• 태양에너지
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• 제18권1호
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• pp.69-79
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• 1998

This paper is concerned about the performance of HCFC22 alternative refrigerants used in heat pumps and industrial chillers. A water-to-water breadboard heat pump with counter-current heat exchangers and a hermetic compressor was built to carry out the experiments with various refrigerants. For each test, more than 40 temperatures, 4 pressures, power input, mass flow rates of the heat transfer fluids were measured. Refrigerants tested were HCFC22, R290(Propane), an azeotrope of 45%Propane/55%R134a mixture, and a nonazeotropic mixture of Calor 50. All tests were conducted under ARI test A condition. It is found that the COP and capacity of propane were 18% and 2.5% higher than those of HCFC22 while the COP and capacity of 45%Propane/55%R134a mixture were 3.5% and 5.3% higher than those of HCFC22 respectively. Also the COP and capacity of Calor 50 were 17% and 7.8% higher than those of HCFC22. Compressor discharge temperatures of alternative refrigerants were roughly $35^{\circ}C$ lower than that of HCFC22 indicating that these refrigerants are good from the view point of compressor reliability. The charging amounts for the alternative refrigerants were reduced by 40-60% as compared to that of HCFC22. Overall, it can be said that hydrocarbon containing alternative refrigerants are excellent in thermodynamic performance but should be used with considerable care due to their flammability.

• 설비공학논문집
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• 제8권1호
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• pp.55-64
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• 1996

A numerical model of refrigerant flow through a capillary tube is developed, which considers the effects of underpressure for vaporization, kinetic energy, and roughness of capillary tube. The numerical model is based on homogeneous flow assumptions for the two-phase flow region. A characteristic chart of HFC refrigerants flow through capillary tubes and correction factor chart of geometry and relative roughness of capillary tube to select a proper capillary for refrigerating machines using alternative refrigerants is presented by this numerical model.

• 대한기계학회논문집B
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• 제21권6호
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• pp.830-840
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• 1997

In this study, condensation heat transfer coefficients(HTCs) of CFC-11, HCFC-123 and HCFC-141b are measured, which are used/or considered as working fluids in centrifugal chillers. The main objectives of this study are to measure and compare the HTCs of various refrigerants on plain and low fin tubes and also to find out the optimum fin density of the low fin tubes. To accomplish these goals, HTCs of three refrigerants are measured for the plain tube as well as 4 types of low fin tubes. All measurements are carried out at the vapor temperature of 39.deg. C with the wall temperature difference of 3 .deg. C ~ 8.deg. C. For all the refrigerants tested, a low fin tube of 28 fins per inch yielded the best performance among all the tubes tested. For the plain tube, the HTCs of CFC-11 and HCFC-141b were very similar and those of HCFC-123 were 10% lower than those of CFC-11.Thus, it can be concluded that HCFC-123 and HCFC-141b are acceptable as alternative refrigerants for CFC-11 from the view point of condensation heat transfer.

• 설비공학논문집
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• 제13권5호
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• pp.377-387
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• 2001

This paper presents leakage characteristics of a scroll compressor applying alternative refrigerants of R22 such as R407c and R410a under actual operating conditions. Because leakage in a scroll compressor produce significant losses and degradation of performance, those should be clarified to design a high efficient scroll compressor with alternative refrigerants of R22. However, flank and tip leakage characteristics of a scroll compressor with alternative refrigerants are very limited in open literature. In the present study, both experimentation and modeling of the leakages in the scroll compressor were performed. As a result, it was observed that the leakages of the scroll compressor with R407c increased by 15%, and that with R410a increased by 76% as compared to the compressor applying R22 under standard load conditions due to a higher upstream pressure and a higher pressure difference between pockets.

• 설비공학논문집
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• 제10권4호
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• pp.411-422
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• 1998

In this study, experiments were carried out to provide nucleate pool boiling heat transfer data for a plain tube and 4 different low fin tubes employing 2 refrigerant mixtures of R410A, R407C, and 12 pure fluids. Low fin tubes were machined on a 19.05mm nominal outside diameter copper block according to the manufacturer's low fin tube specifications. Cartridge heaters were used to generate uniform heat flux on the tubes. For all refrigerants, heat flux varied from 10㎾/$\m^2$ to 80㎾/$\m^2$. It is found that heat transfer coefficients(HTCs) of high vapor pressure refrigerants are usually higher than those of low pressure fluids. On the other hand, the fin effect was more prominent with low pressure refrigerants than with high pressure ones. Optimum fin density as well as the increase in heat transfer coefficient with the increase in fin density were found to be strongly fluid dependent. HTCs of Rl23, a low pressure alternative refrigerant, were similar to those of Rll while HTCs of R134a, an intermediate pressure alternative refrigerant, were roughly 20% higher than those of Rl2. Finally, HTCs of R32, R125, R143a, and R410A were all higher than those of R22 by 30~50%.

