波纹角对波纹竖板冷凝换热特性的影响

Influenceof chevron angle on condensation heat transfer performance of corrugated vertical plates

为了提高板式换热器的换热性能,探究换热板片的波纹角对波纹竖板冷凝侧换热特性的影响,优化其结构参数,采用建模计算的方法定量分析了波纹角对板片换热面积、液膜下落时间、流体努塞尔数、摩擦系数等参数的影响,并用可视化实验观察了不同波纹角下液膜流动路径的特点。分析结果表明,波纹角的变化对板片换热面积影响很小,可以忽略。波纹角越小,液膜下落时间越短,排液速度越快,液膜厚度越小,越有利于冷凝传热。波纹角越大,冷凝液的流动路径越接近波纹状流型,扰动越剧烈,增大了流体的雷诺数和努塞尔数,且雷诺数值越大,努塞尔数对波纹角的变化越敏感。流体与波纹板的摩擦系数也会随着波纹角的增大而增大,蒸气冷凝时产生的摩擦压降也越大。

In order to improve the heat transfer performance of plate heat exchanger and optimize its structural parameters,the influence of chevron angle on condensation heat transfer characteristics of corrugated vertical plates is investigated.The effects of chevron angle on heat transfer area,falling time of liquid film,Nusselt number of fluid and friction coefficient of plate heat exchanger were analized quantitatively.The liquid film flow paths on corrugated vertical plates with different chevron angles were observed by visual experiment.The results indicated that the change of chevron angle has little effect on the heat transfer area of corrugated vertical plates.With the decrease of chevron angle,for the liquid film,the falling time decrease,the discharging speed improve,the thickness reduce,and the condensation heat transfer is enhanced.With the increase of chevron angle,the flow path of condensate is closer to ripple flow pattern,which intensifies the disturbance of condensate and increases the Reynolds number and Nusselt number of flow.The larger the Reynolds number is,the more sensitive the Nusselt number is to the change of chevron angle.The friction coefficient between fluid and corrugated plate will also increase with the increase of chevron angle,and the friction pressure drop of vapor will also increase.