机械加工表面强化管管外全凝与部分凝结换热实验

Experimental Investigation on Whole and Part Condensation Heat Transfer for Mechanically Fabricated Surface Enhanced Tube

以强化传热为目的,对两种机械加工表面强化管——强化管Ⅰ和强化管Ⅱ进行研究.在全凝工况下对该强化传热管与光管进行对比实验,研究表面特殊结构对强化传热的影响,并在部分凝结工况下对强化管的换热情况进行实验和分析.结果表明:强化管能明显提高冷凝传热效果.在测定的雷诺数范围内,以水蒸气为冷凝介质,强化管Ⅰ和强化管Ⅱ的管外凝结传热系数分别约为光管的2.89倍和1.75倍,总传热系数分别约为光管的1.89倍和1.33倍;酒精作为冷凝介质,管径19,mm时部分凝结传热系数分别是全凝工况冷凝传热系数的2.1～3.0倍和1.5～2.0倍,管径25,mm时分别是全凝工况的2.0～3.0倍和1.8～2.5倍.

With the aim of enhancing heat transfer,two kinds of mechanically fabricated surface enhanced tubes,which are namedⅠandⅡ,were proposed.On the condition of whole condensation,heat transfer enhancement ef-fects of special surface structure were studied by comparative experiments on enhanced tubes and smooth tube.The heat transfer performances of enhanced tubes with part condensation condition were also studied experimentally and theoretically.The results show that the enhanced tubes can evidently improve condensation heat transfer.With water vapor as condensation medium,outside condensation heat transfer coefficients ho on whole condensation of two en-hanced tubes are 2.89 and 1.75 times as large as that of smooth tube with the specified Reynolds number,respectively;and the corresponding ratios of total heat transfer coefficients are 1.89 and 1.33.With alcohol vapor as condensation medium,ho values on part condensation are 2.1—3.0 and 1.5—2.0 times as large as the values on whole condensation for two enhanced tubes with the diameter of 19 mm,respectively,and the ratios are 2.0—3.0 and 1.8— 2.5 for tubes with the diameter of 25 mm correspondingly.