Numerical Simulation Study Of Fin-and-Tube Heat Exchangers

Fin-and-tube heat exchanger(FTHE)has been widely applied in petrochemical industry,air-conditioning engineering and refrigeration equipment,etc.Hence,a great number of interests have been given to the studies of flow characteristic,heat-transfer characteristic to enhance heat transfer efficiency.In this study,Computational Fluid Dynamics(CFD)method has been used to optimize the heat-transfer characteristic of FTHE.Three types of pipe(elliptical pipe,large size pipe,small size pipe)as well as three different fins(plain fin,herringbone fin and split fin)are respectively equipped with the FTHE model to investigate the flow characteristics and heat transfer characteristics.In this paper,The experimental model of Wang(1996)is verified by improved CFD method(combined with ANSYS CFX software,four layers of finned structure,single heat exchange pipeline,three layers of air flow are all incorporated for fluid-structure interaction analysis),allowing comparatively accurate configuration on boundary set.The simulation results are compared with the Yaici(2014)simulation.The data analysis process shows that the error of the heat transfer factor j is from 3.1%to 5.7%and the error of friction coefficient f is from 0.9%to 6.3%;While the error of heat transfer factor j in Yaici's simulation is from 5.8%to 21.7%and the error of friction factor f is from 5.4%to 14.1%.The simulation method which is used in this subject is more accurate.Meanwhile,nine kinds of different types of FTHEs were simulated and analyzed.It was found that the elliptical tube had the smallest wake area and pressure loss in three fin types of FTHE while in these FTHEs the air fluid has the least pressure loss when passing the elliptical tube,so the elliptical tube has the smallest tube resistance.The heat transfer characteristics of nine types of FTHEs are analyzed and results show that the three fin types of FTHEs have the most uniform temperature change at the elliptical pipe.FTHEs types enable the heat transfer and heat transfer coefficient of heat exchanger with the elliptical pipe to be lower than those with the large size pipe,however,the regional optimization factor j/f is highest and has better heat transfer performance.According to the principle of heat dissipation,the greater the heat dissipation in the heat transfer process make the better the heat transfer performance of the heat exchanger.In the nine types of FTHEs,the heat exchangers with split fins and elliptical pipes have the highest dissipation of heat dissipation,which is 72.4%?133.5%higher than the heat exchangers with straight fins and small size pipes.Therefore,the heat exchangers with split fins and elliptical pipes have the best heat transfer performance and the elliptical tubes have the highest heat dissipation in three fin types of heat exchangers and have the best heat transfer performance.The thermal resistance of FTHE convective heat transfer is obtained.In the nine types of FTHEs,the heat exchangers with split fins and elliptical pipes have the smallest thermal resistance and FTHE with the elliptical tubes have the smallest thermal resistance in the three types of fins,which means that the FTHEs with split fins and elliptical pipes have the best heat transfer performance,and the elliptical tubes have the best heat transfer performance in all three types of heat exchangers.