BELL PROVER: Used to verify the accuracy of a gas meter, it provides a volume of air that may be predetermined by calculated temperature, pressure and the effective diameter of the bell.

CRITICAL FLOW FACTOR: A parameter dependent on the thermophysical properties of a gas at the throat of a nozzle. Used to calibrate flowmeters in gas flow measurement.

CRITICAL FLOW VENTURI: A flow measurement standard and flowmeter that can be used as a calibration standard for gas flowmeters or any flow measurement device. Also known as Sonic Nozzle.

DEVICE UNDER TEST: A term commonly used to refer to a manufactured product undergoing testing. Also known as Unit Under Test.

FLOW REGIME: The physical geometry exhibited by a multiphase flow in a conduit.

GAS CONSTANT: The constant of proportionality, which relates the pressure and the volume of a quantity of gas to the absolute temperature.

MASS FLOWRATE: The mass of a substance that passes through a given surface per unit time.

METER FACTOR: A factor used with a meter to correct for ambient conditions, for example, the factor for a fluid-flow meter to compensate for such conditions as liquid temperature change and pressure shrinkage.

MULTIPHASE FLOW: A mixture of two or more distinct phases (such as oil, water and gas) flowing through a closed conduit.

ORIFICE PLATE: A disk, with a hole, placed in a pipeline to constrict the flow. Measuring the pressure differential across the constriction gives the flowrate.

PROOF TESTING: Verifies that the device or structure complies with its specification and safety requirements.

REFERENCE METER: Often used in the practical calibration of flowmeters, it is an instrument with a well-known calibration history and normally with an uncertainty of measurement significantly superior to the flowmeter under calibration.

REYNOLDS NUMBER: A dimensionless number which is significant in the design of a model of any system in which the effect of viscosity is important in controlling the velocities or the flow pattern of a fluid.

SONIC NOZZLE: A flow measurement standard and flowmeter that can be used as a calibration standard for gas flowmeters or any flow measurement device.

TWO-PHASE FLOW: A mixture of two distinct phases (such as oil, water or gas) flowing through a closed conduit.

UNCERTAINTY: The estimated amount or percentage by which an observed or calculated value may differ from the true value.

The terms and definitions for this issue’s Word Search were abstracted from a glossary produced by NEL (a subsidiary of TÜV SÜD), a technical consultancy, research, testing, flow measurement, and program management services firm.