StaticDrum

Copyright © EDF 2002 - 2026

ThermoSysPro Version 4.2

This component model is documented in Sect. 14.6 of the ThermoSysPro book.

Static drum

The static drum is a reservoir at the top end of the boiler. It separates water from steam in the mixture generated in the boiler and stores them.
This component can also be used as a simple steam generator.

The static drum is modeled according to the following assumptions:

• heat exchanges between the liquid and steam phases, as well as between drum and external medium, are negligible,

• pressure losses are negligible,

• water is always saturated.

Modelica component model

The equations mentioned below are implemented in the component StaticDrum, located in the WaterSteam.Junctions sub-library.
This component has 9 connectors:

• Ce_eva: saturated water inlet from the evaporator,

• Cs_eva: saturated water outlet toward the evaporator,

• Ce_sup: supplementary water inlet,

• Cs_sup: supplementary water outlet,

• Ce_eco: water inlet from a money saver,

• Ce_steam: steam inlet,

• Cs_sur: saturated steam outlet toward the overheater,

• Cs_purg: saturated water outlet toward the drain,

• Cth: thermal port.

Nomenclature

Symbol	Description	Unit	Definition	Modelica name
\(h_{\text {eco, } i}\)	Specific enthalpy of the liquid at the inlet of the drum, coming from the economizer	\(\mathrm{J} / \mathrm{kg}\)		Ce_eco.h
\(h_{\text {eva }, \mathrm{i}}\)	Specific enthalpy of the fluid at the inlet of the drum, coming from the evaporator	\(\mathrm{J} / \mathrm{kg}\)		Ce_eva.h
\(h_{\text {steam }, \mathrm{i}}\)	Specific enthalpy of the steam at the inlet	\(\mathrm{J} / \mathrm{kg}\)		Ce_steam.h
\(h_{\text {sup }, \mathrm{i}}\)	Specific enthalpy of the fluid at the additional inlet	\(\mathrm{J} / \mathrm{kg}\)		Ce_sup.h
\(h_{\text {drain,o }}\)	Specific enthalpy of the liquid at the outlet, going to the drain	\(\mathrm{J} / \mathrm{kg}\)		Cs_purg.h
\(h_{\mathrm{eva}, \mathrm{o}}\)	Specific enthalpy of the fluid at the outlet, going to the evaporator	\(\mathrm{J} / \mathrm{kg}\)		Cs_eva.h
\(h_{\mathrm{sup}, \mathrm{o}}\)	Specific enthalpy of the liquid at the additional outlet	\(\mathrm{J} / \mathrm{kg}\)		Cs_sup.h
\(h_{\mathrm{sur}, \mathrm{o}}\)	Specific enthalpy of the steam at the outlet, going to the super-heater	\(\mathrm{J} / \mathrm{kg}\)		Cs_sur.h
\(\dot{m}_{\text {drain }, \mathrm{o}}\)	Mass flow rate of the liquid at the outlet, going to the drain	\(\mathrm{kg} / \mathrm{s}\)		Cs_purg.Q
\(\dot{m}_{\mathrm{eco}, \mathrm{i}}\)	Mass flow rate of the fluid at the inlet, coming from the economizer	\(\mathrm{kg} / \mathrm{s}\)		Ce_eco.Q
\(\dot{m}_{\text {eva }, \mathrm{i}}\)	Mass flow rate of the fluid at the inlet, coming from the evaporator	\(\mathrm{kg} / \mathrm{s}\)		Ce_eva.Q
\(\dot{m}_{\mathrm{eva}, \mathrm{o}}\)	Mass flow rate of the liquid at the outlet, going to the evaporator	\(\mathrm{kg} / \mathrm{s}\)		Cs_eva.Q
\(\dot{m}_{\text {steam, } \mathrm{i}}\)	Mass flow rate of the steam at the inlet	\(\mathrm{kg} / \mathrm{s}\)		Ce_steam.Q
\(\dot{m}_{\mathrm{sup}, \mathrm{i}}\)	Mass flow rate of the fluid at the additional inlet	\(\mathrm{kg} / \mathrm{s}\)		Ce_sup.Q
\(\dot{m}_{\mathrm{sup}, \mathrm{o}}\)	Mass flow rate of the liquid at the additional outlet	\(\mathrm{kg} / \mathrm{s}\)		Cs_sup.Q
\(m_{\mathrm{sur}, \mathrm{o}}\)	Mass flow rate of the steam at the outlet, going to the super-heater	\(\mathrm{kg} / \mathrm{s}\)		Cs_sur.Q
\(W\)	Thermal power exchanged from the heat source to the fluid	\(\mathrm{W}\)		Cth.W
\(x\)	Steam mass fraction at the outlet going to the super-heater (steam separation efficiency)	\(-\)		x

