• Journal of Energy Engineering
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• v.9 no.3
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• pp.192-201
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• 2000

증발기와 응축기로 폐회로 냉동 시스템을 구성하여 기존 사용 냉매인 R22와 대체냉매로써 부각되고 있는 R407C, R410A를 사용하여 여러 가지 관 직경과 휜 형상을 가지는 열교환기에 대한 열전달량, 질량유량, 열교환기를 지나가는 냉매의 온도분포 그리고 공기측 압력강하를 측정하였다. 모든 열교환기에서 냉매의 질량유량이 증가함에 따라 열전달량은 증가하였다. R22와 R407C의 경우에 증발기측에서는 거의 같은 열전달량을 나타냈고 응축기측에서는 R407C가 전체적으로 열전달량이 높게 나타났다. 그리고 열교환기의 전달량은 유로의 형상보다는 냉매의 질량유량과 전열면적에 더 많은 영향을 받는다. 공기측 압력 강하는 열수가 많은 열교환기의 경우가 작게 나타났으며 슬릿휜을 가지는 열교환기의 압력강하가 가장 크고 웨이비휜을 가지는 열교환기가 가장 작게 나타났다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.1
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• pp.56-65
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• 1998

In this paper, experimental investigation of capillary tube performance for R-407C is performed. The experimental setup is made of real vapor-compression refrigerating system. In this study, mass flow rate is measured for capillary tubes of various diameter and length as inlet pressure and degree of subcooling are changed. These data are compared with the results of a numerical model. The mass flow rates of the numerical model are less than by 14% compared with the measured mass flow rates. It is found that mass flow rate and length for R-407c are less than those of R-22 under the same condition. Also based on this experimental study and the numerical model, a set of capillary tube selection charts for R-407C is constructed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.4
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• pp.492-498
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• 1999

Mass flow rates of R407C and R290 through capillary tubes were measured with various capillary tube geometries and flow conditions. For all refrigerants tested in the present study, mass flow rate through the capillary tube was strongly dependent on the condensing pressure, subcooling and capillary length and diameter. The flow rate of R407C was 5~10［%］ higher than that of R22 at the same condensing temperature and degree of subcooling, while flow rate for R290 was 40［%］ lower than that for R22. Based on experimental results, an empirical correlation was developed using Pi theorem to predict the mass flow rate through capillary tubes. The predicted flow rates using the model were consistent with the experimental data within ${\pm}$10[%］.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.9
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• pp.706-716
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• 2002

R410A and R407C are considered to be alternative refrigerants to R22 for the air-conditioners. Experimental investigation is made to study the condensation heat transfer characteristics of slit fin-tube heat exchanger using alternative refrigerants R410A and R407C. R407C, a non-azeotropic refrigerant mixture, exhibited a quite different condensation phenomenon from those of R22 and R410A and its condensation heat transfer coefficient was much lower than that of R22 and R410A. Between the R22 and R410A, the condensation heat transfer coefficient of R410A, near-azeotropic refrigerant mixture, was a little higher than that of R22. R410A also showed the lowest condensation pressure drop across the test section. For all refrigerants, the condensation heat transfer coefficient and pressure drop increase as the mass flux increases.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.4
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• pp.70-80
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• 1996

Experimental results for forced convection condensation of R-22 and R-407C inside 7.5mm ID and 4000mm length of horizontal tubes are presented. The experimental data covered total flow rate from 114.3 to 267.1kg/($m^2$.s) and quality from 0 to 1. The vapor temperature and pressure drop along the tube were measured. The pressure drop for R-407C increased with flow rate similar to that of R-22. The experimental data compared with the available perdictions for pressure drop. Based on the data a prediction method was presented for the calculation of pressure drop of R-22 alternative refrigerants.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.607-612
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• 2003

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.8
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• pp.729-735
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• 2005

