Prediction of local thermal contact conductance in plate finned-tube heat exchangers

An inverse problem utilizing the conjugate gradient method (CGM) of minimization with adjoint equation is used successfully to estimate the temporally and circumferentially varying thermal contact conductance of a plate finned-tube heat exchanger by reading the transient temperature measurement data from the thermocouples located on the plate and around the tube. It is assumed that no prior information is available on the functional form of the unknown thermal contact conductance 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 the simulated temperature measurements. Results show that an excellent estimation of the thermal contact conductance can be obtained with any arbitrary initial guesses within a couple of minute's CPU time in HP-730 workstation. The advantages of applying this algorithm in inverse analysis can greatly simplify the experimental set up, diminish the sensitivity to the measurement errors and reduct the CPU time in inverse calculation, while the reliable predictions can still be achieved.