modelPartialDrum2Phase2Volume
Information
// Info below is obsolete. Kept for reference until it can be updated.
Spray stream is assumed to be saturated liquid.
This model describes the cylindrical drum of a drum boiler, without assuming thermodynamic equilibrium between the liquid and vapour holdups. Connectors are provided for surgePort inlet, steamPort 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 steamPort 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 steamPort 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 surgePort 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 p_start, h_liquid_start, h_vapor_start, 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.Temperature | T_liquid_start | Medium.temperature_ph(p_start, h_liquid_start) | |
| SI.Temperature | T_vapor_start | Medium.temperature_ph(p_start, h_vapor_start) | |
| Geometry | |||
| SI.Volume | V_total | Total volume (liquid + vapor) | |
| Assumptions | |||
| Boolean | allowFlowReversal | system.allowFlowReversal | = true to allow flow reversal, false restrics to design direction |
| Assumptions › Dynamics | |||
| Types.Dynamics | energyDynamics | system.energyDynamics | Formulation of energy balance |
| Types.Dynamics | massDynamics | system.massDynamics | Formulation of mass balance |
| Dynamics | substanceDynamics | massDynamics | Formulation of substance balances |
| Initialization | |||
| TRANSFORM.Units.NonDim | Vfrac_liquid_start | 0.5 | Initial fraction of volume in the liquid phase |
| SI.Pressure | p_start | system.p_start | Pressure start value |
| SI.SpecificEnthalpy | h_liquid_start | Medium.bubbleEnthalpy(Medium.setSat_p(p_start)) | Liquid specific enthalpy start value |
| SI.SpecificEnthalpy | h_vapor_start | Medium.dewEnthalpy(Medium.setSat_p(p_start)) | Vapour specific enthalpy start value |
| Initialization › Start Value: Mass Fractions | |||
| Medium.MassFraction[Medium.nX] | X_start | Medium.X_default | Mass fractions m_i/m |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Fluid.System | system | System properties | |
| SI.Pressure | p | Surface pressure | |
| SI.Volume | V_vapor | Volume occupied by vapour | |
| SI.Volume | V_liquid | Volume occupied by liquid | |
| TRANSFORM.Units.NonDim | Vfrac_liquid | Fractional of total volume occupied by liquid | |
| Medium.ThermodynamicState | state_liquid | medium_liquid.state | Liquid state |
| SI.Density | rho_liquid | medium_liquid.d | Liquid density |
| SI.SpecificEnthalpy | h_liquid | Liquid specific enthalpy | |
| SI.Temperature | T_liquid | Liquid temperature | |
| Medium.ThermodynamicState | state_vapor | medium_vapor.state | Vapor state |
| SI.Density | rho_vapor | medium_vapor.d | Vapor density |
| SI.SpecificEnthalpy | h_vapor | Vapor specific enthalpy | |
| SI.Temperature | T_vapor | Vapor temperature | |
| Medium.SaturationProperties | sat | Medium.setSat_p(p) | State vector to compute saturation properties |
| SI.SpecificEnthalpy | h_gsat | Medium.dewEnthalpy(sat) | Saturated vapor specific enthalpy |
| SI.SpecificEnthalpy | h_fsat | Medium.bubbleEnthalpy(sat) | Saturated liquid specific enthalpy |
| ThermoPower.AbsoluteTemperature | Tsat | sat.Tsat | Saturation temperature |
| SI.Energy | U_liquid | Internal energy of liquid | |
| SI.Mass | m_liquid | Mass of liquid | |
| SI.MassFlowRate | mb_flow_liquid | Mass flows across liquid boundaries | |
| SI.EnthalpyFlowRate | Hb_flow_liquid | Enthalpy flow across liquid boundaries or energy source/sink | |
| SI.HeatFlowRate | Qb_flow_liquid | Heat flow across liquid boundaries or energy source/sink | |
| SI.Power | Wb_flow_liquid | Work flow across liquid boundaries or source term | |
| SI.Energy | U_vapor | Internal energy of vapor | |
| SI.Mass | m_vapor | Mass of vapor | |
| SI.MassFlowRate | mb_flow_vapor | Mass flows across vapor boundaries | |
| SI.EnthalpyFlowRate | Hb_flow_vapor | Enthalpy flow across vapor boundaries or energy source/sink | |
| SI.HeatFlowRate | Qb_flow_vapor | Heat flow across vapor boundaries or energy source/sink | |
| SI.Power | Wb_flow_vapor | Work flow across vapor boundaries or source term | |
| Medium.BaseProperties | medium_vapor | ||
| Medium.BaseProperties | medium_liquid | ||
| SI.Mass | mXi_liquid | Substance mass | |
| Medium.MassFlowRate | mbXi_liquid_flow | Independent mass flow rates, source or sink | |
| SI.Mass | mXi_vapor | Substance mass | |
| Medium.MassFlowRate | mbXi_vapor_flow | Independent mass flow rates, source or sink |
Contents
| Name | Description |
|---|---|
 Medium |
Revisions
<htm_liquid>
<ul>
<li><i>30 May 2005</i>
by <a href="mailto:francesco.casella@polimi.it">Francesco Casella</a>:<br>
Initialisation support added.</li>
<li><i>16 Dec 2004</i>
by <a href="mailto:francesco.casella@polimi.it">Francesco Casella</a>:<br>
Standard medium definition added.</li>
<li><i>5 Jul 2004</i>
by <a href="mailto:francesco.casella@polimi.it">Francesco Casella</a>:<br>
Adapted to Modelica.Media.</li>
<li><i>1 Feb 2004</i>
by <a href="mailto:francesco.casella@polimi.it">Francesco Casella</a>:<br>
Improved equations for drum geometry.</li>
<li><i>1 Oct 2003</i>
by <a href="mailto:francesco.casella@polimi.it">Francesco Casella</a>:<br>
First release.</li>
</ul>