.ThermoSysPro.WaterSteam.Junctions.StaticDrum

Information

## 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.  
   
![modelica://ThermoSysPro/UsersGuide/Documentation/ThermoSysPro.WaterSteam.Junctions.StaticDrum.svg](modelica://ThermoSysPro/UsersGuide/Documentation/ThermoSysPro.WaterSteam.Junctions.StaticDrum.svg)  

## 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](https://link.springer.com/book/10.1007/978-3-030-05105-1), sect. 14.6. Springer Nature Switzerland AG.  
    

Revisions