Buildings.ThermalZones.Detailed.Examples.FFD.Tutorial

Tutorial with step by step instructions for how to do coupled simulation

Information

This package contains tutorials for CFD simulations of zones with natural and mixed convection, with step by step instructions for how to build such models.

Extends from Modelica.Icons.Information (Icon for general information packages).

Package Content

Name Description
Buildings.ThermalZones.Detailed.Examples.FFD.Tutorial.MixedConvection MixedConvection Tutorial for Mixed Convection case
Buildings.ThermalZones.Detailed.Examples.FFD.Tutorial.NaturalConvection NaturalConvection Tutorial for Natural Convection case

Buildings.ThermalZones.Detailed.Examples.FFD.Tutorial.MixedConvection Buildings.ThermalZones.Detailed.Examples.FFD.Tutorial.MixedConvection

Tutorial for Mixed Convection case

Buildings.ThermalZones.Detailed.Examples.FFD.Tutorial.MixedConvection

Information

This tutorial gives step by step instructions on building and simulating a mixed convection model. The model tests the coupled simulation of Buildings.ThermalZones.Detailed.CFD with the FFD program by simulating ventilation with mixed convection in an empty room.

Case Description

The temperature of the floor is fixed at 30°C and the temperature of the walls and the ceiling are fixed at 10°C. The supply air temperature is fixed at 10°C.

Figure (a) shows the schematic of the FFD simulation and Figure (b) shows the velocity vectors and temperatures on the X-Z plane at Y = 0.5 m as simulated by the FFD.

image

Figure (a)

image

Figure (b)

Step by Step Guide

This section describes step by step how to build and simulate the model.

  1. Add the following model components into the MixedConvection model:

  2. In the textual editor mode, add the medium and the number of surfaces as below:

    package MediumA = Buildings.Media.GasesConstantDensity.MoistAirUnsaturated (T_default=283.15);
      parameter Integer nConExtWin=0;
      parameter Integer nConBou=0;
      parameter Integer nSurBou=6;
      parameter Integer nConExt=0;
      parameter Integer nConPar=0;
    
  3. Edit roo as below:

    Buildings.ThermalZones.Detailed.CFD roo(
      redeclare package Medium = MediumA,
      surBou(
        name={"East Wall","West Wall","North Wall","South Wall","Ceiling","Floor"},
        A={0.9,0.9,1,1,1,1},
        til={Buildings.Types.Tilt.Wall,
            Buildings.Types.Tilt.Wall,
            Buildings.Types.Tilt.Wall,
            Buildings.Types.Tilt.Wall,
            Buildings.Types.Tilt.Ceiling,
            Buildings.Types.Tilt.Floor},
        each absIR=1e-5,
        each absSol=1e-5,
        each boundaryCondition=Buildings.ThermalZones.Detailed.Types.CFDBoundaryConditions.Temperature),
        lat = 0.012787839282646,
        AFlo = 1*1,
        hRoo = 1,
        linearizeRadiation = false,
        useCFD = true,
        sensorName = {"Occupied zone air temperature", "Velocity"},
        cfdFilNam = "modelica://Buildings/Resources/Data/ThermalZones/Detailed/Examples/FFD/Tutorial/MixedConvection.ffd",
        nConExt = nConExt,
        nConExtWin = nConExtWin,
        nConPar = nConPar,
        nConBou = nConBou,
        nSurBou = nSurBou,
        nPorts = 2,
        portName={"Inlet","Outlet"},
        samplePeriod = 6);
    
  4. Set the parameters for the following components:

    • Set qRadGai_flow, qConGai_flow and qLatGai_flow to 0.
    • Set TFlo to 303.15 Kelvin.
    • Set TOthWal to 283.15 Kelvin.
  5. Set the values for the parameters of bouIn and bouOut as below:

    Fluid.Sources.MassFlowSource_T bouIn(
      redeclare package Medium = MediumA,
      nPorts=1,
      m_flow=0.1,
      T=283.15);
    
    Fluid.Sources.FixedBoundary bouOut(
      redeclare package Medium = MediumA,
      nPorts=1);
    
  6. Connect the components as shown in the figure below.

    image

  7. Confirm in the textual editor that the connections to roo.ports are as follows:

    connect(bouIn.ports[1], roo.ports[1]);
    connect(bouOut.ports[1], roo.ports[2]);
    
