Effect on heat transfer augmentation by some geometric shapes of a turbulence promoter in a rectangular duct.

Abstract

This paper investigates how the local heat transfer coefficient is affected by geometric shape and the clearance "C", when turbulence promoters of various types (blockage ratio D/2H=0.22) are set in staggered arrangement in a rectangular duct in order to augment heat transfer from the wall. The distribution of local heat transfer coefficients depend son the clearance "C", which can be further differentiated by the presence or absence of the Karman vortex shedding. The degree of augmentation is also analysed, taking account of the pressure loss. It was found that the performance ratio η(the ratio of average pumping power) is larger than unity for all types, when the range of clearance "C" is smaller than 3 mm.