AN EXPERIMENTAL INVESTIGATION OF CHEVRON-NOZZLE JET IMPINGEMENT HEAT TRANSFER ON A CONFINED CONICAL-CONCAVE SURFACE

The role of the chevron-nozzle on the jet impingement onto a specifically confined conical-concave target was studied. Five 6-chevrons nozzles with different chevron normal lengths and chevron penetration depths were tested at a fixed dimensionless impinging distance of H/d = 2, under a series of jet Reynolds numbers ranging from 7800 to 39,300. Both the convective heat transfer and the discharger coefficient of the nozzle in a jet impingement configuration were involved. With respect to the baseline round nozzle, the chevron nozzle produced an obvious jet impingement heat transfer enhancement in the vicinity of the concave leading edge. However, the chevron nozzle also increased the pressure drop significantly in a jet impingement configuration. Among the currently concerned chevron nozzles, the chevron nozzle that has a large chevron penetration depth but a short chevron normal length (CN-3) is identified to produce the highest local convective heat transfer enhancement in the vicinity of the concave leading edge, and also the largest pressure loss. By using the heat transfer enhancement ratio and the relevant discharge coefficient ratio of the chevron nozzle relating to the baseline round nozzle, empirical relations for predicting the spatially-averaged Nusselt number and the discharge coefficient are proposed in current situations. For a specific factor that considers both heat transfer enhancement and flow loss, CN-2 and CN-4 are suggested for more promising chevron configurations.