Heat Transfer Augmentation Based On The Flow Pattern Optimization

Energy is a substantial basis of modern society.Improving the performance of heat-exchange equipments plays an important role in efficient energy utilization.Flow pattern optimization is an effective method to improve the heat transfer efficiency of the system.Hence,our research project aims at optimizing flow pattern of rectangular channel and shell and tube heat exchanger through the modification of the internal structure,thus improving the heat exchange performance of the system.First of all,the flow characteristic and heat transfer of the oblique-cut semi-elliptic cylinder shell in a rectangular channel with a Re range of 150~1200 were investigated numerically and experimentally.The heat transfer augmentation mechanism was then analyzed based on the simulation results.The results show that compared with smooth channel,Nu and pressure drop increase simultaneously in the channel with vortex generator,which has an increasingly positive effect on the heat transfer performance with the increasing of Re.Moreover,it is found that the longitudinal vortex was generated around the vortex generator to increase the local vorticity,and thus helps enhancing the heat transfer.Then,the flow pattern of the traditional shell-and-tube heat exchanger was investigated numerically.Simulations revealed a large dead zone behind the segmental baffles,the dead zone of the continuous phase wasted the internal space,increased the heat transfer resistance and finally decreased the heat transfer efficiencyThe flow pattern was optimized with the objective of the heat transfer performance by structure modification,such as changing opening direction of the segmental baffle,using helical baffles and changing installation inclination angle.After then,the flow pattern of all these heat exchanger were investigated by 3D CFD.The results show that the flow pattern was optimized with the modification of the internal structure of shell-and-tube heat exchanger.The dead zone decreased and the velocity distribution became uniform and the whole flow pattern tend to be reasonable.Finally,the helical line heat exchanger was obtained and it turned out that the flow pattern of this special shell-and-tube heat changer was the optimal.Dead zone was disappeared in most of the region.The flow pattern was similar to the ideal spiral flow,makes fluid around the tube can quickly update,not only reduce the pressure drop of the heat exchanger significantly,the fluid around tube can quickly update,which enhance heat transfer coefficient.