Dynamic calibration of temperature sensors from light rays for transient measurement

Abstract

Measurement of transient heat fluxes in the applications involving very short duration of a heating environment which has been promised for the candidate by measurement of surface heating rates with thin film gauges (TFG). They are basically resistance temperature detectors having to measure in a very short duration of time. In the present study, a platinum based TFG has been fabricated and dynamically calibrated (radiation based) in the laboratory with a view to assessing the performance of platinum thin film gauges (PTFG) in the dynamic environment. These examinations are focusing to explore the probability of using TFG for small duration transient measurements with pure radiation mode of heat transfer. Radiation based heat flux is applied on the gauge by using the halogen bulb in a square box and its response is obtained through measured transient temperature. Subsequently, the surface heat fluxes are estimated by using radiation-based heat transfer. The purpose of this work is to statically calibrate each handmade heat transfer gauges by using quartz as substrate material deposited on platinum paste. This experiment has been carried out by oil bath based experimental technique. The similar experimental environment is also studied to observe the transient temperature response by using numerical simulation. The experiments are carried out by exposing the platinum TFG to various known step heat load of known input wattage, for the duration of 10 seconds. Then, the voltage signals are recorded due to change in temperature of air-flow past the TFG. The numerical simulation (ANSYS-Fluent v. 14.5) is performed in the similar experimental environmental conditions, for the same heating loads. Experimentally recorded temperature signals from the gauges are compared with simulated temperature histories obtained through finite element analysis. Cubic spline methods of the 1-D heat conduction equation are used to predict surface heat flux and compared with input heat loads. The presently developed calibration set-up is seen to very useful for radiation-based measurements of TFG.