• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.2
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• pp.209-217
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• 2000

The solubility and miscibility measurement apparatus was developed and used to obtain data for refrigerant/oil mixture. The solubility and miscibility data for R-410A/68 ISO VG polyol ester (POE) oil mixture are obtained over the temperature range from -20 to $60^{circ}C\;with\;10^{\circ}C$ intervals and the oil concentration range from 0 to 90 wt%. Using the experimental data, an empirical model was developed to predict the solubility relations for R-410A/POE oil mixture at equilibrium. In the R-410A/Solest 68 oil mixture, the average root-mean-square deviation between measured data and calculated results from the empirical model is 3.4% and in the R-4104/EMKARATE RL 68H oil mixture, that is 2.86%. For R-410A/68 ISO VG POE oil mixture immiscibility was usually observed at the low oil concentrations(5~30 wt%) over the all experimental temperature range($-20~60^{circ}C$) and at the high oil concentrations(50~90 wt%) over the low experimental temperature range($-2O~0^{circ}C$).

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.6
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• pp.589-598
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• 2000

The vapor-liquid equilibrium and miscibility measurement apparatus was developed and used to obtain data for refrigerant/oil mixture. The vapor-liquid equilibrium and miscibility data for R-410a/POE32 and R-410A/POE46 oil mixtures are obtained over the temperature range from -20 to $60^{\circ}C\;with\;10^{\circ}C$ intervals and the oil concentration range from 0 to 90 wt%. Using the experimental data, an empirical model is developed to predict the temperature-pressure-concentration relations for R-410A/POE oil mixtures at equilibrium. In the R-410A/POE32 oil mixture, the average root-mean-square deviation between measured data and calculated results from the empirical model is 2.00% and in the R-410a/POE46 oil mixture, that is 3.69%. Flory-Huggins theory is also used to predict refrigerant/oil mixture behavior. Miscibility for R-410A/POE32 oil mixture was observed all over the experimental conditions. Immiscibility for R-410A/POE46 oil mixture was observed at the low oil concentrations(10~30 wt%).

• 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.

• Journal of Mechanical Science and Technology
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• v.16 no.5
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• pp.647-654
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• 2002

This study deals with the characteristic of quenching refrigerant for heat treatment deformation control of SM45C steel. Heat-treatment deformation must be controlled for the progress of production parts for landing gear. Most of deformation is occurred on inconsistent cooling. The inconsistent cooling is caused by a property of quenching refrigerant. When a heated metal is deposited in the quenching refrigerant, the cooling speed is so slow in early period of cooling because of a steam-curtain. After additional cooling, the steam-curtain is destroyed. In this progress, the cooling speed is very fast. The object of this study is to control the deformation of heat-treatment for landing gear by improving the conditions of quenching. The cooling curves and cooling rates of water, oil and polymer solution are obtained and illustrated. From the characteristics of the quenching refrigerant, the effects of heat-treatments on thermal deformation and fatigue strength are also investigated.

• The KSFM Journal of Fluid Machinery
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• v.14 no.3
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• pp.28-32
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• 2011

The inverter rotary compressor discharges refrigerant and compressor oil in air-conditioning systems. The compressor oil which discharged form compressor decreases the efficiency of heat exchanger and affects the compressor operation. Recently, several studies are in progress for reducing the compressor oil. Before the reduction of compressor oil discharge rate, the quantitative measurement and evaluation method are required. In order to cope with this requirement we have developed the measurement technic of oil discharge rate. The reliability assessment was carried out approximately 0.1% of the errors with compressor performance indicators. The acceptable errors were to ensure the reliability of measurement technic. In the experiment results at several conditions, The oil discharge rate of heating operation has been confirmed average 3.7 times more than cooling operation. In this study the evaluation method and the experimental results of oil discharge rate in air-conditioning systems are presented with various operating conditions.

