Abstract
This paper describes the experimental study on the effects of grid spacer with mixing-vane (MV) on gas-liquid two-phase annular flow in a vertical circular pipe of 16 mm i.d. In order to know the effects, grid spacers with and without MV were inserted in turn into the test channel. Furthermore, in order to know the effects of inclination angle of the mixing-vane to main flow, two inclination angles, i.e., 30° (MV30) and 20° (MV20) were tested. Pressure drop of flow through the spacer and liquid droplets deposition rate in the section downstream from the spacer were measured with a pressure transducer and double liquid film extraction method, respectively. Experimental data revealed that deposition mass transfer coefficient and the pressure drop were higher for the spacer with MV than that without MV. Regarding the effects of the inclination angle of MV, the vane of MV30 gave higher deposition mass transfer coefficient than MV20 although it increased the pressure drop.
Highlights
Background and IntroductionIn a boiling water nuclear reactor (BWR), a coolant flow in a subchannel of the fuel rod assembly changes from a liquid single-phase flow to an annular two-phase flow, with flowing downstream
A main part of the liquid phase flows as a liquid film on the fuel rod bundle and a remaining part flows as liquid droplets in the gas core
The effects of mixing-vane (MV) attached to a grid spacer on the characteristics of air-water annular flows were experimentally investigated using a 16 mm i.d. circular pipe as the test channel, which was simplified from the center subchannel in a BWR fuel rod bundle
Summary
In a boiling water nuclear reactor (BWR), a coolant flow in a subchannel of the fuel rod assembly changes from a liquid single-phase flow to an annular two-phase flow, with flowing downstream. A main part of the liquid phase flows as a liquid film on the fuel rod bundle and a remaining part flows as liquid droplets in the gas core. Since the liquid in the film evaporate and a part of that entrains as the droplets to the gas core by a high shear gas flow in the gas core, the thickness of the liquid film gradually decreases with flowing downstream. Researches have been conducted recently on the mechanism of liquid film thickness recovery by the deposit of the liquid droplets entrained in the gas core to the liquid film by a mixing-vane (MV) attached to a grid spacer. The published data on the effects of the spacer with MV is limited (e.g. Damsohn and Prasser [1]; Feldhaus et al [2])
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