Vapour Absorption System Research Articles

Parametric Based Techno‐Economic Evaluation for a Solar Thermal‐PV Integrated Multi‐Commodity Storage Facility

ABSTRACTPostharvest losses and spoilage of agricultural products are a major problem for tropical countries, and it is even more challenging for countries encountering fluctuating power shortages, such as Pakistan. Therefore, this study focused on the energy and economic analysis of cold storage to store three products (potatoes, pomegranates, and potatoes) according to the season and storage span throughout the year. The cooling load of the cold store was supported by a LiBr‐H2O vapor absorption and vapor compression refrigeration system to maintain the desired temperature for each product during cold storage. A solar thermal PV system is installed to operate cold storage refrigeration systems. Cold storage performance was analyzed by developing thermal models of integrated systems using the ambient conditions of Lahore, Pakistan. A parametric study was also conducted to analyze the impact of various working parameters on integrated system performance, and it was found that the maximum peak cooling load of 91 kW inside cold storage is attributed to pomegranates owing to high ambient conditions during its loading month. The product loading rate significantly affects the cooling load of cold storage and varies directly with it, as observed for an increase in the product loading rate from 0 to 50 000 kg/day cooling load also increases from 34 to 87 kW. To meet the thermal demand of the generator of the vapor absorption system, parabolic troughs were installed to operate cold storage, and it was found that a minimum of four PTC were needed to support the peak cooling load at the maximum product loading rate and minimum DNI value. To meet the electrical demand of cold storage electrical equipment and the compressor of the vapor compression system, solar photovoltaic panels were installed, and it was found that a minimum of 618 panels was required at a minimum tilted radiation value. To validate the viability of proposed design system economic analysis was also conducted which revealed a payback period of 12 years for Kinnow and potatoes and 16 years for pomegranates.

Thermodynamic and environmental performance of a Kalina-based multigeneration cycle with biomass ancillary firing for power, water and hydrogen production

The performance of a Kalina-based multigeneration cycle for power, water, and hydrogen production is investigated from thermo-environmental, sustainability, and thermo-economic perspectives. The plant comprises a gas turbine (GT), Kalina cycle (KC), and vapor absorption system (VAS) as the bottoming cycle and an integrated domestic water heater and proton-electron membrane (PEM) electrolyzer for hydrogen production. The system's models were simulated with Engineering Equation Solver (EES) codes. The results indicate a net energy efficiency of 53.48% and exergy efficiencies of 50.05 %, with an additional 30,178 kW of products from the bottoming cycles. The GT contributed approximately 85.81 % of the overall exergy destruction. The system's exergo-thermal index (ETI) stood at 1.713, with the GT only having an ETI of 2.106. Similarly, the exergetic sustainability index (ESI) of the multigeneration plant was not greater than 2.04. The exergoeconomic analysis shows a low average energy cost from the GT, estimated at 0.836 $/GJ, compared to the Kalina subsystem, which stood at 6.53 $/GJ. The thermodynamic and cost evaluation of the system demonstrates substantial benefits from the plant, which kept the hydrogen production rate at 0.1524 kg/hr.

Statistical Analysis and Optimization of a Single-Effect Vapor Absorption Refrigeration Cycle

Abstract: This study employs Response Surface Methodology (RSM) with a Box-Behnken design to optimize the Coefficient of Performance (COP) in a Single-Effect Vapor Absorption System. The thermodynamic model considers a 1-ton refrigeration (TR) system utilizing Lithium bromide-water as the refrigerant, and simulations are conducted using the Engineering Equation Solver (EES). The optimization process identifies optimal values for the generator, absorber, condenser, and evaporator temperatures, set at 90°C, 33°C, 33°C, and -5°C, respectively, resulting in an achieved optimum COP of 0.716. Statistical analysis through ANOVA of the quadratic regression model reveals a significant F-value of 110.62, with a low probability value (p=0.0003), attesting to the model's robustness. Key statistical metrics for the model encompass a standard deviation (Std. Dev.) of 0.0059, a mean of 0.8956, a coefficient of variation (C.V. %) of 0.6559, an R² of 0.9901, an adjusted R² of 0.9811, a predicted R² of 0.9159, and an adequate precision of 38.2967. This research offers crucial insights into enhancing the performance of a Single-Effect Vapor Absorption System, thereby contributing to the advancement of energy-efficient refrigeration technologies

