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Modelling vents in EnergyPlus

asked 2015-04-13 11:21:17 -0500

Waseem's avatar

updated 2018-05-26 15:02:08 -0500

What is the best way to model vents in EnergyPlus (e.g. Plant room's outside door, windows for preventing condensation)? Please see the figures.

Normally, in Energyplus vents are modeled using a schedule, does this schedule needs to be ON all the time? this will be uncontrolled natural ventilation or we have to input air flow rate or ach?

Plant room door


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For a mechanical room such as the picture you're describing, I would simply use a high ACH (around 2.0, depending on whether there's also an intake/exhaust fan in that room).

Julien Marrec's avatar Julien Marrec  ( 2015-04-16 02:18:05 -0500 )edit

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answered 2015-04-18 10:49:50 -0500

If I understand correctly you would like to model the air from the outside entering the mechanical room through this vent shown above. If this is the case I would suggest two options:

  1. Use the air flow network. This would be quite precise and probably not necessary but you can define your opening and set it up so that E+ will calculate whether outdoor air is flowing into the space and how much is flowing into the space through the vent.

  2. use the simple ventilation object. Here you can define an opening and add a flow rate and schedule to your zone that will put that amount of OA into your space.

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@Annie Marston: Don't you think that this case is different from a simple window/ventilation object as it have louvers, which can restrict some of the air? I agree that the first options is more detailed and may not be necessary but for your option 2, how can I can get the value of ACH? Thanks

Waseem's avatar Waseem  ( 2015-04-23 04:58:37 -0500 )edit

@Waseem, with the simple ventilation rate you don't actually define the opening just an ACH so it doesn't really matter about the louvers in the object. The louvres are important when it comes to defining the ACH and the schedule that you would put with it. I just looked at a project we did with louvred openings for natural ventilation into an atrium. Although I don't think this would be relevant to your project it might be worth looking at the ZoneVentilation:WindandStackOpenArea object to see if that would help you.

Annie Marston's avatar Annie Marston  ( 2015-04-23 08:23:59 -0500 )edit

Hi Annie, How is possible to modelling physically the vents/grills? Assuming that my model has only two positions (tottaly close or open), i suppose that we can build opennings with "virtual glass" considering high thermal and transmittance coefficients. Am I correct? Thank you!!

luis melo's avatar luis melo  ( 2016-03-17 07:52:53 -0500 )edit

The questions above, refers to double skin façade, when i have multi zones, linked by air flow network. However, i'm not sure about the vents in terms of physical properties.

luis melo's avatar luis melo  ( 2016-03-17 08:01:40 -0500 )edit

@luis melo: if you calculate the actual open area, you can draw a window which represents that, or you could draw multiple for each opening in your grill/vent. The properties of that window would reflect the properties of the grill when closed. Then you can use either of the objects described above to put the outdoor air into your space. That would be my guess from what you have described.

Annie Marston's avatar Annie Marston  ( 2016-03-17 08:34:09 -0500 )edit

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Asked: 2015-04-13 11:21:17 -0500

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Last updated: Sep 11 '17