Effect of axial conduction on heat transfer in a rectangular microchannel with local heat flux

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  • YU Fawen
    Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University
  • WANG Tao
    Shanghai Institute of Satellite Engineering
  • ZHANG Chengbin
    Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University

Abstract

<p>Based on the continuum assumption and Navier-Stokes equation, three-dimensional fluid flow and conjugate heat transfer in heat sinks with rectangle microchannels have been studied by numerical simulation. The validation of this approach has been demonstrated by comparisons with analytical solutions. Results were obtained for the detailed description of the local and average heat transfer characteristics including wall and fluid temperatures, heat flux, Nusselt number (Nu). Effects of the Peclet number (Pe), the relative conductivity (kw/kf) and the relative thickness (W/D) of solid substrate were presented and discussed. At low Pe flow, axial conduction dominates the heat transfer, which results in a large upstream region which is pre-warmed by axial conduction, so axial conduction cannot be neglected at small Pe. The increase of Pe induces an enhancement of convection, the heat exchange mainly happens on heat region by convection under this condition. A more uniform streamwise temperature distribution at fluid-solid interface indicates the enhancement of the pre-warmed effect along with the increase of kw/kf. The study also reveals that the Nux of low kw/kf material is higher than the Nux of high kw/kf material. The increase of wall thickness has an effect on axial distribution of the Nux, the trend is similar to that of an increase of the wall thermal conductivity kw/kf. It was concluded that the average Nusselt number is proportional to thermal conductivity of the wall. For low Pe, the fluid is heated by the wall by means of convection on heat region, when Pe ≤ 1, a slight increase of the Nu on heat region is shown as the increase of Pe. When Pe > 10, the convection is the dominant factor in heat transfer, an obvious increase of Nu is shown with increase of Pe. For high Pe flow, the heat transfer enhancement as increase of Pe is weak.</p>

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