纵向涡强化换热的优化设计及机理分析

Optimal Design and Mechanism Analysis for the Heat Transfer Enhancement with Longitudinal Vortex Generators

对带纵向涡发生器的椭圆管翅片换热器空气侧表面的换热和流动特性进行了三维数值模拟.深入分析了纵向涡对流场和温度场的影响,并通过场协同原理揭示了纵向涡强化换热的根本机理,即减小了速度和温度梯度之间的夹角,改善了速度场和温度场的协同性.在此基础上,对纵向涡发生器的布置位置(上游布置和下游布置)和纵向涡发生器的攻角α(15°,30°,45°,60°)进行了优化设计.结果表明:当纵向涡发生器布置于换热管下游时,具有更好的强化换热能力;在纵向涡发生器采用下游布置的前提下,当纵向涡发生器的攻角α=30°时,具有最佳的强化换热能力.

Three-dimensional numerical simulation was performed for heat transfer and flow characteristics of fined oval tube heat exchangers with longitudinal vortex generators（LVGs）.The effects of longitudinal vortex on flow field and temperature field were deeply analyzed.The fundamental mechanism of heat transfer enhancement with LVGs was also revealed using the field synergy principle,namely the reduction of the intersection angle between the velocity and the temperature gradient improved the synergy between the velocity field and the temperature field.On the basis of the study,the placement of LVGs（upstream and downstream） and attack angles α（15°,30°,45° and 60°） were also optimized and designed.Results indicate that the downstream placement of LVGs is better for heat transfer enhancement.And for the downstream placement of LVGs,when the attack angle of LVGs α=30°,maximum heat transfer enhancement can be achieved.