Application of exergy method to a two-stage irreversible combined refrigeration system

2007 ◽  
Vol 221 (7) ◽  
pp. 807-813 ◽  
Author(s):  
Y-F Su ◽  
C-K Chen
Keyword(s):  
Coefficient Of Performance ◽  
Refrigeration System ◽  
Exergetic Efficiency ◽  
Two Stage ◽  
Efficiency Criterion ◽  
Exergy Method ◽  
Cycle Temperature

The exergy method, based on the maximum exergetic efficiency criterion, is applied to a two-stage irreversible combined refrigeration system. The exergetic efficiency defined as the ratio of rate of exergy output to rate of exergy input is taken as the objective index to be maximized. The related cycle temperature parameters are first solved. The maximum exergetic efficiency is then obtained analytically. Comparisons between the exergetic efficiency and the coefficient of performance of the combined refrigeration system are performed. The influences of various parameters on the system performances are discussed. It shows that the exergy method is practical and effective when operating or designing the combined refrigeration system.

Optimum coefficient of performance and exergetic efficiency of a two-stage vapour compression refrigeration system

2003 ◽  
Vol 217 (9) ◽  
pp. 1027-1037 ◽  
Author(s):  
J S Tiedeman ◽  
S A Sherif
Keyword(s):  
Performance Optimization ◽  
Geometric Mean ◽  
Coefficient Of Performance ◽  
Second Law ◽  
Refrigeration System ◽  
Exergetic Efficiency ◽  
Two Stage ◽  
Optimization Study ◽  
The Common ◽  
Vapour Compression

This paper presents the results of an optimization study for a two-stage vapour compression refrigeration system based on the coefficient of performance (COP) and exergetic efficiency. Traditional studies have focused on the first-law performance, while those studies dealing with the second law have primarily been limited to performance analysis as opposed to performance optimization. The results of this study indicate that the use of the common approximation of the geometric mean to find the optimum interstage pressure can lead to significant errors in interstage pressure. However, an optimum COP or exergetic efficiency based on the same interstage pressure has relatively little error. This trend is valid as long as the isentropic compressor efficiencies are ‘reasonable’. Second-law optimization revealed that the optimum data curves themselves have a maxima for each set of conditions tested. This leads to the conclusion that for a given system there is an optimum set of conditions that lead to the lowest amount of exergy destruction for that system. This is shown to occur consistently for reasons that are, as yet, undetermined. Finally, polynomial equations have been fitted to the resultant optimum data for the interstage pressure, COP and exergetic efficiency. These equations allow for the reproduction of optimum points based on high-and low-pressure compressor efficiencies and condenser and evaporator pressures.

Application of exergy method to an irreversible inter-cooled refrigeration cycle

2005 ◽  
Vol 219 (8) ◽  
pp. 661-667 ◽  
Author(s):  
C-K Chen ◽  
Y-F Su
Keyword(s):  
Heat Transfer ◽  
Working Fluid ◽  
Refrigeration Cycle ◽  
Refrigeration System ◽  
Exergetic Efficiency ◽  
Finite Rate ◽  
Efficiency Criterion ◽  
Internal Dissipation ◽  
Exergy Method ◽  
Internal Irreversibility

The exergy method, based on the maximum exergetic efficiency criterion, has been applied to an irreversible inter-cooled refrigeration cycle. The exergetic efficiency defined as the ratio of the rate of exergy output to the rate of exergy input is taken as the objective function to be maximized. Multi-irreversibilities include finite-rate heat transfer, internal dissipation of the working fluid, and heat leaks between heat reservoirs. The maximum exergetic efficiency can be determined analytically by introducing the internal irreversibility parameter, which represents the degree of internal irreversibility. The corresponding performances of the irreversible refrigeration system are obtained simultaneously. The results show that the exergy method can be used as an effective criterion in designing an irreversible inter-cooled refrigeration system.

scholarly journals Energy and exergy analysis of vapour compression refrigeration system using selected eco-friendly hydrocarbon refrigerants enhanced with tio2-nanoparticle

2017 ◽  
Vol 6 (4) ◽  
pp. 91 ◽  
Author(s):  
Luke Ajuka ◽  
Moradeyo Odunfa ◽  
Olayinka Ohunakin ◽  
Miracle Oyewola
Keyword(s):  
Power Consumption ◽  
Exergy Analysis ◽  
Capillary Tube ◽  
Coefficient Of Performance ◽  
Refrigeration System ◽  
Exergetic Efficiency ◽  
Evaporator Temperature ◽  
Energy And Exergy ◽  
Nano Lubricant ◽  
Energy And Exergy Analysis

