The Effect of Density Ratio on the Heat Transfer Coefficient From a Film-Cooled Flat Plate

[+] Author and Article Information
H. D. Ammari, N. Hay, D. Lampard

Department of Mechanical Engineering, University of Nottingham, Nottingham, United Kingdom

J. Turbomach 112(3), 444-450 (Jul 01, 1990) (7 pages) doi:10.1115/1.2927679 History: Received January 27, 1989; Online June 09, 2008


The effect of density ratio of cooling films on the heat transfer coefficient on a flat plate is investigated using a heat-mass transfer analogy. The experimental technique employed uses a swollen polymer surface and laser holographic interferometry. A density ratio of 1.0 was achieved using air as the injectant. Density ratios of 1.38 and 1.52, representative of turbine operating conditions, were obtained by using foreign gases. The coolant fluids were injected at various blowing rates through a single normal hole or through a row of holes spaced at three-diameter intervals, and inclined at 35 or 95 deg to the mainstream direction. The experiments were conducted under isothermal conditions in a subsonic, zero mainstream pressure gradient turbulent boundary layer. The results indicated large differences in behavior between the two injection angles. For normal injection, the heat transfer coefficient at a fixed blowing parameter was insensitive to the variation of density ratio, whereas for 35 deg injection strong dependence was observed. Scaling parameters for the heat transfer data have been proposed so that use can be made of data obtained at density ratios not representative of gas turbine practice. In addition, a correlation for normal injection data has been formulated.

Copyright © 1990 by The American Society of Mechanical Engineers
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