Investigating the two-phase immersion cooling performance by surface wettability modification

Abstract

This study investigates the effect of surface wettability on nucleate boiling performance in a two-phase immersion cooling system, using static contact angles of 160°, 90°, and 30° to represent hydrophobic, intermediate, and hydrophilic surfaces. A dual-chip configuration is employed to capture the influence of surface orientation on boiling behavior and thermal response. Volume of Fluid (VOF) simulations are conducted to evaluate vapor distribution, temperature fields, liquid coverage, and heat transfer coefficients.

Results show that decreasing the contact angle from 160° to 30° significantly enhances boiling performance. The heat transfer coefficient on the lower chip increases from 600 to 5700 W/m²·K, while the upper chip improves from 440 to 3600 W/m²·K, representing gains of 850 % and 700 %, respectively. Surface temperatures are reduced by up to 2.5 K. However, stronger boiling activity at lower contact angles increases vapor accumulation near the upper chip, resulting in greater temperature asymmetry between the two surfaces.

These findings highlight that while enhanced wettability substantially improves boiling heat transfer, it also intensifies orientation-driven vapor effects. Optimizing performance in immersion-cooled systems requires not only surface engineering but also consideration of vapor management in multi-surface and vertically arranged configurations.