Heat Transfer by a Square Array of Round Air Jets Impinging Perpendicular to a Flat Surface Including the Effect of Spent Air

TLDR

The study develops a correlation for heat transfer from a square array of round impinging jets that incorporates the effects of spent air, jet diameter, spacing, and jet‑to‑surface distance, using data spanning Reynolds numbers 3 × 10²–3 × 10⁴, spacing 3.1–12.5 D, and distances 1.0–4.8 D, with the correlation coefficients φ₁, φ₂, and m plotted against key dimensionless parameters. Experimental results show that the proposed correlation, Nu_D,x = φ₁φ₂Re_Dm(Z_n/D)^0.091Pr^1/3, accurately predicts the average surface heat transfer coefficients for the perforated plate, agreeing reasonably well with prior studies.

Abstract

The results of an experimental investigation on the average surface heat transfer co-efficients under a perforated plate of multiple, square array, round impinging air jets are presented. Correlation of the heat transfer performance in a semi-enclosed environment is presented. The correlation includes the effects of the jet “spent air” flowing perpendicular to the jets; the effects of the jet diameter, jet spacing, and jet-to-surface distance. The data cover a range of jet diameter Reynolds number from 3 × 102 to 3 × 104, jet spacing from 3.1 to 12.5 dia, and plate-to-surface distance of 1.0 to 4.8 dia. The results are compared with previously reported investigations with reasonable agreement. Correlation is in the form NuD,x = φ1φ2ReDm(Zn/D)0.091Pr1/3 where φ1 and m are functions of the jet spacing parameter, Xn/D, and Reynolds number, and φ2 is the heat transfer coefficient degradation factor due to “spent air”. φ1, φ2 and m are presented in graphical form as a function of important dimensionless parameters.