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Is there a way to use a unitary system with AirflowNetwork in OpenStudio?

asked 2022-09-18 18:15:51 -0600

jrmuller's avatar

updated 2022-09-20 21:20:13 -0600

I am trying to develop a measure that will build an air flow network for an HVAC loop that has a unitary system. It fails in the translation from the osm to the idf. The unitary only has an inlet and an outlet node in the osm model, but nodes are added between the coils once the model is translated to an idf.

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FYI, there is a feature request for OpenStudio to allow a way to access the nodes of components contained in Unitary Systems. Your use case is another good example for why that would be useful.

ericringold's avatar ericringold  ( 2022-09-21 10:09:06 -0600 )edit

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answered 2022-11-23 06:27:06 -0600

jrmuller's avatar

I did finally get back around to working on this problem and managed to get it to work. I ended up building most of the AFN in an OS measure and doing clean up work in an E+ measure. The E+ measure mainly added the extra AFN nodes between the fan and the coils and the unitary output. It is very loop specific but our residential loops are created the same way each time. I imagine with a lot more logic it could be extended to a generalized unitary loop.

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answered 2022-09-19 13:25:40 -0600

cdouglass's avatar

I'm not sure if you are modeling residential or commercial buildings, but for res there are a number of examples of air flow networks with unitary equipment. In the "ExampleFiles" that come with EnergyPlus, you can see the example "SingleFamilyHouse_HP_Slab". You could also check out the latest PNNL residential prototype models which use AFNs and unitary equipment, available here:

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Thank you. I have seen the EnergyPlus example files, but I am trying to write a measure that will handle creating an air flow network for residential homes from the osm file. I run parametrics on a base osm file and would like to be able to run various scenarios for air flow networks for these cases. The problem occurs during the translation of the osm to the idf file where the unitary is expanded (I am guessing) from a single object to fan -> cooling coil -> heating coil with loop nodes added between the components

jrmuller's avatar jrmuller  ( 2022-09-19 15:53:03 -0600 )edit

I see, thanks for the clarification. Yeah, I don't have any experience working with AFNs using the osm workflow, unfortunately.

cdouglass's avatar cdouglass  ( 2022-09-20 11:20:05 -0600 )edit

@jrmuller When we did the AFN integration 5 or 6 years ago it was not fancy and the focus was on the non-distribution parts of AFN. As far as I know, there isn't any machinery to do the sort of expansion you're talking about, so your suspicion sounds very possible. If you can upload your files, I can take a look (after I look at @cdouglass files from his question the other day, those are first in the queue). I suspect that an EnergyPlus measure could be used to patch up the model, but it will depend on the details of your model and that may not be a very durable solution.

Jason DeGraw's avatar Jason DeGraw  ( 2022-09-20 18:00:44 -0600 )edit

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Asked: 2022-09-18 18:15:51 -0600

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Last updated: Nov 23 '22