Based on the assumption of locally fully developed flow and slip-fiow theory, we preseota method to simulate the heat transfer and momentum exchange of gas with a solid surfacein micro-channels, and the method was pro...Based on the assumption of locally fully developed flow and slip-fiow theory, we preseota method to simulate the heat transfer and momentum exchange of gas with a solid surfacein micro-channels, and the method was proved by comparing with Pfahler’s exprimentalresults. Effect of the gas compressiblity and slip-flow on the skin friction was discussed indetail, the result demonstrates that Knudsen number should be considered in the analysisof flow in micro-domains. In the second part, the temperaturedump theory was studiedto explain the abnormal phenomina which is different from that of macro-scale channels.Some important conclusions of momentum and heat transports in microscale channels wereobtained.展开更多
This paper presents effects of heating directions on heat transfer performance of R134 a flow boiling in micro-channel heat sink. The heat sink has 30 parallel rectangular channels with cross-sectional dimensions of 5...This paper presents effects of heating directions on heat transfer performance of R134 a flow boiling in micro-channel heat sink. The heat sink has 30 parallel rectangular channels with cross-sectional dimensions of 500mm width 500mm depth and 30 mm length. The experimental operation condition ranges of the heat flux and the mass flux were 13.48 to 82.25 W/cm^2 and 373.3 to 1244.4 kg/m^2 s respectively. The vapor quality ranged from 0.07 to 0.93. The heat transfer coefficients of top heating and bottom heating both were up to 25 k W/m^2 K. Two dominate transfer mechanisms of nucleate boiling and convection boiling were observed according to boiling curves. The experimental results indicated that the heat transfer coefficient of bottom heating was 13.9% higher than top heating in low heat flux, while in high heat flux, the heat transfer coefficient of bottom heating was 9.9%.higher than the top heating, because bubbles were harder to divorce the heating wall. And a modified correlation was provided to predict heat transfer of top heating.展开更多
A solid-phase sintering process for the low-cost fabrication of composite micro-channels was developed. Three kinds of composite micro-channels with metallic porous structures were designed. The sintering process was ...A solid-phase sintering process for the low-cost fabrication of composite micro-channels was developed. Three kinds of composite micro-channels with metallic porous structures were designed. The sintering process was studied and optimized to obtain porous-structured micro-channels with high porosity. The flow resistance and heat transfer performance in the composite micro-channels were investigated. The composite micro-channels show acceptable flow resistance, significant enhancement of heat transfer and dramatic improvement of flow boiling stability, which indicates a promising prospect for the application in forced convective heat transfer.展开更多
文摘Based on the assumption of locally fully developed flow and slip-fiow theory, we preseota method to simulate the heat transfer and momentum exchange of gas with a solid surfacein micro-channels, and the method was proved by comparing with Pfahler’s exprimentalresults. Effect of the gas compressiblity and slip-flow on the skin friction was discussed indetail, the result demonstrates that Knudsen number should be considered in the analysisof flow in micro-domains. In the second part, the temperaturedump theory was studiedto explain the abnormal phenomina which is different from that of macro-scale channels.Some important conclusions of momentum and heat transports in microscale channels wereobtained.
基金supported by the National Natural Science Foundation of China(No.51376019)
文摘This paper presents effects of heating directions on heat transfer performance of R134 a flow boiling in micro-channel heat sink. The heat sink has 30 parallel rectangular channels with cross-sectional dimensions of 500mm width 500mm depth and 30 mm length. The experimental operation condition ranges of the heat flux and the mass flux were 13.48 to 82.25 W/cm^2 and 373.3 to 1244.4 kg/m^2 s respectively. The vapor quality ranged from 0.07 to 0.93. The heat transfer coefficients of top heating and bottom heating both were up to 25 k W/m^2 K. Two dominate transfer mechanisms of nucleate boiling and convection boiling were observed according to boiling curves. The experimental results indicated that the heat transfer coefficient of bottom heating was 13.9% higher than top heating in low heat flux, while in high heat flux, the heat transfer coefficient of bottom heating was 9.9%.higher than the top heating, because bubbles were harder to divorce the heating wall. And a modified correlation was provided to predict heat transfer of top heating.
基金Project(51146010)supported by the National Natural Science Foundation of ChinaProject(S2011040003189)supported by the Doctoral Research Fund of Guangdong Natural Science Foundation,ChinaProject supported by the Fundation of Key Laboratory of Surface Functional Structure Manufacturing of Guangdong Higher Education Institutes,South China University of Technology
文摘A solid-phase sintering process for the low-cost fabrication of composite micro-channels was developed. Three kinds of composite micro-channels with metallic porous structures were designed. The sintering process was studied and optimized to obtain porous-structured micro-channels with high porosity. The flow resistance and heat transfer performance in the composite micro-channels were investigated. The composite micro-channels show acceptable flow resistance, significant enhancement of heat transfer and dramatic improvement of flow boiling stability, which indicates a promising prospect for the application in forced convective heat transfer.
