• 설비공학논문집
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• 제14권6호
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• pp.468-476
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• 2002

This paper deals with heat and mass transfer characteristics and performance evaluation of a counter flow double-tube condenser for a multi-component refrigerant mixture. The local heat and mass transfer characteristics of ternary zeotropic refrigerant mixtures composed of HFC32/HFC125/HFC134a are evaluated for a counter flow double-tube condenser cooled by water. Then, the local values of vapor quality, thermodynamic states at bulk vapor, vapor-liquid interface and bulk liquid, heat flux and condensation mass flux are obtained. The heat exchange performance for ternary zeotropic refrigerant mixtures composed of HFC32/HFC125/HFC134a on the total pressure drop and the heat transfer characteristics are also compared with those for R404A, R410A, R502, R22, R32, Rl23 and R134a.

• 설비공학논문집
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• 제7권4호
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• pp.589-599
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• 1995

The frictional pressure drop of a capillary tube flow is experimentally investigated for pure refrigerants such as R32, R125, and R134a and refrigerant mixtures such as R32/R134a(30/70 by mass percent), R32/R125(60/40), R125/R134a(30/70), and R32/R125/R134a(23/25/52). The binary interaction parameters for the calculation of viscosities of refrigerant mixtures are found based upon the data in the open literature. Several homogeneous flow models predicting the viscosity of two-phase region are compared to select the best model. Cicchitti's equation is known to be the most adequate for the prediction of the viscosity for refrigerant mixtures, which is used in the analysis of adiabatic capillary flows. A model for the prediction of the frictional pressure drop of single and two-phase flow is developed for refrigerant mixtures in this study. This model may be used to design and analyze the performance of a capillary tube in the refrigerating system.

• 설비공학논문집
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• 제9권3호
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• pp.276-283
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• 1997

The nucleate boiling heat transfer experiments are performed using a ternary refrigerant R407C which is a candidate of alternatives of HCFC 22. The boiling phenomena for R-32, R-125, and R-134a which are the constituent refrigerants of R407C are also investigated to give the foundation of theoretical research for the mixture component boiling. The nucleate boiling heat transfer coefficients of R407C is less than those of HCFC 22 which has the similar physical and transport properties. Since the experimental results show the deterioration of boiling heat transfer coefficients of ternary mixture refrigerants R407C, the boiling heat transfer coefficients of R407C cannot be obtained by the linear combination of boiling heat transfer coefficients from its constituent components R-32, R125, and R134a.

• 설비공학논문집
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• 제23권12호
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• pp.791-798
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• 2011

In this study, performance of R410A(50%R32/50%R125) and HFC32/HFC125 mixture is measured to examine the effect of composition shift of R410A used for various air-conditioners and heat pumps. The composition of HFC32/HFC125 mixture varies from the reference composition of R410A ${\pm}10%$ with 5% interval. Tests carried out in a heat pump bench tester at the evaporation and condensation temperatures of $7/45^{\circ}C$ and $-7/41^{\circ}C$ for summer and winter conditions, respectively. Test results show that both the coefficient of performance (COP) and compressor power of the HFC32/HFC125 mixture have the maximum difference of 2.0% as compared to those of R410A. Compressor discharge temperatures of HFC32/HFC125 mixture are increased up to $6.7^{\circ}C$ as compared to that of R410A. The amount of charge for HFC32/HFC125 mixture vary within 5.6% as compared to that of R410A. Overall, performance of R410A is not appreciably affected by the composition shift of ${\pm}10%$ of R32 under both air-conditioning and heat pumping conditions.

• 설비공학논문집
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• 제8권1호
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• pp.45-54
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• 1996

An experimental investigation on the two-phase flow through tube orifices was performed with the refrigerant mixture of R32/125/134a(30/10/60). A series of tests were conducted to generate wide range of data at varying operation conditions with four short tubes. The tests include both single and two-phase flow conditions at the inlet of the short tube with different oil concentrations. Experimental data were presented as a function of major operating parameters and short tube diameter. Based on test results and data analysis, a semi-empirical flow model was developed to predict the mass flow rate through short tube orifices with a given set of conditions. The flow model was formed to cover both single and two-phase flow at the inlet of short tube with considering the effects of oil concentration.

• International Journal of Air-Conditioning and Refrigeration
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• 제6권
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• pp.93-103
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• 1998

The nucleate boiling heat transfer experiments are performed using a ternary refrigerant R407C which is a candidate of alternatives of HCFC 22. The boiling phenomena of R-32, R-125 and R-134a which are the constituent refrigerants of R407C are also investigated. The nucleate boiling heat transfer coefficients of R407C are less than those of HCFC 22 which have the similar physical and transport properties. In our experimental pressure range, which is similar to the operational pressure of air conditioning system, the deterioration of boiling heat transfer coefficients of mixture refrigerant R407C does not appear for moderate wall superheat region. Since nucleate boiling heat transfer coefficients cannot be obtained from ideal mixing law of mixture, Thome's method was used to predict. To account for the heat flux effect and system pressure in Thome's method, the correcting factor, a(P.L1T), was introduced and obtained from experiments for ternary refrigerant R407C.

