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- 저자 : 김건일(Geonil Kim) (검색결과 3 건)
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김병주(Byong Joo Kim),김건일(Geonil Kim) 대한설비공학회 2008 설비공학 논문집 Vol.20 No.12
An experimental study has been performed on the single phase flow and convective heat transfer in trapezoidal microchannels. The microchannel was about 270 ㎛ wide, 800 ㎛ deep. and 7 ㎜ long, which might ensure hydrodynamically fully-developed laminar flow at a low Reynolds number. The experiments were conducted with R113 and water, with the Reynolds number ranging from approximately 30 to 5000 for friction factor and 30 to 700 for the Nusselt number. Friction factors in laminar are found to be in good agreement with the predictions of existing correlation suggesting that a conventional analysis approach can be employed in predicting flow friction behavior in microchannels. However turbulent friction factors are hardly predictable by the existing con-elations. The experimental results show that the Nusselt number is not a constant but increases almost linearly with the Reynolds number even the flow is fully developed (Re<100). The dependence of the Nusslet number on the Reynolds number is contradictory to the conventional theory. At a Reynolds number greater than 100, the Nusselt number increases slowly with the Reynolds number, where thermally developing flow is responsible for the increase of the Nusselt number with the Reynolds number.
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사다리꼴 미세유로의 대류비등 2상유동:1부-압력강하 특성
김병주(Byong Joo Kim),김건일(Geonil Kim) 대한설비공학회 2011 설비공학 논문집 Vol.23 No.1
Characteristics of two-phase pressure drop in microchannels were investigated experimentally. The microchannels consisted of 9 parallel trapezoidal channels with each channel having 205 ㎛ of bottom width, 800 ㎛ of depth, 3.6° of sidewall angle, and 7 ㎝ of length. Pressure drops in convective boiling of Refrigerant 113 were measured in the range of inlet pressure 105~195 ㎪, mass velocity 150~920 ㎏/㎡s, and heat flux 10~100 ㎾/㎡. The total pressure drop generally increased with increasing mass velocity and/or heat flux. Two-phase frictional pressure drop across the microchannels increased rapidly with exit quality and showed bigger gradient at higher mass velocity. A critical review of correlations in the literature suggested that existing correlations were not able to match the experimental results obtained for two-phase pressure drop associated with convective boiling in microchannels. A new correlation suitable for predicting two-phase friction multiplier was developed based on the separated flow model and showed good agreement with the experimental data.
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김병주(Byong Joo Kim),김건일(Geonil Kim) 대한설비공학회 2011 설비공학 논문집 Vol.23 No.11
Characteristics of flow boiling heat transfer in microchannels were investigated experimentally. The microchannels consisted of 9 parallel trapezoidal channels with each channel having 205 m of bottom width, 800 m of depth, 3.6 o of sidewall angle, and 7 cm of length. Tests were performed with R113 over a mass velocity range of 150~920 kg/m 2 s, heat flux of 10~100 kW/m 2 and inlet pressures of 105~195 kPa. Flow boiling heat transfer coefficient in microchannels was found to be dominated by heat-flux. However the effect of mass velocity was not significant. Contrary to macrochannel trends, the heat transfer coefficient was shown to decrease with increasing thermodynamic equilibrium quality. A new correlation suitable for predicting flow boiling heat transfer coefficient was developed based on the laminar single-phase heat transfer coefficient and the nucleate boiling dominant equation. Comparison with the experimental data showed good agreement.
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