The Effect of Heating Direction on Flow Boiling Heat Transfer of R134a in Microchannels

• Published in: 热科学学报：英文版 2017, Vol.26 (2), p.166-174
• Main Author: XU Mingchen JIA Li DANG Chao PENG Qi
• Format: Article
• Language: English
• Subjects: R134a; 内加热; 微通道; 截面尺寸; 换热性能; 流动沸腾传热; 质量流量; 通道宽度
• ISSN: 1003-2169; 1993-033X

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.