NEW BUBBLES BEHAVIOR AND FLOW PATTERN TRANSITION OF OPEN MICROCHANNEL AND JET IMPINGEMENT HYBRID COOLING SCHEME BY SEPARATING LIQUID-VAPOUR PATHWAYS

Four new bubble behaviors and their flow patterns were observed in the visualization experiments, different from the bubbly flow, slug flow, stratified flow and annular flow in the existing research of open micro-channel. In the scheme of separating liquid-vapor pathways, small bubbles are generated from the bottom of the micro-channel, migrate to the top of the channel fins and continue to grow at the top of the channel fins under the condensation and fragmentation effect of the jet impingement, and then the channel flow pushes them away from the test module. From bubble flow to annular flow, there is never any formation of large bubble embolism covering multiple channels. The new flow pattern effectively suppressed the flow instability, allowing the bubbles to disengage in time with the liquid to replenish the drying point. The critical heat flux reached 342 W·cm^-2, realizing enhanced heat transfer. A prediction model of critical heat flux and critical bubbles motion diameter were proposed based on the force balance of a bubble on the sidewall of micro-channel, and bubbles on the fins top. And the maximum errors were 11.3% and 20%, respectively. These findings have an impact on the further development of efficient cooling technology.