The use of capacitance sensors for measuring liquid film thickness or phase concentration in two-phase flow has gained popularity in recent years. In designing such sensors, there are many issues which must be considered in order to optimize performance: desired temporal and spatial resolution, two-phase flow regime, permittivity of the phases, duct geometry, electrical shielding, and temperature variation in the flow field. These issues are discussed, and the design of a 12.7 mm square cross section capacitance sensor which measures liquid film thickness in either stratified are annular two-phase flow is presented. Using a composite material analysis and an effective permittivity ratio, predictive relations for capacitance as a function of liquid film thickness have been derived for stratified and annular film patterns. The analysis eliminates the need for calibrating the sensor for stratified and annular flow regimes. Optical measurements of liquid film thickness using a high resolution CCD camera are compared against those using the capacitance sensor in conjunction with the predictive relations. The sensor was tested on a bench top for a stratified film pattern with no flow and two different electrode configurations (upwards and side configurations) using FC-87, a low-permittivity (εr = 1.72) dielectric fluid. The standard deviations between the film thicknesses measured optically and those predicted using the capacitance sensor and analysis are 0.014 and 0.019 mm for the respective upward and side electrode configurations. The sensor was also implemented in a vertical flow boiling facility, which uses FC-72 (εr = 1.75) as the working fluid. Time-averaged film thicknesses measured using the capacitance sensor are compared against ensemble-averaged measurements using the CCD camera for annular vertical upflow and downflow. The upflow and downflow standard deviations are 0.17 and 0.093 mm, respectively. As expected, the agreement for vertical flow is not as good as that for the horizontal no-flow case, because large fluctuations in film thickness are characteristic of annular two-phase flow, and the uncertainty of the photographic measurement is increased.
Skip Nav Destination
Article navigation
March 1997
Research Papers
A Capacitance Sensor for Two-Phase Liquid Film Thickness Measurements in a Square Duct
G. E. Thorncroft,
G. E. Thorncroft
Department of Mechanical Engineering, University of Florida, Gainesville, FL
Search for other works by this author on:
J. F. Klausner
J. F. Klausner
Department of Mechanical Engineering, University of Florida, Gainesville, FL
Search for other works by this author on:
G. E. Thorncroft
Department of Mechanical Engineering, University of Florida, Gainesville, FL
J. F. Klausner
Department of Mechanical Engineering, University of Florida, Gainesville, FL
J. Fluids Eng. Mar 1997, 119(1): 164-169 (6 pages)
Published Online: March 1, 1997
Article history
Received:
October 9, 1995
Revised:
July 22, 1996
Online:
December 4, 2007
Citation
Thorncroft, G. E., and Klausner, J. F. (March 1, 1997). "A Capacitance Sensor for Two-Phase Liquid Film Thickness Measurements in a Square Duct." ASME. J. Fluids Eng. March 1997; 119(1): 164–169. https://doi.org/10.1115/1.2819103
Download citation file:
Get Email Alerts
Related Articles
Dielectrophoretically-Assisted Electrohydrodynamic-Driven Liquid Film Flow Boiling in the Presence and Absence of Gravity
J. Heat Mass Transfer (March,2023)
Flow Visualization and Local Measurement of Forced Convection Heat Transfer in a Microtube
J. Heat Transfer (March,2010)
Droplet Entrainment From a Shear-Driven Liquid Wall Film in Inclined Ducts: Experimental Study and Correlation Comparison
J. Eng. Gas Turbines Power (October,2002)
Related Proceedings Papers
Related Chapters
Thermal Design Guide of Liquid Cooled Systems
Thermal Design of Liquid Cooled Microelectronic Equipment
Comparison of the Availability of Trip Systems for Reactors with Exothermal Reactions (PSAM-0361)
Proceedings of the Eighth International Conference on Probabilistic Safety Assessment & Management (PSAM)
Liquid Cooled Systems
Thermal Management of Telecommunications Equipment