Abstract:
A change in the dynamic characteristics of sensors on anisotropic thermoelements made of a bismuth single crystal was discovered when measuring intense heat fluxes ($>$ 1 MW/m$^2$) in experiments on shock tubes in the case of using air as a working gas. A noticeable increase in the response time to thermal influence, as well as distortion of the shape and amplitude of the electrical signal and the heat flux calculated from it, are caused by the formation in thermoelements of a near-surface defective layer $<$ 1 $\mu$m thick, which is not involved in the generation of thermopower. This may limit the conditions for applicability of the sensor in experiments on shock tubes and requires periodic calibration of the sensor against the reflected shock wave to monitor the condition of the working surface and the value of the volt-watt coefficient.
Keywords:heat flux, shock tubes, sensors based on anisotropic thermoelements, bismuth.
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