Air conditioner question

[Eliot Pryor]

Question: If you put a 6 in exhaust fan at the end of a 4 inch duct line would it increase the air flow ?

[bboyfromwayback]

If the 4” line is the intake to a 6” fan then no because it’s limiting the air being fed to it. Now on the the other side, using a home duct as a example, if you put a 4” register at the end of a 6” duct it builds pressure which makes the air come out of the vent stronger.

[Eliot Pryor]

I ran a 4 inch line from my a.c. plenum to my tent. With a 4 inch inline fan. I been considering putting a 6 inch exhast fan in the tent to suck air from the line. It seems like it should increase the air flow but then again it don't. Thanks for the reality check.

[Toker1]

A 4 inch register on a 6 inch line does act as a nozzle. This increases exit pressure, but still decreases volumetric flow through that exit.

[Toker1]

No... it would decrease it.