modelShadeConvection

Model for convective heat balance of a layer that may or may not have a shade

Information

Model for the convective heat balance of a shade that is in the outside or the room-side of a window.

The convective heat balance is based on the model described by Wright (2008), which can be shown as a convective heat resistance model as follows:

Wright (2008) reports that if the shading layer is far enough from the window, the boundary layers associated with each surface will not interfere with each other. In this case, it is reasonable to consider each surface on an individual basis by setting the convective heat transfer coefficient shown in grey to zero, and setting the black depicted convective heat transfer coefficients to h=4 W/m² K. In the here implemented model, the grey depicted convective heat transfer coefficient is set set to h' = k h, where 0 ≤ k ≤ 1 is a parameter.

References

Jon L. Wright.
Calculating Center-Glass Performance Indices of Glazing Systems with Shading Devices.
ASHRAE Transactions, SL-08-020. 2008.

Parameters

Type	Name	Default	Description
Modelica.Units.SI.Area	A		Heat transfer area
Boolean	thisSideHasShade		Set to true if this side of the window has a shade
Real	k	1	Coefficient used to scale convection between shade and glass

Connectors

Type	Name	Description
Modelica.Blocks.Interfaces.RealInput	Gc	Signal representing the convective thermal conductance
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a	air	Port that connects to the air (room or outside)
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_b	glass	Heat port that connects to shaded part of glass
Modelica.Blocks.Interfaces.RealInput	QRadAbs_flow	Total net radiation that is absorbed by the shade (positive if absorbed)
Modelica.Blocks.Interfaces.RealOutput	TSha	Shade temperature

Revisions

May 30, 2014, by Michael Wetter:
Removed undesirable annotation Evaluate=true.
June 11, 2013, by Michael Wetter:
Redesigned model to separate convection from radiation, which is required for the implementation of a CFD model.
June 27, 2013, by Michael Wetter:
Changed model because the outflowing radiosity has been changed to be a non-negative quantity. See track issue #158.
April 2, 2011 by Michael Wetter:
Added homotopy operator.
February 3, by Michael Wetter:
Corrected bug in start value of radiosity port and in heat balance of shade.
January 28 2011, by Michael Wetter:
Fixed computation of convective heat balance between air, shade and glass.
November 3 2010, by Michael Wetter:
First implementation.