °C which is supplied by the solar collector. The simulation result indicates that for a post-combustion process, a high-grade electrical energy penalty is found to be about 1.26 MJ/kg CO2 captured, which is better than the most common approaches like absorption, adsorption, and membrane methods. It is also observed that with the increase in the CO2 concentration from 15 to 25 mol% in the flue gas, the energy penalty is reduced by about 37.5%. The performance analysis is also carried out by varying the CO2 recovery rate and purity. It is observed that the energy penalty is decreased by about 10.3% with the increase of CO2 recovery from 90% to 100%. Also, the energy penalty is increased by 4.2% with the increase of CO2 purity from 95% to 100%. The specific CO2 capture process cost is found to be about 1.008 million USD/(kg.s−1).

Recovery and effective utilization of waste heat from the exhaust of internal combustion engines for cooling applications using ANSYS

The exhaust gases from an internal combustion (IC) engine carry away about 75% of the heat energy which means only 25% of heat energy is operated for power production. A recovery unit at the exhaust outlet port can ensure heat exchange between different temperature fluids through conjugate heat transfer phenomena. This study represents heat recovery from exhaust gases that are emitted from IC engines which can be utilized in various applications such as vapor absorption refrigeration systems. In the present work, a new type of perforated fin heat exchanger for waste heat recovery of exhaust gases is designed using SolidWorks, and the flow field design of the heat recovery system is optimized using ANSYS software. Various parameters (velocity, pressure, temperature, and heat conduction) of hot and cold fluid have been analyzed. Inlet velocity of cold fluids including refrigerant (LiBr solution), water, and graphene oxide (GO) nanofluid have been adopted at 0.03 m/s, 0.165 m/s, and 0.3 m/s, respectively. Inlet velocity of hot fluid is taken as 2 m/s, 4 m/s, and 6 m/s, respectively, to develop a test matrix. The results showed that maximum temperature reduction by the exhaust is achieved at 104.8°C using graphene oxide nanofluids with an inlet velocity of 0.3 m/s and exit velocity of 2 m/s in the heat recovery unit. Similarly, temperature reduction by exhaust gases is acquired at 102 °C using water and 96.34 °C by using a refrigerant (LiBr solution) with the same exit velocity (2 m/ s). Furthermore, maximum effectiveness of 0.489 is also obtained for GO nanofluid when compared with water and the refrigerant. On the other hand, the refrigerant has the maximum log mean temperature difference from all fluids with a value of 224.4 followed by water and GO.

Numerical Research of a Solar Driven Bubble Pump for Diffusion Absorption Refrigeration Systems

In conventional vapor compression and absorption refrigeration systems, a compressor or a mechanical pump, respectively circulates the refrigerant. Mechanical input, which is required by the compressor or the pump operation, contributes significantly to the noise level and lessens its reliability and portability. In contrast, diffusion absorption refrigeration (DAR) systems are heat-driven and contain no moving parts. Solar-driven diffusion absorption cooling system uses a low-grade heat to produce a cooling effect, and it's specially tuned for remote locations with high levels of solar radiation. This article studies the performance of a DAR system in Ashdod, Israel. Based on existing models in the literature and on experimental measurement of quantities such as the solar irradiance and the air temperature, the cooling capacity and the COP were simulated. Cooling capacity of the DAR system varies between 100 and 140 W, and COP between 0.09 and 0.17.

