Numercal Simulation On Heat Transfer And Flow Resistance Characteristics Of Finned Tube Heat Exchanger

Finned tube heat exchangers are used in various fields such as chemical industry,construction,air conditioning,etc.due to their high heat exchange efficiency,compact structure and long service life.By changing the base tube shape,tube row number,fin spacing,fin thickness,fin shape and increasing the spoiler,researchers often increase the disturbance in the basin with a small heat transfer coefficient,reduce the boundary layer thickness on the fin side,and then improve the overall heat transfer performance,so as to enhance the heat transfer.In this paper,ICEM CFD software is used to establish a multi-layer fin model for finned tube heat exchangers which are mainly used in dry fan-coil tubes at the end of air conditioners,and the characteristics of heat transfer and flow resistance in the tubes are analyzed.Firstly,the heat transfer model of round,rectangular and square fins was established,and the heat transfer and flow resistance on the air side were analyzed,so as to select the fin with the best heat transfer effect and apply it to the multi-layer fin model.Secondly,the established model is divided into structured grids to keep the grid quality above 0.6.Meanwhile,the mesh independence is verified to determine the reasonable number of grids.Then the grid model was imported into Fluent calculator,and the corresponding boundary conditions were set.The SIMPLE algorithm was used to determine whether the numerical calculation results converged by residual convergence criterion.Through the processing and analysis of the numerical results,it can be concluded that under the same fin surface area,the heat transfer of circular,rectangular and square fins is not significantly different,but the inlet and outlet pressure drop of rectangular fins is lower than that of circular and square fins,and the comprehensive heat transfer performance of rectangular fins is better than the other two fin forms.In the air basin,the maximum velocity of the rectangular fin is smaller than that of the circle and square,and the streamline of the circular fin basin is smoother than that of the rectangle and square.The heat transfer and pressure drop in the pipe of horizontal and staggered discharge modes increased with the increase of inlet water velocity.The heat transfer in the staggered discharge mode was higher than that in the horizontal discharge mode.There was little difference in the pressure drop between the two modes,resulting in the comprehensive heat transfer performance of the staggered discharge mode was better than that in the horizontal discharge mode.When the inlet water temperature changes,the heat transfer of the horizontal and staggered discharge modes decreases linearly with the increase of inlet water temperature,and the heat transfer of the staggered discharge mode is higher,which makes the comprehensive heat transfer performance of the staggered discharge mode better than that of the horizontal discharge mode.Through research on the heat transfer and flow resistance properties of the finned tube heat exchanger resulting numerical simulation,it provides a basis for its enhancement of heat transfer of the heat exchanger.