• International Journal of Air-Conditioning and Refrigeration
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• 제6권
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• pp.67-79
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• 1998

This paper is about the performance of alternative refrigerants for low temperature and transport refrigeration chillers. A breadboard refrigeration chiller was constructed with counterflow heat exchangers. R502, its transitional alternatives of R402A and R402B, and long-term alternatives of R404A and R507 were tested in an attempt to compare the performance of each refrigerant against R502. Measurements were conducted at two condensing temperatures of 43.3$^{\circ}C$ and 52.$0^{\circ}C$ and the evaporating temperature was varied over a range from -$25^{\circ}C$ to -5$^{\circ}C$. The evaporator superheat and condenser subcooling were maintained constant at about 5$^{\circ}C$ for all tests. Test results showed that all alternative fluids tested in this work can be used as 'drop-in fluids' to replace R502 without any major problem. It is also found that in the long run HFC alternatives are to be used due to their favorable environmental characteristics and better performance.

• 한국기계기술학회지
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• 제13권1호
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• pp.73-79
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• 2011

In this paper, cycle performance analysis of cascade refrigeration system using alternative FREON refrigerants are presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooled and superheated degree, and evaporating and condensing temperature, temperature difference of cascade heat exchanger in cascade refrigeration system. The COP of cascade refrigeration system increases with the increasing subcooled degree, but there is no significant changes with the increasing superheated degree. The COP of cascade refrigeration system depends on evaporating and condensing temperatures of cascade heat exchanger. Therefore, subcooled degree, evaporating and condensing temperature of cascade heat exchanger using alternative FREON refrigerants have an effect on the COP of this system. In this paper, COP of cascade refrigeration system using R23 for low temperature system and R507A for high temperature system is higher 8 ~ 29 % than using R13 for low temperature system and R22 for high temperature system.

• 한국산학기술학회논문지
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• 제13권4호
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• pp.1427-1433
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• 2012

본 연구에서는 이원냉동시스템에서 사용되던 저온용 규제프레온냉매 R13 및 고온용 규제프레온냉매 R503의 대체냉매로서 프레온혼합냉매 및 친환경적 자연냉매를 사용하는 이원냉동시스템의 성능특성을 규명하고자 하였다. 이를 위해 일반적인 이원냉동시스템의 운전범위에서 과냉각도, 과열도, 응축온도, 증발온도, 캐스케이드 열교환기에서의 온도변화를 고려하였다. 고온시스템 및 저온시스템의 작동유체의 종류에 상관없이 이원냉동시스템의 COP는 캐스케이드의 온도영향을 받고 있으며, 또한 과냉각도가 증가할수록 COP는 높아지지만, 과열도의 영향은 크게 받지 않았다. 따라서 본 연구에서 고온용 시스템 및 저온용 시스템의 작동유체로 대체 프레온혼합냉매 및 자연냉매의 냉매조합 중에서 (R23/R290), (R23/R600), (R23/R600a), (R23/R717), (R744/R404A) 냉매를 사용하는 이원냉동시스템의 COP는 저온측에 R23, 고온측에 R22를 사용하는 시스템에 비해 20 ~ 36% 높게 나타났다.

• 설비공학논문집
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• 제17권10호
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• pp.883-890
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• 2005

In this study, 2 pure hydrocarbon refrigerants of R1270 (Propylene) and R290 (Propane) and 3 binary mixtures composed of R1270, R29O and R152a were tested in a refrigerating bench tester with a scroll compressor in an attempt to substitute R502 used in most of the low temperature applications. The test bench provided 3\sim3.5$ kW capacity and water and water/glycol mixture were employed as the secondary heat transfer fluids. All tests were conducted under the same external conditions resulting in the average saturation temperatures of -28 and $45^{\circ}C$ in the evaporator and condenser, respectively. Test results showed that all refrigerants tested had $9.6\sim18.7\%$ higher capacity and $17.1\sim27.3\%$ higher COP than R502. The compressor discharge temperature of R1270 was similar to that of R502 while those of all other refrigerants were $23.7\sim27.9\%$ lower than that of R502. For all alternative refrigerants, the amount of charge was reduced up to $60\%$ as compared to R502. Overall, these alternative refrigerants offer better system performance and reliability than R502 and can be used as long term substitutes for R502 due to their excellent environmental properties.

• 대한기계학회논문집B
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• 제22권7호
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• pp.966-979
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• 1998

Thermodynamic and dynamic analysis has been conducted to investigate performance variations induced by substitution of alternative refrigerants, HFC134a or HC600a for CFC12 in hermetic reciprocating compressors. For the thermodynamic analysis, mass and energy conservation laws are applied to the cylinder volume and Helmholtz resonator modeling method is adopted to describe gas pulsations at suction and discharge system. The modeling of the dynamics of the compressor mechanism has been performed with lumped mass method to analyse the bearing loads and friction losses at each bearing. To verify the correctness of this analysis, results of the performance simulation have been compared to those of calorimetric measurrements of compressor operating with CFC12. Analysis of the various losses, noise and reliability as well as performance has been conducted to present the design guideline for the compressor development with alternative refrigerants. It is found that compressors with alternative refrigerants, HFC 134a or HC600a give better COPs than those with CFC12 under the same operating conditions and especially, compressors with HC600a show better reliability and noise characteristics also.