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ISSN Online: 2377-424X

ISBN Print: 1-56032-797-9

International Heat Transfer Conference 11
August, 23-28, 1998, Kyongju, Korea

THE USE OF SQUARE WAVE SURFACE HEAT FLUXES AND PHASE DELAY INFORMATION TO MEASURE LOCAL HEAT TRANSFER COEFFICIENTS

Get access (open in a dialog) DOI: 10.1615/IHTC11.3100
pages 167-172

Resumo

A one-dimensional analytical solution has been derived for unsteady heat conduction within a semi infinite body, of high thermal resistance, that is subject to a square wave surface heat flux. The heat flux is generated within a thin isothermal surface layer. A phase delay develops between the constituent harmonics of the heat flux and those of the surface temperature response. These phase delays are dependent upon the material properties of the substrate and surface layer, on the heat flux driving frequency, the harmonic number, and on the local heat transfer coefficient. With the exception of this last quantity the other parameters are known a priori, hence if the phase delay is measured it can be used to determine the local heat transfer coefficient. The heat flux over the surface considered does not need to be uniform, and absolute values of surface temperature and heal flux are not required. Hence calibration of the temperature sensing device is not required. Fourier analysis and bandpass filtering are used to obtain the phase delay information. No knowledge of the surface heat flux is required other than it's frequency. The general solution to the governing equation is also applicable to other currently available measurement techniques.