Experimental results of the effect of gas composition on void fraction and bubble behavior for gas-liquid two-phase flow under stagnant water condition

Abstract

Fission product removal by pool scrubbing is known to be largely affected by the gas-liquid two-phase flow regime. The pool scrubbing performance of various carrier gases was evaluated in two-phase flow experiments by injecting helium, nitrogen, or argon through a pool of stagnant water in a column with an inner diameter of 0.5 m and a height of 8 m. The gases were supplied through a cylindrical nozzle with an inner diameter 69 mm at superficial gas velocities ranging from 0.013 to 0.053 m s^-1. Measurements were conducted using a camera and two sets of a 128 × 128 wire-mesh sensors, separated by 40 mm. The visually observed gas hold-up and wire-mesh sensor-measured average void fraction decreased with increasing fraction of lighter gas in the supplied gas. Detailed analysis of the flow regime using the obtained wire-mesh sensor signals revealed that lighter gases led to a greater fraction of relatively large bubbles in the flow compared to heavier gases, causing the gas phase with the lighter gases to have a higher average rise velocity in the flow. This leads to a hypothesis that, compared to heavier gases, lighter gases break up less or coalesce more in the flow, resulting in distinct two-phase flow characteristics depending on the inlet gas composition.