I am beginning a mod on Ultra's Aluminus case which i will continue over the summer. I was planning on haveing 1 120mm front intake fan, 1 120mm rear exhaust fan and 1 120mm top exhaust fan. As i have been think my father has brought up the idea of " would there be more air pressure coming in from the front vents if you have all fans exhausting hot air?" I am proposing 1 120mm rear exhaust and the other two 120mm fans exhausting at the top of the case. This image shows the case front vents which i will replace with hexX modders mesh. http://hi-techreviews.com/reviews_2006/Aluminus/ULT31824_LR_1.jpg Any help would be appreciated! Thanks Ace
You need to experiment and see what each of those combinations contribute for your setup I have a P182 case with most of the heat coming from a Q6600 clocked at 3.2GHz. My graphics card is a Radion HD 2600 which does not get very hot. With that setup, I found with a rear exhaust fan, the top fan does very little set either to intake or exhaust neither did a front mounted fan. I think case and CPU temperatures were lowered by 2 C and those fans have been removed. The only other case fan is in the bottom compartment where it cools 3 hard drives.
I think you (or your dad) mean air flow, not pressure. In theory, fans blowing the same way (in or out) create double the flow through the case, but that's in open air, zero restrictions, and no interference as you could get with fans on back and top. In a real case you never get the spec flow. An inlet and an exhaust keep any back-pressure in the case low, but the flow can never be more than the spec flow of a single fan in the open air. Snag with all fans exhausting is you'll suck more dust into the case through every nook and cranny, including the optical drives.
So its better, dust wise, to have a positive pressure in the case? How would that affect temperatures?
Dust wise it's likely better to just seal as many gaping holes as possible for the reasons cpemma mentioned (missing PCI brackets, drive bay covers, unoccupied fan holes, grill or meshy case bits) and put filters on the intake fans. Those blue and white stripey dishcloths work if you're on a shoestring =p. Thinking this through, positive case pressure would mean [ever so ever so] slightly denser air and so in theory better cooling. But, at the same time if the difference between the amount of intake and extractor fans is 'big' (eg 2x120 intake and 1x80 extraction), hot air isn't leaving the case so fast. So, while the air inside will be an infinitesimally 'better' coolant, it will be hanging around longer and hence hotter than it might be if you had e.g. neutral case pressure but 3 h00ge fans on the front and 3 on the back and hence a few hundred CFM of cool fresh air wafting through... so your temps might work out a degree or two higher. OTOH if you have say 2x120 intake and 1x120 + 1x80 outlet then the difference would be a lot smaller, so it's probably not going to make a huge difference either way.
Theoretically, in the absence of resistance, 1 fan blowing in and 1 blowing out won't be better than having just one fan for either intake or exhaust. Multiple inline fans create more static pressure, not more airflow. However, that pressure can help get the air past resistance.
I was always taught to keep cases at positive pressure, and I believe a lot of commercial cases were designed that way. In the end my take on temperatures is is anything overheating to the point it shuts down? if the answer is now than cooling is fine. On the average tower the difference between having 2 fans on intake, 2 fans on exhaust, or 1 of each isn't going to be significant. Of course all this goes out the window if you have a big focus on OCing. However my last case had a total of 0 fans
That's good news as I had already planned to have just an intake fan for my mod, the thing won't generate much heat so I assumed a single intake fan was better than a single output fan...
What you should do with your fans depends on what you want to achieve. For low dust inside, you want all intakes filtered and you want more intakes than exhausts. However, for proper cooling, there's no need for any intakes at all. They are noisier and don't help all that much, since much of the cool air they bring in can be lost through various vents and leaks. If all your fans are exhausts, though, then those same leaks turn into many small sources of cool air, which is all pulled through to one place, cooling all the components along the way. In other words, planning airflow from an intake is tricky because the air can go anywhere, and could potentially miss all the hot components. An exhaust, on the other hand, pulls from everywhere but because it all ends up in the same place you can get a pretty decent idea of what it's flowing past.
