EXPERIMENTAL-VERIFICATION AND CALIBRATION OF THE BLOW-OFF HEAT-FLUX SENSOR

A new heat flux meter to assess the total hemispherical radiation heat flux using the emperature distribution in a porous media crossed by a cooling gas stream is discussed. The paper presents calibration data based on the experimental measurement of the temperature distribution in the porous sensing element. A calibration furnace (black body) was used as radiation source and pressurised air (2 bar) was used as cooli ng gas. The porous specimen, a sintered stainless steel disc, was plac ed in the instrument head with the possibility to control the air mass flow rate. The sensing element was filled with shielded ungrounded th ermocouples positioned in well-defined locations in order to determine the axial temperature distribution in the porous disc. The measuremen ts were performed for the experimental regimes corresponding to the th ermal radiation heat flux levels in the range of 40-150 kW/m(2). A lin ear calibration curve was obtained for the different air mass Bow rate s. It was shown that by adjusting the gas mass flow rate through the p orous sensing element it is possible to control its temperature distri bution and the relative importance of radial conduction losses in the sensing element. (C) 1998 Elsevier Science Ltd.