Performance analysis of ammonia-based vapour absorption refrigeration system

In the past few years, absorption refrigeration systems (ARS) have captivated increasing research interests as it is a promising alternative and tenable solution to replace vapour compression refrigeration systems (CRS). Also, the refrigerants used in this system are environmentally friendly. NH3/H2O and H2O/LiBr are the most commonly used working fluids in ARS. However, the NH3/H2O ARS has a limitation in that it requires additional components such as a rectifier and analyzer. The proposed work focuses on improving the performance of the ARS by using other ammonia-based working fluids, namely NH3/LiNO3 and NH3/NaSCN. Various correlations are used to determine the thermodynamic properties of these working fluids and are later used in the thermodynamic simulation. NH3/H2O, NH3/LiNO3 and NH3/NaSCN ARS performance analyses are carried out using a computer program written in Python 3.0. The coefficient of performance of these systems is compared at different operating parameters, i.e., evaporator, condenser, generator, and absorber temperature. The results indicate that the working fluids, NH3/LiNO3 and NH3/NaSCN, perform better than the NH3/H2O ARS. Thus, NH3/LiNO3, NH3/NaSCN ARS provide better performance in more significant value of COP and do not require additional components such as a rectifier and analyzer. Hence, NH3/LiNO3 and NH3/NaSCN can be considered suitable alternatives to NH3/H2O in a vapour ARS.

Thermo-environmental analysis of a new molten carbonate fuel cell-based tri-generation plant using stirling engine, generator absorber exchanger and vapour absorption refrigeration: A comparative study

This study aims to present a novel tri-generation plant consisting of a molten carbonate fuel cell (MCFC) unit coupled with a Stirling engine (SE), a heat recovery steam generator (HRSG), and two types of absorption refrigeration cycles (ARCs), i.e., Generator Absorber eXchanger (GAX) and Vapour Absorption Refrigeration (VAR). The proposed system is evaluated from energy, exergy, as well as environmental impact (3E) points of view. To carry out the parametric study, three sub-models are also introduced for the whole system. The sub-model (1) investigates the solo MCFC with the new configuration. In the sub-model (2), the SE and HRSG are added to boost the power generation and overall system efficiency through employing the heat wasted in the sub-model (1). In the last sub-model, for cooling purposes, the surplus heat of MCFC is reutilized using an absorption refrigeration cycle. Besides, to make a comparative study between GAX and VAR systems, the sub-model (3) is classified into two different schemes: (a) with a VAR cycle, and (b) with a GAX cycle. The results reveal that the exergy efficiency and CO2 emissions of the sub-models (1), (2), and (3) are 48.04%, 51.24%, 52.35% (VAR cycle), 52.12% (GAX cycle), 0.388 t/MWh, 0.364 t/MWh, 0.357 t/MWh (VAR cycle), and 0.358 t/MWh (GAX cycle), respectively. Either with GAX or VAR cycle, the proposed system indicates an acceptable standard of functionality in thermodynamic and environmental perspectives.

Waste-heat recovery from a vapor-absorption refrigeration system for a desalination plant

• Air-heated HDH coupled with vapor-absorption refrigerator is investigated. • Water production and cooling capacity reach > 2 m 3 /h and 100 TR, respectively. • Compared to the standalone HDH, the water cost is reduced by 2.4 times. • Compared to the standalone refrigerator, the cooling cost is reduced by 3.8 times. • Outstanding performance is also confirmed under different salinities. The waste-heat of vapor-absorption refrigeration (VAR) cycles could efficiently power humidification-dehumidification (HDH) desalination systems for freshwater production. The integrated systems reported in the literature relied on water-heated HDH cycles, in which the waste-heat of VAR systems heats the HDH saline water before entering the humidifier. This paper assesses the coupling of an air-heated HDH system with a double-effect (DE) VAR system by circulating the HDH air to cool the absorber and condenser of the DE-VAR system and concurrently driving the HDH system. In addition to less corrosive issues compared to water-heated HDH systems, the proposed air-heated HDH based system can produce higher freshwater and achieve better performance. Under the investigated conditions, the proposed system produces water amounts of about 2100.0 L/h and a cooling effect of 104.0 tons of refrigeration, with a gained output ratio (GOR) of 4.7, coefficient of performance (COP) of 1.2, energy utilization factor (EUF) of 5.9, water cost of 2.5 $/m 3 , and cooling effect cost of 0.0037 $/kWh. In addition, the suggested integrated system outperforms the standalone air-heated HDH system in terms of water production, GOR, EUF, and water cost reduction by a factor of 2.3, 2.4, 3.0, and 2.4 times, respectively. Compared to a standalone DE-VAR system, the integrated system shows less cooling capacity by about 10.0% but with a significant reduction in the cooling cost by 3.8 times and improved EUF by 4.2 times. Additionally, the present system shows excellent economic feasibility under different salinities.

