Need help understanding cooling fans

[mkraven666]

Hi guys,

 

Long time lurker, made the account specifically to ask my questions here.

 

Summer has arrived and I'm having issues keeping my i5 4690k running cool on my bitfenix prodigy case. I have it overclocked to 4.4GHz and a noctua NH L12 cooler installed. It's not the best and it's been running around 75ºC on load during the last few days (it's been a hot spring here in Belgium).

 

I'm currently running the extremely ghetto setup you can see in the attached picture. This small desk fan is normally used to cool me off and is able to throw out a strong flow of air. I have it pointed downwards directly on top of the cooler and am able to bring the temps down to around 65ºC which is a lot more acceptable. The case has a mounting slot just underneath the grill on that exact spot so I want to buy a good fan. And herein lies the problem, I have no idea which one to purchase.

 

I need a direct airflow fan that would act much like the desk fan, pushing a lot of aird from the top of the case directly on top of the CPU cooler. Which one should I get? A few options (ranging in price) would be greatly appreciated.

 

This whole airflow vs static pressure thing has me pretty confused, I just want a fan that I can point at the cooler to help it out a bit during the summer.

 

Thanks a bunch!

[SeanAngelo]

25 minutes ago, mkraven666 said:

Hi guys,

 

Long time lurker, made the account specifically to ask my questions here.

 

Summer has arrived and I'm having issues keeping my i5 4690k running cool on my bitfenix prodigy case. I have it overclocked to 4.4GHz and a noctua NH L12 cooler installed. It's not the best and it's been running around 75ºC on load during the last few days (it's been a hot spring here in Belgium).

 

I'm currently running the extremely ghetto setup you can see in the attached picture. This small desk fan is normally used to cool me off and is able to throw out a strong flow of air. I have it pointed downwards directly on top of the cooler and am able to bring the temps down to around 65ºC which is a lot more acceptable. The case has a mounting slot just underneath the grill on that exact spot so I want to buy a good fan. And herein lies the problem, I have no idea which one to purchase.

 

I need a direct airflow fan that would act much like the desk fan, pushing a lot of aird from the top of the case directly on top of the CPU cooler. Which one should I get? A few options (ranging in price) would be greatly appreciated.

 

This whole airflow vs static pressure thing has me pretty confused, I just want a fan that I can point at the cooler to help it out a bit during the summer.

 

Thanks a bunch!

can you show us the inside of your case? showing the fans etc.

 

for the fan, you can consider this

http://de.pcpartpicker.com/product/gR7wrH/aerocool-case-fan-shark120mmblackedition

or

http://de.pcpartpicker.com/product/MwR48d/cooler-master-case-fan-r4jfnp20pkr1

 

Airflow fans are for free flowing air space

Static pressure are for radiators

[mkraven666]

14 minutes ago, SeanAngelo said:

can you show us the inside of your case? showing the fans etc.

 

for the fan, you can consider this

http://de.pcpartpicker.com/product/gR7wrH/aerocool-case-fan-shark120mmblackedition

or

http://de.pcpartpicker.com/product/MwR48d/cooler-master-case-fan-r4jfnp20pkr1

 

Airflow fans are for free flowing air space

Static pressure are for radiators

Sure, here it is. My phone's camera is a bit crap but I hope you're able to get the picture.

The front mounted fan is mounted on the up position in the front of the case, same high and opposite to the rear fan you can see in the picture.

When the case is closed the USB 3 cables you can see arc over the area where the HDD bay would be so basically there is nothing blocking airflow, as far as I can tell.

 

So these fans that you propose will be able to push air on top of the CPU cooler? Like direct air not just pulling it from the outside into the case?

 

Thanks again!

[WoodenMarker]

75c isn't that high. You're fine up to 80-90c at load.

[SeanAngelo]

6 minutes ago, mkraven666 said:

Sure, here it is. My phone's camera is a bit crap but I hope you're able to get the picture.

The front mounted fan is mounted on the up position in the front of the case, same high and opposite to the rear fan you can see in the picture.

When the case is closed the USB 3 cables you can see arc over the area where the HDD bay would be so basically there is nothing blocking airflow, as far as I can tell.

 

So these fans that you propose will be able to push air on top of the CPU cooler? Like direct air not just pulling it from the outside into the case?

 

Thanks again!

so the front fan and top fan is blowing air in, am I right?

 

 

[mkraven666]

9 minutes ago, WoodenMarker said:

so the front fan and top fan is blowing air in, am I right?

