Push? Pull? Push/Pull?

[Viper87227]

I am going to be retooling my loop this week. One thing I have been pondering is how my rad should be set up. I am using a BIP2. I currently have 4 fans at 1000 rpm each. Quiet it important. However, is that the best way to have them. I have a push/pull config, and it is intaking air from outside my case. Given the scenerio, is this the best setup, or woudl I be better off with just two fans pushing or pulling?

 

[Dark Prodigy]

I only have a single 120mm rad but when I changed my configuration from a single fan in pull to dual fans in push/pull, I noticed a nice 2C temp drop...

 

[(313)dnoyeb]

I am going to be retooling my loop this week. One thing I have been pondering is how my rad should be set up. I am using a BIP2. I currently have 4 fans at 1000 rpm each. Quiet it important. However, is that the best way to have them. I have a push/pull config, and it is intaking air from outside my case. Given the scenerio, is this the best setup, or woudl I be better off with just two fans pushing or pulling?

im not sure i comprehend your scenario. how many case fans and how man rad fans, which where?

 

[penguin]

I doubt you're going to see any benefit from push/pull on a BIP. Maybe on a BIX, and definately on a heatercore, but I think the BIP is short enough that push/pull is of no benefit. It's a theory, anyway.

 

[Viper87227]

im not sure i comprehend your scenario. how many case fans and how man rad fans, which where?

I have 4 fans on my rad right now, each at 1k rpm, intaking air from outside my case. I am asking it it woudl be more benificial, or no loss in performace to run just two fans in push or pull.

 

[dnottis]

I have a single 120 BIP too and push pull - I would stick with Push pull for maximum airflow through the rad.

 

[malicious]

if you only want to do one or the other which would be better push or pull ... can ANYONE point to a real study of the difference?

mal

 

[sadvocate]

Which side of a fan do you want to stand on when you want it to cool you off? Do you stand so the air blows on you or pulls air off you? If you've ever spent a summer in the south working inside a sheet metal building with a shop fan blowing on you, you know the answer.

Although not the complete answer (as there is no evaporation going on with the watercooling radiator as there is with human skin and sweat), it at least points you in the right direction. The fan feels cooler because of the windchill factor, allowing faster cooling due to the speed of the air flow. In Alaska, oilfield engineers have to time their exposure to the extremely cold temperature based on the wind speed, as hypothermia can set in within minutes. All thanks to windchill. That's an extreme example of a warm object with colder air blowing across it.

The radiator is the warm, inanimate object in a watercooling setup, so windchill factor comes into play. Then comes the question of which side of the fan "feels" cooler (or which side do you feel more airflow), and that's easily measurable without instrumentation (thanks to sensors within our own body). The design of the fan channels the air it pushes, creating more airflow directly in front of that fan than behind where it is pulling in from all directions.

 

[penguin]

But on a radiator, it can't pull from all directions. Because the fan is flush mounted to the radiator, all the air that it is intaking is being pulled through the radiator fins. All your points are valid in any situation other than this, but on a radiator, there is only one place the air can come from, and that's through the fins, resulting in exactly the same airflow as a push configuration.

 

[malicious]

god i wish someone could find an actual study on it...

mal

 

[malicious]

this is from the thermochill site

For best temps on the HE series, pull-pull. IE: On each Thermochill shroud stack a PAIR of fans pulling thru the rad, one fan attached to the other fan attached to the shroud attached to the rad. This has always produced better temps than push, push-pull, push-push, and pull on the HE range cores. Generally this would result in:

Grill/Guard > Fan > Fan > Rad > Case > Grill/Guard
For best temps on the PA series, testing currently shows PUSH to be the best solution... shrouded vs unshrouded exhibits minimal benefits, in the region of upto 2%. Fans pushing as opposed to fans pulling exhibits increases of upto 4%, and is roughly equivalent to running a shroud with fans in a pull configuration.

looks like my 3 yate loons will be pushing on my black ice three

 

[sadvocate]

But on a radiator, it can't pull from all directions. Because the fan is flush mounted to the radiator, all the air that it is intaking is being pulled through the radiator fins. All your points are valid in any situation other than this, but on a radiator, there is only one place the air can come from, and that's through the fins, resulting in exactly the same airflow as a push configuration.

Not the same air pressure, though, on the fins of the radiator. Higher pressure air has a higher heat capacity. Flowing higher pressure cold air over a radiator cools it faster than lower pressure cold air. I found this quote helpful:

There are two other points to worry about here. One is that at higher pressures, the air will have a higher heat capacity per unit volume than at lower pressures, and so flowing high-pressure cold air past the water can freeze the water faster. If the high-pressure air does not flow (that is, if you pressurize a closed container) then this should have almost no effect.

As this quote explains, the dynamics of the airflow in the case can negate any benefits of higher pressure air being pushed across the radiator fins, if that air has nowhere to go because the case lacks even air flow.

The Thermochill quote is enlightening, as that 4% increase in push translates to only about 1C. Throughout any given day, depending on the whimsical fancy of my air conditioner, I can have between two and three times that variation in room temperature.

 

[Oldwolf]

Have the fan blow through the radiator.

And have the air it gets be ducted in from outside.

And use other fans to exhaust the ambient case air.

My $0.02

 

[ikellensbro]

The best plan is to try it out yourself. From what I could tell, you currently have 4 fans on your BIP2: 2 pushing air (intake) and two pulling (exhaust). you may find it quiter to simply run 2 fans pushing or pulling at full speed. If you really want quiet, then your best bet is to:
A: Get a shroud. This both increases performance (no fan deadspot) and decreases noise caused by turbulence.
B: Run your fans in a pull configuration. It is quieter to pull air through radiator fins than to push it through the fins - and with a shroud, pulling becomes nearly, if not just as effective as pushing, performance wise.