FUNCTION ESTIMATION IN PREDICTING TEMPERATURE-DEPENDENT THERMAL-CONDUCTIVITY WITHOUT INTERNAL MEASUREMENTS

The conjugate gradient method of minimization with an adjoint equation is used successfully to solve the inverse problem in estimating the temperature-dependent thermal conductivity of the homogeneous as well as nonhomogeneous solid material. It is assumed that no prior information is available on the functional form of the unknown thermal conductivity in the present study, thus, it is classified as the function estimation in inverse calculation. The accuracy of the inverse analysis is examined by using simulated exact and inexact measurements obtained within the medium. Results show that an excellent estimation on the thermal conductivity can be obtained with any arbitrary initial guesses by using just boundary measurements (i.e., internal measurements are unnecessary) within 1 s CPU time in a VAX-9420 computer. The advantages of applying this algorithm in inverse analysis can greatly simplify the experimental setup, diminish the sensitivity to the measurement errors, and reduce the CPU time in inverse calculation, while the reliable predictions can still be achieved.