Development of capacitive sensor to determine void fraction in horizontal and vertical tubes

Qian, Hongliang

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https://hdl.handle.net/2142/99367 Copy

Description

Title

Development of capacitive sensor to determine void fraction in horizontal and vertical tubes

Author(s)

Qian, Hongliang

Issue Date

2017-12-05

Director of Research (if dissertation) or Advisor (if thesis)

Hrnjak, Predrag

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Void fraction
• Flow regimes
• Round tubes
• Quick closing valves
• Capacitance sensor

Abstract

This study first presents flow regimes and void fraction in horizontal and vertical tubes with R134a in the adiabatic condition and low mass flux range. Visualization results of horizontal flow patterns are compared to Wojtan-Ursenbacher-Thome flow regime map and have a good agreement. Both void fraction results for horizontal and vertical tubes are compared to some widely used correlations. Influences of tube orientation and mass flux on void fraction are discussed. At the same vapor quality condition, void fraction of horizontal tubes is larger than that of vertical tubes. Higher mass flux also results in larger void fraction compared that of lower mass flux. A new capacitive sensor aimed to measure void fraction is designed and built. With this capacitive sensor, characterizing flow patterns appear in low mass flux range and measuring void fraction for horizontal and vertical tubes can be achieved. Signal characterization for each flow pattern is proposed. To apply this sensor to more applications in HVAC&R systems, electrodes with different axial lengths are built together to be compared. The comparison of signals from them show the signals are independent on axial length. Due to the non-uniformity of the electric field between the electrodes of the sensor, a calibration procedure of void fraction measurement must be finished before utilizations. An experiment based (quick closing valves (QCV)) calibration procedure is conducted. Two calibrated curves for measuring void fraction in horizontal and vertical tubes are proposed. With calibrated curves, sensors with similar configurations can be directly utilized to measure void fraction in further studies.

Graduation Semester

2017-12

Type of Resource

text

Permalink

http://hdl.handle.net/2142/99367

Copyright and License Information

Copyright 2017 Hongliang Qian

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