  8. Use the Simplified CFD Interface (SCI) to generate the input file for the FFD.

    • Use a 20 X 20 X 20 stretched grid.
    • Set the time step size of the FFD to 0.1 seconds.
    • Generate the input files, which have by default the names input.cfd (mesh file) and zeroone.dat (obstacles file).
    • Rename the files as MixedConvection.cfd and MixedConvection.dat, respectively.
  9. Revise the FFD parameter input file MixedConvection.ffd (an example file is available in Buildings/Resources/Data/ThermalZones/Detailed/Examples/FFD/Tutorial/):

      inpu.parameter_file_format SCI
      inpu.parameter_file_name MixedConvection.cfd
      inpu.block_file_name MixedConvection.dat
      prob.nu 0.000015 // Kinematic viscosity
      prob.rho 1.205 // Density
      prob.gravx 0 // Gravity in x direction
      prob.gravy 0 // Gravity in y direction
      prob.gravz -9.81 // Gravity in z direction
      prob.cond 0.0257 // Conductivity
      prob.Cp 1006.0 // Specific heat capacity
      prob.beta 0.00343 // Thermal expansion coefficient
      prob.diff 0.00001 // Diffusivity for contaminants
      prob.coeff_h 0.0004 // Convective heat transfer coefficient near the wall
      prob.Temp_Buoyancy 10.0 // Reference temperature for calculating buoyance  force
      init.T 10.0 // Initial condition for Temperature
      init.u 0.0 // Initial condition for velocity u
      init.v 0.0 // Initial condition for velocity v
      init.w 0.0 // Initial condition for velocity w
    
  10. Put the files MixedConvection.ffd, MixedConvection.dat, and MixedConvection.cfd in the directory Buildings/Resources/Data/ThermalZones/Detailed/Examples/FFD/Tutorial/.
  11. Set the simulation stop time of the Modelica model to 180 seconds and choose, for example, the CVode solver.
  12. Translate the model and start the simulation.
  13. Post-process: click the Tecplot macro script Buildings/Resources/Image/Rooms/Examples/FFD/Tutorial/MixedConvection.mcr that will generate the temperature contour and velocity vectors shown in the Figure (b). Note: Tecplot is needed for this.

Extends from Modelica.Icons.Example (Icon for runnable examples).

Parameters

TypeNameDefaultDescription
IntegernConExtWin0Number of constructions with a window
IntegernConBou0Number of surface that are connected to constructions that are modeled inside the room
IntegernSurBou6Number of surface that are connected to the room air volume
IntegernConExt0Number of exterior constructions withour a window
IntegernConPar0Number of partition constructions

