Streamwise Flow and Heat Transfer Distributions for Jet Array Impingement With Crossflow

Abstract

Two-dimensional arrays of circular jets of air impinging on a heat transfer surface parallel to the jet orifice plate are considered. The air, after inpingement, is constrained to exit in a single direction along the channel formed by the surface and the jet plate. The downstream jets are subjected to a crossflow originating from the upstream jets. Experimental and theoretical results obtained for streamwise distributions of jet and crossflow velocities are presented and compared. Measured Nusselt numbers resolved to one streamwise hole spacing are correlated with individual spanwise row jet Reynolds numbers and crossflow-to-jet velocity ratios. Correlations are presented for both inline and staggered hole patterns including effects of geometric parameters: streamwise hole spacing, spanwise hole spacing, and channel height, normalized by hole diameter. The physical mechanisms influencing heat transfer coefficients as a function of flow distribution and geometric parameters are also discussed.

Numerical predictions of jet impingement heat transfer on square pin-fin roughened plates

“…Florschuetz [3,4] pointed out that inline jet arrays typically performed better than the corresponding staggered arrays in terms of average heat transfer rates, because in a given streamwise row jets tended to be protected from the oncoming crossflow by the upstream jets. In the review on the heat transfer characteristics of multiple impinging air jets presented by Weigand and Spring [1], the optimum values for open area, which is defined as the ratio of jet hole area to opposing heat transfer surface area, was suggested to be 1e3%, which was basically equivalent to the jet-to-jet spacing at 4e6 jet diameters.…”

Influence of spanwise pitch on local heat transfer distribution for in-line arrays of circular jets with spent air flow in two opposite directions

“…Kercher and Tabakoff [7], Chance [8], Metzger et al [9], Florschuetz et al [10][11][12][13] studied streamwise distributions of segment averaged Nusselt numbers. But the spanwise variations of heat transfer coefficients were not captured due to the limitations of the apparatus and technique used.…”

Flow and heat transfer of confined impingement jets cooling using a 3-D transient liquid crystal scheme

“…A series of studies of jet impingements heat transfer including the effect of cross-flow were conducted by Florschutz et al [10][11][12]. Florschuetz [13] found that increasing the ratio between the imposed cross-flow mass flow rate and impingement jet flow rate from 0.2 to 0.4 could significantly reduce Nusselt number by a factor greater than 2.5.…”