.ThermoSysPro.WaterSteam.PressureLosses.ControlValve

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.  
   
![modelica://ThermoSysPro/UsersGuide/Documentation/ThermoSysPro.WaterSteam.PressureLosses.ControlValve.svg](modelica://ThermoSysPro/UsersGuide/Documentation/ThermoSysPro.WaterSteam.PressureLosses.ControlValve.svg)  

## 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.  
    

Revisions