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

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.