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 t emperature-dependent thermal conductivity of the homogeneous as well a s nonhomogeneous solid material. It is assumed that no prior informati on is available on the functional form of the unknown thermal conducti vity in the present study, thus, it is classified as the function esti mation in inverse calculation. The accuracy of the inverse analysis is examined by using simulated exact and inexact measurements obtained w ithin the medium. Results show that an excellent estimation on the the rmal conductivity can be obtained with any arbitrary initial guesses b y using just boundary measurements (i.e., internal measurements are un necessary) within 1 s CPU time in a VAX-9420 computer. The advantages of applying this algorithm in inverse analysis can greatly simplify th e experimental setup, diminish the sensitivity to the measurement erro rs, and reduce the CPU time in inverse calculation, while the reliable predictions can still be achieved.