modelDrum
Extends from Icons.Water.Drum.
Information
This model describes the cylindrical drum of a drum boiler, without assuming thermodynamic equilibrium between the liquid and vapour holdups. Connectors are provided for feedwater inlet, steam outlet, downcomer outlet, riser inlet, and blowdown outlet.
The model is based on dynamic mass and energy balance equations of the liquid volume and vapour volume inside the drum. Mass and energy tranfer between the two phases is provided by bulk condensation and surface condensation of the vapour phase, and by bulk boiling of the liquid phase. Additional energy transfer can take place at the surface if the steam is superheated.
The riser flowrate is separated before entering the drum, at the vapour pressure. The (saturated) liquid fraction goes into the liquid volume; the (wet) vapour fraction goes into the vapour volume, vith a steam quality depending on the liquid/vapour density ratio and on the avr parameter.
The enthalpy of the liquid going to the downcomer is computed by assuming that a fraction of the total mass flowrate (afd) comes directly from the feedwater inlet. The pressure at the downcomer connector is equal to the vapour pressure plus the liquid head.
The metal wall dynamics is taken into account, assuming uniform temperature. Heat transfer takes place between the metal wall and the liquid phase, vapour phase, and external atmosphere, the corresponding heat transfer coefficients being gl, gv, and gext.
The drum level is referenced to the centreline.
The start values of drum pressure, liquid specific enthalpy, vapour specific enthalpy, and metal wall temperature can be specified by setting the parameters pstart, hlstart, hvstart, Tmstart
Modelling options
The following options are available to specify the orientation of the cylindrical drum:
- DrumOrientation = 0: horizontal axis.
- DrumOrientation = 1: vertical axis.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| SI.Length | rint | 0 | Internal radius |
| SI.Length | rext | 0 | External radius |
| SI.Length | L | 0 | Length |
| SI.HeatCapacity | Cm | 0 | Total Heat Capacity of the metal wall |
| SI.Temperature | Text | 293 | External atmospheric temperature |
| SI.Time | tauev | 15 | Time constant of bulk evaporation |
| SI.Time | tauc | 15 | Time constant of bulk condensation |
| Real | Kcs | 0 | Surface condensation coefficient [kg/(s.m2.K)] |
| Real | Ks | 0 | Surface heat transfer coefficient [W/(m2.K)] |
| SI.CoefficientOfHeatTransfer | gext | 0 | Heat transfer coefficient between metal wall and external atmosphere |
| SI.CoefficientOfHeatTransfer | gl | 200 | Heat transfer coefficient between metal wall and liquid phase |
| SI.CoefficientOfHeatTransfer | gv | 200 | Heat transfer coefficient between metal wall and vapour phase |
| SI.ThermalConductivity | lm | 20 | Metal wall thermal conductivity |
| Real | afd | 0.05 | Ratio of feedwater in downcomer flowrate |
| Real | avr | 1.2 | Phase separation efficiency coefficient |
| Integer | DrumOrientation | 0 | 0: Horizontal; 1: Vertical |
| Boolean | allowFlowReversal | system.allowFlowReversal | = true to allow flow reversal, false restricts to design direction |
| SI.Acceleration | g | Modelica.Constants.g_n | |
| Real | pi | Modelica.Constants.pi | |
| Initialisation | |||
| Medium.AbsolutePressure | pstart | 1e5 | Pressure start value |
| Medium.SpecificEnthalpy | hlstart | Medium.bubbleEnthalpy(Medium.setSat_p(pstart)) | Liquid enthalpy start value |
| Medium.SpecificEnthalpy | hvstart | Medium.dewEnthalpy(Medium.setSat_p(pstart)) | Vapour enthalpy start value |
| Medium.Temperature | Tmstart | Medium.saturationTemperature(pstart) | Wall temperature start value |
| SI.Length | ystart | 0 | Start level value |
| Choices.Init.Options | initOpt | system.initOpt | Initialisation option |
