Modeling and Design Optimization of Ultrathin Vapor Chambers for High Heat Flux Applications

Ram Ranjan, United Technol Res Ctr
Jayathi Y. Murthy, Birck Nanotechnology Center, Purdue University
Suresh V. Garimella, Birck Nanotechnology Center, Purdue University
David H. Altman, Raytheon Integrated Def Syst
Mark T. North, Thermacore Inc

Abstract

Passive phase-change thermal spreaders, such as vapor chambers have been widely employed to spread the heat from small-scale high-flux heat sources to larger areas. In this paper, a numerical model for ultrathin vapor chambers has been developed, which is suitable for reliable prediction of the operation at high heat fluxes and small scales. The effects of boiling in the wick structure on the thermal performance are modeled, and the model predictions are compared with experiments on custom-fabricated vapor chamber devices. The working fluid for the vapor chamber is water and a condenser side temperature range of 293 K-333 K is considered. The model predictions agree reasonably well with experimental measurements and reveal the input parameters to which thermal resistance and vapor chamber capillary limit are most sensitive. The vapor space in the ultrathin devices offers significant thermal and flow resistances when the vapor core thickness is in the range of 0.2 mm-0.4 mm. The performance of a 1-mm-thick vapor chamber is optimized by studying the variation of thermal resistance and total flow pressure drop as functions of the wick and vapor core thicknesses. The wick thickness is varied from 0.05 to 0.25 mm. Based on the minimization of a performance cost function comprising the device thermal resistance and flow pressure drop, it is concluded that the thinnest wick structures (0.05 mm) are optimal for applications with heat fluxes below 50 W/cm(2), while a moderate wick thickness of 0.1 mm performs best at higher heat flux inputs (>50 W/cm(2)).

Discipline(s)

Nanoscience and Nanotechnology