The effect of inclination on impinging jets at small nozzle-to-plate spacing

The effect of inclination on heat transfer characteristics of an impinging slot air jet is experimentally investigated. The effects of inclination angle (0° ⩽ θ ⩽ 40°) and dimensionless pumping power on the Nusselt number are considered. The focus is on cases where the nozzle-to-plate spacing is equal to or less than one nozzle diameter (H/dh ⩽ 1.0). The results show that the heat transfer characteristics of small nozzle-to-plate spacings are significantly different from those of large nozzle-to-plate spacings. In the cases of fixed flow rate conditions, the impingement point and average Nusselt numbers at small nozzle-to-plate spacing (H/dh ⩽ 1.0) increase as the inclination angle increases due to an increase in the pumping power, while the impingement point and average Nusselt numbers at large nozzle-to-plate spacing (H/dh > 1.0) decrease as the inclination angle increases due to momentum loss of the wall jet. In the cases of fixed pumping power conditions, the impingement point and average Nusselt numbers at both of small and large nozzle-to-plate spacings are independent of the inclination angle. Based on the experimental results, correlations for the impingement point and average Nusselt numbers of the impinging jet are suggested as a function of the pumping power alone.