The flow characteristics of an upward gas‐liquid two‐phase flow in a vertical tube with a wire coil: Part 1. Experimental results of flow pattern, void fraction, and pressure drop

Abstract

Experiments were carried out to investigate the flow pattern, average void fraction, and pressure drop of an upward air-water two-phase flow in vertical tubes of 25-mm inside diameter with wire coils of varying wire diameter, pitch, and number of coils in cross section. Five kinds of flow patterns-bubble, slug, churn, semiannular, and annular flow-were defined based on the observation of flow behavior in the experiments. At higher water flowrates, the bubble-to-slug transition occurred at lower air flowrates in tubes with wire coils than in smooth tubes. The average void fraction was found by using the drift flux model. Further, the experimental results of the friction pressure drop were compared with the Lockhart-Martinelli correlation. As a result, a correlation with the constant C in Chisholm's equation was obtained as a function of the wire coil pitch-to-diameter ratio.

Dynamics and effective distance of gas–liquid two-phase swirling flow induced by vortex tools

“…That is because the vortex tool with a larger helix angle has a longer pitch and the long pitch can reduce resistance along the way. The effect of helix angle on the pressure drop is in good agreement with the study by Takeshima et al 43 and Park and Chang. 44…”

“…The liquid film thickness increases more with an increasing helix angle than with an increasing hub diameter, which means the helix angles have a more dominant effect on the liquid film thickness than hub diameters. The results in respect to liquid film thickness are in good agreement with the experimental results of Takeshima et al 43 and numerical results of Park and Chang. 44 The investigations on gas-liquid two-phase flow characteristics in a helical wire inserted tube by Takeshima and Park demonstrated that the average liquid film thickness increased as the pitch length and the inserted wire diameter increased.…”