Potential role of post-harvest management in agribusiness

Agriculture plays a key role in deciding the economy of the country and agricultural marketing has become the potential driver of the agricultural sector. Green revolution and succeeding technologies made our farmers to succeed in the production front, but lagging appreciably in terms of price realization owing to their inability to stop post-harvest losses and inaccessibility to efficient and scientific marketing system. Post-harvest management includes storage, packaging, coating, disease management, extended shelf life, maintaining food quality. Foods and other products can be preserved by storage at low temperature, which retards the activities of microorganisms and preserve perishable foods in their natural state. Preservation depends on the storage time required whether short or long-term short and the type of product. A cold storage unit works on two principles: Vapour absorption system (VAS), and Vapour compression system (VCS). Although VAS is a bit costlier, but economical in operation. Food irradiation is another recent food preservation technology to address some of post-harvest losses. Food is exposed to ionizing radiation (i.e. radiowaves, microwaves, UV rays, X-rays, gamma rays etc.). Food irradiation can be applied to specific purposes as quarantine treatment of fruits and vegetables and as a method to ensure hygienic quality of foods. Food processing techniques like grading, sorting and packaging, etc add value and enhances shelf life of food. Agricultural productivity augmentation needs a concurrent development of post-harvest support mechanism and efficient and organized marketing system, which would ensure maximum price rrealization to the farmers.

Experimental Study on Performance of a Solar Thermal-Driven Vapor Absorption System Integrated with Hot Thermal Energy Storage for Milk Chilling

Abstract Solar-powered vapor absorption system has proven to be a feasible and viable cooling source. However, most reported installations for milk chilling applications are equipped with an auxiliary heater that consumes significant electricity/gas, making it economically unviable. In this study, the experimental investigation of the performance of a solar-powered vapor absorption chiller has been reported for milk chilling applications as per standard ISO 5708 – 2 II. It has been identified that the performance of the vapor absorption chiller is quite uncertain and underperforming while operated with the heat directly fed through the evacuated tube compound parabolic concentrator solar field due to diurnal and seasonal variations of solar radiation intensity. Therefore, a hot thermal energy storage integration has been studied and analyzed in this study. The performance of the vapor absorption chiller has improved significantly with the use of hot thermal energy storage in the solar circuit as the coefficient of performance of the vapor absorption chiller improved up to 0.4, which was earlier around 0.25. Further, hot thermal energy storage provides better thermal management to increase the productivity and performance of the vapor absorption chiller, and the cooling time for the first milking is 2 hours and 45 minutes. The energy efficiency ratio has a maximum value of 6.1 with an average of 4.3, whereas the thermal COP has an average of 0.35 and a maximum value of 0.52 when run with thermal energy storage alone.

Enhancement of Condenser Performance in Vapor Absorption Refrigeration Systems Operating in Arid Climatic Zones—Selection of Best Option

