Transient response of circular foil heat-flux gauges to radiative fluxes

Abstract

An approximate analytical model of the transient response of a circular foil heat-flux gauge to a step change in incident radiant heat flux is described. This model demonstrates that the sensitivity and the transient response of the gauge are significantly affected by heat flow from the foil to the center lead wire. Results obtained for the transient response to a step change in incident radiant flux from the model agree closely with experimental results from several gauges with different sensitivities. Convolution of the present model and previous exponential models of the unit step response, with a transient incident flux represented by a terminal ramp, shows that the response predicted by a previous exponential model differs significantly from that predicted by the present model.