Exergetic Investigation of the Effects of Superheating and Subcooling on Performance of a Vapor Compression Refrigeration Cycle

Abstract From the last few years, the use of efficient ejector in refrigeration systems has been paid a lot of attention. In this article a description of a refrigeration system that combines a basic vapor compression refrigeration cycle with an ejector cooling cycle is presented. A one-dimensional mathematical model is developed using the flow governing thermodynamic equations based on a constant area ejector flow model. The model includes effects of friction at the constant-area mixing chamber. The current model is based on the NIST-REFPROP database for refrigerant property calculations. The model has basically been used to determine the effect of the ejector geometry and operating conditions on the performance of the whole refrigeration system. The results show that the proposed model predicts ejector performance, entrainment ratio and the coefficient of performance of the system and their sensitivity to evaporating and generating temperature of the cascade refrigeration cycle. The simulated performance has been then compared with the available experimental data from the literature for validation.

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Molecular-level computer simulation of a vapor-compression refrigeration cycle

Fluid Phase Equilibria ◽

10.1016/j.fluid.2007.06.020 ◽

2007 ◽

Vol 259 (2) ◽

pp. 195-200 ◽

Cited By ~ 5

Author(s):

S. Figueroa-Gerstenmaier ◽

M. Francova ◽

M. Kowalski ◽

M. Lisal ◽

I. Nezbeda ◽

...

Keyword(s):

Computer Simulation ◽

Molecular Level ◽

Refrigeration Cycle ◽

Vapor Compression ◽

Vapor Compression Refrigeration Cycle ◽

Vapor Compression Refrigeration

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THEORETICAL AND EXPERIMENTAL ANALYSIS OF A VAPOR-COMPRESSION REFRIGERATION CYCLE WITH A HEAT EXCHANGER BETWEEN THE SUCTION AND LIQUID LINES

Revista de Engenharia Térmica ◽

10.5380/reterm.v18i2.70783 ◽

2019 ◽

Vol 18 (2) ◽

pp. 19

Author(s):

L. S. Santana ◽

J. Castro ◽

L. M. Pereira

Keyword(s):

Heat Exchanger ◽

Experimental Analysis ◽

Thermodynamic Cycle ◽

Electrical Energy ◽

Coefficient Of Performance ◽

Refrigeration Cycle ◽

Vapor Compression ◽

Vapor Compression Refrigeration Cycle ◽

Vapor Compression Refrigeration ◽

Liquid Heat

Vapor-compression refrigeration systems require a significant amount of electrical energy. Therefore, there is a need for finding efficient ways of operating this equipment, reducing their energy consumption. The use of heat exchangers between the suction line and the liquid line can produce a better performance of the thermodynamic cycle, as well as reduce it. The present work aims at an experimental analysis of the suction/liquid heat exchanger present in a freezer running with refrigerant fluid R-134a. Three different scenarios were used in order to evaluate the thermal performance of the refrigeration cycle. The first scenario was the conventional freezer set up to collect the required data for further comparison. Moreover, the second and third scenarios were introduced with a 20 cm and 40 cm suction/liquid heat exchanger, respectively, into the system. From the experiments, it was observed that the heat exchange does not significantly affect the coefficient of performance (COP) of the freezer. It was concluded from this work that the best scenario analyzed was the 20 cm suction/liquid heat exchanger where most of the thermodynamic properties were improved, one of them being the isentropic efficiency.

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Comparison of Subcooling Effect of Water as a Refrigerant With the Current Refrigerants

Process Industries ◽

10.1115/imece2006-13122 ◽

2006 ◽

Author(s):

Ali Kilicarslan ◽

Norbert Mu¨ller

Keyword(s):

Computer Program ◽

Performance Comparison ◽

The Other ◽

Refrigeration Cycle ◽

Vapor Compression ◽

Evaporator Temperature ◽

Vapor Compression Refrigeration Cycle ◽

Condenser Temperature ◽

Vapor Compression Refrigeration ◽

Compressor Efficiency

The performance comparison of water as a refrigerant (R718) with some prevailing refrigerants including R717, R290, R134a, R12, R22, and R152a is presented. A computer program simulating an actual vapor compression refrigeration cycle including subcooling was developed to calculate the coefficient of performances (COPs) for the different refrigerants. Evaporator temperatures above which water yields a better COP over the other refrigerants are investigated for subcooling case. The effect of degree of subcooling on the COPs is elaborated. For most of the refrigerants (R290, R134a, R12, R22, and R152a) the COP increases by around one percent (1%) per one Kelvin (1K) subcooling, while the COP for R718 and R717 increases by around 0.2 % and 0.5 % per one Kelvin (1K) subcooling. At constant evaporator temperature, increasing the degree of subcooling results in decrease of the relative COP gain of R718. R718 gives the highest relative COP increase at constant condenser temperature and polytropic efficiency. The effect of polytropic efficiency on the performance is also investigated. It is observed that the evaporator temperature range at which R718 presents a better COP than other refrigerants increases with increasing values of polytropic compressor efficiency if the degree of subcooling is kept constant.

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Transient Vapor Compression Refrigeration Cycle for Electronics Cooling: Part 2—Multi-Evaporator Dynamics and Control

Volume 10: Heat and Mass Transport Processes, Parts A and B ◽

10.1115/imece2011-62456 ◽

2011 ◽

Author(s):

TieJun Zhang ◽

John T. Wen ◽

Michael K. Jensen

Keyword(s):

Thermal Management ◽

Energy Efficient ◽

Transient Analysis ◽

Electronics Cooling ◽

Refrigeration Cycle ◽

Vapor Compression ◽

Cooling Systems ◽

Computation Efficiency ◽

Vapor Compression Refrigeration Cycle ◽

Vapor Compression Refrigeration

For next-generation sustainable electronic systems, such as high-concentration photovoltaics arrays and high-density super-computers, two-phase cooling technologies are being explored to significantly reduce heat resistance from electronics’ surface to the ambient. Lower electronics operating temperatures lead to higher energy conversion or computation efficiency; therefore, thermal management, especially dynamic thermal management, is able to bring great potential to energy-efficient electronic system operation. These large-scale electronics cooling systems normally include multiple, distributed, and transient heat sources. Multi-evaporator vapor compression refrigeration cycle provides such a promising cooling solution. Due to the complexity of multiple evaporator structure, its transient analysis and active control become very challenging. This paper applies our previous distributed heat exchanger modeling techniques to study the dynamics of multi-evaporator refrigeration cycles. A comprehensive first-principle multi-evaporator vapor compression cycle model is formulated for its transient analysis. Some preliminary expansion valve control results are presented to show the excellent active electronics cooling capability. This general tool is expected to bring instructive guidelines for the optimal design and operation of energy-efficient transient electronics cooling systems with multiple heat loads and hot spots.

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