Numerical heat transfer and flow in narrow channel with attached and detached pin fin

This numerical study comparatively examines the flow and heat transfer characteristics in two rectangular channels with attached and detached pin-fin arrays at Reynolds numbers (Re) of 10000, 15000, 20000, 25000 and 30000 using the commercial code Star CD. Clearances (C) between pin-tips and endwall for the present detached pin-fin array are fixed at 1/4 pin-diameter (d). The presence of pin-to-endwall clearances modifies the endwall flow structures by way of generating the accelerating flows over the pin-tips and results in the large-scale three dimensional vorticall flows along two side walls of the detached pin-fin channel that leads to regional heat transfer enhancements. The lack of vortices and flow separations tripped by the attached pin-fins considerably reduces the inlet-to-exit pressure drops in the detached pin-fin channel. But the absence of horseshoe vortices and the downstream wakes as well as the shear-layer separations over the endwall in the detached pin-fin channel moderates the gradients of endwall Nusselt number (Nu) distributions and reduces the area averaged endwall Nu (Nu). As the endwall Nu with detached pin-fins is somewhat less than that with attached pin-fins but the channel pressure drop is much lower than that of the later, the thermal performance factors for the detached pin-fin channel are improved from those of the attached pin-fin channel.