Governing equations

Static mass balance equation

• Validity domain:

\(\forall \dot{m}\)

• Mathematical formulation:

\[ 0 =\dot{m}_{\mathrm{eco}, \mathrm{i}}+\dot{m}_{\mathrm{eva}, \mathrm{i}} +\dot{m}_{\mathrm{sup}, \mathrm{i}}+\dot{m}_{\text {steam, }} - \dot{m}_{\text {drain }, \mathrm{o}}-\dot{m}_{\mathrm{eva}, \mathrm{o}}-\dot{m}_{\mathrm{sup}, \mathrm{o}}-\dot{m}_{\mathrm{sur}, \mathrm{o}} \]

• Comments:

Static energy balance equation

• Validity domain:

\(\exists \dot{m}\) such that \(\dot{m} \neq 0\)

• Mathematical formulation:

\[ 0=\dot{m}_{\text{eco }, \mathrm{i}} \cdot h_{\mathrm{eco}, \mathrm{i}}+\dot{m}_{\mathrm{eva}, \mathrm{i}} \cdot h_{\mathrm{eva}, \mathrm{i}}+\dot{m}_{\mathrm{sup}, \mathrm{i}} \cdot h_{\text{sup }, \mathrm{i}}\ \quad +\dot{m}_{\text{steam,i }} \cdot h_{\text{steam,i }}-\dot{m}_{\text{drain,o }} \cdot h_{\text{drain,o }}-\dot{m}_{\mathrm{eva}, \mathrm{o}} \cdot h_{\mathrm{eva}, \mathrm{o}}\ \quad -\dot{m}_{\mathrm{sup}, \mathrm{o}} \cdot h_{\mathrm{sup}, \mathrm{o}}-\dot{m}_{\mathrm{sur}, \mathrm{o}} \cdot h_{\mathrm{sur}, \mathrm{o}}+W\]

• Comments:

This equation is valid if some mass flow rates are non-zero. Otherwise, the mixing specific enthalpy is undefined.

Specific enthalpy at the drum liquid outlets

• Validity domain:

\(\exists \dot{m}\) such that \(\dot{m} \neq 0\)

• Mathematical formulation:

\[h_{\mathrm{eva}, \mathrm{o}}=h_{\mathrm{sup}, \mathrm{o}}=h_{\text {drain }, \mathrm{o}}=h_{l}^{\mathrm{sat}}\]

• Comments:

The liquid inside the drum is assumed always at saturation.

Specific enthalpy at the drum vapor outlet

• Validity domain:

\(\exists \dot{m}\) such that \(\dot{m} \neq 0\) and \(x \approx 1\)

• Mathematical formulation:

\[h_{\mathrm{sur}, \mathrm{o}}=(1-x) \cdot h_{l}^{\mathrm{sat}}+x \cdot h_{\mathrm{v}}^{\mathrm{sat}}\]

• Comments:

The vapor inside the drum is assumed always at saturation with possibly small amounts of water.

References

El Hefni, Baligh and Bouskela, Daniel (2019). Modeling and Simulation of Thermal Power Plants with ThermoSysPro, sect. 14.6. Springer Nature Switzerland AG.