• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1518-1523
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• 2003

The objective of the present work is to investigate an effect on the solution crystallization temperature difference and the cooling capacity of the absorption chiller by a solution cooler in the absorber. The cooling capacity of the absorption chiller can be higher, with the enhanced performance of the solution heat exchangers. But, because the solution crystallization temperature difference becomes smaller at the absorber inlet, the heat capacity of the solution heat exchangers might be limited by the danger of crystallization, which can cause the serious damages. In this paper, the heat capacity ratio of the solution cooler is defined as the ratio of the heat capacity of the solution cooler to that of the absorber. If it becomes larger in the additional type solution cooler, the solution crystallization temperature difference is augmented and the cooling capacity is also increased.

• 설비공학논문집
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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.

• 설비공학논문집
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• 제11권5호
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• pp.692-699
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• 1999

The vortex tube is a sample device for separating a compressed gaseous fluid stream into two flows of high and low temperature without any chemical reactions. The phenomena of energy separation through the vortex tube were investigated experimentally, to see the effects of the number of nozzle holes on the energy separation. The experiment was carried out with the number of nozzle holes from 1 to 10 by varying inlet pressure and cold mass fraction. The experimental results were indicated that the effective number of nozzle holes for the best cooling performance was found as 4. Also, to find effective use in a given operation conditions, the temperature difference of cold air and the cooling capacity of vortex tube was compared. The result is that cooling capacity was more important than temperature difference of cold air.

• 설비공학논문집
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• 제16권4호
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• pp.311-317
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• 2004

In the present study, the cooling characteristics of the multi-air conditioner (A/C) using an inverter scroll compressor are experimentally investigated for the number of the indoor units and the operating conditions (2$0^{\circ}C$, 24$^{\circ}C$, 26$^{\circ}C$) under the cooling standard conditions by KS C 9306. In the case of the simultaneous operation for 3 indoor units, the cooling capacity, the mass flow rate and the input power have a decreasing trend and COP has an increasing trend, with decreasing the difference in the operating temperature of the indoor unit and the room temperature. In the case of the simultaneous operation for 2 indoor units, the COP of the indoor unit with large cooling capacity is high when the operating temperature is high, but the COP of the indoor unit with low cooling capacity is high when the operating temperature is low. In the case of the single operation for one unit, when the large cooling capacity of the indoor unit is less than 50％ the compressor operates at the minimum operation frequency region and the COP decreases.

• 설비공학논문집
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• 제16권1호
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• pp.62-69
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• 2004

Thermoelectric module is a device that can produce cooling in a direct manner using the electrical energy. The purpose of this study is to investigate the performance of thermoelectric module and cooling system equipped with the thermoelectric module. The performance of a thermoelectric module is estimated using two methods; theoretical analysis based on one-dimensional energy equations and experimental tests using heat source, heat sink and brass conduction extenders. For the thermoelectric cooling system, the temperatures in the chamber are recorded and then compared with those of lumped system analysis. The results show that the cooling capacity and COP of the thermoelectric module increases as the temperature difference between hot and cold surface decreases, and there is particular current at which cooling capacity reaches its maximum value. The experimental results for the thermoelectric cooling system are similar to those of lumped system analysis.

• 설비공학논문집
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• 제23권8호
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• pp.562-570
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• 2011

In this research, an experimental study is performed to investigate the effects of system operating variables on the cooling and heating characteristics of heat pump system using geothermal heat source and carbon dioxide as a refrigerant. System variables analyzed include compressor frequency, electronic expansion valve opening, refrigerant charge, secondary fluid temperature and flow rate. Results show that optimum refrigerant charge and electronic expansion valve opening position exist at the maximum point of COP curve, and both cooling and heating capacity increase but COPs decrease with the increase of compressor frequency. The change of a secondary fluid temperature leads to variation of overheat area and enthalpy difference in the evaporator and gas cooler. which again results in considerable variations of cooling and heating capacity and COP. In the case of effects of secondary water fluid flow rate, both cooling capacity and COP increase with the increase of secondary flow in evaporator or gas cooler, whereas heating capacity and COP decrease with the increase of flow rate in gas cooler.

