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물 속에서 레이저에 의하여 생성된 기포의 거동 및 복사현상
강상우(Sarng Woo Karng),변기택(Ki-Taek Byun),곽호영(Ho-Young Kwak) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
The bubble behavior and the radiation mechanism from a laser-induced collapsing bubble were investigated theoretically using the Keller-Miksis equation for the bubble wall motion and analytical solutions for the vapor inside bubble. The calculated time dependent bubble radius is in good agreement with observed ones. The half-width of the luminescence pulse at the collapse point, which was calculated under assumption that the light emission mechanism is black body radiation from the vapor bubble agreed well with observed value of several nanoseconds. The gas content inside the vapor bubble was too small to produce the light emission due to bremsstrahlung.
풀비등에서 소형 사각기둥핀 배열형상에 따른 FC-72의 응축특성
강상우(Sarng Woo Karng),김서영(Seo Young Kim) 대한설비공학회 2011 설비공학 논문집 Vol.23 No.7
As the electronic industry rapidly develops, the heat flux from state-of-the-art electronics increases up to 10? W/㎡. For this reason, the development of a new cooling technology for high heat flux applications is strongly required. Recently, some cooling technologies using boiling and condensation of working fluid are being adopted to overcome such a technical barrier. In the present study, a smooth boiling surface (14×14 ㎟) was immersed in FC-72 and its vapor was condensed by four different types of condensation surfaces (30×30 ㎟ base). The condensing surfaces were composed of a smooth surface and 1×1 ㎟ pin-finned surfaces of 2 ㎜ height with 0.3, 0.5 and 1 ㎜ array spacing. Boiling and condensing characteristics were investigated in detail on their combinations of boiling and condensing surfaces. For a smooth boiling surface the results obtained showed that the pin-finned condensing surface with 1 ㎜ array spacing yielded the best performance and the smooth condensation surface did the worst. Furthermore hysteresis phenomena could be reduced by using enhanced condensing surfaces.
평행유동에서 공랭식 열전모듈 냉각시스템의 성능에 관한 연구
강상우(Sarng Woo Karng),신재훈(Jae-Hoon Shin),한훈식(Hun Sik Han),김서영(Seo Young Kim) 대한설비공학회 2011 설비공학 논문집 Vol.23 No.6
Experimental and theoretical studies on cooling performance of two-channel thermoelectric air-cooling system in parallel flow are conducted. The effects of operating temperature to physical properties of thermoelectric module (TEM) are experimentally examined and used in the analysis of an air-cooling system considering thermal network and energy balance. The theoretical predicted temperature variation and cooling capacity are in good agreement with measured data, thereby validating analytic model. The heat absorbed rate increases with increasing the voltage input and decreasing thermal resistance of the system. The power consumption of TEM is linearly proportional to mean temperature differences due to variations of the physical properties on operation temperature of TEM. Furthermore thermal resistance of hot side has greater effects on cooling performance than that of cold side.
강상우(Sarng Woo Karng),변기택(Gi-Taek Byun),곽호영(Ho-Young Kwak) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
The bubble behavior and the radiation mechanism from a laser-induced bubble have been studied<br/> theoretically. The calculated time dependent bubble radius is in good agreement with observed ones. The half<br/> width of the luminescence pulse at the collapse point, which was calculated with an assumption of black body<br/> source turned out to be good agreement with observed value of several nanoseconds.
강상우(Sarng Woo Karng),이석원(Suk Won Lee),황규대(Kyudae Hwang),김서영(Seo Young Kim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
In this study, we compare thermal performance between four different types of cold plates for humanoid robot cooling. Two commercially available cold plates made of copper have different dimensions and internal flow paths: One has 20×20 ㎟ base area with micro-channels and the other has 62.5×62.5 ㎟ base area with 85 round pin-fins. And two different types of cold plates of 20×20 ㎟ base area with 7 ㎜ high are made of PC (polycarbonate), which aims to reduce the weight of cooling system. All cold plates are mounted on a 20×20 ㎟ copper block with two cartridge heaters of 30 W/㎠. The overall heat transfer coefficient and thermal resistances for the liquid-cooled cold plates are obtained. The copper cold plate with micro-channels showed the best performance. Polycarbonate cold plates display fairly good thermal performance with more reduced system weight.
