Using plate thermometer measurements to calculate incident heat radiation

The plate thermometer is a device used mainly to measure temperatures in fire resistance tests according to ISO 834-1 and EN 1363-1 and to measure the so-called adiabatic surface temperature. However, it can also be used to measure incident radiant heat flux () as a simpler, more robust and less-expensive alternative to water-cooled heat flux meters. The accuracy of the measured is subject to simplifications in the heat transfer analysis model and uncertainties of parameters such as convective heat transfer coefficients, emissivities and ambient gas temperatures. This study investigates the accuracy of the model itself, isolated from the uncertainties of the physical surrounding, by comparing a simple one-dimensional model to the results of finite element modelling. The so-obtained model includes a heat transfer coefficient due to heat losses of the plate thermometer, found to be K-PT = 8 W/m(2) K and a heat storage lumped heat capacity C-PT = 4200 J/m(2) K for an ISO/EN standard plate thermometer. The model is also compared to real field experiments.