Schmidt-Boelter gauges [21,25–28] and Gardon gauges [29–34]
are available devices with excellent measurement characteristics with
metal bodies, blackbody sensor foils and water cooled designs.
Schmidt-Boelter and Gardon gauges are classified as diffusiontype
or one-dimensional sensors that deduce the heat flux by
measuring the temperature gradient in a material. The gauges are
more suitable for high radiative or convective heat flux measurements
with long working times in harsh environments such as in
combustion flames, rocket motors, hyper sonic wind tunnels, etc.
For example, Kidd et al. [21] developed a fast-response heat flux
sensor, based on a modified Schmidt–Boelter gauge principle for heat
transfer measurements in hypersonic wind tunnels. Gifford et al.
[26] performed experiments to characterize the performance of
Schmidt–Boelter heat flux gauges in stagnation and shear convective
air flows. Nakos et al. [27] analyzed the heat transfer from an
idealized Schmidt–Boelter heat flux gauge and showed that the theoretical
sensitivity coefficients in radiative and convective
environments differed. Sudheer et al. [28] measured the incident
heat flux on a target for open gasoline pool fires with Schmidt–
Boelter heat flux gauge measurements. The Gardon gauge (also called
a circular foil heat flux gauge) was first introduced by Gardon in
1953 [29]. There have been many applications and calibrations of
Gardon gauges [30–34]. The Gardon gauge is more useful for heat
flux measurements over wide ranges than Schmidt–Boelter gauge
so there is a great need for accurate Gardon gauges for measurements
involving wide ranges of heat fluxes