Button gages have been extensively used to measure convective heat transfer coefficients in a number of short duration experiments. A button gage consists of a small insert made from an insulator material, typically Pyrex, with a thin film of Platinum active element painted on its surface. In a typical short duration experiment, gages are initially at the same temperature as the test article. As the flow is established, convective heat flux results in the surface temperature of the gage to rise much more rapidly than the surrounding metal walls. The influence of this non-isothermal wal condition on the local thermal boundary layer and hence the measured data is the focus of the present program.
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