| 摘要 |
A nonintrusive instrument for measuring the volume flowrate of, and the speed of sound in, an arbitrary fluid in a pipe, tube or duct. The sound speed measured is that of a stationary fluid even though the measurement is made while the fluid may be flowing. These measurements are absolute in that they require no flow calibration, and they are independent of the composition of the fluid and its temperature. For a flowing, approximately perfect gas or gas mixture, given the average molecular weight and ratio of specific heats, the instrument measures the temperature. Also, given an independent measurement of the pressure, it measures the gas density and mass flowrate. The measurement can be made in a high noise level environment even when the temperature varies rapidly over a large range. The instrument uses sound whose wavelength is much longer than the diameter of the pipe, tube or duct. As a result, the temperature and flow measurements are independent of the profiles of those quantities across the pipe profiles.
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