It's simple really ...
Fan orientation is basically a function of location:
A. Air Cooling: The
default is as follows:
Rear = Out
Bottom = In
Front = In
Top = Out
You can not use the default when ....
a) water cooling
b) you don't have 1.33 to 1.5 as many ins as outs
There are four misconceptions which if you can not shake, you will have trouble understanding air cooling:
a) Forget what you learned in 8th grade earth science ... yes hot air rises ... but only in the absence of other factors... like fans spinning at 1000 rpm. The force created by heat rising is of co consequence as the temperature differential (air density) in a PC case is so far past being insignificant. Remember ventilation of enclosed spaces is not a new science. Been here for 1000s of years in its most basic from. The design concepts for a case are the same for any enclosed space, like a room, house or anything else.
b) You do not need fans blowing in two directions. Have an exhaust fan in your kitchen ? ... where's the intake fan ? How about when you put a fan in a bedroom window ? ... do you put another one in blowing opposite way ? No because it is not needed. And unlike your kitchen and bedroom, you don't have an entire wall poked full of holes to let air / in or out.
c) Fans produce anywhere near there published specs ... expect half. When you see 50 cfm @ 1.2 SP, that means 50 cfm @ 0 sp and 1.2 DP @ 0 cfm ... reality -means in the neighborhood 25 cfm @ 0.6
d) Dust is not the major concern in a negative air pressure situation. Here's a common PC case fan mount arrangement
Bottom = 2
Top = 3
Front = 2
Rear = 1
So 4 in and 4 out, sounds OK right ? Nope. The 4 intakes have dust filters which means depending on how clean they are . You are losing anywhere from 1/3of your flow from dust filters depending on how much dust they have collected. Let's say the fans are pushing 40 cfm so the front and bottom fans giving you 4 fans x 40 cfm x 2/3 = 107 cfm ... the other 4 unrestricted are pulling out 160 cfm. The balance is coming in thru the vented flot covers and the giant grille on the back of the case. But what are we concerned about bsides dust then ? How about that 250 watt GFX card exhaust ? Some of that is making it out thru that rear vent. What about the exhaust from that 750 watt PSU ? Much of that is being sucked right back in.
B. Water Cooling: The
default is as follows:
a) All Rad fans blow in, no exceptions. Why ?
1) What's hotter, air outsede the case or air inside the case ? I we can safely presume that you bought the AIO or CPU water block to keep your CPU cool, we must say "it's a given" that the central goal here is to cool the CPU ? So if ambient outside the case is 22C and air inside the case is 25C, then here's your choices with a system designed for 10C delta T:
Heating Removed w/ Ambient Air =150 (watts) a C (heat coefficient) x (water temp 32C - ambient) 22C = 1500C
Heating Removed w/ Inside Case Air =150 (watts) a C (heat coefficient) x (water temp 32C - ambient) 25C = 1050C
By using outside air you are getting 50% more CPU cooling. If your goal is to cool the components that you invested "Mucho Dinero" in, then those components should be your primary concern. But id the science is out, we can always look at what the folks who are "do this for a living" say and read the instruction manual (in this case Corsair) say:
2. As for "But what about the extra heat that's now inside my case ?" ? ... so what ? If your memory is 28C instesad of 25C, is it going to fail or perform better ? recognize that if you have designed your case cooling properly ... (1) 120mm fan for each 50 - 75 watts or (1) 140mm for each 75 - 100 watts, you are likely turning over the entire case volume 1.5 to 2.0 times per second. What component are you concerned about that is getting 2C hotter ? And what's worse, pushing air into the case that is preheated by a 150 watt CPU ... oir sucking air in thru the rear grille that is preheated by a 250 watt GFX card and 750 watt PSU exhaust ?
A $30 investment can help you see very easily what is going on ...
https://www.amazon.com/CHAUVET-H700-Hurricane-Machine-Machines/dp/B0002D0JX8/
We used to use it on every build .... but after a while we learned that if we had 1.3 times as many in's as outs , we were not sucking in air thru thr rear grilles. If you lazy about keeping filters clean, I'd go to 1.5
1- The fans in the bottom chamber could they affect in any way the Negative pressure? .... The 4 fans at the bottom pull air inside the case through the right panel and push is out through the left panel
2 - What could happen if i set the front intake Fans at 1900RPM and the top/rear exhausts lets say to 1000RPM?
1. Depends on how sealed the bottom chamber is. I am assuming that there is some type of heat exchange behind this fans and that ambient air is being sucked in across that heat exchanger creating positive pressure which will be pushed out thru the front (dont see a fan there) , back, left side, bottom and to a lesser extent up theu the top panel. What goes thru which side depends upon relative the "free area" (sum of all openings) in each panel.
However if there is no radiator or heat exchanger in that bottom section, then the fans are basically doing noting. That whole bottom section essentially serves no purpose.
With (3) in (filters assumed) and (4) out you will likely have as much as twice the air being sucked out as coming in thru fan openings ... Obviously with the GFX card water cooled, sucking in hot exhaust is not an issue. The only potential impact other than dust that I see is the PSU exhaust and the rear exhaust from the bottom chamber getting sucked back in.
I don't quite understand the "chiller" concept. I see the tubes leaving the case to what I assume is the off image chiller. If the coolant cooling is provided by the chiller itself, then what is the radiator for ? I would expect, at least in summer, ambient air is warming the coolant.
With a Chiller in the loop, Id have the 3 fans in front blowing in, 1 at the rear and the chiller handling everything else. But can't think of a use for the bottom section. Do you have any tenmp sensors int the loop or in the case to measure air temps ? It's insta;; a teeo in the inlet and outlet to the case an meaore the coolant temp leaving and coming back into the case ... I use 6 of them (1 in and 1 out for each rad plus case air and ambient) and display thm on a 6 channel display.