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Description / Abstract:
This Standard applies only to the steady flow of single-phase
gases and gas mixtures and applies only to bellmouth inlet
flowmeters in which the flow remains subsonic throughout the
measuring section and the flow is steady or varies only slowly with
time. It also addresses procedures by which calibration of the
device can be made to allow for application with consistent
conclusions and within known limits of uncertainty.
Bellmouth inlet flowmeters should be used only within the limits
for which a given unit is tested, or if additional uncertainty can
be tolerated, over a range within which extrapolation is
reliable.
This Standard outlines the general geometry and method of use of
bellmouth inlet flowmeters to determine the mass or volumetric flow
rate of the gas or gas mixture flowing through the device. It also
gives necessary information for calculating the flow rate and its
associated uncertainty.
A bellmouth inlet flowmeter is a device that provides flow
conditioning and flow measurement whose inlet is located or
positioned in a large reservoir or supply source. The reservoir can
be outside ambient, room, or plenum conditions depending on the
application. The bellmouth inlet flowmeter is also referred to as
an airbell, nozzle with zero beta ratio, borda tube, etc. Typical
geometry consists of a convergent inlet followed by a constant
throat area. This flowmeter is a differential pressure type device
that allows determination of the flow rate from the differential
pressure between the total pressure and static pressure at a single
specified axial location in the constant area throat of the
bellmouth.
Purpose
The purpose of this Standard is to provide guidance and
recommendations for fluid flow measurement of gaseous applications
using the bellmouth inlet flowmeter.
This Standard addresses the following:
(a) principle of operation
(b) design parameters and considerations
(c) calibration methods and procedures
(d) instrumentation and calculation methods
(e) installation requirements and considerations
(f) measurement uncertainty