• Transactions of the Korean hydrogen and new energy society
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• v.19 no.4
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• pp.331-339
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• 2008

본 논문은 내경 7.73 mm와 5.80mm의 수평관내 프레온계 냉매 R-22와 탄화수소계 냉매 R-290과 600a의 응축 열전달 계수의 실험적 결과를 나타내었다. 실험장치는 압축기, 응축기, 팽창밸브, 증발기 등으로 구성된다. 응축 실험은 질량유속 $35.5{\sim}210.4\;kg/m^2s$이고, 응축온도 40$^{\circ}C$인 조건에서 수행하였다. 주요 결과를 요약하면 다음과 같다. 탄화수소계 냉매 R-290과 R-600a의 평균 열전달 계수는 프레온계 냉매 R-22보다 높게 나타났으며, R-600a의 평균 열전달 계수가 모든 관경에 대해 가장 높게 나타났다. 실험결과와 종래의 상관식을 비교한 결과, 모든 관경과 냉매에 대해 Haraguchi 등의 상관식이 가장 좋은 일치를 보였다. 그 중에서 Cavallini-Zecchin의 상관식은 7.73 mm 관경의 실험데이터와, Dobson 등의 상관식은 내경 5.80 mm 관경의 데이터와 좋은 일치를 보였다.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1997.10a
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• pp.85-92
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• 1997

R22 대체냉매로 R410A를 사용하는 가정용 분리형 에어컨의 성능을 향상시키기 위한 연구를 실험적으로 수행하였다. R22 시스템에서 냉매와 압축기의 오일만 교체할 경우 기본시스템에 비해 냉방능력은 17% 증가하였고 에너지 소비효율은 29% 감소하였다. 이를 해결하기 위해 고압냉매 R410A에 적합한 압축기와 시스템의 효율을 향상시키기 위한 고효율 응축기를 개발하였다. R410A 압축기와 고효율 응축기를 R410A 시스템에 적용할 경우 냉방능력과 효율이 R22 시스템에 비해 각각 1.8% 와 2.2% 증가하였으며, 소음도 R22 시스템과 동등한 수준을 나타내었다.

• Journal of the Korean Solar Energy Society
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• v.31 no.5
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• pp.67-76
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• 2011

생활공간 냉난방용 열펌프의 성능향상을 위해 R22의 대체 냉매로서 새로운 혼합냉매R22/R23/R152a(RM-1)을 개발하고 U. S. A.의 NIST사의 REFPRO Pprogram을 이용해 이 혼합냉매의 P-h diagram을 구성하여 실용화에 이용할 수 있도록 하였다. 본 연구는 실험을 통해 R22와 RM-1의 열펌프 성능효과를 분석하였다. 입 출구 물의 온도와 제2의 전열매체로서 물의 질량유량, 압축기의 소요 에너지 그리고 열펌프의 기타 열적 특성을 다양한 조건하에서 측정하였다. 이 실험 데이터를 통해 공기-물 열펌프 시스템에서의 RM-1과 R22의 성능계수(COP)를 비교하였다. 이를 통해, 혼합냉매 RM-1을 사용하는 열펌프 시스템은 외기온 $-17^{\circ}C$에서도 2.2의 성능계수로 작동하는 결과를 본 연구에서 보여주었다.

• 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.5 no.2
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• pp.141-155
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• 1993

Thermodynamic properties of R-32 are calculated and its refrigeration performance is evaluated for the purpose the feasibility study of replacing R-22 with R-32. (1) Refrigeration effect of R-32 is superior to that of R-22 because heat of evaporation of R 32 is about 50% higher than that of R-22. However, COP of R-32 system is 10-30% lower than that of R-22 system. It is mainly attributed to the vapor pressore of R-32 being about 62% higher than R-22. (2) Since the pressure ratio and the specific heat ratio of R-32 system is higher than those of R -22, compressor discharging temperature rises as high as to $130-150^{\circ}C$. It may cause mechanical failure of compressor due to the breakdown of lubricant. Compressor should be improved to lower the temperature if R-32 is to replace R-22. (3) Averaged two-phase heat transfer coefficient of R-32 is about 10-20% higher than that of R-22. It may assume better heat exchanger effectiveness but not guarantee the better COP of R-32 system than R-22. (4) The high vapor pressure is the first reason to drop R-32 out of the line of R-22 alternative refrigerant. So, refrigerant mixtures based on R-32 are recommended to adjust the vapor pressure first and keep superior volumetric capacity of R-32.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.2189-2205
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• 1991

