The development of a new direct-heat-flux gauge for heat-transfer facilities

A new type of direct-heat-flux gauge (DHFG) comprising an insulating layer mounted on a metal substrate has been developed. The gauge measures the hea t flux across the insulating layer by measuring the top surface temperature employing a sputtered thin-film gauge (TFG) and the metal temperature usin g a thermocouple. The TFGs are platinum temperature sensors with physical t hickness less than 0.1 mu m. They are instrumented on the insulating layer. The thermal properties and the ratio of the thickness over the thermal con ductivity of the insulating layer have been calibrated. A detailed method o f analysis For calculating the surface heat flux from DHFG temperature trac es is presented. The advantages of the DHFG include its high accuracy, its wide range of frequency response (from dc to 100 kHz) and, most significant ly, that there is no requirement far knowledge of the structure of the meta l substrate. Since the metal substrate is of high conductivity, few thermoc ouples are required to monitor the small spatial variation of the metal tem perature, whereas multiple thin-film gauges may be employed. The DHFGs have been applied to a gas turbine nozzle guide vane and tested in the Oxford C old Heat Transfer Tunnel successfully.