Generators and condensers are the two vital equipment items that determine the output of vapor absorption refrigeration systems. Arid weather conditions produce a significant reduction in the performance of the vapor absorption refrigeration cycle due to low condenser heat dissipation despite high generator temperatures. Although numerous studies on condenser cooling methods in vapor compression systems have been reported in the literature, solar-operated vapor absorption systems have not been studied. Limitations in generator temperatures of solar-operated vapor absorption systems necessitate a focused study in this area. This study makes the selection of the best choice for condenser cooling from among four different condenser cooling methods which have an impact on the performance of the vapor absorption refrigeration system for effective cooling using solar energy. A solar vapor absorption refrigeration system working with low-grade heat using a compound parabolic collector is considered in this study. Analysis of a vapor absorption refrigeration system for cooling in arid weather conditions is carried out using different condenser cooling methods with Engineering Equation Solver. Initially, the model used in the study is compared with a similar study reported in the literature. Techniques considered are air, water, evaporative, and hybrid cooling techniques. The performance of the vapor absorption cooling system was analyzed using experimental values of a solar compound parabolic collector obtained from real-time measurements for simulating the model. Results show that water cooling can provide suitable condenser cooling and improve the coefficient of performance of the solar vapor absorption refrigeration system using the solar collector. The water-cooled condenser has 1.9%, 3.3%, and 2.1% higher COP when compared to air-cooled condensers for spring, summer, and autumn seasons respectively, whereas the water-cooled condenser cooling recorded 6%, 14%, and 8% higher COP relative to the evaporative cooling method. Cost comparison showed maximum cost for water-cooled condensers and minimum cost for hybrid-cooled condensers. The effect of each cooling method on the environment is discussed.

Modeling, optimizing and sizing of a solar air conditioning system with refrigerant storage for meeting the 24-hour cooling load of a restaurant building

A methodology is presented for the sizing of a solar integrated absorption refrigeration system considering the dynamic cooling load, solar energy and ambient conditions. The solar vapor absorption system (single effect, LiBr) is designed to meet the cooling demand of a 200 m2 restaurant building. Using the genetic algorithm, the operating variables of the absorption refrigeration system are optimized The system is to be integrated to a solar collector to meet the varying cooling load profile. The local solar insolation profile at a location is considered in the analysis. The ambient temperature data is utilized to model how the system works in real time. For continuous operation, to meet the 24 h load profile, refrigerant storage is considered for the system. The amount of refrigerant stored is 1529 kg. The optimal area required for the solar collector is found to be 308 m2. The hot water storage tank volume is 5.2 m3. The selection of working fluid (LiBr-water), solar collector (flat plate), and design (single effect system) guarantees that the system is effective, economical, and environmentally favorable.

An efficient optimization strategy for vapor compression–absorption-based cascaded refrigeration system using various evolutionary techniques

ABSTRACT A novel optimization strategy for a compression-absorption cascaded refrigeration system (CACRS) consisting of a single effect vapor absorption system (VARS) and vapor compression system (VCRS), which employs several absorbent solution-refrigerant-refrigerant pairs to consider the combination of absorbent solution-refrigerant in VARS and refrigerants in VCRS as an optimization variable, is successfully implemented using various evolutionary optimization techniques. This article analyzes three different absorbent solution-refrigerant in the VARS with eleven different refrigerants in the VCRS. A nonlinear objective function is formulated based on exergy and environmental analysis, which is minimized using 10 different evolutionary optimization techniques. The proposed novel strategy reduces the complexity of using optimization techniques to select the best optimum absorbent-refrigerant-refrigerant pair. Differential evolution with multi-population-based ensemble of mutation strategies determined the minimum total annual cost as 13,137.78 US$/year for (CaCl2-LiBr-LiNO3-)-H2O-R152a. Lower condenser temperature and higher temperature difference in the cascade-condenser resulted in a minimum value for the total annual cost.

Studies on Vapor Compression System Cascaded to the Ammonia Vapor Absorption System for Deep Freezing Application

Studies on Vapor Compression System Cascaded to the Ammonia Vapor Absorption System for Deep Freezing Application

Parametric analysis of solar-assisted trigeneration system based on energy and exergy analyses

