But how about cooling the entire room with Air conditioner. I’m just adding up this because the room is pretty closed one and can get cooled down pretty fast.
It's nearly impossible to achieve, 1KW of electricity load creates 3412BTU/h, the power required by a decent AC to product 3412BTU/h is 0.33KW, in other words, 1/3 of your power capacity will need to go to AC (you still need to count the room BTU, lights, and what not) but safe to say 33% of your power.
Phil's set up is 192KW which means 63kw worth of cooling needs to be there, so 9-10 pcs of the AC unit he has right now, the cost of running those 10 Aircons or otherwise the lost opportunity of running other gears makes relying on AC only a very terrible idea.
Your second proposal of water chiller is more reasonable, the ratio between cooling and power consumption is a lot better, however, it has a few issues.
1- Can't be done in places where humidity is high
2- Needs a good supply of water
3- Needs a ALOT of intake space
pretty hard to have all of those 3 in one place, so the best option there is, is to force airflow in and out of the farm, ideally, if you had an infinite supply of air flow, your miner temperature will be the exact same as the outside air temp, but that isn't possible, so just increase the airflow as much as possible with every way possible.
Now depending on your climate, it really makes no sense to spend so much on cooling taking into consideration the one single month where temps go above a certain degree, for my case, usually around July-Aug, we have days where temps can go above 50 degrees Celsius, 40c is normal, 30-35 is about average, it would be unwise to spend that much money just to be able to mine at full speed for 1/12 of the year, when the farm becomes extremely hot, I can just underclock my gears, drop my total heat generation by about 30% and then mining at 50c becomes as mining at 35c.
I see a lot of folks who spend TOO much to optimize cooling for a short period of time, I think most of them failed to run the math, the ROI on that is just terrible, my advice is to have enough cooling for the average warm days which would probably make up 70-80% of the year including the cold days, and for that remaining 20-30% just underclock your gears.