Augmentation of Heat Transfer in a Tube with a Blade Wheel at Inlet

Abstract

This paper shows how the heat-transfer coefficients along heated tubes are affected by the clearance against the tube wall, the inlet angle and the widths of various types of blade wheels which are propelled by an internal flow in a circular tube and inserted at the inlet in order to augment heat transfer along the tube. The maximum and averaged heat-transfer coefficients in the region from blade position to far downstream were 3.0 and 2.2 times those in smooth duct respectively, for air ranging in Reynolds number from 15000 to 60000. Moreover, the performance evaluation was carrid out under the condition of fixed pumping power, and it was found that the performace ratio depends more on the inlet angle and the width of the blde than clearence, and the ratio is larger than one.