Liquid film boiling enabled ultra-high conductance and high flux heat spreaders

Abstract

Summary: Many of the advanced technologies, e.g., microprocessors, laser and radar, and power transmitters and amplifiers, are becoming increasingly dependent on the ability to dissipate the enormous amount of waste heat in extremely small areas. Two-phase heat spreaders utilizing the liquid-vapor phase change are appealing due to the high performance and potentially low cost. However, thin film evaporation is limited by the capillary dry-out of wicking structures. We demonstrate here an ultra-high thermal conductance and high flux heat spreader enabled by a capillary-driven liquid film boiling process on a hierarchical mesh wicking structure. By manipulating liquid wicking flow and vapor bubble escape, liquid film boiling is demonstrated to have a heat removal capability of 552 W/cm2 from an area of 25 mm2 with a temperature increase of less than 8 K, corresponding to a heat transfer coefficient of 732.5 kW/m2·K. The effective thermal conductivity of the 1-mm-thick two-phase heat spreader is larger than 104 W/m·K.

Keywords

• heat transfer
• liquid film boiling
• capillary wicking
• high heat flux
• heat spreader
• thermal management