[2L10-15] Gas-liquid Two Phase Flow 1

[2L11] Measurement of Bubbly Layer Void Fraction at the Point of Onset of Significant Void in Subcooled Flow Boiling

*Binh Thanh Nguyen¹, Tomio OKAWA¹, Ryoma TSUJIMURA¹ (1. UEC)

Keywords:2 phase flow, Onset of significant void, Void fraction measurement

In two-phase flow, the formation of a large bubble is an important phenomenon, it is directly related to the inception of departure from nucleate boiling. However, thermal-hydraulic condition imposes a strong impact on the point of onset of significant void, therefore it is troublesome to quantitively detect the point of significant void in subcooled flow boiling. Based on the theoretical assumption of the flow regime transition from bubbly flow to slug flow in the subcooled flow boiling at the bubbly layer by Okawa (2021), the critical local void fraction at the point of onset of significant void is said to be 30%. Therefore, in the present study, by the use of an optical void probe, the experimental measurement for the void fraction at the near-heated wall region was done to quantitively verify the critical void fraction at the point of onset of significant void.