The design and performance of a capacitance sensor for two-phase flow concentration measurements in a square duct

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:435799

Thorncroft, G E; Klausner, J F ^[1]

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1. Univ. of Florida, Gainesville, FL (United States). Dept. of Mechanical Engineering

The use of capacitance sensors for measuring phase concentrations 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: two-phase flow regime, permittivity of the phases, duct geometry, electrical shielding, desired spacial resolution of film thickness, and temperature variation in the flow field. These design issues are discussed and are used to optimize the design of a capacitance sensor which is used to measure vapor volume fraction in annular, two-phase vertical upflow and downflow in a square duct. The sensor was tested and implemented in a 12.7 mm square duct mounted in a flow boiling facility containing FC-72, a low permittivity dielectric fluid ({epsilon}{sub r} = 1.75). Using analytical modeling, an adjustable-length, parallel-plate design was developed and refined to achieve good sensitivity to flow conditions. The sensor output was calibrated for a stratified liquid film using optical measurements of liquid film thickness obtained from a high resolution CCD camera. The measured film thickness agrees well with that predicted, and the stratified liquid calibration curves are used to predict the liquid film thickness for annular flow.

• OSTI ID: 435799
• Report Number(s): CONF-951135--; ISBN 0-7918-1755-5
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
44 INSTRUMENTATION
INCLUDING NUCLEAR AND PARTICLE DETECTORS
CALIBRATION
CAPACITANCE
CONCENTRATION RATIO
DESIGN
MEASURING INSTRUMENTS
PERFORMANCE
TWO-PHASE FLOW
VOID FRACTION