This package provides component models to compute heat convection.

Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).

Name | Description |
---|---|

Exterior | Model for a exterior (outside) convective heat transfer |

Interior | Model for a interior (room-side) convective heat transfer |

Examples | Collection of models that illustrate model use and test models |

Functions | Functions for convective heat transfer |

BaseClasses | Package with base classes for Buildings.HeatTransfer.Convection |

`conMod`

determines the model that is used to compute
the heat transfer coefficient:

If

`conMod= Buildings.HeatTransfer.Types.ExteriorConvection.Fixed`

, then the convective heat transfer coefficient is set to the value specified by the parameter`hFixed`

.-
If

`conMod= Buildings.HeatTransfer.Types.ExteriorConvection.TemperatureWind`

, then the convective heat transfer coefficient is computed based on wind speed, wind direction and temperature difference.The total convection coefficient

*h*is the sum of the temperature-driven free convection coefficient_{t}*h*and the wind-driven forced convection coefficient_{n}*h*,_{f}h

The free convection coefficient_{t}= h_{n}+ h_{f}*h*is computed in the same way as in Buildings.HeatTransfer.Convection.Interior. The forced convection coefficient_{n}*h*is computed based on a correlation by Sparrow, Ramsey, and Mass (1979), which is_{f}h

_{f}= 2.537 W R √( P v ⁄ A )where

*W=1*for windward surfaces and*W=0.5*for leeward surfaces, with leeward defined as greater than 100 degrees from normal incidence,*R*is a surface roughness multiplier,*P*is the perimeter of the surface and*A*is the area of the surface. This is the same equation as implemented in EnergyPlus 6.0.We make the simplified assumption that the surface is square, and hence we set

h

_{f}= 2.537 W R √( 4 v ⁄ √(A) )The surface roughness is specified by the parameter

`surfaceRoughness`

which has to be set to a type of Buildings.HeatTransfer.Types.SurfaceRoughness.The coefficients for the surface roughness areRoughness index *R*Example material VeryRough 2.17 Stucco Rough 1.67 Brick MediumRough 1.52 Concrete MediumSmooth 1.13 Clear pine Smooth 1.11 Smooth plaster VerySmooth 1.00 Glass

Sparrow, E. M., J. W. Ramsey, and E. A. Mass. 1979. Effect of Finite Width on Heat Transfer and Fluid Flow about an Inclined Rectangular Plate. Journal of Heat Transfer, Vol. 101, p. 204.

Walton, G. N. 1981. Passive Solar Extension of the Building Loads Analysis and System Thermodynamics (BLAST) Program, Technical Report, United States Army Construction Engineering Research Laboratory, Champaign, IL.

Extends from Buildings.HeatTransfer.Convection.BaseClasses.PartialConvection (Partial model for heat convection).

Type | Name | Default | Description |
---|---|---|---|

Area | A | Heat transfer area [m2] | |

CoefficientOfHeatTransfer | hFixed | 3 | Constant convection coefficient [W/(m2.K)] |

Angle | til | Surface tilt [rad] | |

ExteriorConvection | conMod | Buildings.HeatTransfer.Types... | Convective heat transfer model |

SurfaceRoughness | roughness | Buildings.HeatTransfer.Types... | Surface roughness |

