Numerical Simulation On Heat Transfer Performance Of Flat Pipe Shell-and-Tube Heat Exchanger

The flow state of the medium in the tube side is similar to that of in the plate bundle, and its thermal performanceis better than that of the typical round tube bundle and close to plate bundle.Because flat tubes are independent from each other,it is easy to replace it where some flat tubes are damaged. Therefore,the flat tube-and-shell heat exchanger, which merges the merits of the plate heat exchanger and the typical shell-and-tube heat exchanger,will be a kind of high efficient heat transfer equipment.In this paper, flat tube is an irregular pipe and the turbulent flow and heat transfer characteristics in the shell side of a flat tube and bow baffle plate-flat tube heat exchangers are simulated numerically using Fluent software. The results of a flat tube analysis show that the pressure drop in a flat tube is greater than that of a round tube and becomes greater with the increase of flatness degree when the inlet flow rates of them are equal. The maximum flow velocity of flat tube-I increases by more than 98%, and the thermal conductivity coefficient of flat tube-I increases by more than 170%, as far as heat transfer is concerned. The results of heat exchanger analysis show that the inlet and outlet pressure drop of experimental square flat tube-heat exchanger are obviously lower than that of the round tube-heat exchanger, and the pressure drop of the former is 60%-70% of the latter. Hot water outlet temperature of the former is also lower than that of the latter, indicating that the degree of heat transfer is enhanced. All of the simulation results above are compared with the results of experiments, with a divergence within±10%, showing that Fluent software is used accurately and the simulation settings are reasonable and have some reference value.An improved scheme is provides based on the experimental heat exchanger, and the turbulent flow and heat transfer characteristics in the shell-side are simulated numerically. The results show that the pressure drop in the shell-side of a flat tube-heat exchanger is slightly less than that of a round tube-heat exchanger, and outlet temperature in the shell-side of the former is lower than that of the latter, indicating that the comprehensive heat exchanger performance of the improved flat tube-heat exchanger is superior to that of the round tube-heat exchanger.