Effect Of Synthetic Jet On Flow And Heat Transfer Characteristics In Tubes

It is well known that pipe flow is widely used in industry.Due to the full development of the fluid in the pipe,the heat transfer coefficient is much lower than the inlet,so it becomes the main problem for heat transfer.Using a variety of tube inserts is one of the usual way of the heat transfer enhancement measures and treatment of inner wall is a common method,but these measures will change the original pipe flow;And the method of electromagnetic excitation and mechanical vibration is limit by the pipe fluid properties and working conditions.As a kind of micro actuator,synthetic jet actuator has been active in flow control and enhanced heat transfer.In this paper,the synthetic jet actuator was used in tube flow to enhance the heat transfer.Adjusting the parameters of synthetic jet actuator,and then found the mechanism of heat transfer enhancement in tube based on active flow control by numerical simulation and experimental study.Through numerical simulation,studied on the characteristics of flow and heat transfer,discussed the unsteady characteristics of synthetic jet effect and found the impact on the mainstream Reynolds number,spacing,number of actuator,the jet angle,phase difference and amplitude,and the calculation results were verified by experiments.Research results showed that: when the Re=500,the enhancement ratio of convective heat transfer coefficient was 2.20 times of the Reynolds number of 14000;The effect of heat transfer increased with increase of the number of actuator,and when the spacing was 14 d,the convection heat transfer coefficient was 1.12 times of the actuator spacing was 30d;When synthetic jet actuator amplitude increased,the jet velocity increased,strengthening also enhance the heat transfer effect of the corresponding;The jet angle influence the vortex structure.In the experimental part,the Reynolds number was 1200~13000.The experimental results showed that the heat transfer enhancement effect of the synthetic jet was higher than that of the main flow when the main flow was laminar.Comparing with the Reynolds number was 8000,the average of the convective heat transfer coefficient enhancement ratio increased by 3.58% when Reynolds number was 2400.The average convective heat transfer coefficient increased with increasing of the number of actuator and decreased with increasing of spacing within the experimental range.