An Impedance Cross Correlation (ICC) Device For Measuring Solids Velocity And Volume Fraction Profiles In Solid-Water Flows

Multiphase flow is the simultaneous flow of two or more
phases, in direct contact, in a given system. It is important
in many fields of chemical and process engineering and in
the oil industry, e.g. in production wells and in sub-sea
pipelines. The behavior of the flow will depend on the
properties of the constituents, the flows and the geometry
of the system.
Upward inclined solids-liquid flows are sometimes
encountered in the process industries for example in water
treatment processes and in oil well drilling operations.
Measurements of the local solids volume fraction
distribution and the local axial solid velocity distribution
are important, for example, in measuring the solids
volumetric flow rate.
This study presents a non-intrusive Impedance Cross-
Correlation (ICC) device to measure the local solids volume
fraction distribution and the local axial solids velocity
distribution in upward inclined solids-water flows in which
these distributions are highly non-uniform.
The ICC device comprises a non-conductive pipe section of
80mm internal diameter fitted with two arrays of electrodes
at planes, A and B, separated by an axial distance of
50mm. At each plane, eight electrodes are equispaced over
the internal circumference of the pipe. A control system
consisting of a microcontroller and analogue switches is
used such that, for planes A and B, any of the eight
electrodes can be configured as an ‘excitation electrode’
(V+), a ‘virtual earth measurement electrode’ (ve) or an
‘earth electrode’ (E) so that different regions of the flow
cross section can be interrogated. Conductance signals
from planes A and B are then cross correlated to yield the
solids velocity in the region of flow under interrogation.
Experiments were carried out in water-solids flows in a flow
loop with an 80 mm inner diameter, 1.68m long Perspex
test section which was inclined at 30o to the vertical. The
most significant experimental result is that, at the upper
side of the inclined pipe, the measured solids velocity is
positive (i.e. in the upward direction), whilst at the lower
side of the inclined pipe the measured local axial solids
velocity is negative (i.e. in the downward direction). This
shows quantitative agreement with previous work carried
out using intrusive local probes to measure the solids
velocity profile. The study also shows qualitative agreement
with high speed film of the flow.
It is believed that this method of velocity profile
measurement is much simpler to implement than dualplane
electrical resistance tomography (ERT).