Analysis of fluid retention zones in heat exchangers with segmental baffle and helical baffle

By using the residence time distribution method (RTD), the fluid retention zones in the shell and tube heat exchanger with segmental baffle (STHX-SB) and the heat exchanger with helical baffle (STHX-HB) are compared and discussed. The flow pattern and fluid retention zone of the similar double helical flow heat exchanger (STHX-SDH) were analyzed by using the same method. The result shows the spiral flow can reduce the fluid retention zone. The flow pattern in the STHX-SDH likes a double helical shape and leads to a very small fluid retention zone. According to the simulation results, the location of the fluid retention zone of STHX-SDH is determined. The verification line method and the zone assessment method were adopted, to discuss the flow velocity of each point on the verification line and the average flow velocities of the selected zones. The change laws of the flow velocities on the verification lines and the average flow velocities of the selected zones at different Reynolds numbers were compared. The result reveals the distribution of the fluid retention zone of the STHX-SDH and the sensitivity of each fluid retention zone to the Reynolds number. By optimization of the angle of the baffle, the volume fraction of the fluid retention zone is reduced to 1.61%, and the heat transfer performance is improved by 13.23%. It is verified that reducing the fluid retention zone can effectively enhance the heat transfer performance. This research method provides a theoretical basis for reducing the fluid retention zone of the heat exchanger and enhancing heat transfer performance.