A fundamental understanding of liquid-vapor phase transitions, mainly boiling phenomenon, is essential due to its omnipresence in science and technology. In industries, many empirical correlations exist on the heat transport to get an optimized and efficient thermal design of the boiling equipment. But nevertheless, a physical understanding of these phenomena remains inconclusive. This is because of the complexity present in the problem due to interconnections between mass, momentum and thermal energy of solid, liquid, and vapor phases. How to understand the observed heat transport and the flow dynamics based on a suitable model with the proper physics of boiling? Boiling phenomena of water at 100 °C under normal pressures in a Rayleigh-Bénard (RB) cell are understood through numerical simulations. Our work highlights the importance of nucleated vapor bubbles on the local and the global properties of the flow (e.g., energy dissipation rates, velocity, temperature, heat flux etc.) in a boiling convection. What we found is vapor bubbles absorb heat from the hot plate (and also from surrounding liquid), grow in size and rise in the flow due to enhanced buoyancy. While in motion, they condense by releasing heat when they encounter a cooler liquid or by reaching the cold plate. Their complex interactions with the liquid significantly change the mentioned local and global properties of the flow. While this study therefore does not address the real phenomenon of boiling, but it is useful to illuminate the relative importance of enhanced convection due to the increased buoyancy of vapor bubbles and their motion relative to the liquid in both the laminar and the turbulent states. This work is a preliminary step to better understand boiling thermal convection in the perspective of fluid dynamics and heat transfer.
|Award date||11 Jan 2013|
|Place of Publication||Enschede|
|Publication status||Published - 11 Jan 2013|