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research-article

Visualization of two-phase flow in serpentine heat exchanger passages with microscale pin fins

[+] Author and Article Information
Dhruv C Hoysall

ASME Student member G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
dhoysall3@gatech.edu

Khoudor Keniar

ASME Student member, G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
kkeniar3@gatech.edu

Srinivas Garimella

Fellow ASME, G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
sgarimella@gatech.edu

1Corresponding author.

ASME doi:10.1115/1.4037342 History: Received May 31, 2016; Revised March 23, 2017

Abstract

Microchannel heat exchangers offer the potential for high heat transfer coefficients; however, implementation challenges must be addressed to realize this potential. Maldistribution of phases among the microchannels and the changing phase velocities associated with phase change present design challenges. Flow maldistribution and oscillatory instabilities can affect transfer rates and pressure drops. In condensers, evaporators, absorbers and desorbers, changing phase velocities can change prevailing flow regimes from favorable to unfavorable. Geometries with serpentine passages containing pin fins can be configured to maintain favorable flow regimes throughout the component for phase-change heat and mass transfer applications. Due to the possibility of continuous redistribution of the flow across the pin fins along the flow direction, maldistribution can also be reduced. These features enable high heat transfer coefficients, thereby achieving considerable compactness. The characteristics of two-phase flow through a serpentine passage with micro-pin fin arrays with diameter 350 µm and height 406 µm are investigated. An air-water mixture is used to represent two-phase flow through the serpentine test section, and flow features are investigated using high-speed photography. Improved flow distribution is observed in the serpentine geometry. Distinct flow regimes, different from those observed in microchannels, are also established. Void fraction and interfacial area along the length of the serpentine passages are compared with the corresponding values for microchannels. A model developed for the two-phase frictional pressure drops across this serpentine micro-pin fin geometry predicts experimental values with a mean absolute error of 7.16%.

Copyright (c) 2017 by ASME
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