• Journal of Fisheries and Marine Sciences Education
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• v.25 no.2
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• pp.301-306
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• 2013

In this paper, cycle performance analysis of two-stage compression and two-stage expansion refrigeration system using alternative freon refrigerants is presented to offer the basic design data for the operating parameters of the system. Alternative freon refrigerant for freon refrigerant R22 were used as working fluids in this study. The operating parameters considered in this study included evaporation temperature, condensation temperature, subcooling degree, superheating degree, and mass flow rate ratio of inter-cooler. The main results were summarized as follows : The COP of two-stage compression and two-stage expansion refrigeration system increases with the increasing subcooling degree and mass flow rate ratio of inter-cooler, but decreases with the increasing evaporating temperature, condensing temperature and superheating degree. Therefore, subcooling degree, mass flow rate ratio of inter-cooler of two-stage compression and two-stage expansion refrigeration system using alternative freon refrigerants have an effect on COP of this system.

• Journal of Power System Engineering
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• v.13 no.6
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• pp.70-75
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• 2009

In this paper, cycle performance analysis of R744($CO_2$) two-stage compression and one-stage expansion refrigeration system is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include superheating degree, compressor efficiency, gas cooling pressure, mass flowrate ratio, outlet temperature of gas cooler and evaporating temperature in the carbon dioxide two-stage refrigeration cycle. The main results were summarized as follows : The cooling capacity of two-stage compression and one-stage expansion refrigeration system increases with the increasing superheating degree, compressor efficiency and gas cooling pressure, but decreases with the increasing mass flowrate ratio and evaporating temperature. The compression work of two-stage compression and one-stage expansion refrigeration system increases with the increasing superheating degree, outlet temperature of gas cooler, gas cooling pressure and evaporating temperature, but decreases with the increasing compressor efficiency and mass flowrate ratio. The COP of two-stage compression and one-stage expansion refrigeration system increases with the increasing compressor efficiency, but decreases with the increasing superheating degree, gas cooling pressure, mass flowrate ratio and evaporating temperature. Therefore, superheating degree, compressor efficiency, gas cooling pressure, mass flowrate ratio, outlet temperature of gas cooler and evaporating temperature of R744($CO_2$) two-stage compression and one-stage expansion refrigeration system have an effect on the cooling capacity, compressor work and COP of this system.

• Journal of Power System Engineering
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• v.18 no.1
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• pp.57-62
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• 2014

This paper present the performance characteristics of R404A two-stage compression refrigeration system. The operating parameters considered in this study include evaporating and condensing temperature, subcooling and superheating degree, compressor efficiency. The main results were summarized as follows: The COP of two-stage compression refrigeration system using R404A has an effect on the variation of evaporation temperature, condensation temperature, subcooling degree and compressor efficiency, but not an effect on the superheating degree. R404A two-stage compression refrigeration system is unstable because COP of this system is significantly changed when evaporating temperature and compressor efficiency decreased. In particular, when compressor efficiency decreased, COP is significantly decreased. This is inefficient for long-term use.

• Journal of Power System Engineering
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• v.19 no.6
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• pp.82-88
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• 2015

In this paper, cycle performance analysis of two-stage compression and one-stage expansion refrigeration system applied various refrigerants is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include degree of superheating and subcooling, compressor efficiency, evaporation temperature, condensing temperature, mass flow rate ration into inter-cooler, effectiveness of internal heat exchanger. The main results were summarized as follows : The COP of two-stage compression and 1-stage expansion refrigeration system increases with the increasing subcooling, mass flow rate ration of inter-cooler, evaporation temperature, but decreases with the increasing condensing temperature and superheating degree. Therefore, subcooling degree, mass flow rate ratio of inter-cooler of two-stage compression and 1-stage expansion using substitute refrigerant have an effect on COP of this system. The COP of alternative refrigerants was higher than the COP of R22 in this study, although the COP of some mixed refrigerants were lower than COP of R22.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.8
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• pp.3106-3111
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• 2010

In this study, a comparative study was performed between one- and two-stage refrigeration system to cool the natural gas temperature down to $-40^{\circ}C$ using propane as a chilling medium. As a thermodynamic model, Peng-Robinson equation of state equation was applied and PRO/II with PROVISION release 8.3 at Invensys company was utilized for the simulation of the refrigeration system. Through this study, optimization work showed that two-stage refrigeration system was proven to save about 33.5% refrigeration power consumption compared to the one-stage refrigeration cycle.

