Just thought I'd post some info that my father has told me about using fans with radiators. He designs systems for large trucks which obviously use fans for cooling their large radiators.
Hopefully it will help people thinking of their own cooling or give a little light reading lol
I have a H50 and have been messing around with cooling in my system.
From reading different forums about cooling, people seem to only be getting differences of 1 or 2 deg in push/ pull systems over the single fan. Also people are experimenting with shrouds with again maybe one or two degrees difference.
From what I understand from my father, a fan needs a certain volume of air to dissipate the heat from the radiator. Now this does not necessarily mean air forced through at a great speed.
If a fan pushes air too fast through a radiator it doesn't have enough time to take away the heat. With the trucks, what they do is work out the rads air volume needed, then they match the right fan to the rad. So sticking ultra kraze 3000 rpm fans will probs get to a point where more rpm doesn't have an effect. Just like our heating systems in UK houses that require you to slow the water speed enough so it has time to be heated. Opening the water valves means too much water is flowing too fast to be heated by the heating system. the same happens in reverse for cooling in our rad and fan systems.
Push/pull setups too would have to be using a push fan and a pull fan rather than just two identical fans. There is a difference in a push fan and a pull fan. So a fan in our systems set up as a pull fan may not have much effect on the rad at all, depending on the fans. So if we get a degree or too difference in our systems using identical fans, well that's as best as we can probs hope for.
I would imagine these pc fans are made to do both pull and push but as each is different they don't always perform the same. Two fans pushing and pulling may also not be in sync, causing air to behave strange maybe even raising temps too.
Using shrouds. Using a shroud with your fan to increase the area of the rad that gets air from the fan. ( As the centre of the fan behind the motor will be warmer) Its actually a little more complicated than sticking a shroud on the fan, the shape of the tip of the blades and the distance between the fan blade tip and its own shell actually makes a difference when using a shroud and when not. A duct is more efficient than just a spacing shroud. Again these have to be matched to the right shape shroud and the right distances between the fan tip and the fan case. You can go on for ever trying to come up with the right duct and fan combination, fan shape ask any R & D department in any major manufacturing plant.
So again the best we could hope for with a shroud on our setups is again 1 or 2 degrees. Even with a shroud the part in the middle of the rad will still not be as efficient as the outside edges. The further back from the rad the fan is set will give better results as the air has time to vortex more or less can't remember which and fill the space more. So maybe setting your fan a little back and have a small duct system rather than just a shroud, which are just usually a fan case, might give better results.
So from what I have seen in my own setup, trying push pull, intake, exhaust, the best thing would be to get your case taking in as much cool air as you can with out, annoying your neighbours, from what ever ambient temp room you have in your room and then have either one or two fans on your rad, exhausting air out of your case. Just have one or two fans on your rad that are not too fast and maybe not too loud. That's as probs as good a system setup you will have in your ambient room. Then enough cool air is blowing over the rad and has enough contact with the fan to dissipate heat.
I have only one graphics card in and even at idle in the bios, you can feel the heat pipes on the card, heat up a fair bit. So having SLI is going to make the heat your then pushing over your radiator and out your case a lot higher. So the question is is that heat lower or higher than pulling air in over your radiator and into your case and then heated by what ever graphics set up you have.
yes,I have had mine cooler intaking cool air from outside the window over the rad and my ambient temp was lower but only at idle. I'm sure when it's on full load the temp inside the case will rise somewhat. With my setup my fans on full don't make any difference from about 50-70% so it means the rad is saturated and the volume of cool air is not enough or going too fast through the rad. Also the motor heat will be adding a little too.
I found my second fan pulling air out of the case and radiator, didn't have any impact on the temp. In fact you could tell from the sound of the fan it wasn't having any resistance from anything, such as air pulled through a radiator behind it. This possibly means that it isn't pulling air very effectively but is pushing air well.
I hope this is helpful, I just found it interesting messing with my own system to see how little things change, in temps. today it's warmer outside and inside so my temps are a few deg warmer and all fan positions seem to have the same temps, even at full fan speed i cant get the temps that I had yesterday and they are not that higher really. Cooling is a bit like bridge building there isn't really a correct way of doing things especially in our cheap manufactured products we seem to be getting now. Every part of the PC I have just built, that was made in a certain developing nation, has been sent back faulty. It's about time our corporations stopped using cheap labour and cheap parts. That's another rant though.