• 설비공학논문집
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• 제16권5호
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• pp.452-458
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• 2004

The major cause of compressor failure is the decrease of oil viscosity due to floodback. In most previous researches on the compressor reliability, the relationship between oil circulation rate and performance or oil viscosity has been studied. Another research topic is flow visualization by using a sight glass on the bottom of a compressor sump area and accumulator. Both oil film thickness and oil level through the sight glass should be assessed for compressor reliability if the oil content of the mixture is small and low viscosity raise poor lubrication of pump bearing. In this study, the compressor reliability was assessed by measuring the viscosity of the mixture and calculating oil film thickness. The analysis of the relationship between bottom shell super heat and oil film thickness at heating operation was peformed. It is concluded that bottom shell superheat does not perfectly stand for the mixture's behavior for a low ambient heating operation and oil film thickness can give more detailed and direct criteria for compressor reliability.

• 설비공학논문집
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• 제13권5호
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• pp.363-363
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• 2001

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1499-1505
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• 2003

Rapid development of electronic technology requires small size, high density packaging and high power of electronic devices. So, in this paper, characteristics on oscillating heat pipe according to operating conditions(environment temperature, charging ratio of working fluid, inclination) based on experimental study was investigated. From the experimental results, $25^{\circ}C$environment temperature), R-141b(working fluid)40%(charging ratio) was best performace at others of inclination angle and The top heating mode of OCHP performed 80% efficiency of the bottom heating mode.

• Journal of Advanced Marine Engineering and Technology
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• 제29권4호
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• pp.436-442
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• 2005

Rapid development of electronic technology requires small size, high density packaging and high power of electronic devices. In this paper, characteristics on oscillating heat pipe according to operating conditions (environment temperature, charging ratio of working fluid, inclination) based on experimental study was investigated From the experimental results $25^{\circ}C$(environment temperature) R-141b (working fluid) $40\%$ (charging ratio) was best performace at others of inclination angle and the top heating mode of OCHP performed $80\%$ efficiency of the bottom heating mode.

• Journal of the Korean Wood Science and Technology
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• 제37권5호
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• pp.440-450
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• 2009

In case of wood flooring, the high emissivity would be one of the most important properties especially as the cover material of underfloor heating system. The FIR (Far Infrared) materials such as wood emit FIR energy by heating, which has been used as the medical therapy such as dry sauna. This research investigated the emissivity and the emission power of wood composites by comparing the amount of the three heat transfer modes transferred by infrared radiation which came from the increased temperature of the bottom board of the plywood box by the heater. The results showed the value of radiation mode was the highest mode for the plywood box, and the convection mode was the main mode for the aluminum box. The rate of convection was 81.8% in the aluminum box and 48.2% in the plywood box, respectively. In case of the rate of radiation, the aluminum box showed only 15.4% and the plywood box showed 51%. The emissivity and the emission power of birch plywood showed the same values as those of wood. The amount of energy required for the temperature rising of water within vial in the aluminum box and in the plywood box were 3.32 kJ and 6.70 kJ respectively, which showed that the vial temperature of the plywood box was two times higher than that of the aluminum box.

• 설비공학논문집
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• 제13권5호
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• pp.368-376
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• 2001

Performance of heat exchanger was evaluated to heat exchanger using oscillating heat pipe for waste heat recovery of low temperature. Oscillating heat pipe used in this study was formed to the closed loop of serpentine shapes using copper tubes. Heat exchanger was formed to shell and tube type and composed of low finned tube. R-22 and R-141b were used to the working fluids of tube side and their charging ratio was 40%. And, water was used to the working fluid of shell side. As the experimental parameters, the inlet temperature difference of heating and cooling part of secondary fluid and the mass velocity of secondary fluid were used. The mass velocity of secondary fluid was changed from 90 kg/$m^2s\; to\;190 kg/m^2$s from the experimental results, heat recovery rate was linearly increased to the increment of the mass velocity of secondary fluid and the inlet temperature difference of secondary fluid. Finally, the performance of heat exchanger was evaluated by using $\varepsilon$-NTU method. It was found that NTU was about 1.5 when effectiveness was decided to 80%.