Energetic and exergetic studies of modified CO2 transcritical refrigeration cycles

Abstract Thermodynamic analysis including energetic and exergetic analysis is carried out employing Engineering Equation Solver for the five modified cycles: dual expansion cycle, internal heat exchanger cycle, work recovery cycle, work recovery with internal heat exchanger cycle and vortex tube expansion cycle. Contours are developed to study the effect of gas cooler temperatures and evaporator temperatures on the system performance and optimum gas cooler pressure. The modified cycle with work recovery turbine offers relatively higher COP and higher exergetic efficiency with lower compressor discharge pressure. The exergy loss in compressor, gas cooler, throttle valve and vortex tube (VT) are considerably higher than that in internal heat exchanger (IHX), evaporator and turbine. It is observed that COP of modified cycle with VT is slightly less than that with IHX, whereas the cycle with work recovery turbine brings the highest COP with the improvement of 25% at the gas cooler exit temperature of 305 K and evaporator temperature of 248 K.

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Cooling Performance of an Modified R744 Air Conditioning System with Vortex Tube and Internal Heat Exchanger for an Electric Vehicle

10.4271/2021-24-0098 ◽

2021 ◽

Author(s):

Barbara Malgorzata Mendecka ◽

Daniele Chiappini ◽

Gino Bella

Keyword(s):

Heat Exchanger ◽

Electric Vehicle ◽

Air Conditioning ◽

Vortex Tube ◽

Internal Heat ◽

Air Conditioning System ◽

Cooling Performance ◽

Internal Heat Exchanger

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Performance and exergetic analysis of vapor compression refrigeration system with an internal heat exchanger using a hydrocarbon, isobutane (R600a)

International Journal of Energy Research ◽

10.1002/er.1396 ◽

2008 ◽

Vol 32 (9) ◽

pp. 824-836 ◽

Cited By ~ 37

Author(s):

Ahmet Kabul ◽

Önder Kizilkan ◽

Ali Kemal Yakut

Keyword(s):

Heat Exchanger ◽

Internal Heat ◽

Vapor Compression ◽

Refrigeration System ◽

Internal Heat Exchanger ◽

Vapor Compression Refrigeration ◽

Exergetic Analysis

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Performance Assessments of Organic Rankine Cycle With Internal Heat Exchanger Based on Exergetic Approach

Journal of Energy Resources Technology ◽

10.1115/1.4040108 ◽

2018 ◽

Vol 140 (10) ◽

Cited By ~ 7

Author(s):

Nurettin Yamankaradeniz ◽

Ali Husnu Bademlioglu ◽

Omer Kaynakli

Keyword(s):

Heat Exchanger ◽

Organic Rankine Cycle ◽

Internal Heat ◽

Rankine Cycle ◽

Performance Assessments ◽

Evaporator Temperature ◽

Pinch Point ◽

Internal Heat Exchanger ◽

Energy And Exergy ◽

Energy And Exergy Analysis

This study makes energy and exergy analysis of a sample organic Rankine cycle (ORC) with a heat exchanger which produces energy via a geothermal source with a temperature of 140 °C. R600a is preferred as refrigerant to be used in the cycle. The changes in exergy destructions (of irreversibility) and exergy efficiencies in each cycle element are calculated in the analyses made based on the effectiveness of heat exchanger used in cycle and evaporator temperature changing between 60 and 120 °C for fixed pinch point temperature differences in evaporator and condenser. Parameters showing system performance are assessed via second law approach. Effectiveness of heat exchanger and temperature of evaporator are taken into consideration within the scope of this study, and energy and exergy efficiencies of cycle are enhanced maximum 6.87% and 6.21% respectively. Similarly, exergy efficiencies of evaporator, heat exchanger, and condenser are increased 4%, 82%, and 1.57%, respectively, depending on the effectiveness of heat exchanger and temperature of evaporator.

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Optimal discharge pressure in transcritical CO2 heat pump water heater with internal heat exchanger based on pinch point analysis

International Journal of Refrigeration ◽

10.1016/j.ijrefrig.2020.06.003 ◽

2020 ◽

Vol 118 ◽

pp. 12-20

Author(s):

Zuliang Ye ◽

Yikai Wang ◽

Yulong Song ◽

Xiang Yin ◽

Feng Cao

Keyword(s):

Heat Exchanger ◽

Heat Pump ◽

Internal Heat ◽

Water Heater ◽

Pinch Point ◽

Internal Heat Exchanger ◽

Heat Pump Water Heater ◽

Point Analysis ◽

Discharge Pressure

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CO2 Trans-Critical Two Stage Compression Refrigeration Cycle with Vortex Tube

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.52-54.255 ◽

2011 ◽

Vol 52-54 ◽

pp. 255-260 ◽

Cited By ~ 3

Author(s):

Ying Bai Xie ◽

Kui Kui Cui ◽

Zhi Chao Wang ◽

Jian Lin Liu

Keyword(s):

Mass Fraction ◽

Vortex Tube ◽

Refrigeration Cycle ◽

Two Stage ◽

Fluid Mass ◽

Cold Fluid ◽

Exit Temperature ◽

Discharge Pressure ◽

Tube Expansion ◽

Cold Gas

The paper analyses CO2 trans-critical two stage compression refrigeration cycle with vortex tube expansion by thermodynamics method. And compare with CO2 trans-critical two stage compression refrigeration cycle with expansion value. The results show that in the calculated conditions of the paper, the performance of the cycle with vortex tube improves 2.4%~16.3% than the cycle with expansion value. The optimal discharge pressure maximizing COP of the cycle with vortex tube exists. With lower evaporating temperature or higher gas cooler exit temperature, COP of system decreases and COP improvement increases. The effect of cold fluid mass fraction on COP is not significant, but COP improvement increases more quickly with cold gas mass fraction increasing.

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