Heat transfer from rough, protruding discretely heated strips with and without flow acceleration

Abstract

Experimental heat transfer results on the effects of rough, protruding, discretely heated strips are presented. Data are presented for two-dimensional (2-D), distributed heat sources for three cases—flush-mounted smooth, protruding smooth, and protruding rough—under zero pressure gradient and accelerated turbulent boundary-layer conditions. For the zero pressure-gradient cases, experiments are performed on repeated, protruding discretely heated strips using surface roughness as a heat transfer enhancement technique. The accelerated cases are conducted to investigate the existence and strength of a synergistic interaction between boundary-layer flow acceleration and surface roughness as a heat transfer enhancement mechanism. For the zero pressure-gradient cases, it is found that under the conditions of these experiments, significant heat transfer enhancements (10–100%) can be obtained with the rough surface. For the smooth-flush arrangement with acceleration, the Stanton numbers decreased by up to 16% with increasing acceleration strength. For the protruding smooth arrangement, the Stanton numbers remain almost constant over all acceleration strengths. For the protruding rough arrangement, the Stanton numbers increase by up to 7% with increasing acceleration strength.