| Boolean | noInitialPressure | false | Remove initial equation on pressure |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| FlangeA | feedwater | ||
| FlangeA | riser | ||
| FlangeB | downcomer | ||
| FlangeB | blowdown | ||
| FlangeB | steam |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Medium.ThermodynamicState | liquidState | Thermodynamic state of the liquid | |
| Medium.ThermodynamicState | vapourState | Thermodynamic state of the vapour | |
| Medium.SaturationProperties | sat | ||
| ThermoPower.System | system | System wide properties | |
| SI.Volume | Vv | Volume occupied by the vapour | |
| SI.Volume | Vl | Volume occupied by the liquid | |
| Medium.AbsolutePressure | p | Surface pressure | |
| SI.SpecificEnthalpy | hl | Liquid specific enthalpy | |
| SI.SpecificEnthalpy | hv | Vapour specific enthalpy | |
| SI.SpecificEnthalpy | hrv | Specific enthalpy of vapour from the risers after separation | |
| SI.SpecificEnthalpy | hrl | Specific enthalpy of liquid from the risers after separation | |
| SI.SpecificEnthalpy | hls | Specific enthalpy of saturated liquid | |
| SI.SpecificEnthalpy | hvs | Specific enthalpy of saturated vapour | |
| SI.SpecificEnthalpy | hf | Specific enthalpy of feedwater | |
| SI.SpecificEnthalpy | hd | Specific enthalpy of liquid to the downcomers | |
| SI.SpecificEnthalpy | hvout | Specific enthalpy of steam at the outlet | |
| SI.SpecificEnthalpy | hr | Specific enthalpy of fluid from the risers | |
| Medium.MassFlowRate | wf | Mass flowrate of feedwater | |
| Medium.MassFlowRate | wd | Mass flowrate to the downcomers | |
| Medium.MassFlowRate | wb | Mass flowrate of blowdown | |
| Medium.MassFlowRate | wr | Mass flowrate from the risers | |
| Medium.MassFlowRate | wrl | Mass flowrate of liquid from the risers | |
| Medium.MassFlowRate | wrv | Mass flowrate of vapour from the risers | |
| Medium.MassFlowRate | wv | Mass flowrate of steam at the outlet | |
| Medium.MassFlowRate | wc | Mass flowrate of bulk condensation | |
| Medium.MassFlowRate | wcs | Mass flowrate of surface condensation | |
| Medium.MassFlowRate | wev | Mass flowrate of bulk evaporation | |
| Medium.Temperature | Tl | Liquid temperature | |
| Medium.Temperature | Tv | Vapour temperature | |
| Units.AbsoluteTemperature | Tm | Wall temperature | |
| Medium.Temperature | Ts | Saturated water temperature | |
| SI.Power | Qmv | Heat flow from the wall to the vapour | |
| SI.Power | Qvl | Heat flow from the vapour to the liquid | |
| SI.Power | Qml | Heat flow from the wall to the liquid | |
| SI.Power | Qme | Heat flow from the wall to the atmosphere | |
| SI.Mass | Ml | Liquid mass | |
| SI.Mass | Mv | Vapour mass | |
| SI.Energy | El | Liquid internal energy | |
| SI.Energy | Ev | Vapour internal energy | |
| Units.LiquidDensity | rhol | Liquid density | |
| Units.GasDensity | rhov | Vapour density | |
| SI.PerUnit | xl | Mass fraction of vapour in the liquid volume | |
| SI.PerUnit | xv | Steam quality in the vapour volume | |
| SI.PerUnit | xr | Steam quality of the fluid from the risers | |
| SI.PerUnit | xrv | Steam quality of the separated steam from the risers | |
| Real | gml | Total heat transfer coefficient (wall-liquid) | |
| Real | gmv | Total heat transfer coefficient (wall-vapour) | |
| Real | a | ||
| SI.Length | y | Level (referred to the centreline) | |
| SI.Area | Aml | Surface of the wall-liquid interface | |
| SI.Area | Amv | Surface of the wall-vapour interface | |
| SI.Area | Asup | Surface of the liquid-vapour interface | |
| SI.Area | Aext | External drum surface |
Contents
| Name | Description |
|---|---|
 Medium |
Revisions
- 30 May 2005
by Francesco Casella:
Initialisation support added. - 16 Dec 2004
by Francesco Casella:
Standard medium definition added. - 5 Jul 2004
by Francesco Casella:
Adapted to Modelica.Media. - 1 Feb 2004
by Francesco Casella:
Improved equations for drum geometry. - 1 Oct 2003
by Francesco Casella:
First release.