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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Microscale Convective Heat Transfer with Plug Flow in Microchannels

Get access (open in a dialog) DOI: 10.1615/IHTC15.tbf.009171
pages 7703-7714

Abstract

In microchannels, due to the small dimension and low fluid speed, the flow is usually laminar and characterized by low Reynolds numbers. Therefore, the heat transfer rate between the fluid and the wall of the microchannel is dominated by thermal diffusion. Without turbulence, the convection of heat is limited. Different strategies have been developed to promote vortices in microchannels, such as curvatures of the microchannels, built-in obstacles in the flow paths. The effects of these methods are not significant, because most rely on high velocities to achieve secondary flows, whereas high velocity requires an extremely high pressure because the small dimension of the channel produces a high flow resistance. Vortices can be simply produced by introducing interfaces into the flow in microchannels. For plug flow, with the presence of the interface, vortices are formed and dominate the whole liquid plug. In this paper, the heat transfer of liquid plugs moving in capillaries with constant surface heat flux boundary condition is investigated. By incorporating the analytical flow field, the heat transfer process is simulated using finite volume method. The effects of Peclet number and the plug length are studied. The results show that the higher Peclet number results in higher Nusselt number and lower maximum fluid temperature. Heat transfer in longer plugs results in lower Nusselt number and higher maximum fluid temperature. In applications of heat exchangers, to achieve higher Nusselt numbers and lower maximum temperatures, high Peclet numbers and shorter plug lengths are favorable.