Effect of Hypervapotron Fin Angle on Subcooled Flow Boiling Heat Transfer Performance Under One-Side High-Heat Load Condition

The effect of the hypervapotron (HV) fin angle on heat transfer was analyzed through visualization experiments and subcooled flow boiling experiments. An HV channel with a fin angle of 45 deg had a higher onset-of-nucleate-boiling heat flux than the typical HV channel. Additionally, as the heat flux increased, the bubble-sliding effect caused by the tilted fin was visualized, and it was observed that the vapor inside the fin was agglomerated by the sliding flow and driven into the side slot. When the fin angle of the typical HV channel was set as 0 deg, as the tilted angle of the fin increased, the heat transfer and critical heat flux (CHF) were improved owing to the secondary flow generated by the sliding effect. When the fin angle reached 45 deg, the CHF value was improved by 81% compared with the typical HV channel, which was the highest enhancement rate among the evaluated HV channels. However, when the fin angle exceeded 45 deg, the vapors aggregated more rapidly as the sliding velocity induced inside the fin increased. Furthermore, the two-phase pressure drop was analyzed through differential pressure measurements. The 45-deg tilted HV channel had a higher onset-of-significant-void heat flux value than all the other channels (HV, swirl, smooth, flat channels).