I don't think you are moving enough air to put them inside the container. Your duct looks insufficient for a single unit let alone 11...

It would be nice if you measured the cfm a single unit wants while outside the container, that would give you a rough idea.

You don't have to worry about the ambient temperature too much, as long as you can take that hot air out. Your warehouse is like a box, if you don't move that air the hot air will remain and quickly heat the place (great for winter warming, not so much in summer lol).

So visualize your warehouse as a box, and think a way to move the required number of cfm in and out. If you put your miners inside another box (container), the same applies.

Hot air likes to go up, big extractors above help. And i really mean BIG extractors. But that would pull air from the outside, you must find a way to let that air in, assisted or not...

I think you simply underestimated the amount of CFM each unit needs.