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열차단막 응용을 위한 Al₂O₃ 에 증착된 Y₂O₃ 나노박막의 열전도도 와 경계면열저항에 관한 연구
김종욱(Jong-Wook Kim),김경천(Kyung-Chun Kim),박건형(Gun-Hyung Park),양호순(Ho-Soon Yang),김청식(Chung-Sik Kim),홍경수(K. S. Hong),김석로(Seok-Ro Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
The effect of interfaces on thermal conductivity is studied with Y₂O₃ thin films deposited on an Al₂O₃ substrate. Y₂O₃ thin films with the thickness between 100 and 500 ㎚ are prepared by RF magnetron sputtering and thermal conductivity of the films is measured by the 3 omega method. The strong film thickness-dependent thermal conductivity is observed due to the interfacial thermal resistance. The relationship between the interfacial thermal resistance and film thickness-dependent thermal conductivity is derived from a temperature profile across a thin film having an interface with a substrate.
김두현(Doohyun Kim),황유진(Yujin Hwang),박재홍(Jae-Hong Park),정성일(Seong-Ir Chung),정영만(Young-Man Jeong),구본철(Bon-Cheol Ku),이재근(Jae-Keun Lee),안영철(Young-Chull Ahn),방선욱(Sunwook Bang),김석로(Seok-Ro Kim) 대한설비공학회 2008 설비공학 논문집 Vol.20 No.6
The presence of non-condensable gases as an additional thermal resistance inside a refrigerating circuit has been found for a general refrigerator. The effect of non-condensable gases was varied by controlling the injection amount of dry air into the refrigerating circuit to increase a thermal resistance. Energy consumption tests for the refrigerator were conducted under the various amounts of non-condensable gases. The tested refrigerating circuit was the household refrigerator. As the molar fraction of non-condensable gases was increased from 0% to 1.46%, the amount of energy consumption was found to increase up to 25%. The increase of the amount of non-condensable gases in refrigerating circuit was found to result in increasing the condensation temperature at the condenser and decreasing the evaporation temperature at the evaporator, which were presumably caused by the low specific heat and increased partial pressure of non-condensable gas.
냉장고 가스켓 형상 변화에 따른 냉장고 열손실 저감 효과
하지수(Ji Soo Ha),정광수(Kwang Soo Jung),김태권(Tae Kwon Kim),김경호(Kyung Ho Kim),정관식(Gwan Sik Jeong),김석로(Seok Ro Kim) 대한설비공학회 2008 대한설비공학회 학술발표대회논문집 Vol.2008 No.2
Insulation of refrigerator with gasket material near door becomes the technical point at the aspect of heat loss and energy efficiency. Heat loss of refrigerator through the gasket is nearly 30%. In this paper, quantitative evaluation method of heat loss through gasket in established suggest the method for the improvement of heat loss. To analyze the heat transfer, we have used the common software Fluent that is used to CFD. Because of using the convection coefficient of heat transfer, we have solved only the equation of energy for heat transfer. As a result, we have known that heat loss flows through the heat flux vector and that the heat gathered out of the outside iron plate is transferred inner part through the gasket and ABS, etc. Through the result of the numerical simulation that use sub-gasket, we have known that we are able to reduce the heat loss about 20~40%. when we applied that sub-gasket on a real refrigerator, the power consumption had reduced about 4.76%. In addition, when we applied a more improved sub-gasket on a real refrigerator and measured the power of the refrigerator the power consumption does reduce about 3% and we will try to apply the improved sub-gasket on a new models of refrigerator.
냉장고 가스켓 형상 변화에 따른 냉장고 열손실 저감 효과
하지수(Ji Soo Ha),정광수(Kwang Soo Jung),김태권(Tae Kwon Kim),김경호(Kyung Ho Kim),김석로(Seok Ro Kim) 대한설비공학회 2009 설비공학 논문집 Vol.21 No.5
The amount of heat loss of a refrigerator through the gasket is nearly 30% of total refrigerator heat loss. In this paper, quantitative evaluation analysis of heat loss through gasket is established with numerical heat transfer analysis. Extending the gasket shape to protect the heat loss from the gasket, power consumption is measured by using real refrigerator in a temperature and humidity chamber and suggest the gasket shape to reduce the heat loss. From the present result of the numerical simulation of heat transfer and experiment with varying gasket shape, we are able to reduce the heat loss about 20~40% by using extended gasket and the power consumption can be reduced about 5%.
Sung-Jool Kim,Ho-Jin Choi,하만영,김석로,방선욱 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.4
The present study numerically solves the flow and thermal fields in the full geometry of heat exchanger modeling with frost layer presence on the heat exchanger surface. The effects of air inlet velocity, air inlet temperature, frost layer thickness, fin pitch, fin thickness,and heat exchanger shape on the thermo-hydraulic performance of a fin-tube heat exchanger are investigated. Heat transfer rate rises with increasing air inlet velocity and temperature, and decreasing frost layer thickness and fin pitch. Pressure drop rises with increasing air inlet velocity and frost layer thickness, and decreasing fin pitch. The effect of fin thickness on heat transfer and pressure drop is negligible. Based on the present results, we derived the correlations, which express pressure drop and temperature difference between air inlet and outlet as a function of air inlet velocity and temperature, as well as frost layer thickness.