Time-dependent heat transfer analysis of ellipsoidal protruded microchannel with multiple pulsating jets

Abstract

Comparing with continuous jets inside microchannel, the heat removal capacity is enhanced by introducing protrusions or pulsating jets individually. Therefore, the preferred heat transfer enhancement and satisfactory thermal performance are investigated after taking both advantages of unsteady properties and ellipsoid protrusions simultaneously in this work. Especially, phase difference, Δφ, as a pivotal parameter, is applied in multiple pulsating jets. The total mass flow rate in microchannel, temperature fluctuation on heated wall, thermal and flow resistance are therefore varied. The largest fluctuation of mass flow rate is achieved when the phase difference between each adjacent jet inlets at Δφ = 0∙π, while the smallest at 0.75∙π, and the temperature distribution of the target wall correspondingly fluctuates. The heat transfer enhancement is most prominent at 0.75∙π. The increment in heat transfer is close to that of flow resistance at Δφ = 0.50∙π, 0.75∙π and 1∙π. The thermal performance TP firstly increases and then decreases with Δφ, and reaches the maximum value at 0.75∙π. Furthermore, due to the phase difference, each jet becomes the one with the highest velocity among all jets periodically, weakening adverse effect of cross flow and suppressing the drift phenomenon effectively. This is exactly the mechanism for heat transfer enhancement of unsteady multiple jets with velocity phase difference in ellipsoid protrusion microchannel.