Which flow regime begins below the core midplane in high powered channels and features significant vapor pockets?

Which flow regime begins below the core midplane in high powered channels and features significant vapor pockets?

• A. Slug Flow
• B. Annular Flow
• C. Bubble Flow
• D. Mist Flow

Answer: (A)

Two-phase flow regimes are identified by how the vapor and liquid occupy the channel cross-section as the fluid moves. Slug flow is the regime where large pockets of vapor (gas slugs) span a significant portion of the channel, separated by relatively long slugs of liquid. In high-powered channels, intense heating generates vapor early along the flow path, and as voids form and coalesce, these large gas pockets become evident lower in the core—below the midplane—before the flow evolves to other patterns higher up. The hallmark here is substantial vapor pockets that dominate portions of the cross-section and alternate with liquid slugs. This is different from bubble flow, where many small bubbles are dispersed through the liquid; from annular flow, where a thin liquid film coats the walls with a central gas core; and from mist flow, where the flow is mainly vapor with fine droplets. Slug flow’s defining feature is those large gas pockets interspersed with liquid, not the continuous gas core or the dispersed small bubbles seen in the other regimes.

Two-phase flow regimes are identified by how the vapor and liquid occupy the channel cross-section as the fluid moves. Slug flow is the regime where large pockets of vapor (gas slugs) span a significant portion of the channel, separated by relatively long slugs of liquid. In high-powered channels, intense heating generates vapor early along the flow path, and as voids form and coalesce, these large gas pockets become evident lower in the core—below the midplane—before the flow evolves to other patterns higher up. The hallmark here is substantial vapor pockets that dominate portions of the cross-section and alternate with liquid slugs.

This is different from bubble flow, where many small bubbles are dispersed through the liquid; from annular flow, where a thin liquid film coats the walls with a central gas core; and from mist flow, where the flow is mainly vapor with fine droplets. Slug flow’s defining feature is those large gas pockets interspersed with liquid, not the continuous gas core or the dispersed small bubbles seen in the other regimes.