인간형 로봇 내부의 다중 열원에 대한 수냉식 냉각판의 성능
강상우(Sarng Woo Karng),김서영(Seo Young Kim),문종민(Jongmin Moon),황규대(Kyudae Hwang),리광훈(Gwanghoon Rhee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
It was investigated thermal performances on two array types of a serial circulation and a two-way parallel circulation for six water-cooled cold plates covered with non-metallic material (polycarbonate, PC) to reduce weight of the cooling devices for humanoid robot cooling. Six cold plates attached on 10×10 ㎟ copper base : 0.5×0.5 ㎟ pin-finned surfaces of 1.5 ㎜ high with 0.5 ㎜ array spacing, was mounted on six copper heating blocks with isothermal conditions of 50~90℃, respectively. In order to compare thermal characteristics according to two circulation types, the surface temperatures of heating blocks and the cooling water temperatures at inlets and outlets of cold plates were measured. From the results, it was found that a two-way parallel circulation was better performance than a serial circulation in terms of total thermal resistance, total heat transfer rate, and surface temperature rises from 1<SUP>st</SUP> heating block to last one for six multiple cold plates.
인간형 로봇냉각을 위한 소형 수냉식 냉각판의 열적 특성
강상우(Sarng Woo Karng),김서영(Seo Young Kim),문종민(Jongmin Moon),황규대(Kyudae Hwang),리광훈(Gwanghoon Rhee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Thermal performance for mini water-cooled cold plates covered with non-metallic polycarbonate (PC) is experimentally measured in this study. The mini cold plates are designed to reduce the overall weight of the cooling device for effective heat dissipation from a humanoid robot. The water-cooled cold plate has a l0×10 ㎟ of base plate which is made of copper or aluminum. Two different types of enhanced surfaces are considered in the present study: copper pin-finned surface of 0.5×0.5 ㎟ area and 1.5 ㎜ high with 0.5 ㎜ fin spacing and aluminum foam-finned surface of 92% porosity and 40 PPI (pores per inch). Heat transfer rates are measured according to the input power and the flow rate of cooling water. The surface temperature of the base plate and the cooling water temperatures at inlet and outlet of each cold plate are measured. From the results, it is found that the copper pin-finned cold plate shows better performance than the aluminum foam-finned cold plate in terms of thermal resistance and pressure drop.
로봇 냉각을 위한 비금속 재질의 이상 냉각판에 대한 열전달 특성
강상우(Sarng Woo Karng),이석원(Suk Won Lee),황규대(Kyudae Hwang),김서영(Seo Young Kim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
It was investigated to compare thermal performances among a metallic cold plate and a non-metallic cold plate by using dielectric fluid (FC-72) as the working fluid in two-phase circulation. Two types of cold plates have the same dimension of 36×30 ㎟ base area with 7 ㎜ high. A metallic cold plate was totally made of copper. A polycarbonate (PC) cold plate, which was designed to reduce the overall weight of robot cooling system, was composed of a PC cover with copper base plate. Two types of cold plates were mounted on a 20×20 ㎟ copper heating block of 30 W/㎠. It was found that PC cold plate showed better thermal performance than the copper cold plate in terms of thermal resistance with considering unit mass. Furthermore, it was known that the two-phase PC cold plate with a copper base can be an effective cooling device for humanoid robots due to keeping below 70℃ of the surface temperature of the heating block at the input power of 10 W/㎠.
강상우(Sarng Woo Karng),이윤표(Yoon Pyo Lee) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
The heat flux on a chip is rapidly increasing with decreasing the size of one. It is necessary to properly cool the high heat flux chip. One of the promising cooling methods is to apply CPL heat pipes with porous materials, for example PVA, polyethylene, and powder sintered metal plate and with microchannels in the evaporator. A small scale CPL heat pipe with PVA as wick was designed and manufactured. Since the height difference between the evaporator and the condenser is a crucial parameter in the CPL heat pipes, the performance of the heat pipes depending on the parameter was investigated. The parameter is higher the performance is better. However, the improvement rate of the performance does not increase the increase rate of the height. In addition to, the parameter effect depending on heat input was investigated.
소형 사각핀의 배열형상에 따른 FC-72 의 비등 및 응축 특성
강상우(Sarng Woo Karng),지태호(Tae Ho Ji),김서영(Seo Young Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
As the electronic industry rapidly develops, the heat flux from state-of-the-art electronics increases up to 10? W/㎡. For this reason, the development of a new cooling technology for high heat flux applications is strongly required. Recently, some cooling technologies using boiling and condensation of working fluid are being adopted to overcome such a technical barrier. In the present study, a smooth boiling surface (30×30 ㎟) and three different types of condensation surfaces (30×30 ㎟) are fabricated: a smooth surface, a mini-stud surface (1×1 ㎟, 2 ㎜ in height) with 1 ㎜ inter-stud spacing, and a mini-stud surface (the same size) with 0.5 ㎜ inter-stud spacing. The effect of surface geometry on boiling and condensation is investigated in detail. The results obtained display that the condensation surface with mini-studs (0.5 ㎜ spacing) yields the best performance until incipient boiling points and the smooth condensation surface does the best after the points. And the hysteresis can be reduced even by being enhanced of a condensing surface.