Turbulent heat transfer coefficients and fluid flow patterns on the faces of a centrally positioned blockage in a duct.

Experiments emcompassing both heat-transfer measurements and flow visualization were performed for turbulent flow in a square duct whose cross section was partially obstructed by a centrally positioned transverse blockage. Heat-transfer coefficients were obtained for both the upstream and downstream faces of the blockage element. Heat-transfer coefficients on the upstream face generally increased with the square root of the Reynolds number; at a given mass flow, higher coefficients are in evidence at smaller blockage heights. The downstream-face coefficients display a complex dependence on both the blockage height and the Reynolds number. In the main, for the Reynolds number range investigated, the upstream-face coefficients are greater than the downstream-face coefficients. Comparisons with the literature showed that the coefficients for a centrally positioned blockage exceed those for a wall-attached blockage by as much as a factor of two. (from Author's abstract)