Remote measurement of transient heat flux based on the thermomagnetic effect

Abstract

Heat flux is a physical quantity that characterises the strength of heat transfer per unit area. Heat transfer occurs with a temperature difference. Herein, a remote heat flux measurement method based on the thermomagnetic effect is proposed. Using Bloch’s law, Faraday’s law of electromagnetic induction, and Fourier’s law, a temperature measurement model from heat flux to magnetization of the magnetic film and finally to the induced electromotive force in the Helmholtz coil is established. A compression corner was fabricated, and the heat flux measurement method was experimentally verified in a Mach 6 shock tube wind tunnel. In addition, a Schlieren experiment was performed for comparison. In the experiments, the temperature resolution of the magnetic film reached 0.36 K, and the temperature response reached 100 kHz. The range of the proposed heat flux measurement method is up to 5 MW/〖mm〗^2, and the measurement error is less than 10%. At a resolution of 10 μs, the change in heat flow is mapped when there is a transition for the magnetic film from flat to turbulent flow, which shows the different effects of hypersonic heat flux on the boundary layer and attachment position. The magnetic thin film shows the potential for heat flux estimation in our experiment.