Nanoengineered Surfaces for High Flux Thin Film Evaporation

Abstract

Abstract : The objective of the work was to investigate nanoengineered surfaces that could modulate the wetting and phase change processes to enhance heat transfer performance. Phase change processes, associated with the large latent heat, have been widely used in applications where high heat fluxes and high heat transfer coefficients are desired. One example is thermal management which has become a critical bottleneck for the advancement of a variety of important defense, space, and commercial systems. Current state-of-the-art cooling approaches have significant limitations, particularly for high heat flux applications. Two-phase fluidic cooling systems, utilizing liquid-vapor phase-change absorbs large fluxes with minimal changes in device temperature [1-3], has been considered as one of the most promising approach to address the demands for thermal management. While efforts have focused primarily on boiling flows in microchannels, liquid-vapor instabilities during phase-change in these systems lead to local dry-out, nonuniform temperature distributions, and significant decreases in critical heat flux [4-8]. Despite extensive research, there remain significant hurdles in the implementation of this technology. In contrast, two-phase jet impingement and spray cooling techniques have been investigated to a much lesser extent, even though such a methods promise high heat transfer coefficients (100 W/cm2K) with high heat dissipation capability (1000 W and 1000 W/cm2) via thin film evaporation [1, 9]. The implementation has comparable challenges. Previous experimental attempts have typically led to pool boiling due to chamber flooding, or liquid dry-out due to insufficient liquid supply [1, 10]. These undesired effects significantly decreased heat transfer coefficients and heat removal rates. In one aspect of this work, we took advantage of state-of-the-art nanoengineering capabilities to address these challenges.