Comparison of thermal characteristics of confined and unconfined impinging jets

Abstract

In the present study, we compared the thermal performance of the two types of impinging jets: confinedand unconfined impinging jets. In order to obtain the thermal characteristics of impinging jets, experimentalinvestigations for air and water are conducted. The effects of dimensionless pumping powersðPpump ¼ 1:35 1010 4 1013Þ on the Nusselt number are considered. The focus is on the cases wherethe nozzle-to-plate spacing is equal to or less than one nozzle diameter (H/d 6 1). The results show thatthe thermal performance of the confined jet is similar to that of the unconfined jet under a fixed pumpingpower condition, while the thermal performance of the confined jet is 20–30% lower than that of theunconfined jet under a fixed flow rate condition. Based on the experimental results, generalized correlationsfor the stagnation and average Nusselt numbers for both confined and unconfined impinging jetsare presented as a function of the dimensionless pumping power and the Prandtl number.