Effect of main and secondary flows on heat transfer in a rib-roughened internal cooling channel

Surface temperature, time dependent surface pressure and flow velocity measurements were carried out in a rectilinear cooling test channel with a square section, roughened on one wall with ribs of high blockage (e/D-h=0.3). Surface temperature distributions were measured on all heat transfer surfaces by means of liquid crystals. The description of the aerodynamic flow field was based on two-dimensional DPIV measurements conducted in the longitudinal symmetry plane and in four planes parallel to the ribbed wall, and on time dependant surface pressure recordings. The results put in evidence the important contribution of the lateral wall cooling compared to the ribbed wall; they also point out the positive effect of the longitudinal secondary flows on the smooth opposite wall heat transfer. The comparison of the thermal and aerodynamic data showed that, in most cases, high heat transfer and high pressure fluctuation regions overlap.