Experimental study of elongated confined bubbles during flow boiling through IR thermometry

Abstract

The phase-change process in microchannels is a promising approach to achieve high heat transfer rates for electronic device cooling. This strategy of heat transfer augmentation minimizes the need for space, and reduces the costs of material and working fluid. However, the thermo-hydraulic behavior of microchannels under flow boiling is not yet completely understood because of the aspects associated with boiling heat transfer under confined conditions, which implies fluid maldistribution, thermal instabilities, and premature surface dryout. Hence, the development of numerical simulations and mechanistic models to predict the heat transfer coefficient in confined conditions are commonly based on speculations of the heat transfer mechanisms. In this context, the combination of infrared thermometry and optical velocimetry techniques for the flow and heat transfer characterization in microchannels is a promising approach, since these techniques are considered non-intrusive and can provide detailed results. Thus, this internship proposal aims to contribute to the development of such techniques to provide reliable measurements of the wall temperature distribution during flow boiling in confined conditions. As the main result of the activities to be performed during the internship period, it is expected to quantify the heat transfer mechanisms associated with the microlayer evaporation and micro-convection close to the back of elongated bubbles. This proposal has also the objective of complementing the education of the candidate, based on a doctoral internship in an internationally recognized research group. (AU)