Corsair Air 540 airflow and pressure

[therealnexion]

Hey guys,

 

I'm trying to figure out the best way to configure the fans and radiators for a Corsair Air 540. I'm getting an H110i GT cooler (113 CFM) and a 980 Ti Hybrid with a radiator and 140mm fan (69.5 CFM). I was thinking of putting the H110i on top and the video card radiator on the back, both as exhausts. The only intake should be the front panel, which has a filter on it. In addition, I want to maintain positive pressure to prevent dust getting in through unfiltered areas and to avoid unexpected turbulence.

 

It sounds like with the stock 140mm fans on the front, I'll have 67.8 * 2 = 135.6 CFM intake, which is WAY less than the 113+69.5=182.5 CFM exhaust. In addition, the graphics card will suck some air from inside the case (it has a fan) and exhaust it out the back. Not sure how much, but that's something to factor in.

 

Am I doing this right? I realize the CFM differs based on the RPM the fan will run at, which complicates things. It seems that the only way to make this positive pressure is to put very high-flow fans on the front. The best I found will give me 60.2*3=180.6 CFM, which is still somewhat lower than the net exhaust.

 

What do you guys think?

 

Update: I found some 120mm fans with much higher airflow so I could bring the intake up to 330 CFM.

[c-attack]

I am going to save the positive vs negative pressure=dust rant for another day, as today is a holiday. However, don't worry about it. You need to remove the air from inside the case and replace it with cooler air from outside the case. There is very little direct cooling to be done and the fans mostly serve to exchange the air.

 

In this set-up, you are going to have positive pressure no matter what you do. The fans on the radiators cannot move their listed CFM when mounted against some kind of resistance, in this case the radiator. You can get a rough idea of how much less by comparing the free air 12V speed to the max speed when mounted. It varies by fan, but you likely loose about 80-100 rpm from the top end. You can try the same trick with the front air filter on vs off to see how much resistance it offers. However, all of this only matters if you are running all the fans flat out at 12v. Even at load, you are not going to want to do this. Nobody likes running their radiator fans flat out -- it will be very loud. Since you will always be running sub-maximal fan speeds, you can always raise one set or the other to create the "pressure balance" you like.

 

The things is, you don't need to. The beauty of the hybrid Ti system is most of the heat is being dumped directly out the back. You don't need these monster air flows because most of your heat is being carried by the water directly to the exit. You are going to be able to use low fan speeds and still have a 45C GPU and a cool CPU as well. It will be very nice. As you mentioned, the whole volume equation is fan speed dependent. Rather than calculate the max values, I would suggest trying to estimate based on your comfortable fan speed settings. For the 540, my personal preferences for 120mmx3 fans in the front are 1000 rpm for moderate duty and I will not let them go over 1500 for very heavy loads. For 140mmx2 intake, I am willing to let them run up to 900 under heavy load. These are tolerable, although at 1500 rpm x3 I would want headphones for gaming, regardless of fan quality. But again, your cooling success is not going to be volume driven. I would select fans based on quality, appearance, and sound instead of raw volume.