A Two-Dimensional Numerical Investigation of Transient Heat Flux Gage Performance in Short-Duration Facilities

Abstract

Thin-film heat-flux gages have been used for the past fifty years in short-duration facilities (test times typically on the order of one to ten milliseconds) to measure local heat flux in a wide variety of high-energy flow situations. These gages consist of a thin platinum strip (typically 1×10−8 m thick) bonded to a substrate material of low thermal diffusivity, e.g., Pyrex glass. The substrate, which can be contoured to almost any desired shape (e.g., strip inserts, leading-edge inserts, buttons, etc.) is then embedded into the surface of a component of interest such as a turbine blade. A photograph of a button gage embedded in turbine blade is shown in Fig. 1. The heat-flux gage is operated in a constant-current circuit (typically 1 mA to avoid excessive heating) from which the film temperature history during the experiment is deduced using a temperature coefficient of resistance calibration for that particular gage. The heat flux that must have produced the inferred temperature history of the substrate surface is then calculated using a one-dimensional, time-dependent heat conduction approximation as described in 1.