Overclock.net › Forums › Cooling › Air Cooling › Noctua CPU heatsink push/pull with two different fan speeds: turbulence or other problems? (Air cooling theory)
New Posts  All Forums:Forum Nav:

Noctua CPU heatsink push/pull with two different fan speeds: turbulence or other problems? (Air cooling theory)

post #1 of 9
Thread Starter 
Hi, everybody. New member here. I'd appreciate a little advice from those of you with more experience than myself in such matters (that'd be anybody).

I'm building a new computer in a few weeks whose parts I have gradually accumulated over an agonizingly patient half year. Its cooling is exclusively Noctua, which I expect will look great in my green Corsair C70 Vengeance case: 5 (possibly 6) NF-S12A FLX and 4 NF-A14 FLX case ventilation fans and even one of their 40mm fans as a tiny upgrade to the ASUS Sabertooth Z77 motherboard's thermal armor feature (the other fan is only around 35mm, as I understand it, and cannot be so upgraded, sadly).

For the CPU, I'm using Noctua's NH-C14 heatsink/cooler, which I selected primarily because the downward airflow is recommended with that Sabertooth motherboard. Now, I'm sure that the fans it comes with are perfectly fine, but if we can't get silly about our hobbies then what's the point? I want to make it even better by using the NF-A15 PWM and NF-A14 PWM, the latter of which should begin to show up in stores in a week or two.

Here's the rub: I would just use two of the A15s, but Noctua show that one would have to be slightly offset from the heatsink in order to fit, as shown here (scroll down a bit for the C14). That offset bothers me. Now, I spoke with Noctua and was assured that it would still represent a performance upgrade, but I want to avoid it anyway; if a thing just doesn't fit right, it will never sit right in the back of my mind. So what I want to do is to use the NF-A15 PWM as the top fan for the NH-C14 and install the new NF-A14 PWM on the bottom, which won't require an offset. What concerns me is that the new A14 PWM has a higher RPM of 1500 versus the A15's 1200 as well as an airflow difference of 140.2 m³/h versus 115.5 m³/h.

I did a lot of research and read conflicting opinions on whether different fan speeds in push/pull configurations could cause turbulence, unwanted wind vortex patterns, decreased performance, or even dangerous mismatched resonances. The PC enthusiast community at large just seems to be uncertain of the science of these air dynamics. Noctua wouldn't give me a straight answer on the matter because they had never tested that configuration (unsurprising since one fan isn't even in stores yet).

One of the features of the Sabertooth motherboard is fan profile configuration where you draw fan speed graphs to correspond to temperature levels so that they don't just run full tilt all the time, but I won't know what this is like to use until I get in there and I just don't know whether you can control the two CPU fans independently, which is what I'd need to do if I wanted to keep their speeds matched. I could probably just attach Noctua's low-noise adapter to limit the voltage of the A14 PWM and bring its RPM down to 1200 as well, but I don't want to do that unless I have to.

So what do you all think about this? Is it a bad idea to allow the two fans to run on either side of that heatsink at these different speeds? Is it dangerous, or would it simply lead to decreased performance? Would I be better off limiting the faster fan? Would I be better off doing something different entirely? I'd appreciate any guidance you can offer, and I'd also be interested in any theoretical conversation on the subject!
post #2 of 9
i would stick to the fans it comes with.there pretty quite and do a good job.i would use two fans with the same spec's.if you haven't already purchased the ch 14,i would check out the one i linked below.

the ch14 can use any 140mm fans that have 120mm mounting holes. but you have to stay with in 25mm thick.theres a couple companies that make these now.i linked one below that would work also.

i found this cooler to do a better job than the ch14. it gave me a better even temp across all cores.

http://www.newegg.com/Product/Product.aspx?Item=N82E16835608019

if you want to push more air though it, maybe try using one of these

http://www.newegg.com/Product/Product.aspx?Item=N82E16835220056&IsVirtualParent=1

or

http://www.performance-pcs.com/catalog/index.php?main_page=product_info&cPath=36_316_850&products_id=35600
Edited by toyz72 - 5/15/13 at 11:13pm
always changing
(16 items)
 
  
CPUMotherboardGraphicsRAM
i5 4690k msi z97i-ack MSI r9 290 2x8 corsair 1600 
Hard DriveHard DriveCoolingOS
m4 128  wd 1tb black noctua u9s win7 64 
MonitorKeyboardPowerCase
benq 2420z corsair  coolermaster v650 rosewell neutron 
MouseMouse PadAudio
rival 300 razer  corsair sp2500 
  hide details  
Reply
always changing
(16 items)
 
