Microchannel evaporator cooling systems are widely studied for their ability to remove high heat fluxes. However, flow instabilities during microchannel boiling, like pressure drop oscillation and flow maldistribution, can cause an uneven temperature variation and deteriorate the cooling performance. This study analyzes the effect of using an oscillatory valve opening on the flow distribution and channel temperatures across a two- channel evaporator. Experiments and prediction models indicate that a specific range of valve oscillation amplitude and frequency may cause synchronization resulting in balancing the flow distribution and temperature across the channels, even when they are thermally isolated from each other. Analysis of system performance at different conditions indicates that larger oscillation amplitudes in the valve opening may allow a wider frequency range for temperature synchronization. For a fixed valve opening amplitude, using either significantly small or large frequencies may not be helpful. Moreover, for small amplitudes in valve opening, synchronization may never occur for any frequency. These observations lead us to believe that deliberate oscillations in the valve opening can serve as an active control strategy to mitigate flow maldistribution in parallel channels, suppress temperature oscillation, and improve the overall cooling performance.
Applied Thermal Engineering, Vol. 204, 2022.