modelControlValve
Control valve
Information
## Copyright © EDF 2002 - 2026
## ThermoSysPro Version 4.2
This component model is documented in Sect. 13.8 of the ThermoSysPro book.
# Control valve
Control valves are used to control the fluid flow, pressure or liquid level. They are usually automatically driven by an electrical, hydraulic or pneumatic actuator. A control valve is the critical part of any control loop. For water/steam, the flow regime is single-phase or homogeneous two-phase flow.
Following assumptions are made in this model:
- the fluid is subsonic and incompressible.
- the volume inside the valve is negligible, and so is its inertia.
If the control valve switches only between fully open and fully closed positions, in negligible time, the [switch valve](modelica://ThermoSysPro.WaterSteam.PressureLosses.SwitchValve) can be used instead.
## Modelica component model
The equations mentioned below are implemented in the component *ControlValve*, located in the *WaterSteam.PressureLosses* sub-library.
This component has 3 connectors:
- C1: fluid inlet,
- C2: fluid outlet,
- Ouv: valve opening.
## Nomenclature
| Symbol| Description| Unit| Definition| Modelica name |
| :----------------------------------------------- | :------------------------------------------------------------------------------------- | :------------------------------- | :-------------------------------- | :----------- |
| \\(C\_{\mathrm{v}}\\)| Flow coefficient of the valve| U.S. [USG/min]|| Cvmax |
| \\(h\\)| Fluid specific enthalpy| \\(\mathrm{J} / \mathrm{kg}\\)|| h |
| \\(m\\)| Fluid mass flow rate| \\(\mathrm{kg} / \mathrm{s}\\)|| Q |
| \\(P\_{\mathrm{i}}\\)| Fluid pressure at the valve inlet| \\(\mathrm{Pa}\\)|| C1.P |
| \\(P\_{\mathrm{o}}\\)| Fluid pressure at the valve outlet| \\(\mathrm{Pa}\\)|| C2.P |
| \\(\Delta P\\)| Fluid pressure loss between the inlet and the outlet| \\(\mathrm{Pa}\\)| \\(P\_{\mathrm{i}}-P\_{\mathrm{o}}\\) | deltaP |
| \\(\rho\\)| Fluid density| \\(\mathrm{kg} / \mathrm{m}^{3}\\) || rho |
| \\(\rho\_{\text {water, } 60^{\circ} \mathrm{F}}\\) | Density of water at \\(60^{\circ} \mathrm{F}\left\(15.5556^{\circ} \mathrm{C}\right\) .\\) | \\(\mathrm{kg} / \mathrm{m}^{3}\\) || rho_15 |
| \\(\Omega\\)| Valve position \(between 0 and 1\)| \\(-\\)|| Ouv.signal |
## Governing equations
### Static momentum balance equation
- Validity domain:
\\(\forall \dot{m}\\) and \\(C\_{\mathrm{v}} \geq 0\\). For \\(C\_{\mathrm{v}}=0, \Delta P\\) must be defined.
- Mathematical formulation:
$$\Delta P \cdot C\_{\mathrm{v}} \cdot \lvert C\_{\mathrm{v}}\rvert =1.732189 \times 10^{12} \cdot \frac{\dot{m} \cdot \lvert \dot{m} \rvert }{\rho \cdot \rho\_{\text {water, } 60^{\circ} F}}$$
- Comments:
The valve flow coefficient \\(C\_{\mathrm{v}}\\) is a function of the position \\(\Omega\\) of the valve: \\(C\_{\mathrm{v}}=f\_{v}\(\Omega\)\\). \\(f\_{v}\\) is called the valve characteristic. The valve is fully closed for \\(\Omega=0\\) and fully open for \\(\Omega=1\\).
## References
El Hefni, Baligh and Bouskela, Daniel (2019). [Modeling and Simulation of Thermal Power Plants with ThermoSysPro](https://link.springer.com/book/10.1007/978-3-030-05105-1), sect. 13.8. Springer Nature Switzerland AG.
Parameters
| Type | Name | Default | Description |
|---|
| ThermoSysPro.Units.xSI.Cv | Cvmax | 8005.42 | Maximum CV [USG/min] (active if mode_caract=0) |
| Real[:,2] | caract | [0, 0; 1, Cvmax] | Position vs. Cv [USG/min] characteristics (active if mode_caract=1) |
| Integer | mode_caract | 0 | 0:linear characteristics - 1:characteristics is given by caract[] |
| Integer | option_interpolation | 1 | 1: linear interpolation - 2: spline interpolation (active if mode_caract=1) |
| Boolean | continuous_flow_reversal | false | true: continuous flow reversal - false: discontinuous flow reversal |
| Integer | fluid | 1 | 1: water/steam - 2: C3H3F5 |
| Integer | option_rho_water | 1 | 1: using (deltaP*Cv^2=A.Q^2/rho^2) - 2: using (deltaP*Cv^2=A.Q^2/(rho*rho_15)); with rho_15 is the density of the water at 15.5556 °C) |
| Units.SI.Density | p_rho | 0 | If > 0, fixed fluid density |
| Integer | mode | 0 | IF97 region. 1:liquid - 2:steam - 4:saturation line - 0:automatic |
Revisions
Author
Daniel Bouskela
