To blow or suck!

[BrianW]

Hehe...

OK so it pretty well established that sucking through a radiator is more effective than blowing air through one. In addition it is agreed that more fans will produce more air flow. I see when people use 2 fans they always have one on each side of the rad.

My question:

Why not just have both fans sucking through? One right next to the other. I tested this with my ears and hands only. When i stacked 2 80 mm panaflow fans together the flow was nearly doubled and noise gain was inaudible.


Idea is having 2 panaflow 120's both at 5-7 watts sucking ait through a black ice to cool 3 3/8 water blocks. Magdrive3 350.

Comments...

[redleader]

2 fans in paralell is always perferable to 2 in serial. Serial fans double the effective airpressure generated, while paralell doubles actual flowrate. Unless your fans are practically stalled, serial fans won't even come close to doubling flow.

I'd say that idea is very good. It takes 8 80mm Panaflos to match the noise of a single 120mm L1a, meanwhile they would flow about 2.5x the air. So your setup will be quiet, assuming 2 24CFM L1As can flow enough.

Why is sucking preferable to blowing? Don't give the old excuse that car radiators suck, because they don't. They bothsuck and blow. Furthermore the fact that the fan is inside is unimportant, I would like to see howexactly you could mount a radiator fan out side of a car's radiator easily.

I'm not saying if sucking is worse then blowing, I have no reason to think so. But I would like a good reason to beleive there is even any difference between the 2.

[BrianW]

My question:

Why not just have both fans sucking through? One right next to the other. I tested this with my ears and hands only. When i stacked 2 80 mm panaflow fans together the flow was nearly doubled and noise gain was inaudible.

I believe i explained myself poorly. I was talking about putting the fans in serial. Stacked one in front of the other blowing in same direction. They would both suck air through the radiator. I am thinking of doing this with 2 120mm low flow panaflow (68 cfm).

2 fans in paralell is always perferable to 2 in serial. Serial fans double the effective airpressure generated, while paralell doubles actual flowrate. Unless your fans are practically stalled, serial fans won't even come close to doubling flow.

I read in an article on this site that said as far as radiator cooling goes it is pressure not flow that is more effective at cooling.

Any ideas or comments people?

Thanks

[redleader]

You mean so that the 2 fans are actually touching each other? I wouldn'trecommend that. AFAIK the turbulance between the two blades would be a problem. On on each side or a 1/2inch buffer between them (say a dead 120mm fan with the blades removed) would help.

Pressure increases your ability to approach the rated flow rate of a fan. Higher pressure means one fan will work closer to its rated max. If you can fit 2 fans side by side it will always do better then 2 stacked. However its very rare to fit 2 120mm fans side by side.

[BrianW]

So how about this:

flow: ----->

rad.1"spacer.fan.1"buffer.fan

thanks again for all the help guys.

[BrianW]

Why is sucking preferable to blowing? Don't give the old excuse that car radiators suck, because they don't. They bothsuck and blow. Furthermore the fact that the fan is inside is unimportant, I would like to see howexactly you could mount a radiator fan out side of a car's radiator easily.

I'm not saying if sucking is worse then blowing, I have no reason to think so. But I would like a good reason to beleive there is even any difference between the 2.

Just a thought. (i only took one year of physics in college)

Air naturally moves from high pressure to low pressure. In other words air is moved by being sucked. At least thats how it works in the atmosphere. So to more easily move air through a channeled thing like a radiator sucking (creating a low pressure enviroment), would be more effevtive than blowing(creating a high pressure enviroment).

What do you guys think?

[platypii]

In response to the last post, that doesn't really prove why sucking would be better. if you are blowwing you simply create higher pressure on the backside that the air flows away from. Either way the air flows through.

[futRtrubL]

I think its more an eveness problem not a flow problem. Blowing is directional, you get a jet, sucking though drags air from anywhere. On fans you also have a dead air space right in the center where the motor is, moving the fan an inch away and sucking should therefor spread air over the whole rad and be more eficient.

Edward

[BrianW]

Well lets have it:

If you were going to use 2 fans for your rad, would you place one in front and one in back, both sucking, or both blowing?

I am planning on going with both sucking:
Flow : ------->
Outer_Case.Black_Ice.1"_Spacer.Low_Flow_Pana_120mm .1"_Spacer.Low_Flow_Pana_120mm.Vent_out_the_case . The fans will be running @ 5-9 watts.

Any ideas or suggestions.

[vfrjim]

one quality 100 CFM or higher sucking is the better way to go.

Jim

[BrianW]

100cfm fan is too load for me. My panaflow 68 is too loud i would like to have it at about 9-11 watts. At that sound level i can tolerate it. Remember my goal is to cool as queitly as possible.

Thanks again

[BrianW]

In response to the last post, that doesn't really prove why sucking would be better. if you are blowwing you simply create higher pressure on the backside that the air flows away from. Either way the air flows through.

Assume im a little air molecule. Say there is an intake vent, then a radiator with holes that I must travel through to get to the exhaust vent. There are two situations: Get blown through the holes or get sucked through the holes. If I get blown in I will probably not be lined up with a hole. Therefore I would have to bounce around the face of the radiator until I found a hole. Slowing me down and making less room for other molecules to go in the holes. Or If you get sucked through as the air is coming from the intake and being sucked through the holes, I get sucked right in a hole w/o even hitting a thing. Wouldn't I go faster that way? With less fan power to boot?

[vfrjim]

My system is soon to be very quiet, 20 Lin Feet of copper baseboard mounted in my crawl space, pump mounted in there too, no need of any extra fans in my case, only PSU and vid card and 2 case fans, nice and quiet ones In the winter with ambient temps outside around 0 F, my system should be quite cold
and in Summer, it is about 70 F under there, so still pretty efficient.

Jim