微槽脉冲加热流动沸腾中气泡的核化和生长

Microbubble Nucleation and Dynamics During Flow Boiling in Microchannel With Pulse Heating

实验研究了脉冲加热条件下PDMS玻璃微槽(300μm×60μm)内FC-72液体的流动沸腾现象,通过研究单个气泡的核化,生长和塌陷来了解微槽内脉冲加热沸腾的机理.核态沸腾发生在加热开始后的一段时间,根据实验条件的不同,沸腾起始的过热度从84.9℃到91.2℃变化,在脉冲加热结束以后液体蒸发仍在继续直到加热片温度降低到92.0℃左右.由于微槽的高宽比非常小,快速生长的气泡迅速覆盖整个微加热片并向上下游扩展导致了加热片的传热恶化.当长气泡被往下游推离加热片上方区域后,一个连接长气泡的薄蒸汽膜将覆盖在加热片上,同时换热效果比气泡覆盖加热片时大幅增加.

F0-72 flow boiling with pulse heating was studied experlmentany ior now 111 i-1Jlvllo-Lr microchannel 300 μm wide and 60 μm deep. The single bubble nucleation, growth and collapse were studied to understand the mechanisms governing the flow and heat transfer for pulsed boiling in microchannels. Nucleation occurs a short time after the pulse begins for superheats from 84.9℃to 91.2℃ depending on the experiment conditions. The boiling continues after the pulse stops until the microheater temperature is approximately 92℃. Since the microchannel aspect ratio is very small, the rapidly growing bubble quickly covers the entire microheater and extends up and down- stream which leads to deterioration of the heat transfer. When the long bubble is pushed downstream away from the microheater, a thin film of vapor covers the heat sink and the heat transfer rate increases.