• Journal of Advanced Marine Engineering and Technology
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• v.30 no.2
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• pp.218-224
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• 2006

Experimental results for pressure gradient of HCs refrigerants R-290. R-600a. R-1270 and HCFC refrigerant R-22 during condensing inside horizontal double pipe heat exchangers are presented. The test sections which have the tube inner diameter of 10.98mm. and the tube inner diameter of 8mm are used for this investigation. Hydrocarbon refrigerants have higher pressure drop than R-22 in both test sections with the diameters of 12.70mm and 9.52mm. Pressure drop increased with the increase of the mass flux. These results form the investigation can be used in the design of heat transfer exchanger using hydrocarbons as the refrigerant for the air-conditioning systems

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.2
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• pp.96-105
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• 2001

R410a which is one of HFC refrigerants is being considered to be a promising replacement for R22 widely used in domestic air conditioners. The rolling piston type rotary compressors for R410a have lower energy efficiency than those for R22 because of the high pressure difference between a suction chamber and a discharge chamber in the compression mechanism. in addition, the re-expansion gas loss of the rotary compressor for R410a which occurs a ta clearance volume in a discharge port becomes larger than that for R22 due to high density of R410a refrigerant. Therefore, Pressure-Volume analyses for various design parameters of a discharge system were carried out to improve efficiency of a R410a rotary compressor. The results such as performance dta, over-compression loss, and re-expansion loss were acquired by P-V analyses and analyzed quantitatively. As a conclusion, the optimal specifications of several design parameters of a discharge system were obtained by analyzing P-V diagrams.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.4
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• pp.306-317
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• 1993

In this study, a performance comparison of scroll compressor for various refrigerants(CFC-12, HCFC-22 and HFC-134a) has been numerically carried out. The thermodynamic properties have been calculated by using the recent experimental equations and the performance has been investigated qualitatively at the same geometric specifications and operating conditions of scroll compressor. The results are as follows; HFC-134a has the highest compression ratio of 5.40. The mass flow rate of HCFC-22, which affects the cooling capacity of refrigerant system, is higher than that of other refrigerants. HFC-134a has the highest adiabatic efficiency in comparison with CFC-12 and HCFC-22.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.2
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• pp.156-162
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• 2008

The condensation pressure drop for R-22 and R-410A flowing in a small diameter tube was investigated. The test section is a counterflow heat exchanger with refrigerant flowing in the inner tube and coolant flowing in the annulus. The test section consists of 1220 mm length with horizontal copper tube of 3.38 mm outer diameter and 1.77 mm inner diameter. The refrigerant mass fluxes ranged from 450 to $1050\;kg/m^2{\cdot}s$ and the average inlet and outlet qualities were 0.05 and 0.95, respectively. The main experimental results were summarized as follows : In the case of two-phase flow, the pressure drop increases with increasing mass flux and decreasing quality. The pressure drop of R-22 is slightly higher than that of R-410A for the same mass flux. Most of correlations proposed in the large diameter tube showed enormous deviations with experimental data.

• Clean Technology
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• v.14 no.1
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• pp.53-60
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• 2008

The condensation heat transfer coefficients and pressure drops of hydrocarbon refrigerants (R-290 and R-600a) and hydrochlorofluorocarbon (HCFC) refrigerants were measured in the two horizontal double pipe heat exchangers with inner diameters of 10.07 mm and 5.80 mm at a mass flux of $35.5{\sim}210.4\;kg/m^2s$ and the condensation temperature of $40^{\circ}C$. The average condensation heat transfer coefficients of hydrocarbon refrigerants were higher than that of HCFC refrigerant(R-22). The pressure drop had a magnitude in the order of R-600a > R-290 > R-22. The pressure drops in the tubes with inner diameter of 10.07 mm were approximately $6{\sim}15%$, $9.8{\sim}12.5%$ and $2.1{\sim}4.6%$ higher for R-600a, R-290 and R-22, respectively, than those with inner diameter of 5.80 mm. The condensation heat transfer coefficients were compared with the published experimental data, and showed the best agreement with Haraguchi et al.'s correlation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.3
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• pp.230-238
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• 2003

