• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 한국초전도저온공학회 1999년도 제1회 학술대회논문집(KIASC 1st conference 99)
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• pp.189-193
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• 1999

An experimental study was carried out to improve the cooling capacity and performance of the pulse tube refrigerator. Three buffer pulse tube refrigerator was designed and fabricated, and the experimental apparatus was constructed. This paper presents operating process of three buffer pulse tube refrigerator and results obtained with the performance test. The cooldown characteristics and load characteristics are described. The lowest temperature measured in three pulse tube refrigerator was 88K and the cooling capacity at the optimum operating condition was 27W at 120K.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제8권1호
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• pp.110-119
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• 1996

A numerical of thermoacoustic refrigerators has been developed. Effects of heat transfer and viscosity on pressure and velocity distributions in resonators and heat exchangers were considered. Predictions of cooling capacity and COP agreed well with previous experimental results. Effects of important design parameters, such as pressure ratio, spacing between the plates in the stack and stack length, on the performance of thermoacoustic refrigerators were shown.

• Proceedings of the KSME Conference
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2597-2602
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• 2007

In this paper, the performance analysis is experimentally carried out in order to select the best cooling fan and shroud considering both cooling performance and noise reduction. 4 cooling fans have been tested in the fan tester and the real excavator. In order to obtain the performance of the cooling fans, flow capacity has been estimated by measuring flow velocity using a hot wire anemometer, and noise radiation has been also measured to estimate the fan noise. Characteristics of a box-type and a streamlined shroud have been examined by changing the immersion depth of cooling fans. Based upon the results, the best cooling fan is selected. Finally, the criterion to select the best cooling fan has been set up.

• Journal of Advanced Marine Engineering and Technology
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• 제18권3호
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• pp.10-16
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• 1994

This study aimed at measuring the latent heat of phase transformation of S45C carbon steel in quenching and at conducting the analytical researches into the calculation of cooling curves including the latent heat. The temperature of phase transformation of steel and its latent heat are dependant upon the cooling rates at the temperature of A1 phase transformation point. The effect of the latent heat of phase transformation is especially manifest at the cooling curve of center of specimens. The higher the cooling rates became, the lower fell the temperature region of phase transformation. In the figures of cooling rates, the phenomena of cooling rate dropping into zero was caused by the latent heat of phase transformation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제8권2호
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• pp.208-218
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• 1996

Performance of a VM heat pump is considerably affected by various losses, such as enthalpy dump, reheat loss, pumping loss, conduction loss and shuttle loss. A second-order analysis model of VM heat pumps, which allows consideration of the major losses, was presented. Actual heat transfer rates for heat exchangers were calculated from the heat transfer rates obtained by the adiabatic analysis and various losses. New effective temperatures of heat exchangers were calculated from the actual heat transfer rates and the mean heat transfer coefficients until there was no appreciable change in the effective temperatures. Effects of design parameters, such as phase angle, swept volume ratio, regenerator length and speed on heating capacity, cooling capacity and COP were shown.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제9권4호
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• pp.462-471
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• 1997

The water-to-air heat pump system requires relatively lower energy consumption and less installation space. The heat exchangers used for this system are the finned-tube type for the indoor unit and the double-tube type for the outdoor unit. Mathematical models for this system are developed and programmed in computer. Experimental data from various conditions are obtained and compared with calculated values from the computer simulation program. Differences of cooling capacity and COP are 1.25% and 0.47%, and those of heating capacity and COP are 0.51% and 0.13%, respectively. Simulation results are in good agreement with test results. Therefore, the developed program is effectively used for the design and the performance prediction of water-to-air heat pump system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제24권8호
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• pp.605-611
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• 2012

The objective of this study is to investigate the influence of the cooling performance for a water-to-water 10 RT ground source heat pump by using the water switching and refrigerant switching method. The test of water-to-water ground source heat pump was measured by varying the compressor speed, load side inlet temperature, and ground heat source side temperature. The cooling capacity and refrigerant mass flow rate of the heat pump increased with increasing ground heat source temperature. But COP of the heat pump decreased with increasing ground heat source temperature. As a result, the water switching method with counter flow, compared to a refrigerant switching method, improves the cooling capacity and COP by approximately 6~9% in average, respectively.

• Proceedings of the SAREK Conference
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.673-678
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• 2009

This paper presents the optimization process of liquid desiccant cooling cycle using LiCl aqueous solution as a working fluid. Operating conditions and design factors for heat exchangers were optimized by response surface method. As a result, we obtained the 7.297 kW of cooling capacity and 0.788 of COP at optimized condition. Effect of $dT_{hw}$ on system performances was also examined. As $dT_{hw}$ increases, the cooling capacity increases and COP decreases.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제22권7호
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• pp.419-428
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• 2010

This paper presents the optimization process of liquid desiccant cooling system using LiCl aqueous solution as a working fluid. Operating conditions(mass flow rate, conditioner outlet concentration, difference concentration) and design factors for heat exchangers(difference temperature of the district heating water, leaving temperature difference of the conditioner, leaving temperature difference of the regenerator, air temperature difference of the conditioner, air temperature difference of the regenerator) were optimized by response surface method. As a result, we obtained the 7.297 kW of cooling capacity and 0.788 of COP at optimized condition. Effect of difference temperature of hot water on system performances was also examined. As difference temperature of the district heating water increases, the cooling capacity increases and COP decreases.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제25권12호
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• pp.641-646
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• 2013

The purpose of this study is to improve the cooling performance of single and cascade refrigeration systems using thermoelectric modules. The system consists of a heat sink, fan, and thermoelectric module. The operating parameters considered in this study include power distribution between the first- and second-stage thermoelectric modules, air flow, and variable condensing unit. The cooling capacity increased with decreases in the temperature difference between hot and cold surfaces, but decreased with increases in the condensing temperature. The COP decreased with increasing electric power of the thermoelectric module because of the increased Joule heat. The cooling performance improvement using the thermoelectric module is represented by the freezer temperature.