blockSideFins

For a window with side fins, outputs the fraction of the area that is sun exposed

Extends from Modelica.Blocks.Icons.Block, Buildings.ThermalZones.Detailed.BaseClasses.SideFins.

Information

For a window with side fins, this block outputs the fraction of the area that is exposed to the sun. This models can also be used for doors with side fins.

Input to this block are the wall solar azimuth angle and the altitude angle of the sun. These angles can be calculated using blocks from the package Buildings.BoundaryConditions.SolarGeometry.BaseClasses.

Limitations

The model assumes that

  • the side fins are placed symmetrically to the left and right of the window,
  • the top of the side fins must be at an equal or greater height than the window, and
  • the bottom of the side fins must be at an equal or lower height than the bottom of the window.

Implementation

The method of super position is used to calculate the shaded area of the window. The area besides the side fin is divided as shown in the figure below.

imaghe

Variables used in the code for the rectangle AEGI, BEGH, DFGI and CFGH are shown in figure below.

imaghe

The rectangles AEGI, BEGH, DFGI and CFGH have the same geometric configuration with respect to the side fin. Thus, the same algorithm is used to calculate the shaded portion in these areas. A single equation in the for loop improves the total calculation time, as compared to if-then-else conditions, considering the various shapes of the shaded portions. To find the shaded area in the window ABCD, the shaded portion of BEGH and DFGI is subtracted from AEGI and CFGH. This shaded area of the window is then divided by the total window area to calculate the shaded fraction of the window.

Parameters

TypeNameDefaultDescription
General › Window
Modelica.Units.SI.LengthhWinWindow height
Modelica.Units.SI.LengthwWinWindow width

Components

TypeNameDefaultDescription
Modelica.Blocks.Interfaces.RealInputaltSolar altitude angle (angle between sun ray and horizontal surface)
Modelica.Blocks.Interfaces.RealInputverAziAngle between projection of sun's rays and normal to vertical surface
Modelica.Blocks.Interfaces.RealOutputfraSunFraction of window area exposed to the sun

Revisions

  • July 5, 2012, by Michael Wetter:
    Changed definitions of side fin height h to be measured from the top of the window. This allows changing the window height without having to adjust the side fin parameters.
  • February 25, 2012, by Michael Wetter:
    Revised implementation.
  • Feb 01, 2012, by Kaustubh Phalak:
    First implementation.