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Description / Abstract:
INTRODUCTION
This Technical Report discusses the existing definitions of "wet
gas flow" and provides suggested definitions for use. Common wet
gas flowmetering terminologies, principles, and limitations of the
available wet gas meter technologies are also discussed.
Wet gas flowmetering is an important flow measurand in many
industries. If a relatively small volume of liquid is present in a
gas it is generally said to be "wet." Wet gas flows are not new
occurrences in industry (e.g., wet saturated steam flows have been
produced since the industrial revolution) but it is only recently
that attempts to meter wet gas flows (e.g., by the oil and gas
industry) with improved and a perhaps better understood
uncertainties have been made. Measurement techniques are being
continuously developed but accepted single-phase (dry) gas meter
uncertainty is as yet not attainable when a wet gas flow is
present. Due to the difficulties involved in wet gas metering it is
unlikely that the same level of uncertainty seen with single-phase
gas metering will be achieved in the foreseeable future.
There are two distinct wet gas-metering situations:
(a) Where some flow rate knowledge is initially known, for
example,
(1) the total mass flow rate is known (such as in a closed cycle
system, e.g., a steam power cycle) and either the ratio of
liquid-to-gas flow rates or one of the phase flow rates is required
to be metered.
(2) one phase flow rate is known (from some other means) and the
other phase flow rate is to be metered.
(b) No flow rate information is known (e.g., unprocessed wet
natural gas flows) and either or both the liquid and gas phase flow
rates are required to be metered. This is a considerably more
difficult metering situation as extra information is required and
meters being developed for this situation are considered to be at
the cutting edge of fluid flowmetering technology.
NOTE: Most of the current technologies ignore the effects of
multi-component liquids present in wet gas flows. However, some
metering systems are designed to estimate the different quantities
of liquid components in a wet gas flow.