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simulating curved external blinds

asked 2020-06-17 10:50:30 -0500

Chris08 gravatar image

updated 2020-06-17 11:23:48 -0500

Dear all,

I am trying to simulate a vertical window with external venetian blinds. For accuracy i want to use angle-dependent properties for the window system (window + blinds).

According to the "engineering reference" energyplus is assuming 1)flat slats 2) does not take any inter-reflections into account for the simulation.

How is it possible to overcome this and ie. simulate curved blinds or any other non-flat external shading device?

Your thoughts on this topic are highly appreciated!

Thank you in advance kind regards, Christiane

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There are no geometrical curves in EnergyPlus, only performance curves. You're going to have to find a (piecewise) linear approximation.

__AmirRoth__ gravatar image__AmirRoth__ ( 2020-06-17 11:37:42 -0500 )edit

thank you for reply Amir, So does this mean, not the geometry is crucial but the optical properties of my shading device? And this won't affect the fact that inter-reflection in between the slats are not accounted for?

thank you! kind regards, Christiane

Chris08 gravatar imageChris08 ( 2020-06-17 12:01:33 -0500 )edit

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answered 2020-06-21 22:16:00 -0500

Rebecca Powles gravatar image

You can model curved slats using the venetian blind shading layer type in WINDOW (enter a non-zero value for rise) to model your venetian blinds:

image description

You can then model the whole window with the shading layer in an exterior or interior position, also including the glazing and frame, in WINDOW and export an idf fragment containing a ComplexFenestrationState object describing the window and a FrameAndDivider object describing the frame.
In the Window library, choose Report, then select Report Type: "EnergyPlus BSDF Idf File". The exported idf fragment includes the BSDF matrices required to model the optical properties of the shading layer and glazing. If you include the WINDOW idf fragment in your main idf file, you can then refer to the complex fenestration and frame objects in your FenestrationSurface:Detailed objects (make sure you match the names output by WINDOW):

in the idf fragment generated by WINDOW:

    WindowProperty:FrameAndDivider,
        NAME_OF_FRAME_OBJECT,  !- Name
        0.038395,                !- Frame Width {m}
        ,                        !- Frame Outside Projection {m}
        ,                        !- Frame Inside Projection {m}
...

    Construction:ComplexFenestrationState,
        NAME_OF_CFS_OBJECT, !- Name
        LBNLWindow,              !- Basis Type
        None,                    !- Basis Symmetry Type
        ThermParam_NAME,  !- Window Thermal Model
        CFS_NAME_Basis,  !- Basis Matrix 
...

in main idf - the Construction Name should be the name of the ComplexFenestrationState object, and the Frame and Divider name should be the name of the FrameAndDivider object:

    FenestrationSurface:Detailed,
    Block1_Zone1_East_Wall_0_0_1_Win,  !- Name
    Window,                  !- Surface Type
    NAME_OF_CFS_OBJECT, !- Construction Name
    Block1_Zone1_East_Wall,  !- Building Surface Name
    ,                        !- Outside Boundary Condition Object
    AutoCalculate,           !- View Factor to Ground
    NAME_OF_FRAME_OBJECT,  !- Frame and Divider Name
    1,                       !- Multiplier
    4,                       !- Number of Vertices
    3.356958552,7.80691071,.6,  !- X,Y,Z ==> Vertex 1 {m}
    3.356958552,9.90691071,.6,  !- X,Y,Z ==> Vertex 2 {m}
    3.356958552,9.90691071,2.1,  !- X,Y,Z ==> Vertex 3 {m}
    3.356958552,7.80691071,2.1;  !- X,Y,Z ==> Vertex 4 {m}
...
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answered 2020-06-18 07:30:07 -0500

You can try approximating it by increasing the front and back side slat beam and diffuse solar reflectance in the WindowMaterial:Blind input object.

Another option is to use WindowMaterial:ComplexShade which does have a slat curve field. That is part of the Constuction:ComplexFenestrationState series of objects. These objects have many inputs but some additional flexiblity.

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answered 2020-06-26 03:36:18 -0500

Chris08 gravatar image

thank you very much for your ideas and answers!!!

regards, Christiane

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Asked: 2020-06-17 10:50:30 -0500

Seen: 137 times

Last updated: Jun 26