Has anyone used one of these for temp control. From floor a/c vent

Really dont what esle to do

It's ductwork, you can move air through it. lol You will need an exhaust fan and a source of cool air to intake. Always best to exhaust the heat outside so you don't warm up the intake air. Intake temperature is the major limiting factor, can't cool a grow with warm air.

Trying to use it with the house a/c on. To provide a/c inside a 4x4x9 tent. With the 4 in exhaust..and led light tent is about 90 degrees

Cool air for the intake is always good, should help as long as the AC is running and you have the exhaust fan to help pull the cool air into the tent.