Actually I teach HVAC but I’m interested in going beyond rule of “thumb” to more scientific approaches.
Many vendors provide actual test data for their diffusers but this is based on good room air mixing. This is a high energy approach with lot’s of tirbulence.
Emerging methods use displacement techiques and a lower velocity that can be largely laminar.
Since you were evacuating smoke of course you wanted a good strong velocity to clear the smoke quickly. You get a lot of mixing with these velocities.
I’m looking forward to your final design.