Isnt that what circulation fans are for? Couldn't you just use a wall mounted fan mounted on the ceiling?
Probably go with the slower one if that's what your set on doing. Might be better having the fan above sucking warm air and pumping it to the bottom thus letting it rise?
Why no exhaust? Is it a sealed room?
Hah, thanks for the reply! I have one circulation fan, I have it mounted slightly higher than the top of the pots, and it intermittently circulates air slightly downward, over the pots surface, in a 4x2x6 = 48 ft3 tent. My exhaust fan, which I run most of the time when the outdoor temps allow, is probably pushing about 1.5 tent evacuations every minute by tent volume when running on half speed ) (blows 135 CFM at full speed, it's probably a little too much fan). I'm awaiting a humidity meter to know how that exhaust fan speed affects humidity.
During winter in my location, it is too cold for cannabis at night (50s recently, but during December, it's common to be 45°F, so I have to turn the exhaust fan off during hours when the outdoor temps are below 65 to 70 °F, and the lights may be on for some of this time, they act as heaters and warm the top of the tent while the bottom is cooler when the exhaust is off. This heat I want better mixed through the tent.
If I use a circulation fan mounted high, the canopy will act as somewhat of a block, so I want to pipe that warm air from the top of the tent, to the bottom, below the canopy, to set up a looped air circulation where the air rises in the tent through the canopy. I want the vent pipe to be inside the tent as I want to run it at night when it's cold outside, and would otherwise chill the air in the duct portion outside of the tent. I've seen other folks tents here on RIU with just such a vertical duct. I was wondering what kind of airflow through it is needed for adequate mixing?
I could either mount the fan at the top and blow into the pipe, or at the bottom and suck air from duct's top, either way it will move air from above to below the canopy. I'm just wondering what kind of CFM I should use for that? Since writing the post, I was leaning toward the larger one which would circulate all the tent air every minute and a half or so, a fan of about 30 to 38 CFM. I can buy a variable speed circuit board for it if needed.
If I ever put a HID in the tent for a couple weeks of conditioning at the end of bloom, it might be a good idea to have the larger one due to those lights greater heat.
Here's a pic of my exhaust fan, that's 6" ducting for size comparison. I'd probably make a similar design for this vertical duct, although the fan is much smaller than in the pic. I was thinking of using 2" ducting or even large PVC pipe, strapped to a corner pole. Top to bottom air circulation in the duct as one "leg" of a loop, air rises through canopy from bottom to top as the other leg.
