ESTIMATION OF TRANSIENT HEAT TRANSFER COEFFICIENTS IN MULTIDIMENSIONAL PROBLEMS BY USING INVERSE HEAT TRANSFER METHOD

The inverse heat transfer problem is one of considerable practical interest in the analysis and design of experimental heat transfer investigations. The present dissertation is concerned with the analytical and experimental investigation of the inverse heat transfer coefficient problem for the estimation of transient heat transfer coefficients in multi-dimensional convective heat transfer applications. An application considered is the sudden quenching of a hot solid in a cold liquid. Other applications include thermal analysis of forced convection over impulsively started solid bodies and investigation of short duration wind tunnel experiments.;The primary aim in the analytical part of the thesis is to describe methods and algorithms for the solution of the "ill-posed" inverse heat transfer coefficient problem. The solution method used is an extension of the sequential future-information method of Beck. The finite-difference method, based on the control volume approach, is used for the discretization of the direct heat conduction problem. The Crank-Nicolson and the alternating-direction implicit schemes are used for the numerical solution of the one- and two-dimensional direct problems, respectively.;Numerical experiments are conducted for a systematic investigation of the developed algorithms on selected heat transfer coefficient test cases. The numerical results show that the sequential future-information method is accurate, efficient, and capable of estimating sharp and large variations (in time and space) in the heat transfer coefficient functions.;The overall objective of the experimental work is to investigate the early transients in the heat transfer coefficients from spheres in one- and two-dimensional quenching experiments. Several experiments were performed by plunging hollow spheres in either ethylene glycol or water. The transient thermocouple data was acquired with a multi-channel data acquisition system. The developed methods are used for the analysis of the quenching experiments for the estimation of the transient heat transfer coefficients. The estimated results show that the early transient values are about 60%-80% higher compared to the well-known empirical correlations. The later values are in good agreement with known steady-state convection correlation. Analysis of the results indicate that the transient inverse technique has the capability of estimating early transients and subsequent quasi-steady state values of the heat transfer coefficients in a single transient experiment.