Modelica definition

model MixedConvection "Tutorial for Mixed Convection case" extends Modelica.Icons.Example; package MediumA = Buildings.Media.Air ( T_default=283.15) "Medium model"; parameter Integer nConExtWin=0 "Number of constructions with a window"; parameter Integer nConBou=0 "Number of surface that are connected to constructions that are modeled inside the room"; parameter Integer nSurBou=6 "Number of surface that are connected to the room air volume"; parameter Integer nConExt=0 "Number of exterior constructions withour a window"; parameter Integer nConPar=0 "Number of partition constructions"; Modelica.Blocks.Sources.Constant qRadGai_flow(k=0) "Radiative heat gain"; Modelica.Blocks.Sources.Constant qConGai_flow(k=0) "Convective heat gain"; Modelica.Blocks.Sources.Constant qLatGai_flow(k=0) "Latent heat gain"; Modelica.Blocks.Routing.Multiplex3 multiplex3_1; BoundaryConditions.WeatherData.ReaderTMY3 weaDat(filNam= Modelica.Utilities.Files.loadResource("modelica://Buildings/Resources/weatherdata/USA_IL_Chicago-OHare.Intl.AP.725300_TMY3.mos"), TDryBul=293.15); Buildings.ThermalZones.Detailed.CFD roo( redeclare package Medium = MediumA, surBou( name={"East Wall","West Wall","North Wall","South Wall","Ceiling","Floor"}, A={0.9,0.9,1,1,1,1}, til={Buildings.Types.Tilt.Wall,Buildings.Types.Tilt.Wall, Buildings.Types.Tilt.Wall,Buildings.Types.Tilt.Wall, Buildings.Types.Tilt.Ceiling,Buildings.Types.Tilt.Floor}, each absIR=1e-5, each absSol=1e-5, each boundaryCondition=Buildings.ThermalZones.Detailed.Types.CFDBoundaryConditions.Temperature), lat = 0.012787839282646, AFlo = 1*1, hRoo = 1, linearizeRadiation = false, useCFD = true, sensorName = {"Occupied zone air temperature", "Velocity"}, cfdFilNam = "modelica://Buildings/Resources/Data/ThermalZones/Detailed/Examples/FFD/Tutorial/MixedConvection.ffd", nConExt = nConExt, nConExtWin = nConExtWin, nConPar = nConPar, nConBou = nConBou, nSurBou = nSurBou, nPorts=2, portName={"Inlet","Outlet"}, samplePeriod = 6); HeatTransfer.Sources.FixedTemperature TOthWal[nSurBou-1](each T=283.15) "Temperature for other walls"; HeatTransfer.Sources.FixedTemperature TFlo(T=303.15) "Temperature of floor"; Fluid.Sources.MassFlowSource_T bouIn( nPorts=1, redeclare package Medium = MediumA, m_flow=0.1, T=283.15) "Mass flow boundary condition"; Buildings.Fluid.Sources.Boundary_pT bouOut( nPorts=1, redeclare package Medium = MediumA) "Pressure boundary condition"; equation connect(qRadGai_flow.y,multiplex3_1. u1[1]); connect(qConGai_flow.y,multiplex3_1. u2[1]); connect(qLatGai_flow.y,multiplex3_1. u3[1]); connect(multiplex3_1.y,roo. qGai_flow); connect(weaDat.weaBus,roo. weaBus); connect(TFlo.port, roo.surf_surBou[6]); connect(TOthWal[1].port, roo.surf_surBou[1]); connect(TOthWal[2].port, roo.surf_surBou[2]); connect(TOthWal[3].port, roo.surf_surBou[3]); connect(TOthWal[4].port, roo.surf_surBou[4]); connect(TOthWal[5].port, roo.surf_surBou[5]); connect(bouIn.ports[1], roo.ports[1]); connect(bouOut.ports[1], roo.ports[2]); end MixedConvection;

Buildings.ThermalZones.Detailed.Examples.FFD.Tutorial.NaturalConvection Buildings.ThermalZones.Detailed.Examples.FFD.Tutorial.NaturalConvection

Tutorial for Natural Convection case

Buildings.ThermalZones.Detailed.Examples.FFD.Tutorial.NaturalConvection

Information

This tutorial gives step by step instructions for building and simulating a natural convection model. The model tests the coupled simulation of Buildings.ThermalZones.Detailed.CFD with the FFD program by simulating the natural convection in an empty room with only surface boundary conditions.

Case Description

The Rayleigh number is a dimensionless number associated with natural convection, defined as

Ra = g β (Tw-Te)L3 ⁄ (ν α)

To get a Rayleigh number of 1E5, the flow properties are manually set as acceleration due to gravity gz=-0.01 m/s2, thermal expansion coefficient β=3e-3 K-1, kinematic viscosity ν=1.5e-5 m2/s, thermal diffusivity α=2e-5 m2/s, and characteristic length L=1 m.

Figure (a) shows the schematic of the FFD simulation. The following conditions are applied in Modelica.:

image

Figure (a)

Figure (b) shows the velocity vectors and temperature contour in degree Celsius on the X-Z plane at Y = 0.5 m as simulated by the FFD.

image

Figure (b)

More details of the case description can be found in Zuo et al. (2012).

Step by Step Guide

This section describes step by step how to build and simulate the model.