Thermodynamic mathematical modelling and analysis of vapour absorption refrigeration system using a novel ant lion optimiser

In an advanced industrial effort, the role of vapour absorption refrigeration system plays a major role. However, the significant eco-friendly and the required cooling capacity rate are the major challenges in the design of refrigeration systems for industrial applications. For this reason, the novel ant lion optimiser (AO) based thermodynamic modelling and analysis of single-effect vapour absorption refrigeration model is proposed in this research for industrial buildings. Here, Lithium Bromide and water (LiBr-H2O) are taken as an absorbent in the refrigeration system. Therefore, an effective novel 5 kW cooling capacity of LiBr-H2O depending upon the vapour absorption refrigeration structure is designed. The analysis of this research is done by the improved polynomial curve fit equation. Moreover, the coefficient of performance of the absorption cycle is optimised using a novel AO method. The implementation of this work is done on the MATLAB platform. In addition, the developed novel 5 kW cooling capacity with AO is applied in industrial building applications to validate the successive measure of the projected replica. Furthermore, the outcome of the projected design is compared with different existing refrigeration designs and the best results by reducing design complexity.

Theoretical design of solar-powered vapor absorption refrigeration system coupled with latent heat energy storage

In this work, the vapor absorption refrigeration system (VARS) with a cooling capacity of 1kW is designed. VARS is designed to be driven by hot water available from the solar thermal collector during the day. In the Sun’s absence, the system is designed to run by a coupled latent heat energy storage system. The unit has three major components: evacuated tube collector, latent heat energy storage, and VARS. The system is designed for a cooling capacity of 1 kW. The size of other components has been calculated by adopting the heat exchanger design approach and the relevant equations presented in the published works. The corresponding size of absorber, generator & condenser comes out to be 1.412kW, 1.46 kW & 0.96 kW, respectively for the cooling capacity of 1 kW. The evacuated tube collector of 100 LPD capacity is sufficient to provide the required heat to run the VARS and charge the thermal energy storage. Latent heat energy storage of 2.25 kW charging and discharging time of 3 hours kW is coupled with the system. The designed system gives the COP of 0.875.

A critical review on nanorefrigerants: Boiling, condensation and tribological properties

A major amount of domestic energy consumption is spent on refrigeration and space cooling appliances. The performance of the refrigeration system depends on the thermophysical properties of the refrigerant. Altering the properties by additives such as nanoparticles has proven to be an effective solution to improve the performance of the system. This work swivels around flow boiling, pool boiling, tribological and condensation characteristics of nanorefrigerants in Vapour Compression Refrigeration System (VCRS) and Vapour Absorption Refrigeration System (VARS). An evolutionary timeline of nanorefrigerants is presented. Energy savings on compressor work by addition of nanolubricants is discussed. A sum of thirteen refrigerants and twelve nanoparticles in various combinations were encountered during this review process. CNTs performed better than metallic (Al, Cu, Au, Ag) and ceramic (Al 2 O 3 , TiO 2 , SiO 2 , ZnO) counterparts. Majority of the work reported enhancement in heat transfer rate and coefficient of performance (COP), however, few studies presented that CuO nanoparticles have shown negative correlation between HF, COP and volume fraction of nanoparticle. The review presents a broad idea on dispersion techniques, stability, properties of boiling and condensation, migration phenomenon of nanoparticles and various novel techniques to improve the performance of the refrigeration systems.

