Case fans: Is bigger better?

I am almost finished on my first custom build PC (just awaiting the HDD). I am pleased with the case I chose (Cooler Master Elite 330 mid-tower). It came with just one fan, a 120mm exhaust in the rear. I was planning on getting another 120mm fan for intake on the bottom front of the case. The case also has a funnel surrounding the CPU heatsink/fan that extends to outside the case door for better CPU cooling. Should the two 120mm fans be enough to cool the system? I figured the two large fans would be better than several smaller fans. What does everybody think?

 

The website is in another language...

 

Turkish, in fact.
The following is not a complete answer to your question - it's mostly the principles by which you can make a decision.
There are two things to consider with fans - the volume of air they pass through, and the areas of the box that the air passes through. The volume is largely determined by the fan diameter and the fan speed. The areas are determined by where the fans are located and which way they point.
Hence, if you are comparing two large fans with a number of smaller ones, the smaller ones would be better, provided they total the same volume of air passing through. They would be better because you would have a better chance of directing the air exactly where you want it. Having said that, I suspect you would need quite a few small fans to equal the two larger ones in throughput. If all the fans had the same speed (and similar blade shapes, etc), one large one would pass about as much air as more than 4 small fans of half the diameter of the large one.
Can you take it from there?

 

thanks for the info. what i really wanted to know is would the two 120mm (one intake, one exhaust) be adequate to cool the system; or in other words: would it keep the system from overheating and causing damage? I just wanted to make sure I wasn't setting myself up to throw away all the money I just spent within the first few days of using the system.

 

I'll have to let someone else have a go at that.
And I take it that the CPU fan is not one of the 120 mm fans (just for the sake of anyone else looking at this).
Wouldn't you have temp monitors and an overheating shutoff?

 

Here's something to ask.

A smaller fan needs to spin faster than a larger one to move the same amount of air.

So, wouldn't that make the smaller fans louder?

 

If you had one small fan and one large fan putting through the same amount of air, yes, the small one would have to be much faster, and therefore is likely to be noisier. There are other things to consider, such as blade vibration, but in general, the smaller one would be noisier.

 

My general rule is "Negative pressure in the case."

If you are forcing more air into the case, than you are exhausting in CFM, the exhaust fan is pointless. You end up pushing it, instead of it working.

I have intake vents, and smaller fans directed for my hardware. HDD cooler, CPU fan, and the graphics card has it's own. The 120mm at the rear of the case, and the graphics card push the air out, and the CPU/HDD cooler depend on the intake air from the vents. PSU exhausts air as well. Most people forget that one. Memory just has heat sinks. I rarely exceed 40 degrees Celsius, and that is only in the summer months, as I don't have air conditioning.

Forcing air in can cool the intake air, same principal as a room fan, accelerating it will cool it somewhat. Pulling the air through smaller intake vents can also have the same effect. Imagine sticking your head out the car window, and trying to breathe at 40, or 50 MPH. Doesn't work so well, does it?

However, too much "push", can increase static pressure inside the case, similar to turbulence above the intake of a carburetor, or fuel injection throttle body impeding performance. Turbulence will actually impede cooling.

I hope this did not confuse you further, it's the best "Mr. Wizard" I could come up with.

 

that's what I've been thinking. It's been a couple years since I've had a desktop PC, and my previous one was a gaming PC with probably 3-4 small (I think 80mm) fans and it was NOT quiet. Now I figure if I have a large fan in front and back, along with the CPU fan counting as another exhaust, I should be fine.

 

I see you have a top mounted PSU so there is a second fan of between 80 and 140mm going out. Also, if you're going to have a dual slot video card, there's another fan going outside. All this negative pressure will suck in cooler outside air through the shroud. It should be good to go.

 

You're right about the PSU and video card. Are you suggesting I don't need a 120mm fan in the front?

 

Generally bigger fans spin slower, which means less noise, but theres so many varibles to noise in a computer, its hard to say 100% but as a rule of thumb, considering fan quality is the same, the bigger 120mm fans "should" be quieter.

 

Keep the front fan, especially if you fill the HDD bay as hard drives also create a lot of heat and need some cooling. The label of one of mine was toasty crisp and dark brown when I took it out, that's too much heat for me.