Gas spreading on a heated wall wetted by liquid

TL;DR

This paper investigates how heating affects the shape and spreading of gas on a heated wall in a near-critical fluid, revealing the role of vapor recoil force and implications for boiling crisis understanding.

Contribution

It introduces a novel explanation of gas spreading behavior influenced by vapor recoil force in near-critical fluids under weightlessness conditions.

Findings

Gas phase spreads over hot surfaces with contact angles >90°

Vapor recoil force significantly influences interface shape

Insights into boiling crisis mechanisms in high-power heat exchange

Abstract

This study deals with a simple pure fluid whose temperature is slightly below its critical temperature and whose density is nearly critical, so that the gas and liquid phases coexist. Under equilibrium conditions, such a liquid completely wets the container wall and the gas phase is always separated from the solid by a wetting film. We report a striking change in the shape of the gas-liquid interface influenced by heating under weightlessness where the gas phase spreads over a hot solid surface showing an apparent contact angle larger than 90{\textdegree}. We show that the two-phase fluid is very sensitive to the differential vapor recoil force and give an explanation that uses this nonequilibrium effect. We also show how these experiments help to understand the boiling crisis, an important technological problem in high-power boiling heat exchange.