Numerical Simulation Of Heat Transfer And Flow Characteristics For Fin And Tube Heat Exchanger

Industrial society will not develop without energy.As the energy production and consumption power,the economy of our country is growing rapidly,but energy efficiency is about only 36.3%,which is far less than developed countries.As the instrument of heat exchange,heat exchanger is widely used in almost all industries,which means it is useful to improve the performance of heat exchangers.This thesis conducts the simulation analysis on heat transfer and flow characteristics of the airside of fin-and-tube heat exchanger and overall heat exchanger by using FLUENT software.Firstly,the thesis conducts the numerical simulation research on the partial fin-and-tube heat exchanger model.Combining with flow field?temperature field and pressure field,it analyzes the effect of air inlet velocity u?tube diameter D and fin pitch H to heat transfer and flow characteristics of the air between fins.The results show airside obtains better heat transfer effect when air inlet velocity accelerates ?tube diameter increases and fin pitch decreases,but energy loss will increase and pressure also rises.When fin pitch H=2.2mm,j/f factor will be the maximum in the conditions of inlet velocity u=4.224m/s and tube diameter D=14mm,which in the range of air inlet velocityand tube diameterin the thesis;when air inlet velocity u=5.632m/s,j/f factor will be the maximum in the conditions of fin pitch H=2.4mm and tube diameter D=14mm,which in the range of fin pitch and tube diameter in the thesis.Then the thesis conducts the simulation on the overall fin-and-tube heat exchanger model.Using porous media model to show the air area which involves fins,the thesis analyzes the heat transfer and flow characteristics of air area and water area in the overall model.The results show temperature drop of water in the former tubes is faster than the last tubes,and the effect of air cooling is better in the faster inlet velocity of air;the velocity of air decreases sharply in the windward side of tubes,the speed separates significantly in the leeward side of tubes,which creates the low speed area of funnel shape,it means leeward side of tubes have bigger influence on fluid flow.Besides,the faster of inlet speed of air,the higer temperature of outlet water,which shows the effect of heat transfer between water and air is better;velocity of water in the tubes near the water inlet face is higher than speed in other tubes.