• Journal of Energy Engineering
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• v.18 no.3
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• pp.203-211
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• 2009

Vapor pressure of HFC-404a and polyol ester system were measured at 56 points from 263.15 to 323.15 K and from 0 to 90 mass %polyol ester. It was found that below 273.15 K, the effect of the polyol ester on the vapor pressure was negligible up to 30 mass % polyol ester. The vapor pressure of the system significantly decreased as the mass fraction of polyol ester increased over 50 percent. Raoult's model and Flory-Huggins model were tested for data reduction. Empirical vapor pressure equations were obtained in terms of temperature and mass fraction of polyol ester.

• Journal of the KSME
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• v.48 no.1
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• pp.53-58
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• 2008

• Proceedings of the SAREK Conference
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• 2006.11a
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• pp.91-91
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• 2006

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.9
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• pp.791-801
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• 2000

An experimental study was conducted to analyze the effects of oil on refrigerant flow through adiabatic capillary tubes, and to develop a model for mass flow rates of refrigerant/oil mixture at various capillary tubes and flow conditions. Mass flow rates and the profiles of the pressures and temperatures along the capillary tubes was obtained with the oil concentration of R-22/SUNISO 4GS oil mixture at various test conditions. The flow trends as a function of geometry and flow conditions for pure refrigerant and refrigerant/oil mixture were similar in adiabatic capillary tubes. Mass flow rate of the refrigerant/oil mixture was less than that of pure refrigerant at the same test conditions.

• Proceedings of the SAREK Conference
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• 2004.06a
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• pp.53-53
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• 2004

• Proceedings of the SAREK Conference
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• 2005.06a
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• pp.70-70
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• 2005

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.8
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• pp.717-724
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• 2000

It is important to investigate characteristics of flow of refrigerant/oil mixture circulating in a refrigeration system. Therefore the oil concentration in refrigerant/oil mixture should be measured exactly by the adequate measuring instrument. In this paper, the oil concentration was measured by density monitoring system(DMS) in the liquid-line of a inverter-driven heat pump. Experimental result follows ; the main factor that have an effect on oil concentration refrigerant/oil mixture circulating in a refrigeration system is the momentum and kinematic viscosity of refrigerant/oil mixture compressed by scroll compressor.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.1
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• pp.1-8
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• 2001

This paper deals with refrigerant-oil mixtures in a dehumidifying cycle. Two different oils such as Alkylbenzene(AB) and Polyol-esters(POE) lubricants are used for R134a to investigate the effect of miscibility on oil returnability. It was found that R134a/AB mixture had more unstable interface between oil and refrigerant than R134a/POE mixture. However, overall flow patterns of both refrigerant-oil mixtures were almost same. The minimum height of oil measured in the compressor was as high as twice of the least permissible height of oil in the compressor required to insure its reliability. Thus, it is considered that immiscible oil, i. e., AB for R134a can be used without causing oil returnability problem.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1440-1446
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• 2012

This paper presents an experimental study of heat transfer and pressure drop characteristics of supercritical carbon dioxide with PAG inside a horizontal microfin tube. Heat transfer coefficient and pressure drop gradients were measured at 10 MPa in pressure and 520 kg/$m^2s$ in mass flux with variation of PAG mass concentration from 0.06% to 2.26%. The tendencies of both heat transfer and frictional pressure drop characteristics show the same as those of pure $CO_2$ up to 0.3% in PAG mass concentration. In case of 2.26% in PAG mass concentration, measured heat transfer coefficients showed 50% lower than those of pure $CO_2$ near the pseudocritical temperature and measured frictional pressure drop gradients show 1.6 times higher in comparison with those of pure $CO_2$ at $60^{\circ}C$ in $CO_2$ bulk temperature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.3
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• pp.254-261
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• 2006

The effect of enhanced geometry (pore diameter, gap width) is investigated on the pool boiling of R-123/oil mixture for the enhanced tubes having pores with connecting gaps. Tubes with different pore diameters (and corresponding gap widths) are specially made. Significant heat transfer degradation by oil is observed for the present enhanced tubes. At 5% oil concentration, the degradation is 26 to 49% for $T_{sat}=4.4^{\circ}C$. The degradation increases 50 to 67% for $T_{sat}=26.7^{\circ}C$. The heat transfer degradation is significant even with small amount of oil (20 to 38% degradation at 1% oil concentration for $T_{sat}=4.4^{\circ}C$), probably due to the accumulation of oil in sub-tunnels. The pore size (or gap width) has a significant effect on the heat transfer degradation. The maximum degradation is observed for $d_p$ = 0.20 mm tube at $T_{sat}=4.4^{\circ}C$, and for $d_p$=0.23 mm tube at $T_{sat}=26.7^{\circ}C$. The minimum degradation is observed for $d_p$=0.27 mm tube for both saturation temperatures. It appears that the oil removal is facilitated for the larger pore diameter (along with larger gap) tube. The highest heat transfer coefficient with oil is obtained for $d_p$ =0.23 mm tube, which yielded the highest heat transfer coefficient for pure R-123. The heat transfer degradation increases as the heat flux decreases.