Study On Characteristics Of Flow And Heat Transfer Enhancement In A Channel Form By Circular Tube Bank Concave Convex Pyramidal Fins

Energy shortage and rapid consumption promote the development of industrial research field in a new direction.Excellent heat exchanger is widely used in petrochemical,aerospace,locomotive and other related fields.As one of the important heat exchange equipment in the industrial field,it has brought great improvement in improving heat transfer.The low efficiency heat transfer performance of flat fin is gradually eliminated by the market.In recent years,the research on the new type of enhanced fin heat exchanger has been intensified.The heat transfer area of the heat exchanger is greatly increased and the heat transfer performance of the whole heat exchanger is optimized.One of the most common forming methods is to punch a specific shape structure on the surface of the fin.In this paper,a new type of enhanced fin,pyramid fin,is studied by means of numerical simulation.In this paper,the solid domain wrapped by fluid domain is selected as the calculation region,in which the solid domain is composed of four rows of circular tubes and pyramidal fins.The selected calculation area is divided into structured grids to ensure the smoothness and smoothness of the grid,and to conform to the characteristics of fluid flow.Three sets of grid systems are used to evaluate the independence of grid.Finally,a grid system with 2.49million grids is selected.The numerical method used in this paper is compared with the previous research methods.Finally,the numerical method of SST k-?turbulence model is used.The average Nu number,resistance coefficient f,flow field,local heat transfer characteristics and secondary flow intensity se of pyramid fins and flat fins are compared.The effects of fin spacing T_p,pyramid height H_c,pyramid elevation angle?on flow and heat transfer performance are compared and analyzed.The results show:(1)That compared with the straight fins,the comprehensive heat transfer performance of pyramid fins is improved,which can destroy the development of boundary layer and enhance the fluid disturbance.(2)The structural parameters of pyramid fins have a significant influence on the flow and heat transfer performance of heat exchanger.When other structural parameters remain unchanged,the average Nu number and resistance coefficient f increase with the decrease of fin spacing T_p and the increase of pyramid height H_c and pyramid elevation angle?.(3)According to the evaluation of enhanced heat transfer factor JF,the comprehensive performance of 1.8mm fin spacing is the best when Re=447?894,and the comprehensive performance of 2mm fin spacing is the best when Re=894?1565;When Re=447?1565,the best comprehensive performance is obtained when the pyramid height is 1.2mm and the pyramid elevation angle is 82°.