The experimental study investigated the energy and exergy performance of a domestic refrigerator using eco-friendly hydrocarbon refrigerants R600a and LPG (R290/R600a: 50%/50%) at 0, 0.05, 0.15 and 0.3wt % concentrations of 15nm particle size of TiO2 nano-lubricant, and R134a. The effects of evaporator temperature on power consumption, coefficients of performance, exergetic efficiency and efficiency defects in the compressor, condenser, capillary tube and evaporator of the system were examined. The results showed that LPG + TiO2 (0.15wt %) and R600a + TiO2 (0. 15wt %) had the best of performances with an average of 27.6% and 14.3% higher coefficient of Performance, 34.6% and 35.15% lower power consumption, 13.8% and 17.53% higher exergetic efficiency, a total exergetic defect of 45.8% and 64.7% lower compared to R134a. The exergetic defects in the evaporator, compressor, condenser, and capillary tube were 38.27% and 35.5%, 49.19% and 55.56%, 29.7% and 33.7%, 39.1% and 73.8% lower in the system when compared to R134a respectively. Generally, the refrigerants with nano-lubricant mixture gave better results with an appreciable reduction in the exergy defect in the compressor than the pure refrigerants, and LPG + TiO2 (0. 15wt %) gave the best result in the refrigeration system based on energy and exergy analysis.

scholarly journals Parametric Optimization of a Two Stage Vapor Compression Refrigeration System by Comparative Evolutionary Techniques

2021 ◽  
Vol 287 ◽  
pp. 03002
Author(s):  
Shuhaimi Mahadzir ◽  
Rasel Ahmed
Keyword(s):  
Energy Consumption ◽  
Computation Time ◽  
Vital Role ◽  
Computational Effort ◽  
Coefficient Of Performance ◽  
Vapor Compression ◽  
Refrigeration System ◽  
Total Energy Consumption ◽  
Two Stage ◽  
Vapor Compression Refrigeration

Multistage refrigeration system plays a vital role in industrial refrigeration for the chemical, petrochemical, pharmaceuticals and food industries. Modern chemical industries are complex, and the problems are commonly multi-dimensional, non-linear and time-consuming. This study presents the application of evolutionary computation techniques, namely PSO (particle swarm optimization), GA (Genetic Algorithm) and SA (Simulated Annealing) to solve a design problem of a two-stage vapor compression refrigeration system. Two objectives are evaluated, namely the minimization of total energy consumption and maximization of the coefficient of performance (COP) of the system. The basis of design for the two-stage refrigeration system is built from and validated against data from published literature. The mass flow ratio, evaporator and condenser temperature, parameters for subcooling and desuperheating, and the coefficient of performance for the basis of design show acceptable results. The errors are below 5% against the data from published literature, which are within errors of significant figures in the calculations. In this work, the optimum solutions show a reduction of the required amount of energy consumption by 30.8% and an increase of the COP by nearly 77% with respect to the basis of design. Further improvements are made to the optimization procedures to prevent early convergence and to increase the search efficiency for finding the global optima. The findings by PSO, GA and SA are in agreement, and all evolutionary techniques achieved proper convergence of the two objective functions. It is also found that PSO requires lower computational effort, less computation time and is also easier to implement compared to GA and SA.

Optimal Allocation of Heat Exchanger Inventory of a Two-Stage Vapor Compression Cycle for Maximum Coefficient of Performance

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
M. J. Morales ◽  
S. A. Sherif
Keyword(s):  
Heat Exchanger ◽  
High Performance ◽  
Optimal Allocation ◽  
Low Cost ◽  
Coefficient Of Performance ◽  
Vapor Compression ◽  
Refrigeration System ◽  
Two Stage ◽  
Inventory Allocation ◽  
Maximum Coefficient

The purpose of this study is to investigate how the heat exchanger inventory allocation plays a role in maximizing the thermal performance of a two-stage refrigeration system with two evaporators. First, the system is modeled as a Carnot refrigerator and a particular heat transfer parameter is kept constant as the heat exchanger allocation parameter is allowed to vary. The value of the heat exchanger allocation parameter corresponding to the maximum coefficient of performance (COP) is noted. The results are compared to those of a non-Carnot refrigerator with isentropic and nonisentropic compression. It is found that the Carnot refrigerator can be used to predict the value of the heat exchanger allocation parameter where the maximum COP occurs for a non-Carnot refrigerator. In order to improve the accuracy of that prediction, the predicted value of the heat exchanger allocation parameter has to be inputted into the set of equations used for the non-Carnot refrigerator. This study is useful in designing a low-cost, high-performance refrigeration system.

