Numerical Study On Heat And Mass Transfer Of Wavy Fin-and-tube Heat Exchanger With Changes Wavy Height

As the essential heat exchanger equipment in industrial production, the heatexchangers is widely used in the field of power, metallurgy, chemical industry,refrigeration and other industrial system. New styles of heat exchangerequipment has become more and more important with the development ofproduction technology,the expansion of production scale and the rapidconsumption of all kinds of energy. The triangular wavy fin can enhance heattransfer performance of the heat exchanger, because of increasing the air heattransfer area, changing the air flow direction, strengthening the flow disturbance.However, we must give sufficient attention to the resistance loss of air flowwhen considering the heat transfer performance, in order to enhance thecomprehensive heat transfer performance of heat exchanger. In recent years,studies have found that the elliptic tube has smaller resistance loss than thecircular tube which usually used.In this paper,3D numerical simulations were performed to investigate thewavy fin-and-elliptic tube heat exchanger with changes wavy height. Firstly, theaverage and local characteristic of wavy fin with different wavy height, and theflow and heat transfer characteristics of wavy fin with uniform changed wavyheight were analyzed. And then, analyzes the fin pitch, fin thickness and the axial ratio of elliptic tube influence to the wavy fin with uniform decline wavyheight. Finally, the wavy fin that the wave which with smaller wavy height haschanged into straight fin was simulated, in order to obtain the fin type not onlyensure the heat transfer performance but also reduce the resistance loss.The simulation results show that: the comprehensive heat transferperformance of wavy fin with uniform decline wavy height under identicalpressure drop and pumping power are superior to the other wavy fin. There is anoptimal fin pitch for each air velocity, which gives the best heat exchangercoefficient from the heat transfer point of view. The pressure drop decreasesgradually with the increase of fin pitch. The influence of fin thickness,transverse spacing of tube and axial ratio of elliptic tube on heat exchangercoefficient is not obvious, the pressure drop increase with the increase of finthickness and decrease with the increase of fin width and axial ratio of elliptictube. The heat exchanger coefficient and pressure drop of wavy fin with the tubebundles in staggered arrangement are higher than the wavy fin with the tubebundles in in-line arrangement. The comprehensive heat transfer performance ofthe wavy fin with the uniform decline wavy height that the last two wave arestraight fin is the best when the inlet velocity is small. The wavy fin with theuniform decline wavy height is the optimal choice when the inlet velocity islarge.