ISSN Online: 2377-424X
ISBN Print: 978-1-56700-421-2
International Heat Transfer Conference 15
Microscale Convective Heat Transfer with Plug Flow in Microchannels
要約
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.