Yoichi Shiomi

Two-phase flow in an annulus with a rotating inner cylinder (flow pattern in bubbly flow region)

Abstract The two-phase flow pattern in a concentric annulus with a rotating inner cylinder have been investigated experimentally. The observed flow patterns were dispersed bubbly, ring-form, single-spiral, double-spiral, triple-spiral flows and transition regions. When the rotational speed was at a relatively low level, the buoyancy effect of bubbles dominated the flow field and a dispersed bubbly flow was formed. On the other hand, when the rotational speed was at a high level, the vortex motion induced by the rotation dominated the flow field and ring-form and spiral flows were formed.

Characteristics of two-phase flow in a channel formed by chevron type plates

Abstract In this paper, characteristics such as the flow pattern and pressure drop of the liquid single-phase flow and gas–liquid two-phase flow in a channel formed by chevron type plates are reported. Especially, how a corrugation angle of the plates affected the flow, was examined experimentally. Four kinds of the plate combination of the corrugation angle were used, i.e., plate A (30°–30°), plate B1 (30°–60°), plate B2 (60°–30°), and plate C (60°–60°). In the liquid single-phase flow, the pressure drops were well expressed by the function of Reynolds number and increased with the increase in the corrugation angle. In the gas–liquid two-phase flow, the stratified flow and dispersed flow were observed in the horizontal condition and only dispersed flow was observed in the vertical condition. The two-phase multipliers calculated from the pressure drops were agreed with the Lockhart–Martinelli correlation in the case of laminar–laminar condition. The corrugation angle of the upper plate strongly affects the flow pattern and the pressure drop in the horizontal condition.

Bubble and Particle Behavior in Taylor- and Spiral-Vortex Flows

The behavior of the bubble and particle in the Taylor-vortex flow was investigated experimentally by using a concentric annulus with a rotating inner cylinder. The flow visualizations by using the tracers indicated that the bubble-ring was located in the out-flow region of the Taylor-vortex close to the inner cylinder, which was also confirmed by the void fraction measurement. The time-averaged radial positions of the particles depended clearly on the specific gravity, and lighter particle was located toward the inner cylinder. The drift velocity of the bubble and particles relative to the volumetric flux decreased with the increase in the Taylor number and became nearly zero or slightly less than zero beyond the certain Taylor number, where the bubble and particles were trapped in the vortex motion. This threshold Taylor number was a decreasing function of the specific gravity of the particles.