Can airflow through an HVAC duct be considered inviscid?
Does viscid flow ever occur for HVAC?
If the answer to (1) is yes, how do we know airflow in an HVAC pipe is inviscid? In general, what's a good method for determining whether a flow is viscid or inviscid?
Intuitively, I associate a viscous flow with something like honey. Airflow is definitely not like honey. But I'm wondering if there's a more quantitative or theory based approach to verify that airflow would be inviscid.