Numerical Simulation Of Jet-enhanced Heat Transfer In Helical Channels With Different Curvatures

The circular cross-section spiral channel,as a common curved channel heat exchanger,is widely used in the chemical,aerospace and other fields.In this paper,the jet impact method is used to strengthen the fluid flow and heat transfer in the circular cross-section spiral channel.Numerical calculations are carried out based on the computational fluid dynamics software Fluent,and the numerical analysis results are compared with the existing experimental results to verify the numerical simulations in this paper The accuracy of the method is to analyze the effects of jet parameters and spiral channel curvature on flow and heat transfer.This paper explores the vortex structure,composite flow field,flow resistance and wall heat transfer characteristics in spiral channels with different curvatures under different jet velocity ratios(ε_j)and incident angles(α).Comprehensive evaluation is made from the perspective of comprehensive enhanced heat transfer factors,and the enhanced heat transfer mechanism is revealed based on the principle of field synergy.In addition,this article examines the consumption of external energy by jets with different parameters.The research results show that when the jet impacts the inner wall of the circular cross-section spiral channel,a pair of jet-induced vortices that rotate in the opposite direction to the Dean vortex will be generated in the channel.In the initial stage of applying the jet,the two pairs of vortices inhibit each other.When the jet velocity is compared When it is large,the jet-induced vortex can completely suppress the development of Dean’s vortex.The impact of the jet will effectively reduce the synergy angle between the temperature field and the velocity field,thereby enhancing the wall heat transfer.In the spiral channel,the jet half-value width increases continuously along the flow direction,and increases with the increase of the jet velocity ratio.Increasing the jet velocity ratio and reducing the jet incidence angle will increase the flow resistance and strengthen the wall heat transfer.Under the working conditions ofα=45°andε_j=5,Compared with a single spiral channel,the enhanced heat transfer of the jet composite circular cross-section spiral channel can increase the local Nusselt number by up to 5 times and the average Nusselt number by up to 60%.Based on the flow rate of the spiral channel before the jet,the JF range of the comprehensive enhanced heat transfer factor obtained by the jet impinging on the inner wall is 1.26～1.67;based on the flow rate of the spiral channel after the jet,the JF range of the jet impinging on the inner wall is 1.008～1.417.In addition,increasing the curvature of the spiral channel will shorten the impact distance of the jet and strengthen the heat transfer strength of the inner wall of the spiral channel.And the range of the wall jet area also increases with the increase of curvature,so the spiral channel with larger curvature is beneficial to the heat exchange of the wall.