A REVIEW OF HEAT-TRANSFER DATA FOR SINGLE CIRCULAR JET IMPINGEMENT

Experimental data for the rate of heat transfer from impinging turbulent jets with nozzle exit Reynolds numbers in the range of 5,000-124,000 have been collated and critically reviewed from the considerable body of literature available on the subject. The geometry considered is that of a single circular jet impinging orthogonally onto a plane surface for nozzle-to-plate distances from 1.2-16 nozzle diameters and over a flow region up to six nozzle diameters from the stagnation point. Existing correlations for local heat transfer coefficient express Nusselt number as a function of nozzle exit Reynolds number raised to a constant exponent. However, the available empirical data suggest that this exponent should be a function of nozzle-to-plate spacing and of the radial displacement from the stagnation point. A correlation for Nusselt number of the form suggested by this evidence has been derived using a selection of the data. The review also suggests that the Nusselt number is independent of nozzle-to-plate spacing up to a value of 12 nozzle diameters at radii greater than six nozzle diameters from the stagnation point. The results from a simple extrapolation for obtaining heat transfer coefficients in the wall jet region compare favourably with published data.