THIN FILM HEAT TRANSFER DATA REDUCTION BY MEANS OF SOME NUMERICAL TECHNIQUES

A thin-film sensor operated in transient mode in principle enables very accurate surface temperature measurements to be obtained partly because the gauge is non-intrusive and partly because the high frequency of its response. The major drawback for its popular use is the complexity of data reduction procedure which involves the solution of the heat conduc-tion in solids. Among different techniques available, numerical discretization is gaining in importance for several applications basically because of their flexibility in treating bound-ary conditions and the low computational cost compared to other methods. After a brief analysis of the heat transfer evaluation criteria and the description of the sensor, a survey of the existing digital data processing technique is discussed in the first part of this paper, and some estimate of the accuracy is presented. The general case of multi-layered geometries of the sensor is analyzed and synthetic expressions for the single and double layer features are given. Among the traditional methods, emphasis was placed on 1-D Finite Elements discretization, and a code has been developed to handle general heat transfer data reduction with arbitrary temperature or heat flux boundary conditions. Temperature dependent physi-cal properties are also implemented. Validation of such a code has been performed by mens known test functions. Finally several experimental signals having different characteristics have been processed and the solution of the various methods compared and discussed