ASME MFC-21.1:2015 pdf download

ASME MFC-21.1:2015 pdf download.Measurement of Gas Flow by Means of Capillary Tube Thermal Mass Flowmeters and Mass Flow Controllers
1 SCOPE
This Standard establishes common terminology and provides guidelines for the quality, description, princi- ple of operation, selection, operation, installation, and flow calibration of capillary tube thermal mass flow- meters and mass flow controllers for the measurement and control of the mass flow rate of gases. The content of this Standard applies to single-phase flows of pure gases and gas mixtures of known composition.
2 TERMINOLOGY, SYMBOLS, AND REFERENCES
2.1 Definitions From MFC-1M accuracy (of measurement): the extent to which a given measurement agrees with a reference for that measure- ment, often used by manufacturers to express the per- formance characteristics of a device. NOTE: Accuracy is not the same as uncertainty [see uncertainty (of measurement)]. bell prover: volumetric gaging device used for gases that consists of a stationary tank containing a sealing liquid into which is inserted a coaxial movable tank (the bell), the position of which may be determined. The volume of the gas-tight cavity produced between the movable tank and the sealing liquid may be deduced from the position of the movable tank. calibration: the experimental determination of the rela- tionship between the quantity being measured and the device that measures it, usually by comparison with a standard, then (typically) adjustment of the output of a device to bring it to a desired value, within a specified tolerance, for a particular value of the input. critical flow devices: a flowmeter in which a critical flow is created through a primary differential pressure device (fluid at sonic velocity in the throat). A knowledge of the fluid conditions upstream of the primary device and of the geometric characteristics of the device and the pipe suffice for the calculation of the flow rate.flow rate: the quantity of fluid flowing through a cross section of a pipe per unit of time. fully developed velocity distribution: a velocity distribution, in a straight length of pipe that has zero radial and azimuthal fluid velocity components and an axisymme- tric axial velocity profile that is independent of the axial position along the pipe. laminar flow: flow under conditions where forces due to viscosity are more significant than forces due to inertia, and where adjacent fluid particles move in essentially parallel paths. NOTES: (1) Laminar flow may be unsteady but is completely free from turbulent mixing. (2) Laminar flow in a pipe follows the Poiseuille law. Mach number: the ratio of the mean axial fluid velocity to the velocity of sound in the fluid at the considered temperature and pressure. mass flow rate: mass of fluid-per-unit-time flowing through a cross section of a pipe. piston prover: volumetric gaging device consisting of a straight section of pipe with a constant cross section and of known volume. The flow rate is derived from the time taken by a piston, with free or forced displacement, to travel through this section. rangeability: the rangeability of a flowmeter is the ratio ofthe maximum to minimumflow rates (Reynolds num- bers, velocities, etc.) in the range over which the meter meets a specified and acceptable uncertainty, also called turndown. repeatability (qualitative): closeness of agreement among a series of results obtained with the same method on identical test material, under the same conditions (same operator, same apparatus, same laboratory, and short intervals of time). NOTE: The representative parameters of the dispersion of the population that may be associated with the results are qualified bythe term repeatability. Examples are standard deviationofrepeat- ability and variance of repeatability.