Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2017-03-31 Cooperative journals: 《热科学学报》
Abstract: This paper presents effects of heating directions on heat transfer performance of R134a flow boiling in mi- cro-channel heat sink. The heat sink has 30 parallel rectangular channels with cross-sectional dimensions of 500m width 500m depth and 30mm length. The experimental operation condition ranges of the heat flux and the mass flux were 13.48 to 82.25 W/cm2 and 373.3 to 1244.4 kg/m2s 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 kW/m2 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 corre- lation was provided to predict heat transfer of top heating.