THEORY OF TRANSIENT EXPERIMENTAL-TECHNIQUES FOR SURFACE HEAT-TRANSFER

The paper describes the unified mathematical procedures of transient m ethods for measuring surface heat transfer rates. Three heat flux gaug es are discussed: thin film, thick-wall gauges placed on semi-infinite substrates and thin-skin calorimeters. The aim of this paper is to pr esent a method for a simple and accurate determination of the time-var ying heat transfer coefficient Cor heat flux) given an accurate temper ature history of the body at a selected point beneath the surface. The interior temperature measurements are converted into local instantane ous heal transfer coefficients by solving the inverse heat conduction problem for the gauge. The effect of the inaccuracies in the measureme nt of the interior temperature was eliminated by cubic spline smoothin g or digital filtering of the raw interior temperature data prior to u sing it in the inverse heat conduction analyses. General case closed f orm equations for instantaneous surface heat flux, or heat transfer co efficient, are developed. Copyright (C) 1996 Elsevier Science Ltd.