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.

Optimum Refrigerating Efficiency and Exergy Index of a Two-Stage Refrigeration Cycle

Volume 1 ◽  
2004 ◽  
Author(s):  
J. S. Tiedeman ◽  
S. A. Sherif
Keyword(s):  
Performance Optimization ◽  
Geometric Mean ◽  
Maximum Error ◽  
Second Law ◽  
Refrigeration Cycle ◽  
Vapor Compression ◽  
Two Stage ◽  
Optimization Study ◽  
Vapor Compression Refrigeration Cycle ◽  
Vapor Compression Refrigeration

This paper presents results of an optimization study for a two-stage vapor compression refrigeration cycle based on the refrigerating efficiency and exergy index. Traditional two-stage refrigeration cycle 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. Results of this study indicate that the use of the common approximation of the geometric mean to find the optimum interstage pressure leads to nearly optimum results for the refrigerating efficiency, with maximum error in the neighborhood of 5%. However, the error associated with using this approximation to find the optimum exergy index is too large, approaching 15%. Second law optimization revealed that the optimum data curves themselves have maxima for each set of conditions tested. There are a series of conditions that lead 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. Polynomial equations have been fitted to the resultant optimum data for the refrigerating efficiency and exergy index. 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 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.

Second law optimization of two-stage transcritical CO2 refrigeration cycles in the cooling mode operation

2009 ◽  
Vol 223 (5) ◽  
pp. 551-561 ◽  
Author(s):  
M Yari
Keyword(s):  
Geometric Mean ◽  
Internal Heat ◽  
Coefficient Of Performance ◽  
Second Law ◽  
Refrigeration Cycle ◽  
Cooling Mode ◽  
Two Stage ◽  
Entrainment Ratio ◽  
Cycle Simulation ◽  
Mean Pressure

Second law optimization studies of two-stage transcritical CO2 (TRCC) refrigeration cycles, incorporating options such as a new ejector-expansion with internal heat exchanger (IHE) and intercooler (IC), flash gas bypass, flash gas intercooling, compressor intercooling with IHE, are presented based on cycle simulation. To validate the simulations, the available numerical data in open literature are used. It is found that the coefficient of performance (COP) and second law efficiency of the new two-stage TRCC cycle are on average 16.5, 18.4, and 28.4 per cent higher than that of the two-stage TRCC with IHE and IC, the two-stage TRCC with flash gas bypass, and the two-stage TRCC with flash gas intercooling cycles, respectively. Hence, the new two-stage refrigeration cycle is a promising refrigeration cycle from the thermodynamic point of view. It is also concluded that for cases of the flash gas bypass and flash gas intercooling the optimum inter-stage pressure deviates significantly from the geometric mean pressure of the gas cooler and evaporator pressure. While for the new two-stage TRCC and the two-stage TRCC with IHE and IC, the optimum inter-stage pressure is approximately equal to geometric mean pressure. Finally, a regression analysis was employed in terms of evaporator and gas cooler exit temperatures to develop mathematical expressions for maximum COP, optimum discharge, and inter-stage pressures and entrainment ratio.

scholarly journals Cop Enhancement of Vapour Compression Refrigeration System

2021 ◽  
pp. 1-6
Author(s):  
B Sairamakrishna ◽  
◽  
T Gopala Rao ◽  
N Rama Krishna ◽  
◽  
...  
Keyword(s):  
Tube Diameter ◽  
Coefficient Of Performance ◽  
Refrigeration System ◽  
Expansion Valve ◽  
Compressor Inlet ◽  
Work Input ◽  
Compressor Work ◽  
Vapour Compression ◽  
Design And Testing ◽  
Nozzle Inlet

This experimental investigation exemplifies the design and testing of diffuser at compressor inlet and nozzle at condenser outlet in vapour compression refrigeration system with the help of R134a refrigerant. The diffuser with divergence angle of 12°,14° and the nozzle with convergent angle 12°,14° are designed for same inlet and outlet diameters. Initially diffusers are tested at compressor inlet diffuser is used with inlet diameter equal to exit tube diameter of evaporator and outlet tube diameter is equal to suction tube diameter of the compressor. Diffuser helps to increases the pressure of the refrigerant before entering the compressor it will be helps to reduces the compression work and achieve higher performance of the vapour compression refrigeration system. Then nozzles are testing at condenser outlet, whereas nozzle inlet diameter equal to discharging tube diameter of condenser and outlet diameter equal to inlet diameter of expansion valve. Additional pressure drop in the nozzle helped to achieve higher performance of the vapour compression refrigeration system. The system is analyzes using the first and second laws of thermodynamics, to determine the refrigerating effect, the compressor work input, coefficient of performance (COP).

Experimental Analysis on Vapour Compression Refrigeration System Using Nanolubricant with HFC-134a Refrigerant

Nano Hybrids ◽  
2015 ◽  
Vol 9 ◽  
pp. 33-43 ◽  
Author(s):  
A. Manoj Babu ◽  
S. Nallusamy ◽  
K. Rajan
Keyword(s):  
Energy Consumption ◽  
System Performance ◽  
Mineral Oil ◽  
Coefficient Of Performance ◽  
Refrigeration System ◽  
Hfc 134A ◽  
Reduce Energy Consumption ◽  
And Performance ◽  
Vapour Compression ◽  
Better Than

