Moiré-Fourier deflectometry for local heat transfer measurement over a backward-facing step

This paper explores the possibility of using the Moire-Fourier deflectometry for measuring the local heat transfer coefficient inside small confined flows (micro-channels) and their relevance for checking theoretical models. This optical technique, supplemented with a digital image processing method of fringes, is applied for studying the local heat transfer over a backward facing step. The experimental results are compared with numerical results obtained from a commercial code, which has been contrasted with relevant solutions from the literature and bulk fluid temperature measurements at the inlet and outlet sections. In order to show the possibilities of the experimental technique, the influence of assuming an adiabatic wall on the numerical heat-transfer model is examined and the degree of agreement is discussed. As a result, the paper shows that the proposed Moiré-Fourier technique is a simple experimental setup suitable for temperature measurements with an accuracy similar to the thermocouples but with a spatial resolution near 0.01 mm.