Orientation Effects in Two-Phase Microgap Flow

[+] Author and Article Information
Franklin L. Robinson

Aerospace Engineer, Thermal Engineering Branch, NASA Goddard Space Flight Center, Greenbelt, MD 20771

Avram Bar-Cohen

ASME Fellow, Distinguished University Professor, Department of Mechanical Engineering, University of Maryland, College Park, MD 20742

1Corresponding author.

ASME doi:10.1115/1.4043483 History: Received January 22, 2019; Revised April 07, 2019


The high power density of emerging electronic devices is driving the transition from remote cooling, which relies on conduction and spreading, to embedded cooling, which extracts dissipated heat on-site. Two-phase microgap coolers employ the forced flow of dielectric fluids undergoing phase change in a heated channel within or between devices. Such coolers must work reliably in all orientations for a variety of applications (e.g., vehicle-based equipment), as well as in microgravity and high-g for aerospace applications, but the lack of acceptable models and correlations for orientation- and gravity-independent operation has limited their use in such applications. Reliable criteria for achieving orientation- and gravity-independent flow boiling would enable emerging systems to exploit this thermal management technique and streamline the technology development process. As a first step toward understanding the effect of gravity on two-phase microgap flow and transport, in the present effort the authors have studied the effect of evaporator orientation and mass flux on flow boiling of HFE7100 in a 1.01 mm tall by 13.0 mm wide by 12.7 mm long microgap channel. Orientation-independence, defined as achieving similar critical heat fluxes, heat transfer coefficients, and flow regimes across orientations, was achieved for mass fluxes of 400 kg/m2-s and greater. The present results are compared to published criteria for achieving orientation- and gravity-independence.

Section 4: U.S. Gov Employees + Reg Authors
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