Thermodynamic properties of binary nonazeotropic refrigerant mixtures are estimated by using a modified Carnhan-Starling equation of state. In this study, pure component refrigerants such as R14, R23, R13, R13 B1, R22, R12, R134a, R152a, R142b, RC318, R114, R11, R123 and R113 are chosen and the thermodynamic properties of enthalpy and entropy are calculated in terms of relevant variables. The modified Carnahan-Starling equation of state is compared with the carnahan-Staring-De Santis equation of sate. Results show that the relative errors become slightly smaller with the equation of state proposed in this study. Correlations are obtained for the mixtures of which the vapor liquid equilibruim data are available to us in the literature. Those mixtures are R14/R23, R23/R12, R13/R12, R13/R11, R13B1/R22, R13B1/RC318, R12/RC138, R12/R114 and R12/R11. The binary interaction coefficients are found under the condition of minimizing the pressure deviations at the vapor liquid equiblibrium state and the estimation of the vapor liquid equilibrium for the refrigerant mixtures is done. Pressure-enthalpy and temperature-entropy diagrams are plotted for the refrigerant mixtures of specific composition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.2
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• pp.129-135
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• 2011

An ice-making model has been developed and analyzed in this study. The effects of the following on the ice formation on the outer surface of a tube in which a refrigerant flows and boils are numerically investigated: thermal resistance of the refrigerant and thermal resistance of the ice formed on the outer surface of the tube. The ice thickness and related variables are analyzed in the case of the refrigerants R22 and R134a by using the expressions for phase-change heat transfer and boiling heat transfer coefficient. Vapor qualities of the refrigerants range from 0 to 0.8. As a result, up to the first 30 min, the internal convection resistance is higher than the thermal resistance of the ice on the external surface of the tube. However, after about 30 min, the thermal resistance of the ice increases remarkably due to the increase in the ice thickness. Thus, the heat flux to the refrigerant decreases, and further, the refrigerant quality and the boiling heat transfer coefficient also decrease. As the heat transfer coefficient of R22 is higher than that of R134a, the mass of the ice formed when R22 is used is higher than that formed when R134a is used.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.3
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• pp.423-436
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• 1996

Thermodynamic performance of eight zeotropic R-22 alternative refrigerant mixtures selected by AREP(R-22 Alternative Refrigerants Evaluation Program) and R-32/R-125/R-134a(23%/25%/52%), namely R-407C were evaluated by the "drop-in" simulation method. An existing air conditioner was selected and its design data were used for the simulation. "ARI Test A" air conditions were applied. The degree of vapor superheat at the compressor inlet fixed at $5^{\circ}C$ for all the mixtures. The results of the simulation were compared with those of R-22. COPs of all mixtures except for R-32/R-227ea(35%/65%) and R-32/R-125/R-134a(10%/70%/20%), were higher than that of R-22 by 2%~8%, while the capacities were all lower than that of R-22 by 13%~27%. COP of R-32/R-134a(40%/60%) was 2.4% higher but the capacity was 15% lower than those of R-22. In the case of R-32/R-134a(30%/70%), COP and capacity were 5.5% higher and 15% lower than those of R-22, respectively. Among the ternary mixtures, R-407C and R-32/R-125/R-134a(30%/10%/60%) showed the best performance. COP of R-407C was 2.4% higher than those of R-22 but the capacity was 15% lower.

• 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[%］.

• 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.