I am having a hard time Mentally undertandsing what you have going there. Do you have those evga's in a sealed box and pumping Air-conditioned air through he box? If so how much air? Are the cards you can see all that is in the box? Overall how well has the design worked for you?
It is a quite easy. Inside the electric cabinet are 10x rx vega 64 from sapphire. Top of the cards(where is the exhaust of hot air) are inside sealed air tunnel (so there is no hot air inside the cabinet) where are two industrial fans - on each side to vent hot air out of the tunnel (on the left side is connected hose which is leading to the stairway for heating of the house). Two hoses leading to the bottom of the cabinet are for the fresh cold air from the outside of the house -5celsius by now.
Dust filters are on all intake fans. Industrial electric cabinet is ip66, so I do not worry about dust and so on... Air flow is about 2000m3/h.
I see so that whole cabinet picture you have is not a different AC box. The cards are in there. What do the temps look like? IS there anything you would change up about your setup? Do you think you could put more cards in there or have them closer together?
Yes, the gpus are inside. Temperatures are about 43-56degree celsius. It depends on the positions of the cards. And outside temp matters too. With -10 it is about 40for all cards(3600rpm on gpus fans). It is possible to install one more gpu into the middle - there is a space for one and in the air tunnel is cutted window for this, but for now it is sealed... For the second build I will make some changes. (I am not mentioning that I am already changed mobo from asrock h110 btc+ to asus mining expert. Asrock was a junk unable to run more than 9x Vegas, with 10x, there was no post, just fans spinning...)
The air tunnel with two fans inside - that was a very difficult to build because of airtight of all sides... So for the new build will be better to just cut windows for gpus exhaustion on the top of the cabinet, so you do not need to build air tunnel and hot air will flow most smoothly and without aditional two fans.
Anyway for the summer I am planing water cooling for each gpu, and with that, the number of gpus will be 15 or more...