Dynamics study on bubble wake effect under short period of microgravity

The influences of wake on bubble dynamics under various heat fluxes have been studied experimentally in microgravity. Results indicate that wake has little influence on bubble dynamics at low heat fluxes, but its effect on bubble dynamics is very greater at middle or high heat fluxes. More important, the bubble wake effect appears even more significant in microgravity. In the wake field, the horizontal flow of the liquid on micro-pin-finned silicon chips promotes the collision, coalescence and movement of bubbles, and the vertical flow of liquid phase can exert an upward force on bubbles, which can effectively shorten the growth cycle and decrease the departure radius of bubbles. Furthermore, subcooled liquid in wake field can create a negative pressure zone in bubbles and the fresh liquid can easily be inhaled into the micro-pin-finned structure covered by bubbles, which can supply sufficient liquid for the growth of bubble, avoiding film boiling. The interaction between the micro-pin-finned structure and the wake effect can promote the process of bubble coalescence and departure effectively, and then enhance heat transfer of micro-pin-finned surface.