A numerical study on thermal-hydraulic characteristics of turbulent flow through a circular tube fitted with pipe inserts

A numerical investigation is carried out for turbulent flow in a circular tube with pipe inserts. Pipe inserts with different node installation are carefully investigated at the Reynolds number range of 2892-28,915. Liquid water is used as the working fluid. The results show that the pipe inserts have an excellent heat transfer performance in the turbulent regime. The heat transfer rate decreases with the increase in spacer length. However, the flow resistance increases with the decrease in spacer length. Therefore, a suitable spacer length has to be taken into consideration in the design of heat exchanger. Compared with three pipe inserts, four pipe inserts have a better heat transfer performance, especially at high Reynolds number. The maximal PEC (performance evaluation criterion) values resulting from four pipe inserts were approximately 1.4-3.0. Heat transfer performance of pipe inserts is also affected by the installation angle between insert nodes. Although installation angle has a limited impact on the heat transfer rate, the friction factor increase is also very low. It is still valuable to adopt an installation angle for heat transfer enhancement.