Ultrasonic Flowmeter for flow rates below 100 l/h |
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| R. Kramer, T. Dietz |
- Abstract:
- The paper describes an ultrasonic flow meter with an axial measuring path, which uses acoustic plane waves propagating through pipes with a sufficiently small diameter. The propagation of plane waves in a circular pipe depends on the pipe diameter and the wavelength of the acoustic signal. Therefor, the design of the meter has to consider the speed of sound for the gases intended to use, e.g. nitrogen, methane, hydrogen and any mixture of these. In order to measure low flow rates with small uncertainties, a great acoustic path length, i.e. a pipe with long length is advantageous. On the other hand, the signal attenuation increases proportionally with the length of the measuring pipe. The paper provides information about the basic conditions to reach plane waves in a pipe with small diameters.
The investigated prototype uses an inner pipe diameter of 4 mm and a path length of 320 mm. The ultrasonic transducers and the electronics are taken from a commercially available ultrasonic meter with two paths and a working frequency of 135 kHz. In this configuration, the signal quality is already very good with nitrogen under atmospheric conditions, but due to the acoustic attenuation, methane is only measurable with more than 2 bar absolute pressure. The results for nitrogen and methane show nearly linear behaviour over a flow range from 10 to 1,000 l/h. At the lower flow range of the meter the zero flow uncertainty is the limiting influence value. The protype has shown stabilities of lower than qz = 0.1 l/h. The meter may be used for quality assurance of test rigs such as checking small nozzles and as transfer standard for intercomparisons. - Download:
- IMEKO-TC9-2019-086.pdf
- DOI:
- -
- Event details
- IMEKO TC:
- TC9
- Event name:
- FLOMEKO 2019
- Title:
18th International Flow Measurement Conference 2019
- Place:
- Lisbon, PORTUGAL
- Time:
- 26 June 2019 - 28 June 2019