Radiation based calibration of thin film gauge for transient measurement

Abstract

Surface temperature history and determination of heating rate are the two important designing aspects in many research activities involving the surface heating due to thermal radiation encountered to the rocket base surface from the exhaust plumes, internal combustion engine surfaces due to burned gases etc. The measurement of heat flux attributed to thermal radiation for such application involves the use of thermal gauges to estimate the values from measured surface temperature history. Thin film gauges in general are preferred for the measurement of heat flux for its ability to give faster response along with high sensitivity value. The heat flux measurement using thin film gauge is mainly based on the sudden application of heat load to the sensor. In the present study, in order to produce the sudden heat load, a shutter is imposed in between incident radiation and the fabricated thin film gauge. The thin film gauge is in-house built with platinum as sensing element and quartz as an insulating substrate. This study aims to establish a new calibration technique for radiation based heat transfer mode. A fabricated calibration set-up is used to expose the thin film gauge to an environment where heat transfer will take place only due to radiation. The recorded transient temperature data during the experiment is further used to estimate heat flux. Moreover, the finite volume based numerical analysis is also carried out to recover the heat flux values. The excellent agreement of the experimental and numerical analysis results, authenticate the experimental set up as well as the effectiveness of the thin film gauge.