  1. Add the following component models to the NaturalConvection model:

    Note that for the other four walls with adiabatic boundary conditions, we do not need to specify a zero heat flow boundary condition because the heat flow rate transferred through a heat port from the outside is zero if the heat port is not connected from the outside.
  2. In the textual editor mode, add the medium and the number of surfaces as shown below:

    Buildings.ThermalZones.Detailed.CFD roo(
      package MediumA = Buildings.Media.GasesConstantDensity.MoistAirUnsaturated(
        T_default=283.15);
      parameter Integer nConExtWin=0;
      parameter Integer nConBou=0;
      parameter Integer nSurBou=6;
      parameter Integer nConExt=0;
      parameter Integer nConPar=0;
    
    
  3. Edit roo as below:

     edeclare package Medium = MediumA,
    surBou(
      name={"East Wall","West Wall","North Wall","South Wall","Ceiling","Floor"},
      each A=1*1,
      til={Buildings.Types.Tilt.Wall,
        Buildings.Types.Tilt.Wall,
        Buildings.Types.Tilt.Wall,
        Buildings.Types.Tilt.Wall,
        Buildings.Types.Tilt.Ceiling,
        Buildings.Types.Tilt.Floor},
      each absIR=1e-5,
      each absSol=1e-5,
      boundaryCondition={
        Buildings.ThermalZones.Detailed.Types.CFDBoundaryConditions.Temperature,
        Buildings.ThermalZones.Detailed.Types.CFDBoundaryConditions.Temperature,
        Buildings.ThermalZones.Detailed.Types.CFDBoundaryConditions.HeatFlowRate,
        Buildings.ThermalZones.Detailed.Types.CFDBoundaryConditions.HeatFlowRate,
        Buildings.ThermalZones.Detailed.Types.CFDBoundaryConditions.HeatFlowRate,
        Buildings.ThermalZones.Detailed.Types.CFDBoundaryConditions.HeatFlowRate}),
      lat = 0.012787839282646,
      AFlo = 1*1,
      hRoo = 1,
      linearizeRadiation = false,
      useCFD = true,
      sensorName = {"Occupied zone air temperature", "Velocity"},
      cfdFilNam = "modelica://Buildings/Resources/Data/ThermalZones/Detailed/Examples/FFD/Tutorial/NaturalConvection.ffd",
      nConExt = nConExt,
      nConExtWin = nConExtWin,
      nConPar = nConPar,
      nConBou = nConBou,
      nSurBou = nSurBou,
      T_start=273.15,
      samplePeriod = 60);
    
  4. Connect the component as shown in the figure below.

    image

  5. Set the values for the following components:
    • Set qRadGai_flow, qConGai_flow and qLatGai_flow to 0.
    • Set TEasWal to 273.15 Kelvin.
    • Set TWesWal to 274.15 Kelvin.
  6. Use the Simplified CFD Interface (SCI) to generate the input file for FFD.
    • Use a 20 x 20 x 20 uniform grid.
    • Set the time step size of the FFD to 10 seconds.
    • Generate the input files which have the default names input.cfd (mesh file) and zeroone.dat (obstacles file).
    • Rename the files as NaturalConvection.cfd and NaturalConvection.dat, respectively.
  7. Revise the FFD parameter input file NaturalConvection.ffd (an example file is provided in Buildings/Resources/Data/ThermalZones/Detailed/Examples/FFD/Tutorial/):
      inpu.parameter_file_format SCI
      inpu.parameter_file_name NaturalConvection.cfd
      inpu.block_file_name NaturalConvection.dat
      prob.nu 1.5e-5 // Kinematic viscosity
      prob.rho 1 // Density
      prob.gravx 0 // Gravity in x direction
      prob.gravy 0 // Gravity in y direction
      prob.gravz -0.01 // Gravity in z direction
      prob.cond 0.02 // Conductivity
      prob.Cp 1000.0 // Specific heat capacity
      prob.beta 3e-3 // Thermal expansion coefficient
      prob.diff 0.00001 // Diffusivity for contaminants
      prob.alpha 2e-5 // Thermal diffusivity
      prob.coeff_h 0.0004 // Convective heat transfer coefficient near the wall
      prob.Temp_Buoyancy 0.0 // Reference temperature for calculating buoyance force
      init.T 0.0 // Initial condition for Temperature
      init.u 0.0 // Initial condition for velocity u
      init.v 0.0 // Initial condition for velocity v
      init.w 0.0 // Initial condition for velocity w
    

    Please note that some of the physical properties were manipulated to obtain the desired Rayleigh Number of 105.

  8. Store NaturalConvection.ffd, NaturalConvection.dat, and NaturalConvection.cfd at Buildings/Resources/Data/ThermalZones/Detailed/Examples/FFD/Tutorial.
  9. Set simulation the stop time of the Modelica model 7200 seconds and choose for example the CVode solver.
  10. Translate the model and start the simulation.
  11. Post-process: click the Tecplot macro script Buildings/Resources/Image/Rooms/Examples/FFD/Tutorial/NaturalConvection.mcr that will generate the temperature contour and velocity vectors shown in the Figure (b). Note: Tecplot is needed for this.