Angle | azi | Surface azimuth [rad] | |

Initialization | |||

TemperatureDifference | dT.start | 0 | = solid.T - fluid.T [K] |

Type | Name | Description |
---|---|---|

HeatPort_a | solid | |

HeatPort_b | fluid | |

input RealInput | v | Wind speed [m/s] |

input RealInput | dir | Wind direction (0=wind from North) [rad] |

model Exterior "Model for a exterior (outside) convective heat transfer" extends Buildings.HeatTransfer.Convection.BaseClasses.PartialConvection; parameter Buildings.HeatTransfer.Types.ExteriorConvection conMod= Buildings.HeatTransfer.Types.ExteriorConvection.TemperatureWind "Convective heat transfer model"; parameter Buildings.HeatTransfer.Types.SurfaceRoughness roughness= Buildings.HeatTransfer.Types.SurfaceRoughness.Medium "Surface roughness"; parameter Modelica.SIunits.Angle azi "Surface azimuth";Modelica.Blocks.Interfaces.RealInput v(unit="m/s") "Wind speed"; Modelica.Blocks.Interfaces.RealInput dir(unit="rad", displayUnit="deg", min=0, max=2*Modelica.Constants.pi) "Wind direction (0=wind from North)"; Modelica.SIunits.CoefficientOfHeatTransfer hF "Convective heat transfer coefficient due to forced convection"; Modelica.SIunits.HeatFlux qN_flow "Convective heat flux from solid -> fluid due to natural convection"; Modelica.SIunits.HeatFlux qF_flow "Convective heat flux from solid -> fluid due to forced convection"; protected parameter Real R(fixed=false) "Surface roughness"; Real W(min=0.5, max=1) "Wind direction modifier"; initial equation if (roughness == Buildings.HeatTransfer.Types.SurfaceRoughness.VeryRough) then R=2.17; elseif (roughness == Buildings.HeatTransfer.Types.SurfaceRoughness.Rough) then R=1.67; elseif (roughness == Buildings.HeatTransfer.Types.SurfaceRoughness.Medium) then R=1.52; elseif (roughness == Buildings.HeatTransfer.Types.SurfaceRoughness.MediumSmooth) then R=1.13; elseif (roughness == Buildings.HeatTransfer.Types.SurfaceRoughness.Smooth) then R=1.11; elseif (roughness == Buildings.HeatTransfer.Types.SurfaceRoughness.VerySmooth) then R=1.00; else R=0; end if; equation if (conMod == Buildings.HeatTransfer.Types.ExteriorConvection.Fixed) then qN_flow = hFixed * dT; W = 1; hF = 0; qF_flow = 0; else // Even if hCon is a step function with a step at zero, // the product hCon*dT is differentiable at zero with // a continuous first derivative if isCeiling then qN_flow = Buildings.HeatTransfer.Convection.Functions.HeatFlux.ceiling( dT=dT); elseif isFloor then qN_flow = Buildings.HeatTransfer.Convection.Functions.HeatFlux.floor( dT=dT); else qN_flow = Buildings.HeatTransfer.Convection.Functions.HeatFlux.wall( dT=dT); end if; // Forced convection W = Buildings.HeatTransfer.Convection.Functions.windDirectionModifier( azi=azi, dir=dir); hF = 2.537 * W * R * 2 / A^(0.25) * Buildings.Utilities.Math.Functions.regNonZeroPower(x=v, n=0.5, delta=0.5); qF_flow = hF*dT; end if; q_flow = qN_flow + qF_flow;end Exterior;

`conMod`

determines the model that is used to compute
the heat transfer coefficient:

If

`conMod= Buildings.HeatTransfer.Types.InteriorConvection.Fixed`

, then the convective heat transfer coefficient is set to the value specified by the parameter`hFixed`

.- for floors the function Buildings.HeatTransfer.Functions.Convection.ConvectiveHeatFlux.floor
- for ceilings the function Buildings.HeatTransfer.Functions.Convection.ConvectiveHeatFlux.ceiling
- for walls the function Buildings.HeatTransfer.Functions.Convection.ConvectiveHeatFlux.wall

If ```
conMod=
Buildings.HeatTransfer.Types.InteriorConvection.Temperature
```

, then
the convective heat tranfer coefficient is a function of the temperature difference.
The convective heat flux is computed using

Extends from Buildings.HeatTransfer.Convection.BaseClasses.PartialConvection (Partial model for heat convection).

Type | Name | Default | Description |
---|---|---|---|

Area | A | Heat transfer area [m2] | |

CoefficientOfHeatTransfer | hFixed | 3 | Constant convection coefficient [W/(m2.K)] |

Angle | til | Surface tilt [rad] | |

InteriorConvection | conMod | Buildings.HeatTransfer.Types... | Convective heat transfer model |

Initialization | |||

TemperatureDifference | dT.start | 0 | = solid.T - fluid.T [K] |

Advanced | |||

Boolean | homotopyInitialization | true | = true, use homotopy method |

Type | Name | Description |
---|---|---|

HeatPort_a | solid | |

HeatPort_b | fluid |

model Interior "Model for a interior (room-side) convective heat transfer" extends Buildings.HeatTransfer.Convection.BaseClasses.PartialConvection; parameter Buildings.HeatTransfer.Types.InteriorConvection conMod= Buildings.HeatTransfer.Types.InteriorConvection.Fixed "Convective heat transfer model"; parameter Boolean homotopyInitialization = true "= true, use homotopy method"; protected constant Modelica.SIunits.Temperature dT0 = 2 "Initial temperature used in homotopy method"; equation if (conMod == Buildings.HeatTransfer.Types.InteriorConvection.Fixed) then q_flow = hFixed * dT; else // Even if hCon is a step function with a step at zero, // the product hCon*dT is differentiable at zero with // a continuous first derivative if homotopyInitialization then if isCeiling then q_flow = homotopy(actual=Buildings.HeatTransfer.Convection.Functions.HeatFlux.ceiling(dT=dT), simplified=dT/dT0*Buildings.HeatTransfer.Convection.Functions.HeatFlux.ceiling(dT=dT0)); elseif isFloor then q_flow = homotopy(actual=Buildings.HeatTransfer.Convection.Functions.HeatFlux.floor(dT=dT), simplified=dT/dT0*Buildings.HeatTransfer.Convection.Functions.HeatFlux.floor(dT=dT0)); else q_flow = homotopy(actual=Buildings.HeatTransfer.Convection.Functions.HeatFlux.wall(dT=dT), simplified=dT/dT0*Buildings.HeatTransfer.Convection.Functions.HeatFlux.wall(dT=dT0)); end if; else if isCeiling then q_flow = Buildings.HeatTransfer.Convection.Functions.HeatFlux.ceiling(dT=dT); elseif isFloor then q_flow = Buildings.HeatTransfer.Convection.Functions.HeatFlux.floor(dT=dT); else q_flow = Buildings.HeatTransfer.Convection.Functions.HeatFlux.wall(dT=dT); end if; end if; end if;end Interior;

Automatically generated Wed Feb 29 16:53:48 2012.