Heat transfer from a plate impinging swirl jet

Heat transfer and flow visualization experiments were conducted to investigate the performance of swirling and multi-channel impinging jets and compare the results with those of a multi-channel impinging jet (MCIJ) and conventional impinging jet (CIJ) for the present work at the same conditions. Swirling impinging jets (SIJs) employed the fixed blade lengths of 12.3 mm with four blades at the exit of the housing tube to divert the air flow through four narrow channels with a desired swirl angle (theta of 22.5, 41 and 50degrees). The MCIJ jet had the same dimensions as the SIJs, except that the narrow channels in the solid insert were vertical (theta = 0degrees). The local and surface average Nusselt numbers of MCIJ were generally higher than those of the CIJ and SIJs. The SIJs, however, demonstrated significant improvement in radial uniformity of heat transfer compared to the MCIJ and CIJ. In the region of 2.7 greater than or equal to X/D greater than or equal to 0 for H/D = 8 and Re = 20000, the average Nusselt number for the MCIJ was 11, 33, 72 and 98 per cent higher than that of the CIJ, theta = 22.5, theta = 41 and theta = 50degrees, respectively. Copyright (C) 2002 John Wiley Sons, Ltd.