Heat Transfer Characteristics of a Slot Jet Reattachment Nozzle

Abstract

A two-dimensional reattachment nozzle called the Slot Jet Reattachment (SJR) nozzle was designed and built with a zero degree exit angle. The heat transfer characteristics of this submerged nozzle were investigated by varying the Reynolds number, nozzle exit opening, and nozzle to surface spacing. The pressure distribution on the impingement surface for different Reynolds numbers and exit openings were measured. Correlations for location of the maximum local Nusselt number and local Nusselt number distribution along the minor axis of the SJR nozzle were determined. A nondimensional scheme for generalized representation of heat transfer data for two-dimensional separated/reattaching flows was developed. The local and average heat transfer characteristics along the minor axis of the SJR nozzle were compared to a conventional slot jet nozzle under identical flow power condition. The comparison showed that the peak local heat transfer coefficient for the SJR nozzle was 9 percent higher than that for a standard slot jet nozzle, while its average heat transfer coefficient was lower or at best comparable to the slot jet nozzle based on the same averaged area. The net force exerted per unit width by the SJR nozzle flow was 13 times lower than the slot jet nozzle flow under this criterion. Additional experiments were conducted to compare the SJR and slot jet nozzles under matching local peak pressures exerted by the jet flow on the impingement surface. The results indicated 52 percent increase in the peak local heat transfer coefficient, and a maximum enhancement of 35 percent in average heat transfer coefficient for the SJR nozzle over the slot jet nozzle based on the same averaged area under this criterion.