Experimental and Theoretical Study of the Gas-water Two Phase Flow through a Conductance Multiphase Venturi Meter in Vertical Annular (wet Gas) Flow

Annular gas-liquid two phase flow is widely encountered in the nuclear industry. Various combinations of techniques have been employed in annular gas-liquid two phase flows to measure the flow parameters (e.g. liquid film thickness, gas volume fraction and the phase flow rates). One of the most useful techniques which has proven attractive for many multiphase flow applications is the electrical conductance technique. This paper presents an advanced Conductance Multiphase Venturi Meter (CMVM) which is capable of measuring the gas volume fractions at the inlet and the throat of the Venturi. A new model was investigated to measure the gas flow rate. This model is based on the measurement of the gas volume fractions at the inlet and the throat of the Venturi meter using a conductance technique rather than relying on the prior knowledge of the mass flow quality x. We measure conductance using two ring electrodes flush with the inner surface of the Venturi throat and two ring electrodes flush with the inner surface of the Venturi inlet. The basic operation of the electrical conductance technique in a multiphase flow is that the conductance of the mixture depends on the gas volume fraction in the water. An electronic circuit was built and calibrated to give a dc voltage output which is proportional to the conductance of the mixture which can then be related to the water film thickness in annular flow (and hence to the gas volume fraction). It was inferred from the experimental results that the minimum average percentage error of the predicted gas mass flow rates (i.e. -0.0428 %) can be achieved at the optimum gas discharge coefficient of 0.932.