Problems with heat recovery system (of the ventilation system) after adding add zone mixing object

asked 2021-01-13 05:40:31 -0600

Pieter_Proot gravatar image

updated 2021-01-13 15:30:39 -0600

Together with a fellow student, I have to model a residential building in OpenStudio. We have made a lot of progress, but we still have the following problem:

We think that the airflow between different zones is very important, especially in residential buildings where you have an outside air supply (coupled with the heat recovery to ensure the correct supply temperature) to various zones. Which then flows through a zone (like a hall) with no supply air or no extraction air. Thereafter, an airflow has to be possible from that zone to another zone (for example a bathroom) provided with an exhaust fan to extract the air. ( just for your information, we didn't draw any interior doors)

To implement those airflow's we used the add zone mixing object and manually balanced all the zones. We didn't get any extra errors or revere warnings after simulating, so we thought everything worked well. However, when we zoomed in on the heat recovery, we saw that it no longer works. We conclude that adding the Fan Zone Exhaust occurs problems with the heat recovery system, which makes sense because those exhaust fans aren't coupled with the main ventilation system.

Link to our model (latest version of OpenStudio):

We are looking for a correct method to couple our exhaust fans with the mains system (with heat recovery). I don't know if this is possible? Or, are there other ways to model a good airflow?

Before using exhaust fans: image description

After using exhaust fans: image description

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Are you using this Add Zone Mixing measure from the BCL? This will incorporate one-way mixing, but not related to the pressure-driven airflow network. I ask because you included the airflow-network tag in your post.

Aaron Boranian gravatar image Aaron Boranian  ( 2021-01-13 09:00:55 -0600 )edit

If you can provide images of results showing that ventilation system heat recovery isn't working, or share links to the model input files via Dropbox, Google Drive, etc. then others can provide better help.

Aaron Boranian gravatar image Aaron Boranian  ( 2021-01-13 09:02:20 -0600 )edit

Thanks for your response! Yes, indeed we used the Add Zone Mixing measure from the BCL to make the airflow between zones possible. I added our model and some images of the results to my original post.

Pieter_Proot gravatar image Pieter_Proot  ( 2021-01-13 15:22:08 -0600 )edit