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How to model Double-Height Space

asked 2016-01-02 05:08:12 -0600

Gurneet's avatar

updated 2016-01-04 04:53:50 -0600

Hi All,

I need advice on what is the best way to model a double height space that is spread across different spaces so that we have the simulation accurately modeling the thermal and daylight effect. I am attaching a .jpg of the scenario (top section) and possible zoning conditions. The middle one is vertical zoning and the bottom one is horizontal zoning. Following are my queries

  1. If I follow vertical zoning what is the best way to treat the top section of the wall so that we have the daylighting penetration from the left/right zone to the middle office zone.
  2. On the other hand if I follow horizontal zoning , is it a good idea to delete the roof and floor of the zones or make a void on the roof and floor?
  3. How does energyplus react to this kind of situation when we leave a void between two zones or delete the surfaces between two zones.

Regards

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@Gurneet, please use existing tags (including which software you are using) rather than creating custom tags that people are unlikely to be subscribed to or to search for.

__AmirRoth__'s avatar __AmirRoth__  ( 2016-01-02 09:58:25 -0600 )edit

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answered 2016-01-03 13:54:23 -0600

If you check the Engineering Reference document for how EnergyPlus calculates heat transfer through the external surface and internal surface of each construction assembly, you'll find that calculations are done on a heat transfer per area basis. EnergyPlus then uses the area information from the building and fenestration surface objects in the model to calculate a total heat transfer. This means that if you were to remove a surface between two adjacent zones, then EnergyPlus is unable to calculate heat transfer between them! The same can be said for solar radiation (daylighting), but in this case if there is no transparent surface (window, eg.) between two adjacent zones, EnergyPlus is unable to calculate daylight transfer between them. Even if there is a void in between zones in reality, EnergyPlus still requires some sort of surface to properly calculate energy transfer (thermal, solar, etc.).

The best way to capture both thermal and daylight effects is to model a "high transfer window" that has high transmittance to allow more solar distribution and high U-value to allow more thermal heat transfer. As far as placing these "high transfer windows", at the very least you should use your horizontal zoning to allow daylight to pass from the upper zone into the three lower zones. If you think that having one large upper zone at a single temperature is too simplistic, then use vertical zoning in combination (three upper zones and three lower zones).

NOTE: Depending upon how much detail you want to capture, you can also include air mixing effects between zones through the Zone Mixing and/or Zone Cross Mixing objects. These include some convection heat transfer between adjacent zones instead of only modeling conduction heat transfer based on temperature difference between adjacent zones.

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Aaron, Thanks for your valuable inputs, it has given me direction on how to model the space. Just one more query, if I model or follow the vertical zoning, is it possible to specify/tell energyplus to throw/place the cool air/diffuser at 10 feet so that it only cools the lower portion of the double height space which will be exactly as it will be in reality. If there is an option in energyplus then as suggested by you, I will place high transfer windows in the upper part of the vertical zones and might also add zone mixing or zone cross missing objects.

Gurneet's avatar Gurneet  ( 2016-01-04 22:47:49 -0600 )edit

EnergyPlus normally assumes a zone is "well-mixed" and the entire volume is at one temperature. To account for only the bottom 10 feet of the zone receiving cooling from the diffuser, make the bottom zone 10 feet tall. If you want to have more detailed zone air, you can perform use the Room Air Model objects. Check the CrossVent_1Zone_AirflowNetwork.idf and CrossVent_1Zone_AirflowNetwork_with2CrossflowJets.idf example files for how to model cross ventilation.

Aaron Boranian's avatar Aaron Boranian  ( 2016-01-05 10:53:15 -0600 )edit

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Asked: 2016-01-02 05:08:12 -0600

Seen: 1,180 times

Last updated: Jan 04 '16