Understanding the role of wettability on nucleate boiling heat transfer coefficient for large-scale boiling surfaces*

Boiling phenomena has an important role in many industrial applications, being a very efficient heat transfer mode.

Although several experiments have been conducted to investigate boiling, its mechanisms and heat transfer characteristics are still not understood completely, at larger scales. Analysing and accessing this phenomenon accurately is still a challenge, due to the complexity associated with non-equilibrium thermodynamics at the liquid-vapour interface and its coupling with the fluid dynamics.

For this purpose, here, we employ advanced parallelised multiphase numerical schemes implemented in our in-house solver, TPLS, using the Diffuse Interface Method to simulate pool boiling. This method enable us to model contact line physics with appropriate boundary conditions by eliminating the stress singularity at the three-phase contact line, allowing us to analyse the effect of substrate wettability on boiling performance.

We validate our simulations against nucleate boiling experiments using FC72 on silicon surfaces and we observed that the hydrophilic substrates enhance the heat transfer coefficient (HTC) promoting the departing conditions in multiple bubble systems intensifying the coolability of the surface. We also perform simulations at increasing site-densities from O(10) nucleation sites (for lab-scale surfaces) to O(100) sites (for pilot-scale surfaces) to O(1000) sites (industrial-scale surfaces). This is important because these simulations enable us to determine the heat transfer coefficient as a function of nucleation site-densities.