Temperature Compensation for Conductivity-Based Phase Fraction Measurements with Wire-Mesh Sensors in Gas-Liquid Flows of Dilute Aqueous Solutions

Abstract

Wire-mesh sensors are well-established scientific instruments for measuring the spatio-temporal phase distribution of two-phase flows based on different electrical conductivities of the phases. Presently, these instruments are also applied in industrial processes and need to cope with dynamic operating conditions increasingly. However, since the quantification of phase fractions is achieved by normalizing signals with respect to a separately recorded reference measurement, the results are sensitive to temperature differences in any application. Therefore, the present study aims at proposing a method to compensate temperature effects in the data processing procedure. Firstly, a general approach is theoretically derived from the underlying measurement principle and compensation procedures for the electrical conductivity from literature models. Additionally, a novel semi-empirical model is developed on the basis of electrochemical fundamentals. Experimental investigations are performed using a single-phase water loop with adjustable fluid temperature in order to verify the theoretical approach for wire-mesh sensor applications and to compare the different compensation models by means of real data. Finally, the preferred model is used to demonstrate the effect of temperature compensation with selected sets of experimental two-phase data from a previous study. The results are discussed in detail and show that temperature effects need to be handled carefully—not merely in industrial applications, but particularly in laboratory experiments.

Towards Real-Time Analysis of Gas-Liquid Pipe Flow: A Wire-Mesh Sensor for Industrial Applications

“…Furthermore-and much more seriously-pure single-phase liquid flow is hardly obtained at saturation temperature, which is usually the region of interest for two-phase flow measurements. Therefore, the temperature compensation method proposed by [22] was implemented in the real-time data processing unit of the indWMS system. The adapted formulation for the quantification of phase fractions reads…”

“…Here, F denotes the temperature compensation factor that is calculated on the basis of the ISO 7888 model [23] using the temperatures of the reference and two-phase measurement, T re f and T, respectively, cf. [22]. Hence, the single-phase reference matrix U liquid i,j recorded at an arbitrary reference temperature T re f can be converted to a reference matrix at temperature T corresponding to the present conditions of the two-phase measurement U meas i,j,k .…”

Combined Finite Element and Electronic Circuit Model of a Wire-Mesh Sensor

“…The gray pixels mean that the measured signal is greater than the calibration data (when the sensor is fully filled with tap water). This nonlinear effect is commonly attributed to temperature drifts between calibration and measured signals [35]. Based on numerical and experimental observations, it was found that such nonlinearities may also occur when a low conductivity component is passing through a crossing-point [27].…”

“…This problem can be corrected by experimental correlations, as proposed by Manera et al [34]. More recently, Wiedemann et al [35] provided the theoretical basis for temperature compensation and suggested sub-models that are suitable for different types of fluids.…”

Improvement of wire-mesh sensor accuracy via adapted circuit design and integrated energy loss measurement

“…However, the effectiveness of this approach is reduced if the flow is composed of dispersed phases. As detailed in [11], one of the causes of negative void fraction may be associated with temperature changes of the flow. Hence, a theoretical basis for temperature compensation and sub-models suitable for different types of fluids were provided to address this problem.…”