Minimum size for an exchange chamber.

In an attempt to save some space, I'm thinking of building a box in an adjacent space that would separate the indoor side of a window/wall mount A/C unit from the outdoor side. I'd provide appropriate ducting to the outside world on the outdoor side for hot air out and fresh air in, likely with a fan, and provide supply and return ducting with additional fan circulation to my adjacent studio space from the indoor side of the unit. I figure the volume of my actual exchange chamber (indoor side) would only be maybe 8 cubic feet. The potential benefits would be space saving. You could put a table/storage on top, etc. Its almost just like ducting in an inexpensive unit, except being able to introduce fresh air. Would an exchange chamber that is just big enough to accommodate the window/wall mount unit, duct attachments, fan units, etc. work properly? Does there need to be a certain volume of air in the chamber to be effective?

I can't see that happening. But if you still are want to attempt this you have to DUCT the exhaust side out of the interior environment...period. A fan will not do the job...you still have to take into account the condensation that a window unit will produce and prepare for an extraction method. You can purchase an ac unit designed to be inside of a structure...but the price ain't pretty.