Buildings.HeatTransfer.Convection.Functions

Information

Package Content

Name	Description
HeatFlux	Correlations for convective heat flux
windDirectionModifier	Wind direction modifier that is used to compute the wind-driven convective heat transfer coefficient

Buildings.HeatTransfer.Convection.Functions.windDirectionModifier

Information

Function that outputs 1 if the incidence angle is below 100 degrees, and 0.5 otherwise. The implementation is once continuously differentiable in its input arguments.

See Buildings.HeatTransfer.Examples.ExteriorConvection for an example that uses this function.

Inputs

Type	Name	Default	Description
Angle	azi		Surface azimuth [rad]
Angle	dir		Wind direction (0=wind from North) [rad]

Outputs

Type	Name	Description
Real	W	Wind direction modifier

Modelica definition

function windDirectionModifier 
  "Wind direction modifier that is used to compute the wind-driven convective heat transfer coefficient"
  input Modelica.SIunits.Angle azi "Surface azimuth";
  input Modelica.SIunits.Angle dir(min=0, max=2*Modelica.Constants.pi) 
    "Wind direction (0=wind from North)";
  output Real W "Wind direction modifier";
protected 
  constant Modelica.SIunits.Angle lee = Modelica.SIunits.Conversions.from_deg(100);
  constant Real cosLee = Modelica.Math.cos(lee);
algorithm 
// The wind direction is defined in TMY3 as dir=0 if from North, and 0 <= dir < 2*pi
// Hence, we subtract pi to redefine dir=0 as wind coming from the south.
// This simplifies the implementation since a surface azimuth is defined as azi=0
// if the surface is south-facing
  W:=Buildings.Utilities.Math.Functions.spliceFunction(
    pos=0.5,
    neg=1,
    x=cosLee-Modelica.Math.cos(azi+Modelica.Constants.pi-dir),
    deltax=0.05);
end windDirectionModifier;