Buildings.HeatTransfer.Convection.Functions
Functions for convective heat transfer
Information
This package contains functions that are used in the package Buildings.HeatTransfer.Package Content
| Name | Description |
|---|---|
 windDirectionModifier
|
Wind direction modifier that is used to compute the wind-driven convective heat transfer coefficient |
 HeatFlux
|
Correlations for convective heat flux |
Buildings.HeatTransfer.Convection.Functions.windDirectionModifier
Wind direction modifier that is used to compute the wind-driven convective heat transfer coefficient
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.Convection.Exterior for an example that uses this function.
Extends from Modelica.Icons.Function (Icon for functions).
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"
extends Modelica.Icons.Function;
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)
"Angle at which the transition occurs";
constant Real cosLee=Modelica.Math.cos(lee)
"Cosine of the angle at which the transition occurs";
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;