modelInterface_liq_gas
Information
This components allows to model a flat interface between a liquid and surrounding gas where evapo-condensation, boiling, radiation and convection occur. This component is designed to work with moist air media.
Evapo-condensation
The mathematical model of evapo-condensation uses the same approach than in the Condensation module. It assumed that the limiting phenomenon for the transfer is the ability to bring the mass of moist air into contact to a wall.
Convection
Regarding the convection, the approach is the same than for the FreeConvection module of the HeatTransfer package. The correlation used is ground_ASHRAE.
Radiation
The radiative heat transfer is computed using the CarrollRadiation module.
Boiling
The boiling is modelled by an homogeneneous formation of bubbles of equal diameter (no coalescence, no growth, no collapse) that would be formed in the liquid node and that escape by the interface. The bubble formation rate is deduced from the fraction of gas itself deduced from the liquid node specific enthalpy, the bubble and dew specific enthalpy:
The diameter of bubble is computed from the amount of gas, from an arbitrary number density of bubble (number of bubble per cubic meter of liquid) and from the knowledge of the state of the liquid node connected to the interface. By default n_bubbles = 150e6 m
-3
The velocity of bubbles is computed from the steady balance between the buoyancy force and the friction force. The weight of the bubble in neglected and the density term of liquid phase regarding the density of the gas phase in neglected in the buoyancy force claculation. The flow regime considered for the friction is laminar and the bubbles are assimilated to spheres.
The boiling mass flow rate derives from the surface aera of the interface corrected by the ratio between the volume of bubbles and the total volume of the liquid node connected to the interface module.
Where:
-
Xgis ratio between the mass of bubble (m) in the liquid node connected to the interface and the total mass (bubblem) of the liquid node -
his the specific enthalpy of the liquid node connected to the interface,h_bubbleandh_dewbeing its respectively the saturated liquid and gas specific enthalpy -
d_satis the density of bubble -
Vis the volume of the liquid node connected to the interface -
n_bubblesis the number density (number/m3) of bubbles in the liquid node -
d_bubbleis the diameter of a bubble -
dis the total density of the liquid node connected to the interface -
Velis the ascending velocity of bubble -
μis dynamic viscosity of the liquid node connected to the interface -
gis gravitationnal acceleration -
m_flowis the mass flow rate of leaving bubble -
Ais the surface area of the interface
Port heat and mass flows
The heat exchanged from radiation, convection, evapo-condensation and boiling is transfered via the heatPort_a. The fluidPort_a is just used to transfer mass from the liquid to the atmosphere for evaporation and the vice versa for condensation. It is not used to transport energy.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.SIunits.NumberDensityOfMolecules | n_bubbles | 150*1e6 | Number density of bubble in node |
| Modelica.SIunits.CoefficientOfFriction | Cx | 0.47 | drag coefficient for a sphere |
| Geometrical properties | |||
| SI.Area | A | 0 | Interface surface Area |
| SI.Length | Lc | 4*A^0.5 | Perimeter of the surface Area |
| SI.Emissivity | eps | 0.96 | Emissivity of liquid interface |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| TAeZoSysPro.HeatTransfer.Interfaces.HeatPort_a | heatPort_a | ||
| TAeZoSysPro.FluidDynamics.Interfaces.FlowPort_b | flowPort_b | ||
| TAeZoSysPro.HeatTransfer.Interfaces.HeatPort_b | port_rad | ||
| Modelica.Blocks.Interfaces.RealInput | F_view | ||
| Modelica.Blocks.Interfaces.RealOutput | A_wall | ||
| Modelica.Fluid.Interfaces.FluidPort_a | fluidPort_a |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Medium.Temperature | T_mean | Mean temperature between fluid and wall | |
| SI.TemperatureDifference | dT | Temperature difference Interface - gas | |
| SI.Pressure | p | Pressure of the atmosphere | |
| SI.CoefficientOfHeatTransfer | h_cv | Heat transfert coefficient | |
| SI.Density | d | Density of fluid at T_mean | |
| SI.SpecificHeatCapacity | cp | Specific heat capacity of fluid at T_mean | |
| SI.DynamicViscosity | mu | Dynamic viscosity of fluid at T_mean | |
| SI.ThermalConductivity | k | Thermal Conductivity of fluid at T_mean | |
| SI.PrandtlNumber | Pr | Prandtl Number | |
| SI.GrashofNumber | Gr | Grashof Number | |
| SI.RayleighNumber | Ra | Rayleigh Number | |
| SI.NusseltNumber | Nu | Nusselt Number | |
| Real | betaV | Mass transfer coefficient | |
| SI.HeatFlowRate | Q_flow_conv | Heat flow rate from convection | |
| SI.HeatFlowRate | Q_flow_evap | Heat flow rate from evaporation | |
| SI.EnthalpyFlowRate | H_flow_evap | ||
| SI.MassFlowRate | m_flow_evap | Mass flow rate from evaporation | |
| SI.Density | d_sat | Saturation density of the condensable species | |
| SI.SpecificEnthalpy | h_dew | Specific dew enthalpy of liquid medium | |
| SI.SpecificEnthalpy | h_bubble | Specific bubble enthalpy of liquid medium | |
| SI.SpecificEnthalpy | h | Specific enthalpy of liquid medium | |
| SI.Density | d_liq | Density in the liquid medium | |
| SI.Diameter | d_bubble | Diameter of bubble in liquid medium | |
| SI.Velocity | Vel | Ascending velocity of bubble in the liquid medium | |
| SI.MassFlowRate | m_flow_bubble | Mass flow rate from boiling | |
| Real | Xg | Mass fraction of gas in the liquid medium | |
| SI.ReynoldsNumber | Re | Reynold number of a bubble | |
| SI.Energy | E | Energy passed throught the component | |
| Modelica.Thermal.HeatTransfer.Sources.PrescribedTemperature | prescribedTemperature | ||
| TAeZoSysPro.HeatTransfer.BasesClasses.CarrollRadiation | carrollRadiation |
Contents
| Name | Description |
|---|---|
 Medium | |
 MediumLiquid |