Measurement of Dynamic Liquid Distributions in a Fixed Bed Using Electrical Capacitance Tomography and Capacitance Wire-Mesh Sensor

Abstract

An intricate problem associated with fixed bed operation is liquid maldistribution, which denotes the fact that the liquid does not homogeneously flow through the bed. In a comparative study we evaluated two capacitance imaging methodsscapacitance wire-mesh sensor and electrical capacitance tomography (ECT)swith respect to their capability of measuring static and dynamic liquid holdup in a fixed bed. The capacitance wire-mesh sensor as an invasive instrument is able to disclose flow structures at higher spatial resolution and was therefore considered the reference instrument for liquid holdup measurement. We found that both methods predict dynamic liquid holdup in the column in a similar way with only small systematic deviation. The results therefore prove that noninvasive electrical capacitance tomography can reliably measure cross-sectional dynamic liquid holdup in a fixed bed, even with a simple and fast linear back projection reconstruction algorithm.

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.…”

Applications of tomography in bubble column and trickle bed reactors

“…Alternatively, it is possible to devise portable CT systems that can achieve relatively high spatial resolution and full tomographic reconstructions, though these may have other restrictions regarding the size of the equipment on which they can be applied (Bieberle et al, 2013;Kim et al, 2012). Electrical tomography techniques have also proven beneficial for studying trickle bed reactors owing to the high time resolution that can be achieved (Bieberle et al, 2010;H€ afeli, Hutter, Damsohn, Prasser, & Rudolf von Rohr, 2013;Llamas et al, 2008;Matusiak, Jose, Hampel, & Romanowski, 2010;Reinecke & Mewes, 1997). Measurements of the conductivity require the conductive phase to be continuous, which is not often the case in a trickle bed.…”

“…Wire mesh sensors provide a higher spatial resolution than capacitance tomography measurements; however, they are invasive so not suitable for all applications. In one recent study, wire mesh sensors were compared with capacitance tomography (Matusiak et al, 2010). Both techniques were shown to yield very similar measurements of the average liquid hold-up and were able to identify macroscopic heterogeneity of the liquid distribution.…”

Void Detection in Dielectric Films Using a Floating Network of Substrate-Embedded Electrodes

“…Wire mesh sensors can produce images of bubbles in real time through signal measurement at a higher frequency than the timescale of flow dynamics [9][10][11]. They have also proven useful for characterization of trickling flows in packed beds [12,13]. Comparisons to capacitance tomography applied to the cross section of 6.7 and 10 cm pipes [13,14] have demonstrated an advantage in spatial resolution with the wire mesh, for which the resolution corresponds to the electrode pitch.…”

“…They have also proven useful for characterization of trickling flows in packed beds [12,13]. Comparisons to capacitance tomography applied to the cross section of 6.7 and 10 cm pipes [13,14] have demonstrated an advantage in spatial resolution with the wire mesh, for which the resolution corresponds to the electrode pitch. Paranjape et al [15] demonstrated that bulk impedance could be used to characterize the void fraction of two-phase flow within a 0.78 mm square microchannel.…”