TY - JOUR
T1 - Sensitivity studies on the multi-sensor conductivity probe measurement technique for two-phase flows
AU - Worosz, Ted
AU - Bernard, Matt
AU - Kong, Ran
AU - Toptan, Aysenur
AU - Kim, Seungjin
AU - Hoxie, Chris
N1 - Funding Information:
This research was performed in part under appointment (first author) to the Rickover Fellowship Program in Nuclear Engineering sponsored by Naval Reactors Division of the U.S. Department of Energy .
Publisher Copyright:
© 2016 Elsevier B.V.
PY - 2016/12/15
Y1 - 2016/12/15
N2 - The objective of this study is to advance the local multi-sensor conductivity probe measurement technique through systematic investigation into several practical aspects of a conductivity probe measurement system. Firstly, signal “ghosting” among probe sensors is found to cause artificially high bubble velocity measurements and low interfacial area concentration (ai) measurements that depend on sampling frequency and sensor impedance. A revised electrical circuit is suggested to eliminate this artificial variability. Secondly, the sensitivity of the probe measurements to sampling frequency is investigated in 13 two-phase flow conditions with superficial liquid and gas velocities ranging from 1.00–5.00 m/s and 0.17–2.0 m/s, respectively. With increasing gas flow rate, higher sampling frequencies, greater than 100 kHz in some cases, are required to adequately capture the bubble number frequency and ai measurements. This trend is due to the increase in gas velocity and the transition to the slug flow regime. Thirdly, the sensitivity of the probe measurements to the measurement duration as well as the sample number is investigated for the same flow conditions. Measurements of both group-I (spherical/distorted) and group-II (cap/slug/churn-turbulent) bubbles are found to be relatively insensitive to both the measurement duration and the number of bubbles, as long as the measurements are made for a duration long enough to capture a collection of samples characteristic to a given two-phase flow system (or a statistical ensemble). Fourthly, investigation into the orientation of a double-sensor probe in the pipe indicates that the sensors should be oriented parallel to the pipe wall to ensure symmetric bubble velocity measurements. Lastly, Monte Carlo simulations are performed to study the effects of the axial (s) and lateral (d) probe sensor separation distances. In addition to previous criteria on the ratio of s to the bubble diameter, it is found that s/d should be greater than four to minimize errors in the measured bubble velocity.
AB - The objective of this study is to advance the local multi-sensor conductivity probe measurement technique through systematic investigation into several practical aspects of a conductivity probe measurement system. Firstly, signal “ghosting” among probe sensors is found to cause artificially high bubble velocity measurements and low interfacial area concentration (ai) measurements that depend on sampling frequency and sensor impedance. A revised electrical circuit is suggested to eliminate this artificial variability. Secondly, the sensitivity of the probe measurements to sampling frequency is investigated in 13 two-phase flow conditions with superficial liquid and gas velocities ranging from 1.00–5.00 m/s and 0.17–2.0 m/s, respectively. With increasing gas flow rate, higher sampling frequencies, greater than 100 kHz in some cases, are required to adequately capture the bubble number frequency and ai measurements. This trend is due to the increase in gas velocity and the transition to the slug flow regime. Thirdly, the sensitivity of the probe measurements to the measurement duration as well as the sample number is investigated for the same flow conditions. Measurements of both group-I (spherical/distorted) and group-II (cap/slug/churn-turbulent) bubbles are found to be relatively insensitive to both the measurement duration and the number of bubbles, as long as the measurements are made for a duration long enough to capture a collection of samples characteristic to a given two-phase flow system (or a statistical ensemble). Fourthly, investigation into the orientation of a double-sensor probe in the pipe indicates that the sensors should be oriented parallel to the pipe wall to ensure symmetric bubble velocity measurements. Lastly, Monte Carlo simulations are performed to study the effects of the axial (s) and lateral (d) probe sensor separation distances. In addition to previous criteria on the ratio of s to the bubble diameter, it is found that s/d should be greater than four to minimize errors in the measured bubble velocity.
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U2 - 10.1016/j.nucengdes.2016.10.046
DO - 10.1016/j.nucengdes.2016.10.046
M3 - Article
AN - SCOPUS:85002715367
SN - 0029-5493
VL - 310
SP - 552
EP - 563
JO - Nuclear Engineering and Design
JF - Nuclear Engineering and Design
ER -