• Title/Summary/Keyword: 냉매123

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Numerical Study on the HCFC-123 Leak in Turbo Chiller by using CFD (터보냉동기의 HCFC-123 누출에 대한 수치해석 연구)

  • Seo, Hoekyeong;Song, Sewook;Hwang, Yangin;Ha, Hyunchul
    • Journal of the Korean Institute of Gas
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    • v.18 no.5
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    • pp.85-90
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    • 2014
  • Turbo chiller is widely used for the air conditioner and uses hydrochlorofluorocarbon 123 (HCFC-123) as a refrigerant. HCFC-123 is one of the chemicals being considered as a replacement for the chlorofluorocarbons. High concentrations of HCFC-123 cause a deficiency of oxygen with the risk of unconsciousness or death, the vapour is heavier than air and may accumulate in low ceiling spaces causing deficiency of oxygen. In this study, the concentration distribution of oxygen indoor was investigated by using computational fluid dynamics(CFD) as four workers were killed in HCFC-123 gas leaks at machine room of hypermarket in 2011.

Performance Analysis of the Flooded Refrigerant Evaporators for Large Tonnage Compression-Type Refrigerators Using Alternative Refrigerants (대체냉매를 적용한 대형 압축식 냉동기의 만액식 증발기에 대한 성능 해석)

  • Kim, Nae-Hyun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.6
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    • pp.18-25
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    • 2016
  • Enhanced tubes are used widely in the evaporators of large tonnage compression-type refrigerators. The evaporators consist of tube bundles, and the refrigerant properties are dependent on the locations in the tube bundles. In particular, the saturation temperatures of low pressure refrigerants (R-11, R-123) are strongly dependent on the locations due to the saturation temperature-pressure curve characteristics. Therefore, for the proper design of evaporators, local property predictions of the refrigerants are necessary. In this study, a computer program that simulates the flooded refrigerant evaporators was developed. The program incorporated theoretical models to predict the refrigerant shell-side boiling heat transfer coefficients and pressure drops across the tube bundle. The program adopted an incremental iterative procedure to perform row-by-row calculations over the specified incremental tube lengths for each water-side pass. The program was used to simulate the flooded refrigerant evaporator of the "T" company operating with R-123, which yielded satisfactory results. The program was extended to predict the performance of the flooded refrigerant evaporator operating with R-11, R-123, and R-134a. The effects of bundle aspect ratio are investigated.

Pool Boiling Heat Transfer Charcteristics of Low-Fin Tubes in CFC11, HCFC123 and HCFC141b (CFC11, HCFC123, HCFC141b 풀내에서 낮은 핀관의 비등 열전달특성)

  • 김주형;곽태희;김종보
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.9
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    • pp.2316-2327
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    • 1995
  • Experimental results from nucleate pool boiling heat transfer with various finned tubes in CFC11, HCF123 and HCFC141b are reported. One plain tube and four low fin tubes of various fin densities were tested in an attempt to find out the optimum fin density in the heat flux range of 10-60 kW/m$^{[-992]}$ at near atmospheric pressure. The results indicated that CFC11 showed the highest heat transfer coefficients. Its alternatives, HCFC123 and HCFC141b, showed 3-5% lower heat transfer coefficients than those of CFC11 at the same heat flux. As the fin density increases, so does the heat transfer surface area. Measured heat transfer coefficients, however, do not necessarily always increase as the fin density increases. This unique phenomenon seems to be caused by the coalescence of the bubblers that prevent the cool liquid from entering into the fin valleys. For all the refrigerants tested, the optimum fin density yielding the highest performance was 28 fins per inch confirming the previous results by other researchers.

