A nonlinear inverse problem for the prediction of local thermal contact conductance in plate finned-tube heat exchangers

A nonlinear inverse problem utilizing the Conjugate Gradient Method (CGM) o f minimization is used successfully to estimate the temporally and circumfe rentially varying thermal contact conductance of a plate finned-tube heat e xchanger by reading the simulated transient temperature measurement data fr om the thermocouples located on the plate. The thermal properties of the fi n and tube are assumed to be functions of temperature, and this makes the p roblem nonlinear. It is assumed that no prior information is available on t he functional form of the unknown thermal contact conductance in the presen t study, thus, it is classified as the function estimation in the inverse c alculation. The accuracy of the inverse analysis is examined by using the s imulated temperature measurements. Finally the inverse solutions with and w ithout the consideration of temperature-dependent thermal properties are co mpared. Results show that when the nonlinear inverse calculations are perfo rmed an excellent estimation on the thermal contact conductance can be obta ined with any arbitrary initial guesses within a couple of minute's CPU tim e on a HP-730 workstation.