SELECTION OF SURFACE THERMOMETERS FOR MEASURING HEAT FLUX
CORNELL AERONAUTICAL LAB INC BUFFALO NY
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Classical solid conduction theory is applied to a composite semi- infinite slab for the constant surface heat flux case to determine the operating limits of surface thermometers. It is shown that two dimensionless parameters specify the operating range of surface thermometers. A surface thermometer is selected on the basis of these dimensionless parameters, the heat flux range, the testing time, and the output sensitivity. Experimental results of thin and thick film surface thermometers are compared with solid conduction theory to indicate the effect of thermal contact resistance between the film and the mounting material, and to verify the theoretical film thickness. The results indicate that thick film thermometers calorimeters can measure heat flux one to two orders of magnitude higher than thin film thermometers for the same time interval. The thin film thermometers are useful for measuring lower flux where high sensitivity is required. A comparison of experimental heat flux results using thin and thick film thermometers indicated that the thin film data was 15 to 40 below the thick film data.
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