In this study, external condensation heat transfer coefficients (HTCs) were measured on a horizontal smooth tube at the saturated vapor temperature of $30^{\circ}C,\;39{\circ}C,\;and\;50^{\circ}C$ for R22, R410A, R407C, and R134a with the wall subcooling of $3\~8^{\circ}C$. The HTCs of all refrigerants are the highest at $30^{\circ}C,\;39{\circ}C,\;and\;50^{\circ}C$ in order. This trend is due to its excellent thermodynamic properties of the liquid phase. The measured data of HTCs were compared with the calculated ones by Nusselt's equation for a smooth tube. Measured HTCs of R22, R134a, R410A are $4.2\~7.5\%$ higher than prediction respectively while those of R407C are $15.6\~28.9\%$ lower than the prediction.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.2
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• pp.144-156
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• 1997

Experimental results for forced convection heat transfer of pure refrigerant and nonrefrigerant mixtures during condensing inside horizontal smooth tubes, double pipe heat exchanger of 7.5 mm ID and 4 000 mm long inside tube, are presented. Pure refrigerant R - 22 and R - 407 c, the mixture of R - 32 + R - 125 + R - 134a (23/25/52, wt %) are used as the test fluids. The ranges of parameters are $114.3{\sim}267.1 kg/(m^2 {\cdot} s)$ of mass velocity, <0$\sim$1.0 of quality. The vapor pressure, vapor temperature and tube wall temperature were measured. Using these data, the local and average heat transfer coefficients for the condensation are obtained. At the same given experimental conditions, the condensation heat transfer coefficients for NARMs R - 407c were lower than those for the pure refrigerant of R - 22. Local heat transfer characteristics for R - 407c were different from pure refrigerant R - 22. The condensaheat transfer coefficients for R - 407c and R - 22 increased with mass velocity. Based on the data a prediction method was presented for the calculation of dimensionless average heat transfer coefficient.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.31 no.7
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• pp.65-70
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• 2002

지구의 오존층을 보호하기 위한 몬트리올 의정서가 1987년 채택된 이후 오존층 파괴물질의 사용이 점차 감소되고 있다. 선진국의 경우 1995년 말부터 CFC냉매의 생산을 전폐하였고, HCFC냉매의 경우는 2020년 전폐를 목표로 대체냉매를 이용한 응용 기술개발 및 제품 생산이 진행되고 있다. 가정용 냉장고 및 차량용 에어컨에는 R-12의 대체냉매로 R-134a가 도입되었으며, 유럽을 중심으로 냉장고에는 HC계 냉매인 R-600a도 대체냉매로 사용되고 있다. 가정용 에어컨에는 혼합냉매인 R-407c 와 R-410a가 R-22 냉매를 대체하여 적용되고 있다. 그러나 현재, CFC및 HCFC 대체 냉매로 많이 사용되고 있는 HFC계 냉매도 지구 온난화 지수가 대단히 큰 문제를 가지고 있다. 1997년 채택된 교토의 정서에는 HFC계 냉매가 온실효과가 가스 배출규제물질에 포함되어 있다. 이에 따라서 오존층의 파괴지수가 영이고 지구온난화지수도 거의 없는 자연냉매가 주목을 받게 되었으며, 자연 냉매의 하나인 이산화탄소 ($CO_2$R744) 냉매의 응용기술 및 제품개발 연구가 선진국을 중심으로 폭넓게 진행되고 잇다. 본고에서는 $CO_2$냉매의 일반적인 특성을 간단히 소개하고 일본에서 진행되고 있는 $CO_2$냉매를 적용한 급탕시스템의 제품개발 및 시장현황에 대해서 기술하기로 한다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.4
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• pp.473-483
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• 1996

To protect the ozone layer, R22 will be replaced with HFCs. R407C is a leading candidate as alternative refrigerant for air conditioner due to its similar thermodynamic characteristics with R22. In replacing R22 with R407C, the compatibility with lubricating oil is of major concern. Polyol ester (POE) oil among the synthetic oils is considered to be the best lubricant for use with R407C because of good electrical properties and miscibility. However, lubricating ability of mixture of R407C/POE oil is lower than that of R22/mineral oil due to the production of acid by hydrolysis which causes corrosive wear. Therefore, to minimize water content, it is needed to develop a molecular sieve desiccant which is compatible with R407C and ester oil. This paper discusses (1) the change of properties of POE oil when current molecular seive is used, (2) the effects of POE oils and additives on durability of compressor. Through compressor life test and bench wear test, it was found that inadequate use of POE oils and additives may promote the deteriation of molecular sieve, resulting in decrease of durability of compressor.