Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
This is a big issue that hasn't been resolved yet as most laboratory applications are variable air volume. There was a 2012 SimBuild paper on this topic.
The work around is to come up with an aggregate schedule for the air flow based on the flow rate it should be. Simply put 12 hours at 6 air changes per hour and 12 hours at 4 air changes per hour would be 5 air changes per hour for 24 hours. Of course this doesn't capture peak demand charges correctly if that's a factor in the design and over sizes the water side because you're only providing 5 air changes rather than 6.
Note that the induction ratio is not linear with air flow and drops off dramatically below 50% of design flow.
As far as I know only IES-VE does this correctly today.
