Direct numerical simulation of gravity effects on pool boiling heat transfer*

Design of efficient thermal systems for satellites and spacecrafts that operate in varying environments require an understanding of how pool boiling scales with gravity. Experimental investigations have identified existence of two distinct boiling regimes dominated by buoyancy (BDB) and surface tension (SDB). Quantitative assessment shows a mathematical relationship between wall heat transfer and gravity as a function of heater size, superheat and degree of subcooling. However, a qualitative understanding of how these parameters affect bubble dynamics is still elusive. High fidelity simulations can reveal useful information about these processes which can be useful in improving the mathematical model. This talk will discuss a numerical framework to simulate pool boiling in low gravity conditions, and show the effects of gravity and subcooling through three-dimensional calculations. Focus will be given towards explanation of dynamics in transition gravity levels between BDB and SDB regimes. Results will be verified with experiments and computational challenges associated with resolving the thin liquid thermal boundary layer will be addressed. A statistical description of heat transfer, near wall flow and bubble dynamics will also be presented.