两种三维双侧强化管管外R245fa凝结换热的实验对比

为研究环保制冷剂R245fa在水平强化管外凝结换热特性及表面结构对管内外换热性能的影响,分别对三维齿结构低肋管(A管)和斜翅管(B管)进行管外凝结换热实验。在数据处理方法上,采用Wilson-Gnielinski图解法获得管内水侧对流换热系数及其计算关联式,再利用热阻分离法获得管外凝结换热系数。实验结果分析得出A管和B管的管内换热系数强化倍率分别为2.04和2.98,管外强化倍率分别为1.77～1.94,1.87～2.14,B管管内外换热性能都优于A管,造成两种强化管内外换热性能差异的主要因素是强化管内的螺纹高度和管外翅化比。

Experimental Comparison of Condensation Heat Transfer Performance of R245fa on Two Kinds of Three Dimensional and Double-Sided Enhanced Tube

In order to study the effect of eco friendly refrigerant R245fa on the condensation heat transfer characteristics and the influence of the surface structure on the heat transfer performance inside and outside of the tube,with R245fa as refrigerant,the external condensation heat transfer experiment is carried out in the low rib tubes with three dimensional tooth structure (A tube) and inclined fin tube (B tube).In the data processing,the convective heat transfer coefficient of the water side in the tube and its calculation correlation are obtained by using the Wilson Gnielinski plot method,and the condensation heat transfer coefficient outside the tube is obtained by thermal resistance separation method.The experimental results show that the inner tube heat transfer coefficient intensification ratio of tube A and tube B is 2.04 and 2.98,respectively,and the outer tube intensification ratio is 1.77~1.94 and1.87~2.14,respectively.The inside and outside heat transfer performance of tube B is better than tube A.The main reasons for the difference in the inside and outside heat transfer performance between the two enhanced tubes lie in the thread height inside the tube and the wing ratio outside the tube.