R407C is considered as alternative refrigerant of R22 for air conditioners. Experimental investigation is made to study the condensation heat transfer characteristics of slit fin-tube heat exchanger using alternative refrigerant, R407C. Experiments are carried out at condensation pressure of 2110 kPa and 1943 kPa with the degree of superheat of 1$0^{\circ}C$ and mass flux varying from 150 to 250 kg/$m^2$s for refrigerant side. The inlet air condition is dry bulb temperature of 35$^{\circ}C$, relative humidity of 50% and air velocity varying from 0.8 to 1.6 m/s. Experiments show that pressure drop gets smaller at a higher condensation pressure especially when condensation pressure is raised from 1943 to 2110 kPa. Heat transfer rate gets smaller at a lower condensation pressure in the range of experimental condition.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.2
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• pp.254-266
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• 1996

Boiling heat transfer coefficients of pure refrigerants(R22, R32, R125, R134a, R290, and R600a) and refrigerant mixtures(R32/R134a and R290/R600a) are measured experimentally and compared with several correlations. Convective boiling term of Chen's correlation predicts experimental data for pure refrigerants fairly well(root-mean-square error of 12.1% for the quality range over 0.2). An analysis of convective boiling heat transfer of refrigerant mixtures is performed for an annular flow to study degradation of heat transfer. Annular flow is the subject of this analysis because a great portion of the evaporator in refrigeration or air conditioning system is known to be in the annular flow regime. Mass transfer effect due to composition difference between liquid and vapor phases, which is considered as a driving force for mass transfer at interface, is included in this analysis. Correction factor $C_F$ is introduced to the correlation for the pure substances through annular flow analysis to apply the correlation to the mixtures. The flow boiling heat transfer coefficients are calculated using the correlation considering nucleate boilling effect in the low quality region and mass transfer effect for nonzazeotropic refrigerant mixtures.

• Journal of Mechanical Science and Technology
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• v.15 no.9
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• pp.1328-1338
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• 2001

The objective of this study is to present flow and pressure drop characteristics of R22 in adiabatic capillary tubes of inner diameters of 1.2 to 2.0mm, and tube lengths of 500 to 2000mm. Distributions of temperature and pressure along capillary tubes and the refrigerant flow rates through the tubes were measured for several condensing temperatures and various degrees of subcooling at the capillary tube inlet. Condensing temperatures of R22 were selected as 40, 45, and 50$^{\circ}C$ at the capillary tube inlet, and the degree of subcooling was adjusted to 1 to 18$^{\circ}C$. Experimental results including mass flow rates and pressure drops of R22 in capillary tubes were provided. A new correlation based on Buckingham II theorem to predict the mass flow rate through the capillary tube was presented considering major parameters which affect the flow and pressure drop characteristcis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.3
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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.

• Journal of the Korean Institute of Gas
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• v.12 no.1
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• pp.48-53
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• 2008

The condensation heat transfer coefficients of R-22 and R-410A in a small diameter tube were investigated. The main components of the refrigerant loop consist of a receiver, a variable-speed pump, a mass flowmeter, an evaporator (preheater), and a condenser (test section). The test section consists of smooth, horizontal copper tube of 3.38 mm outer diameter and 1.77 mm inner diameter. The refrigerant mass fluxes varied from 450 to $1050\;kg/(m^2s)$ and the average inlet and outlet qualities were 0.05 and 0.95. The main results were summarized as follows : the condensation heat transfer coefficient also increases with increasing mass flux and quality. The condensation heat transfer coefficient of R-410A was slightly higher than that of R-22. Most of correlations proposed in the large diameter tube showed significant deviations with experimental data except for the ranges of low quality and low mass flux.