ID 106

Spray cooling in the nucleate boiling regime: Hydrodynamics and heat transfer

 

Abstract:

Spray cooling is an efficient technology for achieving high cooling performance. The technique is used for different applications e.g. to cool high power electronics or tools for hot forging. The resulting local heat flux density is highly dependent on surface properties, superheat and spray characteristics like droplet diameter, droplet speed and mass flux density. To date, heat flux density is mainly predicted using empirical correlations, often covering only a small range of operational parameters. Analytical models are available only for very special cases, since the physics of spray cooling is not entirely understood. The aim of this study is to develop a model for spray cooling in the nucleate boiling regime. For validation of the model, measurements of the local heat flux with varying spray parameters and visual observations of drop impact during spray cooling have been performed. The experimental setup consists of the spray system, a heated target, a visual observation system and a data acquisition system. The spray is produced by conventional atomizers and characterized with a dual-mode phase-Doppler system. A patternator is used to determine the local mass flux density. Heat flux is measured by solving the inverse heat conduction problem, given temperature measurements in the substrate. In this study we show the outcomes of heat flux measurements and visualization for different kinds of sprays.