A COMPARATIVE THEORETICAL EVALUATION OF FIVE COMMONLY USED TYPES OF UNSTEADY HEAT FLUX SENSOR

摘要

Five commonly used types of heat flux sensor are compared to establish ranges of applicability in terms of heat flux level, testing time, and required frequency response. The frequency ranges in which various data reduction techniques give accurate results are also delineated. The five, sensors considered are, the thin film sensor or surface thermometer, the thick film sensor, the wall calorimeter or slug calorimeter, the gradient sensor, and the thin disk sensor Gardon foil gage, asympto¬tic calorimeter, or thermal window. It is concluded that, for all but very short test times, the best choice is either the gradient sensor or the thin disk sensor, both of which are available commercially in simple forms giving outputs proportional to temperature difference. It is shown that these sensors must be modified to measure a temperature as well as the temperature difference if accur¬ate results are to be obtained under all mounting conditions, and that their frequency response deteriorates as the heat sink becomes less perfect. Charts are given to assist the selection of a sensor to meet particular experimental con-ditions.