Experimental Study on the Effect of Synthetic Jets on Flow Boiling Heat Transfer in Microchannels

Abstract

Two-phase flow instabilities in micro-channel exhibit pressure and temperature fluctuations with different frequencies and amplitudes. An active way to suppress the dynamic instabilities in the boiling micro-channels is to introduce synthetic jets into the channel fluid. Thus the bubbles can be condensed before they clog the channel and expand upstream causing flow reversal. The present work experimentally investigated the effect of synthetic jets on the suppression of flow boiling instabilities exhibited in a micro-channel heat sink. The heat sink is consisted of five parallel rectangular microchannels measured 500 μm wide, 500 μm deep each. An array of synthetic jets was placed right above the micro-channels with each channel corresponds to 8 jet orifices. The strength and frequency of the jets are controlled by changing the driving voltage and frequency of the piezoelectric driven synthetic jet actuator. Tests were performed with synthetic jets operating at 80 Hz and 150 Hz respectively. It is found that the bubbles were effectively condensed inside the jet cavity. The boiling flow reversals were notably delayed by the synthetic jets. Meanwhile, the pressure fluctuation amplitudes were substantially reduced. Test results were analyzed and discussed in detail.