  
CPUMotherboardGraphicsRAM
i5 4690k msi z97i-ack MSI r9 290 2x8 corsair 1600 
Hard DriveHard DriveCoolingOS
m4 128  wd 1tb black noctua u9s win7 64 
MonitorKeyboardPowerCase
benq 2420z corsair  coolermaster v650 rosewell neutron 
MouseMouse PadAudio
rival 300 razer  corsair sp2500 
  hide details  
Reply
post #3 of 9
Will a bottom mounted A15 clear everything on motherboard?
post #4 of 9
I would honestly just use one fan on top. In terms of Noise/performance the second fans reallly only helps at low rpms. You could also think about using an F12 on bottom, since you cant mount fans with 140mm holes like the A14, at least no with the standard clips that come with the cooler.
My System
(14 items)
 
  
CPUMotherboardGraphicsRAM
i5 3570k @4,6GHz ASUS P8Z77-I Deluxe Sapphire 7870XT @1,2GHz 16GB DDR3 
Hard DriveCoolingPowerCase
Crucial Noctua U14S & Prolimatech MK26 (+1x Noctua A15) Antec HCP 1300 Lian Li X1000 
  hide details  
Reply
My System
(14 items)
 
  
CPUMotherboardGraphicsRAM
i5 3570k @4,6GHz ASUS P8Z77-I Deluxe Sapphire 7870XT @1,2GHz 16GB DDR3 
Hard DriveCoolingPowerCase
Crucial Noctua U14S & Prolimatech MK26 (+1x Noctua A15) Antec HCP 1300 Lian Li X1000 
  hide details  
Reply
post #5 of 9
I agree with Elohim. I would also just use a single fan; either an NF-F12 on top, or even a TY-141 (which incidentally also has the sort of earth tone that may match the Sabretooth). The NF-P14s that come with the NH-C14 are one of Noctua's more disappointing fans.
    
CPUMotherboardGraphicsRAM
3570k@4.5ghz 1.21v Gigabyte Sniper M3 Sapphire 6950 Samsung 8g1866 
Hard DriveHard DriveHard DriveCooling
Samsung 830 Samsung F1 500 Crucial M4 64 (SRC) cpu:Noc NF-F12 / case:4x TY-141/gpu: 2x NB-Multi 
CoolingOSMonitorKeyboard
Venomous X, Accelero TT Win 7 64 Acer X213H Saitek Eclipse 
PowerCaseMouse
Superflower 650 plat Fractal Arc Midi G500 
  hide details  
Reply
    
CPUMotherboardGraphicsRAM
3570k@4.5ghz 1.21v Gigabyte Sniper M3 Sapphire 6950 Samsung 8g1866 
Hard DriveHard DriveHard DriveCooling
Samsung 830 Samsung F1 500 Crucial M4 64 (SRC) cpu:Noc NF-F12 / case:4x TY-141/gpu: 2x NB-Multi 
CoolingOSMonitorKeyboard
Venomous X, Accelero TT Win 7 64 Acer X213H Saitek Eclipse 
PowerCaseMouse
Superflower 650 plat Fractal Arc Midi G500 
  hide details  
Reply
post #6 of 9
True, but the new A15 > TY-14X > P14 imo...
My System
(14 items)
 
  
CPUMotherboardGraphicsRAM
i5 3570k @4,6GHz ASUS P8Z77-I Deluxe Sapphire 7870XT @1,2GHz 16GB DDR3 
Hard DriveCoolingPowerCase
Crucial Noctua U14S & Prolimatech MK26 (+1x Noctua A15) Antec HCP 1300 Lian Li X1000 
  hide details  
Reply
My System
(14 items)
 
  
CPUMotherboardGraphicsRAM
i5 3570k @4,6GHz ASUS P8Z77-I Deluxe Sapphire 7870XT @1,2GHz 16GB DDR3 
Hard DriveCoolingPowerCase
Crucial Noctua U14S & Prolimatech MK26 (+1x Noctua A15) Antec HCP 1300 Lian Li X1000 
  hide details  
Reply
post #7 of 9
Indeed. A15 is an amazing fan.
post #8 of 9
hmm, I need to get around to checking out an A15. The A14 pleasantly surprised me.
    
