Arrays of Impinging Jets with Spent Fluid Removal through Vent Holes on the Target Surface—Part 1: Average Heat Transfer

Abstract

Measurements of average convective heat transfer are reported for square arrays of impinging air jets. The target plate on which the jets impinge is perforated so that spent air is withdrawn through the plate rather than at one or more edges of the array, as is usually the case in such investigations. Jet holes and vent holes had the same diameters, but the spacing of the jet holes was twice that of the vent holes. This information is especially relevent to the design of hybrid cooling configurations, in which a surface is cooled by the combined mechanisms of impingement and transpiration. Tests were conducted for both inline arrangements (with a vent hole opposite each jet orifice) and for staggered arrangements; and the latter always yielded higher average heat transfer. The degradation of performance of inline arrays was most pronounced when the clearance between the jet orifice plate and the target plate was small. Under these conditions, a significant portion of each jet flows directly out through the opposing vent without “scrubbing” the target surface. Arrays with staggered vent holes yield heat transfer rates consistently higher (sometimes by as much as 35 percent) than the same jet array with edge venting. The authors attribute the superior performance of the former geometry to high local heat transfer due to boundary layer suction in the vicinities of the vent holes.

Rotation Effect on Jet Impingement Heat Transfer in Smooth Rectangular Channels with Film Coolant Extraction

“…This may be because the film extraction holes create a boundarylayer suction, which thins the boundary layers, and produces high local heat transfer coefficients in the vicinities of the film extraction holes. However, the present results are lower than those in Hollworth and Dagan (1980). This may be because they use a different film extraction hole diameter and its distribution, although they use a similar jet spacing and jet impinging distance.…”

“…Hollworth and Dagan (1980), and Hollworth et al (1983) varied jet Reynolds number and jet-to-jet spacing of square arrays on jet walls containing the effusion holes and found that staggered jet arrays with respect to effusion hole arrays on target walls out perform inline configurations for non-rotating target wall heat transfer. Andrews et al (1988) studied non-rotating impingement and effusion cooling individually and in combination.…”

Experimental investigations of a double‐decker jet impingement/film structure's cooling effectiveness

“…Hollworth et al [1,2] investigated the average heat transfer of array impingement jets with fluid removal through vent holes. Ekkad et al [3] studied the effect of outlet position on the heat transfer of impingement with film outflow.…”

Conjugate Heat Transfer Study at Interior Surface of NGV Leading Edge with Combined Shower Head and Impingement Cooling

“…Probably the first investigations on air jet impingement with film cooling holes were reported by Hollworth et al [1,2]. They considered flat plate jet impingement with same diameter effusion holes.…”