Comparison between wire mesh sensor and gamma densitometry void measurements in two-phase flows

Abstract

Wire mesh sensors (WMS) are fast imaging instruments that are used for gas–liquid and liquid–liquid two-phase flow measurements and experimental investigations. Experimental tests were conducted at Helmholtz-Zentrum Dresden-Rossendorf to test both the capacitance and conductance WMS against a gamma densitometer (GD). A small gas–liquid test facility was utilized. This consisted of a vertical round pipe approximately 1 m in length, and 50 mm internal diameter. A 16 × 16 WMS was used with high spatial and temporal resolutions. Air–deionized water was the two-phase mixture. The gas superficial velocity was varied between 0.05 m s−1 and 1.4 m s−1 at two liquid velocities of 0.2 and 0.7 m s−1. The GD consisted of a collimated source and a collimated detector. The GD was placed on a moving platform close to the plane of wires of the sensor, in order to align it accurately using a counter mechanism, with each of the wires of the WMS, and the platform could scan the full section of the pipe. The WMS was operated as a conductivity WMS for a half-plane with eight wires and as a capacitance WMS for the other half. For the cross-sectional void (time and space averaged), along each wire, there was good agreement between WMS and the GD chordal void fraction near the centre of the pipe.

Void fraction measurement of gas–liquid two-phase flow from differential pressure

“…When inlet air flow rate remains constant, differential pressure decreases with the decrease of inlet water flow rate. Differential pressure subtracted from two absolute pressure sensors was fed into mathematical model in equation (11). The change of air void fraction with air/water flow rate is illustrated in Figure 4.…”

“…Both ERT and WMS can measure gas void fraction without the consideration of friction loss in the two-phase flow, which provides an alternative approach to validate the gas void fraction model based on differential pressure. The void fraction measurement accuracy of ERT and WMS were discussed by Faraj [10] and Sharaf [11]. The principle behind ERT is to determine the electrical conductivity by measuring the voltage between the ERT electrodes mounted on the internal circumference of the conveying conduit.…”

Subatmospheric boiling study of the operation of a horizontal thermosyphon reboiler loop: Instability

“…The spatial resolution is 3 mm which also equals the pitch of the wires. The technique has been tested by carrying out simultaneous measurements with other techniques, i.e., using Electrical Capacitance Tomography , gamma-ray absorption (Sharaf et al, 2011), ultrafast X-ray tomography Zhang et al (2013) and found to produce good agreement between the instruments.…”

On the characteristics of the roll waves in gas–liquid stratified-wavy flow: A two-dimensional perspective

“…However, the data from the first WMS is used to calculate time-averaged flow quantities such as liquid holdup, liquid film height, wetted wall perimeter and interfacial surface area. The effect of the WMS intrusiveness on these quantities is considered minimal based on the comparisons of WMS data with other non-intrusive tomographic techniques reported in the literature [29][30][31][32][33][34][35]. The sensors are installed in the second run of the flow loop (Fig.…”