functionpowerLaw05
Extends from Modelica.Icons.Function (Icon for functions).
Information
This model describes the mass flow rate and pressure difference relation of an orifice in the form
V̇ = C sign(Δp) |Δp|m
where V̇ is the volume flow rate, C > 0 is a flow coefficient Δ p is the pressure drop and m =0.5 is a constant flow coefficient. The equation is regularized for |Δp| < Δpt, where Δpt is a parameter.
The model is used for the interzonal air flow models. It is identical to Buildings.Airflow.Multizone.BaseClasses.powerLawFixedM but it is optimized for the common case of m=0.5.
Implementation
For |Δp| < Δpt, the equation is regularized so that it is twice continuously differentiable in Δp, and that it has an infinite number of continuous derivatives in k.
If m, and therefore also a, b, c and d, change with time, then it is more convenient and efficient to use Buildings.Airflow.Multizone.BaseClasses.powerLaw.
If m is constant but different from 0.5, use Buildings.Airflow.Multizone.BaseClasses.powerLawFixedM.
Inputs
| Type | Name | Default | Description |
|---|---|---|---|
| Real | C | Flow coefficient, C = V_flow/ sqrt(dp) | |
| Modelica.Units.SI.PressureDifference | dp | Pressure difference | |
| Real | a | Polynomial coefficient | |
| Real | b | Polynomial coefficient | |
| Real | c | Polynomial coefficient | |
| Real | d | Polynomial coefficient | |
| Modelica.Units.SI.PressureDifference | dp_turbulent | Pressure difference where regularization starts | |
| Modelica.Units.SI.PressureDifference | sqrt_dp_turbulent | Square root of dp_turbulent (exposed as it usually is a parameter expression) |
Outputs
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.VolumeFlowRate | V_flow | Volume flow rate |
Revisions
-
September 19, 2025, by Michael Wetter:
First implementation.
This is for IBPSA, #2043.