Numerical simulation of flow-through heat exchanger having helical flow passage using high order accurate solution dependent weighted least square based gradient calculations

ABSTRACT Improving the fluid flow and heat transfer characteristics of a heat exchanger has always been desired for any heat transferring application. Various active, passive, and combined methods were adopted for heat transfer improvements by different heat exchangers. Here, an investigation on an annulus heat exchanger having a helical flow passage – known as a helixchanger is presented. A continuous helical fin is inserted in an annulus region which forces the fluid to flow in a helical manner. This helixchanger is planned to be used as a part of the absorber in a solar-assisted vapor absorption refrigeration system. In this paper, a high-order accurate numerical simulation of the three-dimensional flow through a helixchanger is presented. Three-dimensional Navier-Stokes equations for unsteady incompressible flows are written in artificial compressibility formulation. The convective fluxes at the cell interface are estimated using Harten Lax and van Leer with Contact for artificial compressibility Riemann solver. The high order accuracy over unstructured meshes is obtained by finding the gradient using solution-dependent weighted least squares approach. The flow-through helixchanger is simulated for various Reynolds numbers (Re = 1500–6500), corresponding pressure drop, and the average heat transfer coefficient is presented. It has been observed that, due to the helical flow path, the flow becomes naturally turbulent, thereby helping in increasing heat transfer. The experimental setup is also developed, and the numerical results are validated against the experimental results. A correlation is also proposed for the heat transfer through the helical flow path.

Performance Investigation of a Vapor Adsorption Refrigeration System Based on Adsorption/Desorption Time and Heat Transfer

Abstract In the past two decades, the development of sustainable refrigeration systems such as thermally operated vapor adsorption refrigeration systems achieved unparalleled growth in the research world as compared to conventional vapor compression systems and even thermally operated vapor absorption refrigeration system. Yet, the commercial success of the adsorption refrigeration system could not be achieved due to mainly its higher space area required per kilowatts of refrigeration capacity. With the focus to look improvement on this issue, the performance of the adsorption refrigeration system has been studied concerning adsorption/desorption time and heat transfer of adsorber. It is proposed to reduce the adsorption/desorption time, due to which the concentration (ratio of the mass of adsorbed refrigerant to the mass of activated carbon) will not reach its equilibrium value, but it is possible to get a higher mass flow in a shorter period. In turn, the cooling capacity will increase. In view of this, a mathematical model has been developed to study the performance and applied to three adsorbent–adsorbate pairs, namely, Maxsorb III–ethanol, Maxsorb III–R507a, and Maxsorb III–R134a. Based on the mathematical investigations, it is observed that the cooling capacity can be improved significantly at a litter higher cost of the heat transfer mechanism.

Design and Performance of Solar PV Integrated Domestic Vapor Absorption Refrigeration System

The arrival of new technologies has increased the energy demand day by day and does not seem to slow down at any time soon. High energy demand is adding risk on energy depletion and cause of various environmental issues. Air conditioner, chiller, and refrigerator occupy a considerable amount of the world’s total energy usage and have also proved to be a massive contributor to various environmental impacts. This technology might sound like a luxury on the surface, but they are in high demand to achieve food security. They can also help lifesaving vaccines to reach even the isolated parts of the world. Even though solar thermal refrigeration is a popular field, this paper solely concentrates on PV integrated refrigeration. In this paper, a renewable integration technology where a solar photovoltaic system is used to supply the electrical energy required to drive an absorption cycle is studied and compared with the commercial AC absorption refrigeration system. The Coefficient of Performance (COP) of the AC and DC system was 0.18 and 0.14. The simple payback of the system is 10.2 years.

Modeling and analysis of a solar thermal-photovoltaic-hydrogen-based hybrid power system for running a standalone cold storage

In this paper, a solar-hydrogen-based hybrid power system has been proposed to run a remotely located cold storage facility for developing countries on a sustainable basis. The proposed system includes an array of parabolic trough collectors with short-term thermal storage, an array of solar photovoltaic modules, an electrolyzer bank, compressed hydrogen storage, and a proton exchange membrane fuel cell stack to satisfy the thermal and electrical demands of a standalone multi-commodity cold storage. The cold storage is operated on a double-effect vapor absorption refrigeration system. A mathematical model of the integrated system has been developed and validated against a reference study available in the literature. The proposed system has been analyzed from the energy, economic, and environmental point-of-view. The study reveals that after meeting the in-house power requirements of the proposed cold storage facility, the designed power system can produce 2.17 MWh of surplus energy, which can be used to support the load during an exigency. The carbon dioxide mitigation potential of the proposed power system is estimated to be about 350 tons that can save an annual carbon tax of $ 5067. The estimated payback period of about seven years indicates the economic viability of the integrated system.

Analyzed of vapor absorption refrigeration systems powered by geothermal energy: Site in Ethiopia

Geothermal energy, one of the renewable energies on the earth, have extensively been used worldwide. Its applications fall into two classifications; first, utilizing heat energy in the source directly and second, indirectly converting it into another energy form (electricity). The objective of this analysis to vapor absorption refrigeration system (VARS), the systems powered by geothermal energy for thermal cooling of waste. In the second part, mass & energy conservation principles have been used to analyze VARS components to cool drinking water of Dilla University from 37.8 °C to 16 °C within 16 hrs. In the second part, designed VARS operating at an evaporation rate of 103.12 kW can cool 66,000 L of drinking water to the required temperature within 16 hrs each day. It has to be noted that the evaporation rate varies with the time needed to cool. If the water to be cooled is within a short time, a high evaporation rate is then required. Based on the results obtained, it is clear that geothermal energy at Gedeo and Gujji Zones can be utilized for VAR systems.

Energy and exergy optimisation of parallel flow direct and indirect fired triple effect vapour absorption systems

In this study, optimisation of operating parameters (generator temperatures, concentrations, and solution distribution ratios) have been performed to achieve maximum thermodynamic performance and minimum energy consumption in the parallel flow triple effect direct and indirect-fired vapour absorption refrigeration systems. Energy and exergy analyses are considered for the formation of the objective function to optimise the above operating parameters. Moreover, comparison of performance parameters have been shown with parallel flow double effect, series flow double effect, and series flow triple effect cycles. After optimisation of triple effect parallel flow cycles, results show that coefficient of performance of both triple effect direct and indirect fired cycles are the same. While exergy performance of direct fired cycle is around 70 to 80% lower than indirect fired cycle. Moreover, COP of parallel flow triple effect cycle is 7 to 10% higher than its series flow configuration. Also, flow rate of gaseous fuels of parallel flow triple effect cycle require 5% less as compared to series flow. Moreover, exergy performance of parallel cycles was found to be around 9-11% better than series flow cycles, but at the expense of 5-10% higher inlet temperature of the main generator.

Energy and exergy optimisation of parallel flow direct and indirect fired triple effect vapour absorption systems

In this study, optimisation of operating parameters (generator temperatures, concentrations, and solution distribution ratios) have been performed to achieve maximum thermodynamic performance and minimum energy consumption in the parallel flow triple effect direct and indirect-fired vapour absorption refrigeration systems. Energy and exergy analyses are considered for the formation of the objective function to optimise the above operating parameters. Moreover, comparison of performance parameters have been shown with parallel flow double effect, series flow double effect, and series flow triple effect cycles. After optimisation of triple effect parallel flow cycles, results show that coefficient of performance of both triple effect direct and indirect fired cycles are the same. While exergy performance of direct fired cycle is around 70 to 80% lower than indirect fired cycle. Moreover, COP of parallel flow triple effect cycle is 7 to 10% higher than its series flow configuration. Also, flow rate of gaseous fuels of parallel flow triple effect cycle require 5% less as compared to series flow. Moreover, exergy performance of parallel cycles was found to be around 9-11% better than series flow cycles, but at the expense of 5-10% higher inlet temperature of the main generator.