Dryout characteristics and flow behavior of gas-water two-phase flow through U-shaped and inverted U-shaped bends

Abstract

Experimental results are presented on the flow behavior, pressure drop characteristics, and dryout characteristics by joule heating for the gas-water two-phase flow through U-shaped and inverted U-shaped tubes in vertical plane. The height of the vertical straight section of the test tube is 4100 mm, and two bend radii, 116 mm and 435 mm, are chosen for the experiments. The test tubes used are of transparent acrylic resin for the flow behavior test, and of stainless steel for the other tests, inside diameter being 18 mm for the former and 18.5 mm for the latter. Flow patterns in the vertical upflow and downflow sections are shown on the diagram of the superficial gas velocity versus liquid velocity. Further, the flow behavior in the bend section is made clear in relation to flow rates of gas and liquid. The pressure drop between inlet and outlet of the test tube for the two-phase flow is shown in comparisons with that for the single-phase flow of water. The threshold conditions of dryout in the bend section by joule heating are shown on the diagram of the superficial gas velocity versus liquid velocity. The location of the dryout in the bend section is also clarified.