Heat Transfer in Free Swirling Flow in a Pipe

Abstract

The local heat transfer coefficient, for air flowing through a pipe with a swirling motion, was measured at various stations downstream of the swirling air inlet. The swirling motion of the air was produced by a single tangential slot, initially at 90 deg to the pipe axis, through which the air was introduced. The dimensions of the slot and the angle of tangency were varied and the resultant flow field inside the pipe was measured and expressed in the form of local “swirl numbers”. The augmentation of heat transfer was found to be a function of the swirl number and a correlation for this function is presented. At some locations, the augmentation can be as much as eight times the value for fully developed nonswirling turbulent flow.