Heat transfer enhancement by sinusoidal-shaped disk rotating in a forced flow

Abstract

The geometric characteristics of the heat transferring surface and the outer flow conditions have a significant impact on heat transfer augmentation. Both, the surface roughness and the pressure gradient attribute to an enhanced heat transfer. These two effects are utilized in this study to enhance the convective heat transfer rate in a non-similar boundary-layer flow induced by the rotation of a sinusoidal-shaped disk in an external forced flow. The heat transfer coefficient is calculated numerically for the laminar boundary-layer flow with the help of the Keller-box method. The numerical solution of the governing system of equations is first validated by previous published (theoretical and experimental) results for a wavy rotating disk in the absence of an external flow field and also for a flat disk rotating in a forced flow. It is observed that the effect of surface waviness along with a relative fluid motion on heat transfer rate, shear stresses, and shaft torque is quite pronounced. Specifically, enhancement of moment coefficient due to waviness of the disk leads to increase the power of a wavy disk pump in comparison to a smooth one. Furthermore, 119%, 174%, 86%, and 86% enhancement in the heat transfer rate, the radial shear stress, the tangential shear stress, and the moment coefficient, respectively, is observed for a rotating wavy disk subjected to a forced flow (at fixed a/? = ? and a0/? = 0.125) in comparison to a free rotating flat disk.