TURBULENT DECAYING SWIRLING FLOW IN A PIPE

In this work, a solution is applied to investigate the heat transfer characteristics in a pipe with turbulent decaying swirling flow by using the boundary layer integral scheme. The governing equation is solved using the forth-order Runge-Kutta scheme resulting in thermal boundary-layer thickness and dimensionless heat transfer coefficient, namely, the Nusselt number. Both forced- and free-vortex profiles are considered for the tangential velocity component. A comparison of the results obtained for the Nusselt number with available experimental data shows that this scheme has good capability in predicting the heat transfer parameters of swirling flow especially in the entrance region of a pipe. The results of the present work specify that in swirling flow, the forced- vortex velocity profile is more accurate in predicting the heat transfer coefficient as compared with the free-vortex one. Also, the effects of the inlet Reynolds number, inlet swirl intensity, and of the Prandtl number on the thermal boundary-layer thickness and Nusselt number are studied, and it is realized that the variation of these two parameters depends on the inlet Reynolds number, inlet swirl intensity, and the Prandtl number. The results show that increasing the inlet swirl intensity has a strong increasing effect on the heat transfer rate.