Design of an evaporator heat exchanger for R123 and R134a refrigerants (Rl23, R134a냉매 특성에 따른 증발기 설계)

  • 김익생
    • The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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    • v.28 no.5
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    • pp.368-374
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    • 1999
  • 최근 세계적으로 환경보호에 대한 관심이 고조됨에 따라 기술개발 방향이 환경을 고려한 규정 및 장치에 제한을 받고 있다. 따라서 냉동 공조 기기에 사용되는 기존의 CFC계열 냉매가 오존층 파괴의 주 원임이 판명됨에 따라 환경 문제가 없는 HCFC계열인 R123와 HFC R134a로의 대체가 불가피하게 되었다.

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Condensation Heat Transfer Coefficients of Binary Refrigerant Mixtures on a Horizontal Smooth Tube (수평관에서 이원 혼합냉매의 응축 열전달계수)

  • 김경기;서강태;정동수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.12
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    • pp.1049-1056
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    • 2000
  • In this study, condensation heat transfer coefficients(HTCs) of 2 nonazeotropic refrigerant mixtures of HFC32/HFC134a and HFC134a/HCFC123 at various compositions were measured on a horizontal smooth tube. All data were taken at the vapor temperature of 39$^{\circ}C$ with a wall subcooling of 3~8K. Test results showed that HTCs of tested mixtures were 11.0~85.0% lower than the ideal values calculated by the mass fraction weighting of the pure components HTCs. Thermal resistance due to the diffusion vapor film was partly responsible for the significant reduction of HTCs with these nonazeotropic mixtures. The measured data were compared against the predicted ones by Colburn and Drew\`s film model and a good agreement was observed.

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Flow Condensation Heat Transfer Characteristic of R245fa in a Horizontal Plain Tube (수평 평활관내 R245fa의 흐름 응축 열전달 특성)

  • Park, Hyun-Shin;Park, Ki-Jung;Jung, Dong-Soo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.20 no.2
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    • pp.87-96
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    • 2008
  • Flow condensation heat transfer coefficients(HTCs) of R123 and R245fa are measured in a horizontal plain tube. The main test section in the experimental flow loop is made of a plain copper tube of 9.52 mm outside diameter and 530 mm length. The refrigerant is cooled by passing cold water through an annulus surrounding the test section. Tests are performed at a fixed saturation temperature of $50\;{\pm}\;0.2\;^{\circ}C$ with mass fluxes of 50, 100, $150\;kg/m^2s$ and heat flux of $7.3{\sim}7.7\;kW/m^2$. Heat transfer data are obtained in the vapor quality range of $10{\sim}90%$. Test results show that the flow condensation HTCs of R245fa are overall 7.9% higher than those of R123 at all mass fluxes. The pressure drop of R245fa is smaller than that of R123 at the same heat flux. In conclusion, R245fa is a good candidate to replace ozone depleting R123 currently used in chillers from the view point heat transfer and environmental properties.

An Experimental Study of Nucleate Boiling Heat Transfer With EHD Technique in CFC-11 and HCFC-123 (Chiller용 냉매 CFC-11과 대체냉매 HCFC-123의 전기장을 사용한 핵비등 열전달 촉진에 관한 연구)

  • Kwak, T.H.;Kim, J.H.;Jung, D.S.;Kim, C.B.;Cha, T.W.;Han, C.S.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.6 no.4
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    • pp.365-379
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    • 1994
  • Pool boiling experiments were carried out to study the effect of electric field on nucleate boiling heat transfer. CFC-11 and its alternative HCFC-123 were used as working fluids. Boiling on both single tube and a bundle of five tubes was investigated. Heat flux varied from 5 to $25kW/m^2$ while the applied voltage changed from 0 to 1kV. The results showed that at low heat flux where boiling was not present or very weak, electric field-induced forced convection helped increase the heat transfer coefficients of CFC-11 and HCFC-123 significantly(4-15 times increase). However, at higher heat flux, nucleate boiling of CFC-11 which is a highly dielectric fluid, was not affected significantly by the application of electric field. In contrast to CFC-11, even at high heat flux, nucleate boiling of CFC-11 which has a relatively larger electric conductivity than CFC-11, was vigorously increased up to 2-4 times. The additional power required to apply the electric field was 1-2% of the total power consumption by the heater. The increase in overall heat transfer coefficient of evaporators with HCFC -123 was about 40%, suggesting a considerable reduction in evaporator size with EHD technique.