• 한국수소및신에너지학회논문집
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• 제15권4호
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• pp.341-347
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• 2004

An experimental study has been carried out on cooling perfonnance of a thennoelectric module. This problem is of particular interest in the design of the refrigeration systems using thermoelectric module, such as cosmetic refrigerator, wine cellar and air cooler. The effect of the input voltage and the hot side temperature on the cooling performance is studied in detail. The $\Delta$T, temperature difference between cold side and hot side surface of thermoelectric module, is described in terms of the input voltage and the hot side temperature. It is found that the cooling capacity can be improved by increasing the input voltage and by reducing the heat from the hot side of the thermoelectric module. However, COP is decreased with an increase in the input voltage, since power consumption is also increased. Thus, optimum input voltage can be selected based on cooling capacity and COP.

• 농업과학연구
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• 제33권2호
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• pp.107-114
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• 2006

An all-aluminum radiator made of aluminum was more excellent on environment friendliness, productivity, and cooling efficiency than the plastic tank radiator which was currently widely used in same size as above. A newly designed and manufactured radiator with all parts made of aluminium was ready to re-use without any disassembly process in recycle system so as to improve environment friendliness with low waste cost. Several manufacturing processes of the current plastic tank radiator such as O-ring inserting, and clinching of core to the tank, were eliminated on the manufacturing processes of the all-aluminium radiator, which would increase productivity and reduce production cost. Design criterion of all-aluminum radiator was presented by carrying out theoretical analysis of cooling capacity and there was no difference between analytical data and measurements. Cooling capacity of the all-aluminum radiator increased generally 13% up compared with the plastic radiator even though the pressure drop of air increased.

• 한국초전도ㆍ저온공학회논문지
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• 제17권3호
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• pp.51-56
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• 2015

Cryogenic cooling system for HTS electric power devices requires a reliable and efficient high-capacity cryocooler. A Striling cryocooler with a linear compressor can be a good candidate. It has advantages of low vibration and long maintenance cycle compared with a kinematic-driven Stirling cryocooler. In this study, we developed dual-opposed linear compressor of 12 kW electric input power with two 6 kW linear motors. Electrical performance of fabricated linear compressor is verified by experimental measurement of thrust constant. The developed Stirling cryocooler has gamma-type configuration. Piston and displacer are supported with flexure spring. A slit-type heat exchanger is adopted for cold and warm-end, and the generated heat is rejected by cooling water. In cooling performance test, waveforms of voltage, current, displacement and pressure are obtained and their amplitude and phase difference are analysed. Moreover, temperatures of cooling water, housing and linear motor are recorded and electric power parameters of driving circuit are also obtained. The developed Stirling cryocooler reaches to 47.8 K within 23.4 min. with no-load. From heat load tests, it shows cooling capacity of 440 W at 78.1 K with 6.45 kW of electric input power and 19.4 of % Carnot COP.

• 한국항공우주학회지
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• 제32권4호
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• pp.67-72
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• 2004

경험식을 이용한 1차원 해석에 의하여 30톤급 재생냉각 연소기의 냉각 유로 설계를 수행하였다. 1차원 해석에 의한 벽온도는 3차원 CFD 해석과 비교하여 약 100 K의 온도차이를 보였다. 동일한 냉각성능을 유지하면서 냉각 채널의 최대 폭이 4mm 와 2mm인 두 가지 설계안을 제시하였다. 냉각유체의 압력강하는 20% 증가할 것으로 예측되었다. 열차 폐 코팅과 탄소 침착물의 열저항을 고려한 경우, 최대 벽온도는 700K로 예측되었다. 본 연구에서 제시한 냉각 방법은 용량이 부족한 것으로 판단되는 바 막냉각이 추가적으로 적용되어야 할 것으로 판단된다.