Numerical Prediction of Convective Heat Transfer in Self-Sustained Oscillatory Flows

Numerical investigations of the flow pattern and heat transfer enhancement in supercritical grooved-channel and communicating-channels flows are presented. For Reynolds numbers above the critical one, R-c = 0(100), these flows exhibit laminar self-sustained oscillations at the plane channel Tollmien-Schlichting frequency. These ordered, very well-mixed flows require significantly less pumping power than the random fluctuating turbulent flows to achieve the same transport rates. Comparing different heat transfer augmentation schemes in grooved channels, it is shown that the best enhancement system regarding minimum power dissipation corresponds to passive flow modulation in the range of low Nusselt numbers. However, spontaneous supercritical flow destabilization becomes competitive as the Nusselt number is increased. It is found that on an equal pumping power basis, the heat transfer in communicating channels flows is up to 300% higher than the one in flat channel flow.