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Compute simulation of a three-stage condensation heat pump (3단 응축 고온/고효율 열펌프의 전산해석)

  • 이윤학;정동수;김종보
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.10 no.3
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    • pp.303-314
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    • 1998
  • In this study, the performance of a multi-stage condensation heat pump was examined. Computer simulation programs were developed for 1-stage, 2-stage, and 3-stage heat pumps and R11, R123, R141b were tested as working fluids. The results showed that coefficients of performance(COPs) of an optimized 3-stage condensation heat pump are 25∼40% higher than those of a conventional 1-stage heat pump. The increase in COP, however, differed among the fluids tested. The improvement in COP largely stems from the decrease in average LMTD values in the condensers of the multi-stage system. For the 3-stage condensation heat pumps, optimized UA values of three condensers were determined to be 30∼40% of the UA value of the total condenser regardless of the working fluid. When the amount of cooling water entering into the intermediate and high-stage subcoolers is roughly 10% of the total condenser cooling water respectively, the optimum performance was achieved for the 3-stage condensation heat pump.

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A Study on Forced Convective Boiling Heat Transfer of Non-Azeotropic Refrigerant Mixture R134a/R123 Inside Horizontal Smooth Tube (수평 전열관내 비공비 혼합냉매 R134a/R123의 강제대류비등 열전달에 관한 연구)

  • Lim, Tae-Woo;Han, Kyu-Il
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.3
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    • pp.381-388
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    • 2003
  • An experimental study was carried out to measure the heat transfer coefficient in flow boiling to mixtures of HFC-l34a and HCFC-123 in a uniformly heated horizontal tube. Tests were run at a pressure of 0.6 MPa and in the ranges of heat flux 1-50 kw/$m^2$, vapor quality 0-100 % and mass velocity 150-600 kg/$m^2$s. Heat transfer coefficients of mixture were less than the interpolated values between pure fluids both in the low quality region where the nucleate boiling is dominant and in the high quality region where the convective evaporation is dominant. Measured data of heat transfer are compared to a few available correlations proposed for mixtures. The correlation of Jung et. al. satisfactorily predicted the present data, but the data in lower quality was overpredicted and underpredicted the high quality data. The correlation of Kandlikar considerably underpredicted most of the data. and showed the mean deviation of 35.1%.

Condensation heat transfer characteristics of alternative refrigerants for CFC-11, CFC-12 for enhanced tubes (열전달 촉진관에서 CFC-11 및 CFC-12 대체냉매의 응축 열전달 특성 연구)

  • 조성준;황수민;정동수;김종보
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.10 no.5
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    • pp.569-580
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    • 1998
  • In this study, condensation heat transfer coefficients(HTCs) of a plain tube, low fin tube, and Turbo-C enhanced tube for CFC-11, HCFC-123, CFC-12, HFC-l34a are measured and compared against each other. All data are taken at the vapor temperature of 39$^{\circ}C$ with a wall subcooling temperature 3~8$^{\circ}C$. Test results show that HTCs of a low vapor pressure refrigerant, HFC-123, for a plain, low fin, and Turbo-C tubes are 10.5~20.5%, 8.2~12.2%, 16.5~19.2% lower than those of CFC-11, respectively. On the other hand, HTCs of a medium vapor refrigerant, HFC-l34a, for a plain, low fin, and Turbo-C tubes are 20.6~31.8%, 0.0~8.0%, 13.2~20.9% higher than those of CFC-12, respectively. For all refrigerants tested, HTCs of Turbo-C tube are the highest among the three tubes showing almost 8 times increase in HTCs as compared to those of a plain tube. Nusselt's prediction equation for a plain tube yielded 12% deviation for all plain tube data while Realty and Katz's prediction equation for a low fin tube yielded 20% deviation for all low tube data.

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