CPUMotherboardGraphicsRAM
3570k@4.5ghz 1.21v Gigabyte Sniper M3 Sapphire 6950 Samsung 8g1866 
Hard DriveHard DriveHard DriveCooling
Samsung 830 Samsung F1 500 Crucial M4 64 (SRC) cpu:Noc NF-F12 / case:4x TY-141/gpu: 2x NB-Multi 
CoolingOSMonitorKeyboard
Venomous X, Accelero TT Win 7 64 Acer X213H Saitek Eclipse 
PowerCaseMouse
Superflower 650 plat Fractal Arc Midi G500 
  hide details  
Reply
    
CPUMotherboardGraphicsRAM
3570k@4.5ghz 1.21v Gigabyte Sniper M3 Sapphire 6950 Samsung 8g1866 
Hard DriveHard DriveHard DriveCooling
Samsung 830 Samsung F1 500 Crucial M4 64 (SRC) cpu:Noc NF-F12 / case:4x TY-141/gpu: 2x NB-Multi 
CoolingOSMonitorKeyboard
Venomous X, Accelero TT Win 7 64 Acer X213H Saitek Eclipse 
PowerCaseMouse
Superflower 650 plat Fractal Arc Midi G500 
  hide details  
Reply
post #9 of 9

Looking at the C14 diagram, it occurs to me that you could fit two A15's without offsetting the bottom fan if the bottom fan is installed crosswise, rather than lengthwise.

 

The A15, like the P14, has a flared fan chamber along the long axis. That is why a lengthwise installation of a bottom A15 must be offset to avoid the heatpipes. A crosswise installation would avoid that issue and allow the bottom A15 to fit into the lower space without an offset.

alpha updated
(19 items)
 
secundus
(14 items)
 
 
CPUMotherboardGraphicsRAM
i7 4790k Gigabyte GA-Z97X Gaming-7 Intel HD4600 Crucial Ballistix Sport Very Low Profile 8GB Ki... 
Hard DriveCoolingOSMonitor
Samsung 840 EVO 500GB Prolimatech Megahalems Rev. C Windows 8.1 Home Premium 64-bit Acer K242HL 
KeyboardPowerCaseMouse
Dell SK-8110 (PS/2) Seasonic X460 Fanless motherboard tray from CM ATCS 840 Logitech MX 1100 
Mouse PadAudio
Dell Creative SoundBlaster X-Fi MB3 
CPUMotherboardGraphicsRAM
i7 860 Gigabyte GA P55M UD2 ZOTAC/NVidia GTX 650 Ti 2GB 4x4GB G.Skill Ripjaws DDR3-1333 CAS9 
Hard DriveOptical DriveCoolingOS
Samsung 1TB Spinpoint F3 7200.12 Plextor 24x DVD burner Cooler Master Hyper Z600R Win7 64-bit 
MonitorKeyboardPowerCase
Dell E207WFP 20-inch flat panel Logitech Wireless 510 Seasonic X-650 fully modular 80+ Gold Lian Li PC-7FN 
MouseMouse PadAudio
Wireless Mouse WACOM Intuos 3 generic 
  hide details  
Reply
alpha updated
(19 items)
 
secundus
(14 items)
 
 
CPUMotherboardGraphicsRAM
i7 4790k Gigabyte GA-Z97X Gaming-7 Intel HD4600 Crucial Ballistix Sport Very Low Profile 8GB Ki... 
Hard DriveCoolingOSMonitor
Samsung 840 EVO 500GB Prolimatech Megahalems Rev. C Windows 8.1 Home Premium 64-bit Acer K242HL 
KeyboardPowerCaseMouse
Dell SK-8110 (PS/2) Seasonic X460 Fanless motherboard tray from CM ATCS 840 Logitech MX 1100 
Mouse PadAudio
Dell Creative SoundBlaster X-Fi MB3 
CPUMotherboardGraphicsRAM
i7 860 Gigabyte GA P55M UD2 ZOTAC/NVidia GTX 650 Ti 2GB 4x4GB G.Skill Ripjaws DDR3-1333 CAS9 
Hard DriveOptical DriveCoolingOS
Samsung 1TB Spinpoint F3 7200.12 Plextor 24x DVD burner Cooler Master Hyper Z600R Win7 64-bit 
MonitorKeyboardPowerCase
Dell E207WFP 20-inch flat panel Logitech Wireless 510 Seasonic X-650 fully modular 80+ Gold Lian Li PC-7FN 
MouseMouse PadAudio
Wireless Mouse WACOM Intuos 3 generic 
  hide details  
Reply
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Air Cooling
  • Noctua CPU heatsink push/pull with two different fan speeds: turbulence or other problems? (Air cooling theory)
Overclock.net › Forums › Cooling › Air Cooling › Noctua CPU heatsink push/pull with two different fan speeds: turbulence or other problems? (Air cooling theory)