Experimental studies of augmented heat transfer and friction in asymmetrically heated rectabgular ducts with ribs on the heated wall in transverse, inclined, v-continous and v-discrete pattern

Abstract

This paper presents results of an experimental investigation of heat transfer and friction in rectangular ducts with repeated rectangular cross-section ribs on one broad wall in transverse, inclined, v-continous and v-discrete pattern. The ribs in v-pattern are tested for both pointing upstream (v-up) and downstream (v-down) to the flow. The duct has width-to-height ratio of 7.19 to 7.75; the relative roughness pitch of the rib arrangement is 10; the relative roughness height is 0.0467-0.050; the angle if inclination of the ribs in inclined and v-patterns is 60°. The Reynolds number ranges from 2800 to 15000 and the roughness Reynolds number is 17 to 90. The roughened wall of the duct is uniformly heated while the remaining three walls are insulated. These boundary conditions correspond closely to those found in solar air heaters. Performance comparison of the different rib patterns for equal pumping power shows that the v-down discrete arrangement gives the best heat transfer performance. Friction factor and heat transfer coefficient correlations have been developed based on the law of wall similarity and heat-momentum transfer analogy. © 2003 Elsevier Science Ltd.