Experimental results on local heat transfer coefficient inside a rectangular channel with chevron-shaped ribs

A non-intrusive measurement technique of the heat transfer coefficient field, based on IR-thermography, is applied on a 12-mm-height rectangular channel of 1:10 aspect ratio, whose lower surface is enhanced by chevron-shaped square-cross-section ribs. The channel is operated at imposed heat flux while forced-air flows for Reynolds numbers ranging from 700 to 8000. In particular, the technique uses local temperature measurements to retrieve the radiative heat flux with a three-wavelength-band model for partially transparent enclosures, and the conductive flux towards the backside with a FEM model, which allow an edge-to-edge estimation of the local convective heat transfer. The resulting local Nusselt number maps are presented and compared to data obtained operating both at fixed temperature and inside a channel with flat surfaces.