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

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.

Invisibly at Risk: Low-Income Students in a Middle- and Upper-Class World

“…The heat transfer coefficients were measured for a uniform impingement surface temperature. Results of crossflow on streamwise resolved Nusselt numbers were comparable to that of Chance (1974), kercher andTabakoff (1970). Hollworth and Wilson (1984) [11] conducted experiments to characterize a heated turbulent air jet discharged from a square-edged orifice having length to diameter equal to unity.…”

“…Where Zn: nozzle-target spacing, b: widh of an actual or equivalent two-dimensional nozzle. Kercher and Tabakoff (1970) [2], carried out an experimental research on heat transfer coefficients for impingement on a surface under a perforated plate of multiple square arrays and round air jets. Data collection was done over a range of jet Reynolds number from 300 to 30000, plate to surface distance of 1.0102 to 3.104, jet spacing from 3.1 to 12.5 diameter and plate-tosurface distance of 1 to 4.8 diameter.…”

Gas Turbine Engines: Turbine Cooling

“…Impingement jet array heat transfer coefficients may be obtained from the correlation of Florschuetz, Truman and Metzger (1981) for average jet Reynolds numbers typical in engine design. For square arrays of jets at somewhat lower Re numbers, the graphical data of Kercher and Tabakoff (1970) may be used. Impingement cooling that involves the use of individual jets, or slot type jets, or other non-standard configurations, may be determined by correlations in the summary paper of Martin (1977).…”

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

“…While investigations for impingement heat transfer by jet arrays with cross flow effect are numerous (Kercher and Tabakoff, 1970;Chance, 1974;Florschuetz et al, 1981;Van Treuren et al, 1994;Huang et al, 1998), there are relatively few investigations for jet impingement heat transfer with film coolant extraction (also called impingement/effusion cooling, impingement/film cooling, and impingement with removal through vent holes). 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.…”