Rapid deterioration of environment has led researchers to explore feasible forms of energy which could produce multiple energy forms with minimum inputs. Hence, in this study a nov-el trigeneration setup is explored so as to achieve simultaneous forms of energy in the form of electrical energy, heating and cooling, driving its primary energy requirements through a solar power tower. Molten salt is used in this study to transfer the heat from the solar component to the vapor absorption apparatus. Further the vapor absorption system is tested for thermody-namic performance for a couple of refrigerants (LiNO3-H2O and LiBr-H2O), so as to establish the Pareto-optimal fluid among them. In order to remove any adherent error in the measuring procedure, all equipment’s uncertainty analysis was performed which was negligibly small approximately at 5.34 % in terms of power plant efficiencies. An exact analysis was performed so as to estimate energy and exergy in efficiencies in the equipment while varying input pa-rameters. Zenith exergy destruction was achieved in 33.6% by the central receiver, followed by 24.9% by heliostat, and 7.8% in heat recovery steam generator. The highest energy and exergy efficiencies (62.6% and 20.6%) are attained on system working on LiBr-H2O, whereas (60.9% and 19.6%) were obtained in LiNO3-H2O operated system.

Designing of system for high grade heat recovery in thermal coolingsystem for process heat applications

An experimental investigation on design of a vapour absorption system using LiBr-H2Ofor high grade heat recovery in thermal cooling system for process heat applications has been conducted. A 1.5 kW cooling capacityof the LiBr-H2O vapour absorption system has beend esigned and tested under various operating conditions. Generator temperature, absorber tem-perature, condenser temperature and evaporator temperature have been varied and perfor-mance of LiBr-H2O vapour absorption system has been analysed. Experimental results are presented in terms of COP and circulation ratio. Further, to validate the results thermody-namic model is developed using first law of thermodynamics and simulate in Engineering Equation Solver. The COP and the circulation ratio estimated through simulationsand exper-iments have been in good agreement with ±5% standard deviation. Further, this this research work is beneficial for dairy industries in process heat applications and realizing the impor-tance of the need for energy conservation in dairy industries.

Multi-attribute decision-making tools for selection of PCMs as latent heat thermal energy storage integrated with solar-driven LiBr-H2O vapor absorption system

The selection of PCM is quite decisive for the efficient and effective design of latent heat thermal energy storage to be coupled with a solar-powered single-effect LiBr-H2O vapour absorption system. Aligned to the operating characteristics of a solar-powered LiBr-H2O vapour absorption system, PCM must have a melting temperature between 80 and 100°C and high latent heat of fusion. A total of 14 PCMs are first scrutinised in the present research work based on melting temperatures ranging from 80 to 100°C. Further, their ranking is done and verified with the MADM examination. Thermophysical properties (latent heat, density, thermal conductivity, specific heat) and cost have been considered the criteria for selecting PCM. AHP is used to calculate the relative weights among the criteria identified. After that, the ranking is done with the help of TOPSIS. MODM is used to optimise these PCMs by drawing variations between the objective functions of thermal energy storage density and thermal diffusivity. Xylitol, Acetamide, (NH4)Al(SO4)·6H2O have been ranked as the top three due to TOPSIS and MODM examination. This research output supports selecting the appropriate PCM when designing latent thermal energy storage systems to integrate an application.

Evaluation and optimization of single-effect vapour absorption system for the dairy industry using design of experiment approach

Several investigations have emphasized process parameters of single-effect v apour absorption system; yet, the influence of process parameters on thermodynamic performance of the absorption system has not been focussed for the best performance conditions. Several process parameters such as absorber, generator, evaporator, and condenser temperatures influence an absorption refrigeration system’s exergetic and energetic performance. In the present study, the design of experiments has been used for the optimization of process parameters. A 1.5 kW cooling capacity of the LiBr-H2O absorption system has been developed and tested under various operating conditions. Performance characteristics such as in COP and heat dissipated by the condenser (Qc) of the ARS system have been studied at different ranges of operating parameters. For the process parameter optimization, a central composite design under Response Surface Methodology has been used. The m aximum COP and Qc have been obtained as 0.827 and 2488.79, respectively at optimum values of generator temperature (Tg) = 95.1 oC, condenser temperature (Tc) = 45.3 oC, absorber temperature (Ta) = 28.4 oC and evaporator temperature (Te) =15 oC. The optimum conditions obtained by the design of experiments have been validated through experiments on the ARS system, and experiments have been conducted at closer conditions of the optimized values of the operating parameters and found the maximum COP and Qc as 0.926 and 2518.01, respectively. The results of this paper have been very useful in designing a better vapour absorption system.

