A liquid-independent volume flow measurement principle
article
A novel flow measurement principle is presented enabling non-intrusive volume flow measurements of liquids in the ml/min range. It is based on an opto-acoustical time-of-flight principle, where the time interval is recorded in which a thermal label travels a known distance through a flow channel. Big advantages are the insensitivity to temperature drift and the fact that user calibration is unnecessary. The paper presents a set of physics-based criteria that define the working range of the measurement principle. A prototype of a flow meter was developed and evaluated in a test rig with flows of water, isopropyl alcohol (IPA) and mixtures of both liquids. Pure water and IPA flows of 0.1 to 2 ml min<sup>-1</sup> were measured and found to coincide with the reference flows within 4%. The root-mean-square (RMS) value of the fluctuations did not exceed 3%. For flows of 2 ml min<sup>-1</sup> the limited power of the laser source caused deviations of 7% with 5% fluctuations. Finally, flow measurements were done in water-IPA mixtures with concentrations between 10% and 90%-w/w at a flow rate of 15 g h<sup>-1</sup> (≈0.3 ml min<sup>-1</sup>). The ratio of measured and reference flow appeared to be 4% to 5% below the theoretical value, but it was hardly a function of mixture composition. Hence, liquid independence of the measurement principle was proven. © 2010 IOP Publishing Ltd.
Topics
A-thermalFlow channelsIsopropyl alcoholslaboratory equipment applicationsLaboratory equipmentsLaser sourcesMeasurement principleMixture compositionsNon-intrusivePhysics-basedPure waterRoot mean squaresTemperature driftsTest rigsTheoretical valuesTime intervalTime of flightUser calibrationVolume flowWorking rangeFlowmetersLiquidsMeasurementsMixturesPosition controlFlow measurement
TNO Identifier
364410
ISSN
09570233
Source
Measurement Science and Technology, 21(7)
Article nr.
074001
Collation
7 p.
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