Does a fans positioning affect it's performance?

trawetSluaP · May 30, 2015

Does a fans orientation affect performance?
Hi,

I recently bought a Swiftech H220-X. I had the fans in a pull configuration pushing cool air through the radiator from the top of the case with an exhaust fan on the rear of the case pulling the hot air out.

I've recently gone SLI with 980s and they generate considerably more hot air in my case so I decided to reverse the cooler's fans so they are now pulling air from inside the case and exhausting it out the top. This has had the obvious out come as my GPUs are running cooler and my CPU is running a few degrees hotter.

Now my question is does a fans static pressure rating change depending on if it's pushing or pulling? I ask as I plan to change the H220-X's fans for something with a little more oomph and was wondering if there are fan available that are geared specifically toward a pull layout as this is what I'm aiming for?

Thanks,
Paul

Gam3r01 · May 30, 2015

It is easier for fans to push than it is for them to pull.
The original orientation is not the optimal one, the way you have it now is better.

JackNaylorPE · May 30, 2015

Push is more effective at 1500 rpm and less ..... 1750 and above and pull is more effective....it's pretty much the same in between.

Your result is unusual....I have not observed this on our 240-X installation. For some reason, there's an expectation that fans blowing out need to be balanced closely with fans blowing in. These is totally unnecesssary.

-Your home's attic fan cools your house ... it manages to do that w/o any fans in windows sucking air in
-A restaurant's kitchen has a hood and exhaust fans ... it manages to keep the room as cool as can be expected w/o any fans sucking air in
-Your car's AC blows air in ... it manages to keep the car cool a scan be expected w/o any fans blowing air out
-If two guys are pushing a stalled car, you don't go any faster if you have one push and one pull.

A PC case behaves no differently..... there is absolutely no need for an exhaust fan at all .... every cfm being blown in will get out thru the grilles. The reason we have intakes on bottom, sides and front is based upon the desire to move heat and noise away from the user and not have the fans working against each other.

Every single radiator manufacturer advises that radiator fans blow in..... forget the 7th grade lesson that we all remember that heat rises and realize that that's true only when you don't have a fan that's 100 times more powerful than the forces convection

It must however be said that air turbulence **can** be a factor which overrides the "rad fans always blow in" thing because what *can happen* if you have inadequate case ventilation. If your 2 swiftech fans are blowing in, and you have a rear fan blowing out, the air from the Swiftech is going out immediately thru the rear grille. There therefore needs to be something that circulates air around the cards and keeps the bottom card from preheating the air going into the top card....this is especially true if you didn't select a MoBo that provided an empty slot between the two cards.

My suggestion for improving the overall performance of the system would be.

1. Install fans in the bottom of the case bowing air in to the extent possible (1200 rpm, normal SP fans i.e. Phanteks PH-F140SP).
2. Mount a fan or fans on the back of the HD cages so as to blow air under and between the cards and prevent it from getting trapped there. These fans should be medium pressure fans (1500 rpm, medium SP fans i.e. Phanteks PH-F140MP).
3. Reinstall the Swiftech fans as per manufacturers recommendations.

You didn't indicate what case you have and what fans are where but if ya post that... things could be fine tuned.

If the case is designed for water cooling and you can add another radiator in front or bottom, the real solution would be to open the loop, add a radiator and water cool the 980s. The Swiftech pump is certainly strong enough t handle the load.

trawetSluaP · May 30, 2015

I have a Corsair 450D, two 140mm front intakes, one 120mm rear exhaust and the two 120mm fans on the Swiftech radiator acting as top exhaust.

I won't need fans on the HDD cages as I've removed them completely so the 140mm intakes at the front are blowing directly toward the cards and there is a one slot gap between the cards.

All my system info is in my sig.

JackNaylorPE · May 30, 2015

You will need fans on the back of the cage(s) if you want to solve your problem. The front fans won't cut it.....they are doing nothing for your GFX cards.

https://www.youtube.com/watch?v=fNlIY7yUtLY

Go here and slide over to the 1:00 mark.... you can clearly see in the in the simulation how then air flow from the front fans flows up and over the GFX cards. They are too far away and by changing the top fans to exhaust you are pulling that air stream up further as is shown in the video. Where else can it go ?

Your 2 fans blowing in low.... 3 fans going out high.... your rear grilles are doing nothing to vent heat out of the case and are actually bringing air (and dust) into the case ... in fact since you have more air going out than in thru the fans, I'd bet that the heat exhaust from your PSU is being sucked right back in thru the open grilles in the case's card slot covers and preheating the air cooling the lower GFX card.

Because of the low front intake => High fan exhaust the air makes a beeline from point A to point B with no circulation under / between the cards. My son has that case from the video.....pretty much the exact same fan configuration as the 450D. A THG forum member had an issue earlier this week with same case that he wanted to resolve where the top card was over 80C with the front fan blowing exactly as you describe.... adding the fan on the back of the HD cage, dropped the temperature by 10C.

Your set up is :

Top: 3 x 120mm (2 here)
Bottom: 2 x 120mm (nothing here fans here would stop the rear grilles from being hot air intakes and change them to exhaust.)
Rear: 1 x 120mm (in place)
Front: 2 x 140mm (in pace)

Looking here:

We can see that a fan mounted on the back of the HD cage will force air flow under the cage because it would be practically touching the card. Again a user with the same setup saw an immediate 10C drop.

The key to good cooling is maximizing air changes per minute and having no dead air space:

-By not having the case grilles move any significant amount of air, you eliminate one of the major pathways to move air thru the case.

-By having a straight low front intake => high rear exhaust no air circulates under / between the cards ... the GFX card fans blow air up thru the heat sink which exhaust thru the sides and it gets sucked back down again and recirculates back thru the fans as there's nothing breaking up the dead air space and there is no outside source of intake air.

I have had a lottta fun playing and testing these concepts. In my test rig I have (6) temperature sensors, a 6 channel LED display and use this to track air flow patterns.

http://www.amazon.com/Chauvet-Hurricane-700-Fog-Machine/dp/B0002D0JX8/ref=sr_1_1?ie=UTF8&qid=1433038406

When I use top exhaust and have less intakes than exhausts, you can clearly see the fog being drawn in thru rear case and slot cover grilles. Letting it get drawn in thru the front, it goes right up and out the rear and top case fans.

The more intakes that exhausts puts the rear grilles in play and the back of HD cage fan, especially a medium static pressure fan changes the whole lower rear case area circulation dynamic.

Search

Does a fans positioning affect it's performance?

trawetSluaP

Distinguished

JackNaylorPE

Gam3r01

Titan

JackNaylorPE

Titan

trawetSluaP

Distinguished

JackNaylorPE

Titan

TRENDING THREADS

Latest posts

Moderators online

Share this page