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Trying to model blinds wider than 2.5 cm with WindowMaterial:Blind:EquivalentLayer

asked 2019-05-09 02:41:14 -0500

Samuel de Vries gravatar image

updated 2019-05-09 11:00:57 -0500

I am trying to model 12.7 cm wide vertical blinds using WindowMaterial:Blind:EquivalentLayer. When I do so I get the following errors:

* Severe * Out of range value Numeric Field#1 (Slat Width), value=0.12700, range={>0 and <=0.025}, in WINDOWMATERIAL:BLIND:EQUIVALENTLAYER=WMTEUQL_BLND_KINDV_RF80_T02_A18_RB45 * Severe * Out of range value Numeric Field#2 (Slat Separation), value=0.12700, range={>0 and <=0.025}, in WINDOWMATERIAL:BLIND:EQUIVALENTLAYER=WMTEUQL_BLND_KINDV_RF80_T02_A18

The input should be in meters. It seems a bit strange that the slat width would be limited to a maximum of 2.5 cm. Wider products are quite common and for vertical blind a slat width as small as 2.5 cm doesn't exist. The input output reference also state that 2.54 cm should be the default value.

I am using EP 8.5. I have also tried updating to 9.0 but this still gave the same error. My WindowMaterial:Blind:EquivalentLayer object: (I am aware I am omitting visible properties. I am not interested in these and the exmple IDF shows they are not required)

WindowMaterial:Blind:EquivalentLayer,
  WMTEUQL_BLND_KINDV_RF80_T02_A18_Rb45,          !- Name
  Vertical,              !- Slat Orientation
  0.127,                  !- Slat Width {m}
  0.127,                  !- Slat Separation {m}
  0.0000,                !- Slat Crown {m}
  45,                      !- Slat Angle {deg}
  0.02,                 !- Front Side Slat Beam-Diffuse Solar Transmittance
  0.02,               !- Back Side Slat Beam-Diffuse Solar Transmittance {dimensionless}
  0.80,                 !- Front Side Slat Beam-Diffuse Solar Reflectance {dimensionless}
  0.45,                 !- Back Side Slat Beam-Diffuse Solar Reflectance {dimensionless}
  ,                !- Front Side Slat Beam-Diffuse Visible Transmittance {dimensionless}
  ,                  !- Back Side Slat Beam-Diffuse Visible Transmittance {dimensionless}
  ,                   !- Front Side Slat Beam-Diffuse Visible Reflectance {dimensionless}
  ,                    !- Back Side Slat Beam-Diffuse Visible Reflectance {dimensionless}
  0.02,                   !- Slat Diffuse-Diffuse Solar Transmittance {dimensionless}
  0.80,              !- Front Side Slat Diffuse-Diffuse Solar Reflectance {dimensionless}
  0.45,               !- Back Side Slat Diffuse-Diffuse Solar Reflectance {dimensionless}
  ,                     !- Slat Diffuse-Diffuse Visible Transmittance
  ,                !- Front Side Slat Diffuse-Diffuse Visible Reflectance {dimensionless}
  ,                 !- Back Side Slat Diffuse-Diffuse Visible Reflectance {dimensionless}
  ,                        !- Slat Infrared Transmittance
  0.9,                     !- Front Side Slat Infrared Emissivity {dimensionless}
  0.9,                     !- Back Side Slat Infrared Emissivity {dimensionless}
  FixedSlatAngle;    !- Slat Angle Control
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I tried editing the maximum values in the IDD file. For energyPlus 8.5 this takes out the maximum slat width limitation. I then run in to the problem that there appears to be an error where EP doesn't use the slat angle given to it (a bug solved in newer versions of EP).

If I try editing the IDD file in the same way with energyPlus 9.0. Changing the maximum fields here doesn't have any effect. Does anyone know the change these type of limitations for newer versions of EP?

Samuel de Vries gravatar imageSamuel de Vries ( 2019-05-09 03:49:51 -0500 )edit
1

Later versions of EP us an epJSON file instead of the the IDD. @MarkAdams might be able to help.

MatthewSteen gravatar imageMatthewSteen ( 2019-05-09 09:35:24 -0500 )edit

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answered 2019-05-09 09:34:14 -0500

Samuel de Vries gravatar image

The maximum slat width error can be resolved by editing the .IDD file. Apparently the IDD file is no longer read at runtime for newer versions of EnergyPlus so with these versions you need to recompile EP after editing the .IDD (see)

I found that EnergyPlus 8.8 has the slat angle bug solved and it also still allows you to edit the .IDD without compiling so I continued with this version.

Although everything simulates without errors now I have some doubts about the results. I tested the vertical blinds, 127 cm wide and positioned at a static 45 degrees using both the Equivalent layer approach (Red: ASHWAT in graph) and the WindowMaterial:Blind (Blue:Winkelman in graph) approach.

Transmitted solar radiation is consistent for both models but the equivalent layer approach gives extremely low indoor surface temperatures, no radiative exchange and very high convective exchange.

These links contain the two IDF's I used for this comparison:

ASHWAT EquivalentLayerModel

Winkelman model

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@Samuel de Vries your first two paragraphs are a great solution to your original post, but please ask about this discrepancy between the two models as a new question post.

Aaron Boranian gravatar imageAaron Boranian ( 2019-05-09 10:58:18 -0500 )edit

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Asked: 2019-05-09 02:41:14 -0500

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Last updated: May 09