6.3 Limitations with Water-Glycol Mixtures
There is little available data on the specific heat capacity (K factor) for water glycol mixes and there
is no practical method of determining the percentage of glycol in a system or the type of glycol in
use. The flow calculations are based on a Water/Ethylene glycol mix of 30%.
In practical terms the results should not be considered more than an approximation as:
The fluid speed of sound can vary between 1480 ms and 1578 ms
No temperature compensation curve is available for water/glycol mixes,
The percentage of Glycol can vary the specific heat capacity from 1.00 to 1.6 J/M3 * K
The type of glycol added can change the specific heat capacity and fluid speed of sound
considerably.
The Factory enabled user set-up of the application relies on the installer to set the correct operating
parameters, a considerable variation in results can be obtained from incorrectly set-up units.
6.4 Positioning
For accurate measurements, the UFM2/UBT must be installed at a position where the fluid flows
uniformly. Flow profile distortions can result from upstream disturbance such as bends, tees, valves,
pumps and other similar obstructions. To ensure a uniform flow profile, the unit must be mounted
away from any cause of flow disturbance.
As a guide, we suggest this is best achieved by ensuring there is a straight length of pipe upstream
of the transducers of at least 10 times the pipe diameter, and 5 times the pipe diameter on the
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