Critical Heat Flux Dependence on Surface Orientation and Bubble Dynamics in Pool Boiling Over Silicon and Silicon Dioxide Surfaces

Abstract

In the evolving energy landscape, there is an increasing demand for efficient and reliable heat transfer methods to prevent overheating in renewable energy systems. Pool boiling presents viable solutions, and the surface orientation of the heated surface is a key parameter which affects its performance. This research investigates the effect of surface orientation on critical heat flux (CHF) in pool boiling using silicon (Si) and silicon dioxide (SiO₂) surfaces. Experiments were conducted across seven preset orientation angles ranging from 0° to 180°. The experimental results indicated that these conditions had a notable effect on heat transfer performance, with the highest CHF observed at a 60° orientation for both types of surfaces. At 180°, a significant reduction in CHF was exhibited at the SiO₂ surface, with CHF values less than 5% of those at 0°. Si surfaces exhibited larger bubble departure angles and smaller bubble sizes at higher orientation angles compared to SiO₂ surfaces. These findings, in which CHF peaks at 60°, challenge the predictions of many existing models that predict a steady decrease of CHF as the surface orientation increases. This research involves a detailed analysis of vapor bubble dynamics, and the interactions between bubbles and the heating surface across different surface orientations. Through the examination of bubble detachment, coalescence, and liquid-vapor interactions, this study aims to provide a clearer understanding of the mechanisms driving CHF variations.