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FC-21 Flow Computer
7.4 Calculating the Expansion Factor
The liquid density is a function of the flowing temperature for many fluids. This unit
solves an equation which represents this physical property of the fluid.
The information which the unit uses to describe the fluid is entered by the user in
the following variables: Reference Temperature, Reference Density, Expansion
Factor.
This information is available for many fluids in one or more of the following forms:
Fluid Specific Gravity vs. Temp. Table
Specific Gravity vs. Temp. Graph
Fluid Density vs. Temp. Table
Fluid Density vs. Temp. Graph
Begin by obtaining one of the fluid properties for the fluid you are using from
available manufacturers information or Engineering Handbooks. In some cases this
information is listed on the Material Safety Data Sheet for the fluid.
Two temperature-specific gravity pairs will be required to compute the temperature
coefficient.
The reference temperature is simply chosen by the user. Common reference
temperatures are 60
°
F or 15
°
C.
However, for cryogenic fluids, the normal boiling point may also be used. In some
cases the fluid data may list properties at 100
°
F, this temperature may also be used
as the reference temperature.
The reference temperature should be chosen so that it is in the application
temperature range. i.e. application temperature range -10 to 120
°
F, reference
temperature of 60
°
F chosen.
Enter the reference temperature you have chosen at this point.
The reference specific gravity corresponds to the fluid SPECIFIC GRAVITY at the
reference temperature chosen.
You may convert the fluid density information to specific gravity if it is in units other
than specific gravity. Use EQ1.
EQ1.
Spec.Grav. = Density of Fluid / Density of Water
Given the reference temperature, reference specific gravity, a second temp. and a
second Spec.Grav., the Expansion Factor (C Factor) can be computed as follows:
EQ2.
Used for Liquid Mass and Corrected Volume Equations
1 - (Spec.Grav.2 / Ref.Spec.Grav.)
Temp.2 - Ref.Temp
√
[
]
x 1,000,000
C =
Given the reference temperature, reference density, a second temp. and a second
density, the Expansion Factor (C Factor) can be computed as follows:
EQ3.
Used for Liquid Mass and Corrected Volume Equations
Calculating
Expansion Factor
Expansion Factor
Equations
1 - (Dens.2 / Ref.Dens.)
Temp.2 - Ref.Temp
√
[
]
x 1,000,000
C =