Performance analysis and optimization of nano particle base Libr-H2o vapor absorption system by using Taguchi, Grey relational analysis and ANOVA

Present study deals with the thermodynamic analysis and optimization of vapour absorption refrigeration system (VARS) using CuO nanoparticles in LIBr-H2O working fluid. The performance of VARS is extensively investigated by considering system parameters such as operating temperature of generator, absorber, condenser, and evaporator. Herein CuO nanoparticles are dispersed in LiBr-H2O working fluid ultrasonically using a tip sonicator having intermittent sonication time. A stable nanoparticle base working fluid is prepared for experimentation. Experiments were carried out on a physically designed and developed 2 TR vapor absorption system. The experimental result indicates 17% enhancement in COP of system by the incorporation of CuO nanoparticles. For all the operating temperature range the heat transferred in generator, condenser, evaporator, and absorber is more with CuO based working fluid. In comparison with the normal system, nanoparticle based VARS system is more stable and shows very small variation in COP for the entire range of operating temperature. The order of the influence of process parameters in thermodynamic performance of VARS is obtained by using ANOVA method. Optimum operating conditions are determined for VARS. As per ANOVA result absorber temperature followed by evaporator temperature is having major contribution for the system performance.

Mini cold storage using the parabolic solar trough: An appropriate technology for perishable agricultural product

Limited storage of perishable agricultural products is a common problem for small-scale farmers. Therefore, our approach for this problem is to develop a low operating cost mini cold storage using solar energy. The integration of solar thermal energy with vapor absorption refrigeration systems was studied. In vapor absorption systems, heat energy is taken as the source of input energy and the performance characteristics depend on heat energy supplied and pump work used. The novelty of our project is that it uses a parabolic solar heat collector to run a vapor absorption refrigeration system using heat energy extracted from solar energy. In this cyclic process, the refrigerating effect is produced. By utilizing this mini cold storage system, tomatoes can be stored for four weeks whereas, with room temperature storage, it only lasts one week. This appropriate technology promises small-scale farmers to keep their perishable agricultural products for several weeks without additional storage costs.

Area Optimization of a Flat Plate Collector for Meeting the Air Conditioning Load of an Office Building Using a Solar Vapor Absorption System

A solar single effect vapor absorption system is designed to meet the cooling demand of an office building having a floor area of 100 m2. The absorption system operating parameters are optimized using Genetic algorithm to maximize the coefficient of performance (COP). The solar insolation at a location is used as the heat source for the absorption refrigeration generator heat input. The monthly total global radiation at the location for a particular year is found. The insolation profile of a representative day of the year is the input source for the sizing of the solar flat plate collector. Also, the ambient temperature variation profile is used to dynamically simulate the system performance. The refrigeration system is integrated with the solar collector and storage tank to meet the varying cooling load. The total generator load required to meet the cooling load profile of the building is found from the vapor absorption system model in Matlab. The solar flat plate collector system is modelled in such a way that the energy output from the solar collector matches the generator load required. The hot water temperature to generator (heat supplied) is kept constant at 85°C. The generator load required to meet the varying cooling load is achieved by controlling the solution pump flow rate in absorption system. The optimal area of the collector required for meeting the total generator load is found as 14.6 m2. The storage volume required in the storage tank is 0.48 m3. In the solar collector, a variable water flow system profile is used to maintain the constant temperature required in the generator.

