Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
The general strategy here is to set up the AirflowNetwork objects so that the airflow through them at a given pressure difference matches a given value. The ideal case would be to have an experimental measurement of airflow.
The documentation is advising the use of the AirflowNetwork:MultiZone:Surface:Crack object because other objects aren't appropriate in this case. Don't get too caught up in the "crack" in the name, you'll want to think of it more like flow through an orifice (see, for example, https://en.wikipedia.org/wiki/Orifice_plate) where the flow rate is proportional to the square root of the pressure difference. If you lack specific information, a place to start is using 0.5 as the exponent for the crack object.
To set the flow coefficient, if you don't have a measurement, then the next best thing would be to find something in the literature. Then there's some algebra to do to get the flow coefficient that's needed. I've answered a question on that process here, so I won't repeat all that. Follow that procedure with n=0.5.
