Development of a novel method to measure unsteady heat transfer caused by flow turbulence using infrared thermography

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Convective heat transfer via turbulent flow fluctuates complicatedly in time and space, the phenomenon of which is generally seen inside and outside heat transfer equipments. To improve thermal performance and reliability of the equipments, it is necessary to evaluate the fluctuating heat transfer quantitatively. In this work, a novel method was developed to measure the complicated fluctuating heat transfer between a solid-wall and a fluid-flow caused by flow turbulence by using high-speed infrared thermography. A test model was devised to measure the heat transfer coefficient which excludes the effect of thermal inertia and thermal diffusion of a solid-wall. In addition, data analysis technique was developed to evaluate instantaneous distribution of the heat transfer coefficient and its temporal fluctuation. As a result, it was demonstrated that the quantitative evaluation was possible for turbulent flows on a flat plate and in a circular pipe.