Flow Resistance (IL)
Hydraulic resistance.
blockType: AcausalFoundation.IsothermalLiquid.Elements.FlowResistance
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Description
Block Flow Resistance (IL) It represents a pressure drop in an isothermal fluid line. The pressure drop is proportional to the square of the mass flow. The proportionality coefficient is determined based on the entered parameters of the nominal operating mode.
Use this unit when only the flow rate and pressure drop are known for the component. This block is useful for representing complex components where it is difficult to determine theoretical pressure losses from geometric constructions.
It is assumed that the volume of liquid inside the resistance is negligible. Then the mass flow rate at the entrance through one port should exactly equal the mass flow rate at the exit through the other port.:
where and They are defined as mass expenses through ports A and B, respectively.
The pressure drop is assumed to be proportional to the square of the mass flow rate. The square of the mass flow is linearized in a small region of the laminar flow near zero flow, resulting in
where
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and — pressure at ports A and B, respectively;
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— threshold value of mass flow rate for laminar-turbulent transition;
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— proportionality coefficient:
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where — parameter value Nominal pressure drop and — parameter value Nominal mass flow rate.
Ports
Conserving
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A
—
inlet or outlet
Isothermal liquid
Details
The isothermal liquid port is an inlet or outlet of hydraulic resistance. This unit has no internal orientation.
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B
—
inlet or outlet
Isothermal liquid
Details
The isothermal liquid port is an inlet or outlet of hydraulic resistance. This unit has no internal orientation.
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Parameters
Parameters
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Nominal pressure drop —
pressure drop at a known operating mode
Pa | uPa | hPa | kPa | MPa | GPa | kgf/m^2 | kgf/cm^2 | kgf/mm^2 | mbar | bar | kbar | atm | ksi | psi | mmHg | inHg
Details
The pressure drop from the inlet to the outlet at a known operating mode. The unit uses the nominal parameters to calculate the proportionality coefficient between the pressure drop and the mass flow rate.
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| Default value |
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| Evaluatable |
Yes |
#
Nominal mass flow rate —
mass flow rate at a known operating mode
kg/s | kg/hr | kg/min | g/hr | g/min | g/s | t/hr | lbm/hr | lbm/min | lbm/s
Details
Mass flow rate at a known operating mode. The unit uses the nominal parameters to calculate the proportionality coefficient between the pressure drop and the mass flow rate.
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| Default value |
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| Evaluatable |
Yes |
# Fraction of nominal mass flow rate for laminar flow — ratio of threshold flow to nominal mass flow
Details
The ratio of the threshold mass flow to the nominal mass flow. The unit uses this parameter to calculate the threshold mass flow rate — and, ultimately, to set linearization limits for differential pressure.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |