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GAS-ASSISTED EVAPORATION HEAT AND MASS TRANSFER

DOI: 10.1615/AnnualRevHeatTransfer.2016013517
pages 159-198

Shankar Narayanan
Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA; Currently, Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY

Peter A. Kottke
Department of Mechanical Engineering, Georgia Institute of Technology, 337 Ferst Drive, Atlanta, GA 30332

Yogendra K. Joshi
Naval Postgraduate School, Monterey, CA 93943; G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA

Andrei G. Fedorov
Georgia Institute of Technology, George W. Woodruff School of Mechanical Engineering, Parker H. Petit Inst. for Bioengineering and Bioscience, USA


KEY WORDS: Evaporation, Phase-change, Thin-film, Nanoporous membrane, Electronic cooling, Spray cooling, High heat flux, Water purification, Membrane distillation, Desalination

Abstract

Evaporation plays a critical role in nature and many industrial applications. Evaporation has been studied extensively to address extreme thermal challenges in electronics. This chapter presents an overview of evaporation-based cooling techniques, followed by a detailed description and performance characterization of two novel techniques that leverage gas-assisted thin film evaporation. These methodologies combined can potentially address both localized and averaged cooling requirements, which are critical bottlenecks in high-performance microelectronics. One of the techniques utilizes a novel hybrid thermal management device, which improves the performance of conventional air-cooled heat sinks using on-demand and spatially controlled droplet impingement evaporative cooling. The other cooling methodology makes use of microscopically thin liquid films to provide efficient heat and mass transfer. In this technique, the use of nanoporous membranes maintains thin liquid films, minimizing the possibility of dry-out by exploiting capillary confinement of the fluid. In combination with flow of dry air, this arrangement yields record high heat and mass fluxes. A detailed computational analysis is carried out to determine the relative effects of the performance-governing parameters, which is also supported by experiments, using a microscale device supporting gas-assisted thin film evaporation. While the understanding gained in these techniques enables dissipation of high heat fluxes for electronic cooling, it is also relevant in applications relying on efficient evaporation and phase separation such as membrane distillation and climate control systems.

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