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Research Papers: Techniques and Procedures

Theoretical, Numerical, and Experimental Study of the Time of Flight Flowmeter

[+] Author and Article Information
Ian Gaskin

 Servomex Ltd, Jarvis Brook, Crowborough, East Sussex, TN6 3FB, EnglandIGaskin@servomex.com

Evgeniy Shapiro1

Fluid Mechanics and Computational Science, School of Engineering,  Cranfield University, Cranfield, Bedfordshire, MK43 0AL, Englande.shapiro@cranfield.ac.uk

Dimitris Drikakis

Fluid Mechanics and Computational Science, School of Engineering,  Cranfield University, Cranfield, Bedfordshire, MK43 0AL, Englandd.drikakis@cranfield.ac.uk

1

Corresponding author.

J. Fluids Eng 133(4), 041401 (May 03, 2011) (8 pages) doi:10.1115/1.4003852 History: Received November 05, 2009; Revised November 04, 2010; Published May 03, 2011; Online May 03, 2011

Time-of-flight flowmeters offer advantages over other flowmeter types since these are less sensitive to the physical properties of the fluid. However, calibration of the flowmeter for a particular working fluid is still required. A flowmeter that does not require re-calibration with different fluids is desirable in many applications. This paper investigates the performance of a device that measures the time of flight of a heat pulse in a gas stream to determine the flow rate in a pipe. A fusion of the theoretical, experimental, and numerical data is used to suggest a gas-independent correlation function between the response time and flow rate. In particular, the numerical data augmented by the theoretical analysis to account for the wire response time is validated against experimental data and used to further enhance the experimental data set. Nitrogen, helium, and tetrafluoroethane (R134a) are investigated, as these gases provide a wide range of physical and thermodynamic properties. Simulated results match the trends of experimental data well and allow good qualitative analysis. The results also show that using detected pulse width information together with the time of flight can yield a 20% reduction in the errors due to gas type than by using time of flight data alone. This gives a relatively gas-independent function over a dynamic range of 1:400.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Diagram showing time of flight principle using a heat pulse

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Figure 2

Longitudinal cross sections of 55 mm spaced experimental device

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Figure 3

Control circuit diagram

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Figure 4

Computational domain schematic (dimensions in mm)

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Figure 5

Comparison of measured flow speed and actual bulk speed; log scale

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Figure 6

Gas temperature pulse at low flow rates

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Figure 7

Gas temperature pulse at high flow rates

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Figure 8

Simulation/experiment comparisons

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Figure 9

Typical detected pulse characteristics

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Figure 10

Error comparison for tof and ti data

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