Numerical study of boiling of Liquid Nitrogen on a liquid-liquid contact plane

TL;DR

This study uses numerical simulations to analyze boiling behaviors of liquid nitrogen on solid and liquid surfaces, revealing different boiling modes, bubble dynamics, and vapor film characteristics relevant for cryogenic applications.

Contribution

It provides new insights into multi-mode boiling phenomena and vapor film dynamics of LN2 on solid and water surfaces through detailed numerical analysis.

Findings

Bubble growth and heat flux increase linearly with superheat.

Asymmetry observed in bubble departure due to turbulence.

Vapor film thickness decreases to 7.62 micrometers before rupture.

Abstract

In this paper, a numerical study is conducted to investigate boiling of a cryogen on a solid surface as well as on a liquid surface. Both single mode and multi-mode boiling is reported for boiling on to a solid surface. In case of boiling on a liquid surface, liquid nitrogen is selected as the cryogen (boiling fluid) and water is chosen as the base fluid (heating fluid). Different flow instabilities and their underlying consequences during boiling of a cryogen are also discussed. For the boiling on a solid surface, in the single mode, bubble growth, its departure, and area weighted average heat flux are reported, where they increase linearly with increase in the wall superheat. Asymmetry in the bubble growth and departure of 2nd batch of the vapor bubbles have been observed due to local fluctuations and turbulence created just after the pinch off of the 1st batch of vapor bubbles in case of multi-mode boiling on the solid surface. Boiling of LN2 on a liquid surface is reported for a base fluid (Water) temperature of 300 K. Vapor film thickness decreases with time and the minimum film thickness just before rupture is 7.62 micrometer, dominance of thermocapillary over vapor thrust causes breaking of the vapor film at 0.0325s. The difference in evaporation rate and vapor generation, before and after vapor film collapse is significant.