Effect Of The Thermal Property Of Twisted Tape And Fluid On The Heat Transfer Characteristics In A Tube Fitted With Twisted Tape Insert

Nowadays, the problem of energy is become more and more tight. The heat exchangers play an important role in the industrial production. We hope the exchangers become light weight and low loss. When the fluid flow into the tube with twisted tape insert, the twisted tape force fluid rotation. The tube with twisted tape insert is an effective element to enhance the heat transfer and is widely used. Numerous studies have shown that the heat transfer effect of the tube with twisted tape insert is very remarkable, but the tape also promotes the flow resistance. The correlations based on existing experimental dates do not contain twisted tape’s thermal property variables. The thermal property of twisted tape impacts on the temperature field of fluid flow inside tube, thereby affects the heat transfer on inner surface of tube.In order to explore this effect, numerical simulation by FORTRAN assembly language is applied to make a deep analysis on the dependency between twisted tape’s thermal property and fluid thermal property. In this paper, the physical model has been reasonable simplified to build mathematical model,then choose the uniform wall temperature(UWT) and uniform wall heat flux(UWHF) boundary condition. The main aspects of the study involve that the Nusselt number of inner tube, resistance coefficient, average and local heat transfer rate, distribution of heat flux vector on the cross section of twisted-tape and the temperature field and mainstream speed field of the tube. And based on the original three regional model,a new model that combine with the actual situation has been built. The numerical results are compared with the original model to examine its rationality.The main conclusions are:(1) by coupling the heat transfer calculations, results of the numerical model applied in this paper agree well with existing correlations.(2) The thermal property ratio of twisted tape to fluid is a parameter to quantify the impact of the inner tube heat transfer. The larger the ratio is, the greater the heat transfer capability of the twisted tape is.(3) The ratio have a remarkable effect on the temperature field of inner tube, but nearly no effect on the speed field. And the influence degree decreases with the ratio increases. The mechanism is that large thermal property ratio makes the temperature field of both fluid flow and tape more uniform, therefore, heat transfer capacity of inner tube is enhanced.(4) The heat transfer enhanced by the increase of ratio mainly due to the temperature more propinquity between tape and fluid, the latter enhance the heat transfer intensity.