Performance Studies of Solar-Powered Absorption-Type Refrigeration System and Characterization of Deposits on its PV Panel

The demand for refrigeration and air-conditioning systems has been increasing in recent years. In order to reduce the demand for fossil fuels, renewable energy sources can be used to drive these systems. Also, renewable energy sources will reduce global warming, increase energy security, and generate employment opportunities. The conventional vapor compression system used in domestic applications needs electrical energy and a vapor absorption system can be used as an alternative to a vapor compression refrigeration system. In this work, a refrigeration system of solar-type has been developed and tested as the demand for the refrigeration system is increasing, which directly and indirectly increases global warming. The use of a renewable energy-driven alternative cooling system such as an absorption system will reduce the impact of refrigeration systems on the environment. The experimental work concluded that the vapor absorption system driven by the solar photovoltaic (PV) system could be a substitute for the conventionally used vapor compression system. The accumulation of the dust reduces the performance of Solar PV panels. The characterization of dust particles is important in deciding further growth and subsequent deterioration of the solar PV panels and the power output. The scanning electron microscopy study and energy dispersive X-ray analysis have helped to find the chemical composition of the dust particles. The X-ray diffraction results have helped in further investigation of the severity of the deposits by identifying possible compounds. Based on this analysis, the periodic cleaning of solar PV panels must be carried out at regular intervals.

Exergy destruction rate minimization in the absorber of a double effect vapor absorption system

Despite the wide applications of multi-effect vapor absorption systems, their energy requirement is relatively higher. Also, their exergy analyses found in the literature reveal that the exergy destruction rate at the absorber is quite significant and has the potential for improvement in its energy efficiency. In this work, the exergy destruction rate at the absorber is minimized using the penalty factor method against the optimized generator temperature of the double-effect vapor absorption system by considering absorber, evaporator, and condenser temperatures into consideration. Modeling of the double-effect vapor absorption system was performed using a thermodynamic toolbox in SIMULINK. The present model employed a refrigerant heat exchanger to enhance the system cooling capacity. The liquid-vapor ejector valve at the absorber also improved the mixing of the solution and refrigerant vapor resulting in lower irreversibility of the system. Results show that the coefficient of a performance increase by 2.4% with refrigerant heat exchanger and exergy loss at absorber decrease by 9.4% with ejector. The optimum performance was seen at the condenser and evaporator temperatures of 308.8 K and 278.1 K, respectively with an 8.2% improvement in exergetic efficiency. Finally, it is concluded that the multi-effect absorption system shows better performance by minimizing the irreversibility.

Experimental Analysis of Performance Improvement of a Modified Vapour Absorption System (VAS-GAX) for Cooling Applications

Experiments on an enhanced “Generator-Absorber-Heat Exchanger” (GAX) Vapour Absorption System (VAS) for cooling purposes were carried out using water-ammonia in present study. The new experimental setup was fabricated using modern and complex technologies for the GAX absorption system which includes tiny heat exchangers, allowing the system to be both compact and efficient. The coefficient of performance (COP) of a system was analyzed for different temperatures of Generator, Condenser, Evaporator and Absorber. The results show that the maximum performance (COP=0.63) is achieved at 25℃ Generator temperature. The system has a low carbon footprint because it does not use effluent water or tower electricity and invention enables the recovery of hot air, which may then be used for several drying applications, including agricultural drying, resulting in a fully cascaded system with a three-fold increase in Coefficient of Performance (COP). A modified VAS-GAX absorption system in present analysis be a good fit for high-performance modern cooling applications.

Comparative experimental investigations of pumpless vapour absorption system using high- and low-grade energy

This work presents an experimental investigation of Pumpless Vapour Absorption System (PVAS) by supplying the high-grade (electric power) and low-grade energy (LPG). The work experimentally investigates the behaviour of the PVAS components by using both energy sources. Experimental result shows the generator takes more time to warm up, around 120 and 35 s by supplying high-grade and low-grade energy, respectively. In the evaporator, the rate of decreasing temperature is higher by low-grade than the high-grade energy supply. It takes only 22 min to reach the steady state in low-grade energy input, while in high-grade energy it takes about 34 min. The work further investigated the mass flow rate of refrigerant and heat supplied in the generator with variation of refrigerating effect. Highlights Air conditioning industry consumes around 10–20% of the world energy. Supplying low-grade energy in pumpless vapour absorption system is suitable. Pumpless vapour absorption system is more beneficial in rural areas.