Optimal Allocation of Heat Transfer Surface of a Two-Stage Refrigeration System

Volume 4 ◽  
2004 ◽  
Author(s):  
M. J. Morales ◽  
S. A. Sherif
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
High Performance ◽  
Optimal Allocation ◽  
Low Cost ◽  
Coefficient Of Performance ◽  
Refrigeration System ◽  
Two Stage ◽  
Isentropic Compression ◽  
Inventory Allocation

The purpose of this study is to investigate how the heat exchanger inventory allocation plays a role in maximizing the thermal performance of a two-stage refrigeration system with two evaporators. First, the system is modeled as a Carnot refrigerator and a particular heat transfer parameter is kept constant as the heat exchanger allocation parameter is allowed to vary. The value of the heat exchanger allocation parameter corresponding to the maximum coefficient of performance (COP) is noted. The results are compared to those of a non-Carnot refrigerator with isentropic and non-isentropic compression. It is found that the Carnot refrigerator can be used to predict the value of the heat exchanger allocation parameter where the maximum COP occurs for a non-Carnot refrigerator. In order to improve the accuracy of that prediction, the predicted value of the heat exchanger allocation parameter has to be inputted into the set of equations used for the non-Carnot refrigerator. This study is useful in designing a low cost, high-performance refrigeration system.

Study on the Hybrid Liquid Desiccant Evaporative Cooling Air-Conditioning Refrigeration Circulation System

2012 ◽  
Vol 516-517 ◽  
pp. 1250-1256 ◽  
Author(s):  
Liu Xiong
Keyword(s):  
Air Conditioning ◽  
Evaporative Cooling ◽  
Coefficient Of Performance ◽  
Circulation System ◽  
Refrigeration System ◽  
Conventional System ◽  
Liquid Desiccant ◽  
Two Stage ◽  
Cooling Air ◽  
New System

This article presents a new hybrid evaporative cooling air-conditioning refrigeration system using two-stage liquid desiccant, and carries off the theoretical study on it. Compared with the conventional liquid desiccant air-conditioning refrigeration system, the new system adopts direct mixing heat transfer technology and evaporative cooling technology instead of water-cooled or air-cooled technology. Thus the cooling water usage is reduced. Using the two-stage adiabatic absorber and using refrigerant rather than water as the cooling medium of desiccant solution, the pressure difference of mass transfer is increased. Compared with the conventional system, the heat of regenerating solution is decreased because the mass ratio of air to desiccant solution is increased which gives rise to the decline of solution's mass rate. The results of theoretical calculation show that the new system has the better performance in power consumption, usage of water and equivalent coefficient of performance than the conventional system.

Exergy Analysis of a Solar-Driven Dual Parallel-Connected Ejector Refrigeration System

2016 ◽  
Vol 839 ◽  
pp. 100-106
Author(s):  
Yahya Gaafar Abdella Mohammed ◽  
Tawat Suriwong ◽  
Sakda Somkun ◽  
Timeyo Mkamanga Maroyi
Keyword(s):  
Solar Collector ◽  
Exergy Analysis ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Saturated Steam ◽  
Working Fluid ◽  
Electric Heater ◽  
Exergy Destruction ◽  
Refrigeration System ◽  
Exergetic Efficiency

Nowadays, developing solar cooling technologies, especially ejector refrigeration system, has become preferable to scientific researchers. Exergy analysis is a technique in which the basis of evaluation of thermodynamic losses follows the second law rather than the first law of thermodynamics. An experimental exergy analysis of a solar-driven dual parallel-connected ejector (DPE) refrigeration system was conducted using water as working fluid. Saturated steam with 2 bar and 120oC was provided by heat–pipe evacuated tube solar collector with an assistant of an electric heater. The saturated stream was used as a motive flow for the ejectors. The exergy destruction and exergetic efficiency of the main components of the DPE refrigeration system were determined and compared with those when using a single ejector (SE) under same operating conditions. It was found that the most irreversibilities of both systems occurred at the solar collector, electric boiler and ejectors, respectively. Also, the total irreversibility (Exergy destruction) of the system when using DPE was lower than using a SE. In additions, the exergetic efficiency of the ejector, evaporator, and overall system when using DPE were increased by 21%, 10%, and 27%, respectively. The system thermal ratio (STR) and coefficient of performance (COP) of the system using DPE compared with SE were increased by 20% and 23%, respectively.

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