Improvement of the pulsed photothermal technique for the measurement of the convective heat transfer coefficient

The present study concerns the measurement of the convective heat transfer coefficient on the solid-fluid interface by the pulsed photothermal method. This non-intrusive technique is applied for the measurement of the local heat transfer coefficients in cooling of a rectangular slab that simulates an electronic component. The heat transfer coefficient is deduced from the evolution of the transient temperature induced by a sudden deposit of a luminous energy on the front face of the slab. In order to draw up the heat transfer cartography by a non-destructive tool, the infrared thermography has been used. Two inverse techniques for the identification of the heat transfer coefficient are presented here. The first one is based on the assumption that heat transfer coefficient remains constant during the pulsed experiment, and the second one considered it variable in space and time. The temporal and spatial evolutions are expressed as a constant heat transfer coefficient (h₀) multiplied by a function of time and space f(x,t). The function f is deduced from the resolution of the conjugated convection-conduction problem, by a control volume technique for the case of thermally thick sample. The results are given for different air velocities and deflection angles of the flow.