板式换热器相变流动的传热及压降特性

Heat transfer and pressure drop characteristic of phase change flow in plate heat exchanger

建立了三维单流道模型,模拟了波纹倾角和波纹节距对相变流动传热和压降特性的影响。结果表明,沸腾传热和压降特性同时受到流动形式和触点影响,"曲折型"流动有利于液膜蒸发增强传热,触点对气相的扰动作用小于液相,因此在气相体积分数较高的区域的触点处气液相变转化现象不明显。传热系数随波纹倾角的增加而增大,随波纹节距的增加而减小,但在相同入口Reynolds数下波纹节距λ=16 mm比14 mm的传热系数大,主要是因为流动形式的改变在某种程度上减弱了触点数目减少对传热的影响。β=75°和λ=10mm时传热性能最好。沸腾流动的压降随波纹倾角的增大先升高后降低,在β=65°左右达到峰值,随着波纹节距的增大而降低。

A three-dimensional one-channel model was established,the effect of corrugated clination angle and corrugated pitch on heat transfer and pressure drop of phase change flow was simulated.The results show that the heat transfer characteristics of the flow boiling are affected by both the flow pattern and the contact point.The'helical flow'promots evaporation of liquid film,and the contact point has less effect on gas than liquid,therefore,the phenomenon of gas-liquid phase transition is not obvious at the higher gas volume fraction.The heat transfer coefficient increases with the increasing of the corrugated inclination angle,and decreases with the increasing of the corrugated pitch.The heat transfer coefficient ofλ=16mm is larger than that ofλ=14mm at same Reynolds number,because the change of the flow pattern may prevent the heat transfer caused by the reduction of the number of contacts.The heat transfer is the best atβ=75°andλ=10 mm.The pressure drop of the flow boiling increases at first and then decreases with the increasing of the corrugated inclination angle,and reaches the peak at aboutβ=65°,and decreases with the increasing of the corrugation pitch.