• 설비공학논문집
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• 제5권3호
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• pp.217-225
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• 1993

Nonflammable mixtures of flammable and nonflammable refrigerants are possible as substitute refrigerants for use in domestic heat pumps and refrigerators. Refrigerant leakage from such a system is of paramount concern since it is possible that the resulting mixture composition remaining in system will reside in the flammable range. This paper presents a simulation of a leakage process of refrigerant mixtures. Idealized cases of isothermal leakage process are considered in this study representing a slow leak. Simulation is performed for selected composition of binary and ternary refrigerant mixture; R-32/134a and R-32/125/134a. Mixture compositions with respect to percentage leak of original charge are presented. In isothermal leakage process, both vapor and liquid compositions of more volatile refrigerant decrease during vapor and liquid leak, but the total composition of this component decreases during vapor leak and increases during liquid leak. Vapor and liquid compositions are determined depending on the vapor-liquid equilibrium relation of the refrigerant mixture. The refrigerant mixture left in the system can go to a nonflammable direction relying on which component in the mixture is flammable.

• 태양에너지
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• 제15권3호
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• pp.75-90
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• 1995

본 논문은 가정용 냉방기에 널리 사용되고 있는 HCFC22를 대체할 수 있는 혼합냉매의 개발 및 이들의 성능 연구에 관한 것이다. 현재까지 HCFC22를 대체할 수 있는 순수냉매가 없으므로, 혼합냉매 개발에 본 연구의 초점이 맞추어졌고, 이를 위해 가정용 냉방기를 모사 하는 컴퓨터 프로그램이 개발되었다. 연구에서 개발된 혼합냉매를 구성하는 순수냉매들은 다음과 같다: R32, R124, R125, R134, R134a, R143a, R152a. 컴퓨터 모사 결과들은 다음의 혼합냉매들에 대해서 발표되었다: R32/R134a, R32/R152a, R32/R134, R32/R124, R143a/R134a, R143a/R152a, R143a/R124, R125/R134a, R125/R152a, R125/R124, R32/R152a/R134a, R32/R152a/R134, R32/R152a/R124. 가장 좋은 에너지 효율을 보인 것은 삼원 혼합냉매인 R32/R152a/R124로서, HCFC22에 비해 이것의 성적 계수는 13.7% 높고 냉동 능력은 23% 낮은 것으로 판명되었다. 한편 이원 혼합냉매 중 가장 성능이 좋은 것은 R32/R124로서 이것의 성적 계수는 HCFC22에 비해 13.4% 높고 냉동 체적 용량은 9.6% 낮은 것으로 판명되었다.

• 설비공학논문집
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• 제13권4호
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• pp.262-270
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• 2001

This paper deals with a prediction method for the condensation of ternary refrigerant mixture inside a horizontal smooth tube. Based on some reliable assumptions, the governing equations for the local heat and mass transfer characteristics are derived, and the prediction for the condensation of ternary zeotropic refrigerant mixtures composed of HFC32/HFC125/HFC134a, including R407C, is carried out. The local values of vapor quality, thermodynamic states at bulk vapor, vapor-liquid interface and bulk liquid, mass flux etc. are obtained for a constant wall temperature and a constant wall heat flux conditions, and the effects of the composition of HFC32/HFC125/HFC134a on heat transfer characteristics are examined. The prediction result is also compared with experimental data for condensation of ternary refrigerant mixtures. The predicted wall temperature distribution has a similar trend with experimental data but the predicted local heat transfer coefficients are 20-30% higher than the experimental data.

• 설비공학논문집
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• 제8권2호
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• pp.177-186
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• 1996

The characteristics of the flow of pure HFC refrigerants(R32, R125, and R134a) and their mixtures through capillary tubes were investigated experimentally. Two capillary tubes with 1.2mm and 1.6mm inner diameter and 1.5m length were adopted as test sections. Mass flow rates and temperatures and pressures were measured for several condensing temperatures and degrees of subcooling at capillary tube inlet. The effects of the condensing temperature, inner diameter of capillary tube, and subcooling on the mass flow rate of refrigerants were discussed, and the mass flow rates of HFC refrigerants were compared with that of R22. The pressure and temperature distributions along the capillary tube compared with that of R22. The pressure and temperature distributions along the capillary tube show that there is a metastable equilibrium state in the flow through the tube. Underpressure for vaporization increases as refrigerant mass flux increases and inlet subcooling decreases. Empirical correlation was suggested to predict underpressure for vaporization of the HFC refrigerants.