Extends from Modelica.Icons.Example (Icon for runnable examples).

Parameters

TypeNameDefaultDescription
IntegernConExtWin0Number of constructions with a window
IntegernConBou0Number of surface that are connected to constructions that are modeled inside the room
IntegernSurBou6Number of surface that are connected to the room air volume
IntegernConExt0Number of exterior constructions withour a window
IntegernConPar0Number of partition constructions

Modelica definition

model NaturalConvection "Tutorial for Natural Convection case" extends Modelica.Icons.Example; package MediumA = Buildings.Media.Air ( T_default=283.15) "Medium model"; parameter Integer nConExtWin=0 "Number of constructions with a window"; parameter Integer nConBou=0 "Number of surface that are connected to constructions that are modeled inside the room"; parameter Integer nSurBou=6 "Number of surface that are connected to the room air volume"; parameter Integer nConExt=0 "Number of exterior constructions withour a window"; parameter Integer nConPar=0 "Number of partition constructions"; Modelica.Blocks.Sources.Constant qRadGai_flow(k=0) "Radiative heat gain"; Modelica.Blocks.Sources.Constant qConGai_flow(k=0) "Convective heat gain"; Modelica.Blocks.Sources.Constant qLatGai_flow(k=0) "Latent heat gain"; Modelica.Blocks.Routing.Multiplex3 multiplex3_1; BoundaryConditions.WeatherData.ReaderTMY3 weaDat(filNam=Modelica.Utilities.Files.loadResource("modelica://Buildings/Resources/weatherdata/USA_IL_Chicago-OHare.Intl.AP.725300_TMY3.mos"), TDryBul=293.15); Buildings.ThermalZones.Detailed.CFD roo( redeclare package Medium = MediumA, surBou( name={"East Wall","West Wall","North Wall","South Wall","Ceiling","Floor"}, each A=1*1, til={Buildings.Types.Tilt.Wall,Buildings.Types.Tilt.Wall, Buildings.Types.Tilt.Wall,Buildings.Types.Tilt.Wall, Buildings.Types.Tilt.Ceiling,Buildings.Types.Tilt.Floor}, each absIR=1e-5, each absSol=1e-5, boundaryCondition={Buildings.ThermalZones.Detailed.Types.CFDBoundaryConditions.Temperature, Buildings.ThermalZones.Detailed.Types.CFDBoundaryConditions.Temperature,Buildings.ThermalZones.Detailed.Types.CFDBoundaryConditions.HeatFlowRate, Buildings.ThermalZones.Detailed.Types.CFDBoundaryConditions.HeatFlowRate, Buildings.ThermalZones.Detailed.Types.CFDBoundaryConditions.HeatFlowRate, Buildings.ThermalZones.Detailed.Types.CFDBoundaryConditions.HeatFlowRate}), AFlo = 1*1, hRoo = 1, linearizeRadiation = false, useCFD = true, sensorName = {"Occupied zone air temperature", "Velocity"}, cfdFilNam = "modelica://Buildings/Resources/Data/ThermalZones/Detailed/Examples/FFD/Tutorial/NaturalConvection.ffd", nConExt = nConExt, nConExtWin = nConExtWin, nConPar = nConPar, nConBou = nConBou, nSurBou = nSurBou, samplePeriod = 60, lat=0.012787839282646, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial); HeatTransfer.Sources.FixedTemperature TWesWal(T=274.15) "Boundary condition for the west wall"; HeatTransfer.Sources.FixedTemperature TEasWal(T=273.15) "Temperature of east wall"; equation connect(qRadGai_flow.y, multiplex3_1.u1[1]); connect(qConGai_flow.y, multiplex3_1.u2[1]); connect(qLatGai_flow.y, multiplex3_1.u3[1]); connect(multiplex3_1.y, roo.qGai_flow); connect(TEasWal.port, roo.surf_surBou[1]); connect(TWesWal.port, roo.surf_surBou[2]); connect(weaDat.weaBus, roo.weaBus); end NaturalConvection;