That's right! The front fan is blowing air in and the rear fan is exhausting it out of the case. The ghetto fan on top is blowing a stream of air inwards directly on the CPU cooler through the top grill of the case.

 

9 minutes ago, WoodenMarker said:

75c isn't that high. You're fine up to 80-90c at load.

You're correct and thanks for confirming it. That said I do feel like I'm nearing the safety edge here and wouldn't want to risk going to the 80s when the temperature rises a few more degrees. I'm just looking for some headroom.

 

Can you guys help me understand what performance metric should I be looking at when comparing fans? Do I want the highest CFM for this particular scenario?

 

Cheers!

[WoodenMarker]

8 minutes ago, mkraven666 said:

You're correct and thanks for confirming it. That said I do feel like I'm nearing the safety edge here and wouldn't want to risk going to the 80s when the temperature rises a few more degrees. I'm just looking for some headroom.

80c is perfectly safe and you already have good amount of headroom.. 

[StormFalcon32]

28 minutes ago, mkraven666 said:

Sure, here it is. My phone's camera is a bit crap but I hope you're able to get the picture.

The front mounted fan is mounted on the up position in the front of the case, same high and opposite to the rear fan you can see in the picture.

When the case is closed the USB 3 cables you can see arc over the area where the HDD bay would be so basically there is nothing blocking airflow, as far as I can tell.

 

So these fans that you propose will be able to push air on top of the CPU cooler? Like direct air not just pulling it from the outside into the case?

 

Thanks again!

What do you mean by "direct" air? Any air is going to come from the outside of the case. Fans don't just make air you know? The air has to come from somewhere and that "somewhere" is usually from the outside of your case.

[mkraven666]

Sure, obviously a fan only moves air around, they don't "make" air.

 

What I mean is that this is a "strong" fan with large blades that create a a strong stream of air as opposed to a fan with smaller blades that circulate the air through the case. I'm trying to understand the basic difference between the two and what should I keep an eye open for when comparing fans. Sorry if I'm not being crystal clear, I'm a bit confused here.

[WoodenMarker]

12 minutes ago, mkraven666 said:

What I mean is that this is a "strong" fan with large blades that create a a strong stream of air as opposed to a fan with smaller blades that circulate the air through the case. 

Circulating air through the case is what case fans do.

[ThomasD]

1 hour ago, mkraven666 said:

Hi guys,

 

...This whole airflow vs static pressure thing has me pretty confused...

 

Yep, that is a point of confusion.  Because it is not a matter of one versus the other.  All fans generate airflow - expressed in terms of volume over time - cubic feet per minute or CFM.

 

Pressure data is a means of indicating how well any given fan will continue to provide good (but never maximum) airflow in the presence of flow restrictions like vents, filters, radiators, etc.

 

Generally speaking, anywhere you will have restrictions of airflow, and all other things being equal, you will probably get better performance from the fan with the higher SP rating. 

 

My recommendation is, when in doubt, go for SP type fans and that AF fans are really only useful for unrestricted/unfiltered exhausts.  But as with all things, the Devil is in the details, and YMMV.

[mkraven666]

5 minutes ago, ThomasD said:

...My recommendation is, when in doubt, go for SP type fans and that AF fans are really only useful for unrestricted/unfiltered exhausts.  But as with all things, the Devil is in the details, and YMMV.

Thanks ThomasD!

 

I'm realizing that I should get something with a high static pressure then. For example the desk Fan you see in the first picture is something along the lines of this one here: https://www.amazon.com/niceEshop-Portable-LaptopPC-Cooler-Cooling/dp/B00DIXP4KM?ie=UTF8&*Version*=1&*entries*=0 It's got 4 massive blades and generates a lot of pressure since it needs to be able to move enough air to reach someones face at least half a meter away.

 

Any recommendations on a static pressure fan that would achieve a similar effect?

 

Cheers!

[ThomasD]

I'm assuming that is a Bitfenix Prodigy case.  If so then the front will fit a 200 mm fan.  The Bitfenix Spectre Pro 200 is a good large fan for that application.  The Spectre Pro 230 mm fan might also fit, and is even better in terms of airflow and static pressure.

 

If you want to stay with a 140 mm then the Fractal Design Venturi PWM is about as good as it gets.

 

Also, rather than trying to force air in from the top you could add two 120 mm top exhaust fans. That will make your case pressure rather negative - which could lead to greater dust accumulation, but you are probably already dealing with that with your current approach.