ControlValve#
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 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:
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, sect. 13.8. Springer Nature Switzerland AG.