• International Journal of Air-Conditioning and Refrigeration
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• v.17 no.3
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• pp.81-87
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• 2009

The effect of oil on convective boiling of R-123 in an enhanced tube bundle is experimentally investigated at $26.7^{\circ}C$ saturation temperature. The enhanced tube had pores (0.23 mm diameter) and connecting gaps (0.07 mm width), which had been optimized using pure R-123. The effects of oil concentration (0 to 5%), heat flux (10 to $40\;kW/m^2$), mass velocity (8 to $26\;kg/m2^s$) and vapor quality are investigated. The oil significantly reduces the bundle boiling heat transfer coefficient. With 1% oil, the reduction is approximately 35%. Further addition of oil further reduces the heat transfer coefficient. The data are also compared with the pool boiling counterpart. The reduction in the heat transfer coefficient is smaller in a bundle (convective boiling) than in a pool (single-tube pool boiling), with larger difference at a smaller heat flux. Similar to pure R-123 case, the effects of mass velocity and vapor quality are negligible for the convective boiling of R-123/oil mixture.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.52 no.3
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• pp.257-262
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• 2016

Flexible two-phase thermosyphons are devices that can transfer large amounts of heat flux with boiling and condensation of working fluid resulting from small temperature differences. A flexible two-phase thermosyphon consists of a evaporator, an insulation unit, and a condenser. The working fluid inside the evaporator is evaporated by heating the evaporator in the lower part of the flexible two-phase thermosyphon and the evaporated steam rises to the condenser in the upper part to transfer heat in response to the cooling fluid outside the tube. The resultant condensed working fluid flows downward along the inside surface of the tube due to gravity. These processes form a cycle. Using R134a refrigerant as the working fluid of a loop type flexible two-phase thermosyphon heat exchanger, an experiment was conducted to analyse changes in boiling heat transfer performances according to differences in the temperature of the oil for heating of the evaporator, the temperature variations of the refrigerant, and the mass flows. According to the results of the present study, the circulation rate of the refrigerant increased and the pressure in the evaporator also increased proportionally as the temperature of the oil in the evaporator increased. In addition, the heat transfer rate of the boiler increased as the temperature of the oil in the evaporator increased.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.2129-2134
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• 2004

The present study has been conducted to develop a heat pump system using river water of temperature energy which not only belongs to unutilized energy but is a kind of good heat source due to maintain its temperature in a certain degree regardless of seasonal variation. The system did not meet the proposed performance after setup. In this paper, the system performance affected by refrigerant Oil, by pressure drop, or by other factors has been discussed. The followings were obtained : (1) Refrigerant Oil mixture rate was 2.5 in weight percentage, (2) Pressure drop through evaporator was 29.1kPa($3.1^{\circ}C$ in saturated tempearture) (3) Pressure drop from the end of evaporator to compressor inlet was 39.8kPa($4.0^{\circ}C$ in saturated tempearture). (4) The system performance can to be improved by modifying a part of pipe line to compressor, and reducing pressure drop through heat exchangers.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.590-595
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• 2006

This paper presents the friction and anti-wear characteristics of nano-oil with a mixture of a refrigerant oil and carbon nano-particles in the thrust slide-bearing of scroll compressors. Frictional loss in the thrust slide-bearing occupies a large part of total mechanical loss in scroll compressors. The characteristics of friction and anti-wear using nano-oil are evaluated using the thrust bearing tester for measuring friction surface temperature and the coefficient of friction at the thrust slide-bearing as a function of normal loads up to 4,000 N and orbiting speed up to 3,200 rpm. It is found that the coefficient of friction increases with decreasing orbiting speed and normal force. The friction coefficient of carbon nano-oil is 0.015, while that of pure oil is 0.023 under the conditions of refrigerant gas R-22 at the pressure of 5 bars. It is believed that carbon nano-particles can be coated on the friction surfaces and the interaction of nano-particles between surfaces can be improved the lubrication in the friction surfaces. Carbon nano-oil enhances the characteristics of the anti-wear and friction at the thrust slide-bearing of scroll compressors.

• Journal of Energy Engineering
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• v.12 no.4
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• pp.253-258
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• 2003

Manual type manifold gauge has been used for charging the refrigerant in the refrigeration systems. In this case, the refrigerant is released to the ambient during the hose-switching period. :he objectives of this study are to develop a novel automatic refrigerant charging system, and to quantify the effect of the automatic systems on the reduction of the non-condensable gas and the contamination of the compressor oil. The automatic charging system makes the pressure test, vacuum test, and refrigerant charging work very simple and easy because the charging hose does not have to be switched many times. It is found that the amount of water in the SiO$_2$and the compressor oil reduces to l/4 times of that for the manual type manifold gauge and the refrigerant is not released to the ambient at all when the automatic charging system is adopted.