Pool boiling heat transfer and bubble behavior on the treelike networks with wedge-shaped channels

Abstract

This paper designs the treelike networks with the wedge-shaped channel from the idea of bionics. Pool boiling heat transfer experiments of FC-72 under different liquid subcoolings were conducted on the networks with different branch levels. The bubble phenomenon was recorded to reveal the boiling mechanism. The bubble pumpless movement towards the diverging direction in the wedge-shaped channel under the action of capillary force was observed. Under the saturated condition, the surfaces are easier to be completely covered by bubbles and the effect of treelike networks is hindered, which results in similar heat transfer performance. With the increase of liquid subcoolings, the bubble fraction decreases and the effect of the branch level comes into effect. On the surface with high branch level, the bubbles are transported immediately at small radius by the narrow wedge-shaped channel. The moving bubbles disturb the fluid and coalesce with other bubbles, which increases the heat transfer coefficient. There are also more liquid supply pathways between small bubbles, which increases the critical heat flux. The importance of this research is to provide a solution to the difficulty of bubbles vertical departure caused by the lack of buoyancy under microgravity.