Effect of Impingement Surface Velocity on Slot Jet and Slot Jet Reattachment Nozzles’ Flow Field

Abstract

Slot jet reattachment (SJR) nozzle is developed in an attempt to enhance heat and mass transfer characteristics while effectively controlling the impingement surface force exerted by the jet flow. In the SJR nozzle, the jet is directed outward from the nozzle exit and it then reattaches on an adjacent surface in its vicinity. The turbulent mixing occurs at the boundaries of the free stream induces secondary flow by mass entrainment and causes the flow to reattach the surface in the form of an oval reattachment at close nozzle to surface spacing [1]. All the previous studies had considered a stationary reattachment surface. This paper, for the first time, investigates the impact of reattachment surface movement on the flow structure of SJR nozzle with three different exit angles of +45°, +20°, and +10°. Specifically, this numerical study is carried out by varying the surface-to-jet velocity ratio (u* = up/ue) from 0 to 1.5 and comparing of flow reattachment flow fields to those of a regular slot jet (SJ) nozzle, where up is the speed of reattachment surface (moving plate) and ue is the jet exit velocity. In this study, jet exit temperature is kept constant at the room temperature of 20°C and all comparisons were performed at the same Reynolds number of 7,900. Additionally, the effect of SJR air exit angle on the peak surface pressure is investigated.

Enhancement of Drying of Food Products with Slot Jet Reattachment Nozzles in a Convective Oven with a Moving Belt

“…There is little information available in the literature about comparing the efficiency of different impingement nozzles based on the drying kinetics of food products and their quality attributes. Farzad et al [10][11][12][13] evaluated the heat transfer enhancement of SJR by using a laboratory scale static dryer on which the drying parameters are controlled. In the static configuration, the compressed air is impinged on the top surface of the samples.…”

Impact of Reattachment Surface Characteristics on the Slot Jet Reattachment Nozzle’s Performance

“…Senter and Solliec [12] used PIV for SJ and showed that at a given surface-to-jet velocity ratio, flow field patterns are independent of Reynolds number for 5,300-10,600. As for SJR, Farzad and Yagoobi [13] combined SJR and SJ with a moving reattachment surface for the first time and numerically studied the impact of reattachment surface velocity with a solid moving plate. They reported that SJR and SJ flow fields are greatly affected by surface-to-jet velocity ratios of 1 and 0.5, respectively, under a turbulent flow regime.…”