This paper investigates the reliability and performance of a refrigeration system using nanolubricant with 1, 1, 1, 2-Tetrafluoroethane (HFC-134a) refrigerant. Mineral Oil (MO) is mixed with nanoparticles such as Titanium Dioxide (TiO2) and Aluminium Oxide (Al2O3). These mixtures were used as the lubricant instead of Polyolester (POE) oil in the HFC-134a refrigeration system as HFC-134a does not compatible with raw mineral oil. An investigation was done on compatibility of mineral oil and nanoparticles mixture at 0.1 and 0.2 grams / litre with HFC-134a refrigerant. To carry out this investigation, an experimental setup was designed and fabricated in the lab. The refrigeration system performance with the nanolubricant was investigated by using energy consumption test. The results indicate that HFC-134a and mineral oil with above mentioned nanoparticles works normally and safely in the refrigeration system. The refrigeration system performance was better than the HFC-134a and POE oil system. Thus nanolubricant (Mixture of Mineral Oil (MO) and nanoParticles) can be used in refrigeration system to considerably reduce energy consumption and better Coefficient of Performance (COP).

Environment Friendly Mixed Refrigerant to Replace R-134a in a VCR System with Exergy Analysis

2014 ◽  
Vol 984-985 ◽  
pp. 1174-1179
Author(s):  
N. Austin ◽  
P.M. Diaz ◽  
D.S. Manoj Abraham ◽  
N. Kanthavelkumaran
Keyword(s):  
Global Warming ◽  
Global Warming Potential ◽  
Ozone Depletion ◽  
Exergy Analysis ◽  
Coefficient Of Performance ◽  
Refrigeration System ◽  
Evaporator Temperature ◽  
Environment Friendly ◽  
A Charge ◽  
Vapour Compression

Study on environment friendly mixed refrigerant to replace R134a in vapour compression refrigeration (VCR) System. The mixed refrigerants investigated are propane (R290), butane (R600), isobutene (R600a) and R134a. Even though the ozone depletion potentials of R134a relative to CFC-11 are very low; the global warming potentials are extremely high and also expensive. For this reason, the production and use of R134a will be terminated in the near future. Hydrocarbons are free from ozone depletion potential and have negligible global warming potential. The results showed that, mixed refrigerant with charge of 80 g satisfy the required freezer air temperature when R134a with a charge of 110 g is used as refrigerant. The actual COP of refrigerator using mixed refrigerant was almost nearer that of the system using R134a as refrigerant. The coefficient of performance of the vapour compression refrigeration system using mixed refrigerant MR-3 [R134a/R290/ R600a/ R600 (20/35/40/5)] is having very close value with R134a and the Global warming potential of MR-3 is negligible when compared with R134a. Hence the mixed refrigerant MR-3 is chosen as an environmental friendly alternate refrigerant to R134a. The exergy analysis of the vapour compression refrigeration system using R134a and all the above mixtures are investigated. The effect of evaporator temperature on exergy efficiency and exergy destruction ratio of the system are experimentally studied. The exergy defect in the compressor, condenser, expansion device and evaporator are also obtained. Key words: R134a, Mixed refrigerant, Chlorofluorocarbons, Propane, Butane, Isobutene, REFPROP, COP, ODP, GWP, Exergy, VCR System.

scholarly journals Exergy Analysis of VCR Systemwith Air-Cooled Condenser Working with Refrigerants R-134a & Hydrocarbon

2019 ◽  
Vol 9 (2) ◽  
pp. 2834-2839
Keyword(s):  
Global Warming ◽  
Global Warming Potential ◽  
Exergy Analysis ◽  
Exergy Destruction ◽  
Refrigeration System ◽  
Exergetic Efficiency ◽  
Domestic Refrigerator ◽  
R 134A ◽  
Main Components ◽  
Vapour Compression

This paper gives a detailed exergy analysis of a Vapour Compression Refrigeration System with the refrigerants R-134a and HC (mixture of R-290/R-600a). The aim of this paper is to find out the Exergy Analysis, Exergetic efficiency, Exergy Product, Exergy Destruction Ratio (EDR), Co-efficient of performance and 2nd law efficiency for the main components of the system such as compressor, condenser, evaporator and expansion device (throttle valve). The objective of this work is to find out an exergy analysis of the Hydrocarbon refrigerant as an alternative for R-134a. The VCRS performance using R134a will be evaluated for the effect of evaporating temperature on COP, exergetic efficiency and EDR and then compared with Hydrocarbon refrigerant. Due to prevention of GWP (Global Warming Potential), Hydrocarbon and R-134a are used as refrigerants to give better result for domestic refrigerator operation[8] .

A Review on Energy and Exergy Analysis of Two-Stage Vapour Compression Refrigeration System

2019 ◽  
Vol 27 (02) ◽  
pp. 1930001 ◽  
Author(s):  
Shounak Chowdhury ◽  
Ranendra Roy ◽  
Bijan Kumar Mandal
Keyword(s):  
Exergy Analysis ◽  
Refrigeration System ◽  
Alternative Refrigerants ◽  
Governing Equations ◽  
Two Stage ◽  
Numerical Investigations ◽  
Energy And Exergy ◽  
Energy And Exergy Analysis ◽  
Exergetic Analysis ◽  
Vapour Compression

This paper presents a review on energy and exergy analysis of two-stage vapour compression refrigeration (VCR) system. The use of alternative refrigerants instead of conventional refrigerants has also been addressed. The governing equations for the energetic and exergetic analysis of two-stage VCR system have been identified and presented. Several experimental and numerical investigations and their findings on the performance of the two-stage VCR system available in the literature have been discussed in brief. Some of the results have also been reproduced as case studies.

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