It depends if you expect AFN to model the inner workings of the HVAC system as part of the flow network, or not. If so, there are various limitations in terms of the type of air handler that can be represented in AFN and those are showing up in the documentation. The main application for this would be to model leaks in ducts or plenums.
However most AFN users probably don’t really want to model the guts of the HVAC system but are interested in the impact of the HVAC system operation on air transfer in the building. The good news is that the HVAC system nodes that are connected to a zone can also be connected to AFN. The HVAC system model will set a mass flow on these nodes in the flow network as well as for the zone heat balance model. So if you are happy to just take the air system flow rates at face value and ignore leaks, then those flows can be modeled in AFN. I agree that the documentation isn’t too clear on this point, but I understand it is a feature that goes back many years to when it first became allowable to simulate with both mechanical air systems and AFN at the same time.
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Tuesday, October 7, 2014 9:30 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] How does Airflow Network really work?
Hello all,
It seems that Airflow Network has some things that "Cannot Do or Restricted".
For example, IOReferece says specifically:
"The model is restricted to using a constant volume fan (Fan:ConstantVolume and Fan:OnOff) and cannot model variable volume fan equipment."
However, it seems that AirflowNetwork:Distribution:Component:Fan admits a Variable Fan.
Is IOReference outdated?
Also, what happens if you define an AirLoopHVAC but do not "connect" its definition to the AirflowNetwork (e.g. you define a Fan:VariableVolume but don't define the corresponding AirflowNetwork:Distribution:Component:Fan)
Or if you use IdealLoads systems, which do not have any connection to the Airflow Network definition?
What aspects from the HVAC systems are considered somehow in the Airflow Network simulation and which are not?
I think this is not clear in E+ reference.
Regards,
Germán Campos
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Posted by: "Brent Griffith" <Brent.Griffith@xxxxxxxxxxxxxxxxxx>
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