A conjugate heat transfer analysis of performance for rectangular microchannel with trapezoidal cavities and ribs

Abstract

Abstract A numerical investigation has been taken up to assess the efficacy of a design innovation for rectangular microchannel heat sink by applying the concepts of maximization of thermal performance (TP) and minimization of entropy generation (EG). The channel is conceived as a serial arrangement of modifying units, each with a rib symmetrically located between trapezoidal cavities (TRC) on opposite side walls. Based on SIMPLEC algorithm for the flow along with conduction through the bounding walls and the internal ribs, a three dimensional laminar-flow conjugate heat-transfer study has been carried out between Reynolds number (Re) of 140 and 600 following a validation against a representative numerical and experimental study. A comparison among the predictions of constant fluid property model and models incorporating their realistic variations with temperature has shown the cooling to be dominated by convection, of course more strongly at higher Re. Substantially higher thermal conductivity of copper than that of silicon have revealed moderate increase in bulk fluid temperature and even lower increase of substrate temperature. Four different rib structures have been considered that are rectangular (RR), backward triangular (BTR), forward triangular (FTR) and diamond (DR). The predictions against Re indicated the best TP with diamond rib combination (TRC-DR) and the highest EG with backward triangular rib combination (TRC-BTR). A notable contribution of this work is establishing the concept of minimization of EG under the constraint of given pumping power to be equivalent to the concept of maximization of TP. The effects of parametric variations of relative width and length of cavity and relative width and pitch of rib have been investigated and the highest TP has been predicted around Re of 328.