MEASUREMENT OF LOCAL CONVECTIVE HEAT-TRANSFER COEFFICIENTS USING 3-DIMENSIONAL INTERFEROMETRY

The reconstruction of the three-dimensional temperature distribution above a horizontal heated disk in air is used to determine the local heat transfer coefficients. Holographic interferometry is used to obtain instantaneous, three-dimensional information on the local index of refraction distribution. Several reconstruction procedures are tested under the constraints of limited field of view and limited fringe order data. These techniques are used to accurately measure the instantaneous local temperature distribution. Subsequently, the surface temperature gradients are specified by curve fitting procedures and the local heat transfer coefficients determined. The surface averaged Nusselt number agrees very well with previous studies in the literature. Real time holographic interferometry is also used to suggest some of the dynamic characteristics of the convective heat transfer process. Results show local instabilities in the form of distributed bursting of thermal energy from the surface. Also, at sufficiently high surface temperatures the entire temperature field shows evidence of oscillation or pulsation which indicates a global heat release mechanism.