• Journal of the Korean Institute of Gas
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• v.14 no.1
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• pp.1-7
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• 2010

In this paper, cycle performance analysis of $NH_3-CO_2$(R717-R744) two-stage cascade refrigeration system is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooling and superheating degree, compressor efficiency, and condensing and evaporating temperature in the ammonia(R717) high temperature cycle and the carbon dioxide low temperature cycle. The main results were summarized as follows : The COP of two-stage cascade refrigeration system increases with the increasing subcooling degree, but decreases with the increasing superheating degree. The COP of two-stage cascade refrigeration system decreases with the increasing condensing temperature, but increases with the increasing evaporating temperature. And the COP of two-stage cascade refrigeration system increases with increasing the compressor efficiency. Therefore, superheating and subcoolng degree, compressor efficiency, and evaporating and condensing temperature of $NH_3-CO_2$(R717-R744) two-stage cascade refrigeration system have an effect on the COP of this system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.625-631
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• 2014

In order to obtain a low evaporation temperature ranging from $-30^{\circ}C{\sim}-50^{\circ}C$, a cascade refrigeration system and two-stage compression one-stage expansion refrigeration system is required. However, the research results of performance comparison of these refrigeration system are very scarce. This paper were compared the performance characteristics of R744-R404A cascade refrigeration system and R404A two-stage compression refrigeration system. The COP of R404A two-stage compression refrigeration system is about 36~57% greater than that of R744-R404A cascade refrigeration system in the range of evaporation temperature of $-30^{\circ}C{\sim}-50^{\circ}C$. But R404A two-stage compression refrigeration system is unstable because COP is significantly changed when evaporating temperature and compressor efficiency decreased. In particular, when compressor efficiency decreased, COP is significantly decreased. In this case, not efficient for long-term use. Whereas R744-R404A cascade refrigeration system using natural refrigerants. Therefore, it is environmentally friendly. And this system is high-efficiency refrigeration system. The reason it can be configured by selecting the suitable refrigerant at high-temperature side and low-temperature side. From the above results, select the appropriate low temperature refrigeration system by considering the environmental and performance aspects.

• Journal of Power System Engineering
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• v.20 no.2
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• pp.85-90
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• 2016

Coefficient of performance (COP) for two-stage compression system is investigated in this paper to develop seawater ice machine. The system performance is analyzed with respect to degrees of superheating and subcooling, condensing and evaporating temperatures, compression and mechanical efficiencies and mass flow ratio in an inter-cooler. The main results are summarized as follows : The COP of the system grows when the mass flow ratio, subcooling degree and evaporating temperature edge up. Contrariwise, the system performance descends in case that superheating degree and condensing temperature increase. The most effective factor for the COP is the mass flow rate ratio. Each refrigerant has different limitation for a value of the mass flow ratio in the inter-cooler because of difference in material property.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.2
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• pp.81-86
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• 2015

Performance of freezing and refrigeration systems in supermarket, which utilized $CO_2$ as a refrigerant, was investigated by using the Pack Calculation II. The configuration of simulated systems was basic parallel refrigeration system, cascade system, and two-stage system. The $CO_2$ cascade system showed higher COP than basic parallel R404A system by 13% for MT and 62% for LT, respectively. Among the $CO_2$ cascade systems, R717(MT)-$CO_2$(LT) showed the highest performance. Open-type intercooler method showed higher performance than liquid injection for the two-stage $CO_2$ systems.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.28.2-28.2
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• 2005