Heat Exchange & Fans question

Posted: Wed Dec 21, 2011 1:43 pm

Just a quick question for pc builders out there.
When your building a pc, a certain airflow has to be achieved within the case, But which would you consider as Primary Importance:
1) Airflow INTO and around the chassis
2) Airflow Out from the chassis
My question arises as my old pc had fans covering just about every orifice sucking air into the chassis, but remains very hot in normal everyday usage. Speccy states 55c on the hdd's (3.0Ghz P4 4Gb ram, 250Gb x2 ATA)
My newer pc has just 3 fans, 1 on the main heatsink, 1 at the rear blowing inwards and a tiny little one covering the gap between the Hdd's (3.06 core 2 duo, 4Gb ram, 2x 1Tb & 1x 500Gb, all sata if that makes a difference) Speccy states 42c on the 1Tb's & 38c on the 500.

Would it make any difference if I added a fan on my newer pc to direct the airflow out so I had a throughput of airflow? Is there any 'rule of thumb' for airflow? Preferences etc?
I ask as i'm hoping to build my own system from scratch after xmas, hopefully based around an i5 processor & an intel h61 board that I have been given, just need to buy the ram, case etc etc.

Many thanks for reading

Posted: Wed Dec 21, 2011 1:57 pm

You cant really go wrong as long as you have an air in - air out configuration, with many new high air flow cases such as the Cooler Master cases they have a large fan directing cold air across however many HDD's you have installed, I'm using the Cooler Master HAF X case at the moment which has a 210mm fan at the front pushing cold air across my HDD, a side panel 230mm fan pushing cold air over my GPU and I have installed the two optional 2 X 210mm fans pulling the warm air out of the case from the top.

I'm also looking to do a new build as soon as I get the money together, I will be going heavily into water cooling this time though and I will be getting the Lian-Li PC-X2000FB Black Aluminium Full Tower Case. If you want to have a look at it> http://www.scan.co.uk/products/lian-li-pc-x2000fb-black-aluminium-full-tower-case-usb-30-esata-w-o-psu

Or the Corsair 800D, I haven't made up my mind yet lol. http://www.scan.co.uk/products/corsair-obsidian-series-800d-black-full-tower-case-with-side-window-3-x-140mm-fans-w-o-psu

I'm no expert though when it comes to builds but I think what I have said is OK, I'm sure someone will correct me if I'm wrong. Good thread. Very Happy

My Rig now on the "Pic of your Rig Thread" http://ca.isohunt.com/forum/viewtopic.php?p=1986853#1986853

Posted: Wed Dec 21, 2011 2:46 pm

i have two Corsair Obsidian Series 650D (CC650DW-1) and i really like the airflow on them.

big fan in front carries air in across the hdd's,one in back brings air in through the cpu's radiator,and another big fan with the option to use two smaller fans on top to exhaust the air out.the psu is turned down to bring air in from the bottom and out through it's back.

my temps tend to stay in the 29-32 °C for the mobo and hdd's,cpu is 33-34 °C probably less at idle,the gpu's vary but idle is in the 30-32 °C range.

Posted: Wed Dec 21, 2011 2:52 pm

my biggest obstacle is cleaning the fan and other innards of the PC i use. i have been successful in the past clearing up all the dust and fluff that gets stuck. all i had to do is unscrew the screws holding the PC together, take a duster, vacuum cleaner and a slightly damp towel and clean it inside out. alas that was my old PC.

as for my ACER All in One Z5 desktop PC there is a slight problem with dismantlement. i've tried to but feel inadequate from my results. i believe i might have missed a few screws so i will try again later.

Posted: Wed Dec 21, 2011 3:02 pm

killa1986 wrote:

my biggest obstacle is cleaning the fan and other innards of the PC i use. i have been successful in the past clearing up all the dust and fluff that gets stuck. all i had to do is unscrew the screws holding the PC together, take a duster, vacuum cleaner and a slightly damp towel and clean it inside out. alas that was my old PC..

alot of the new boxes have filters that will catch most of the dust trying to get in.mine stay very clean,since i chose minimal outside fanciness,pretty much just straight lines the pc takes very little time to clean and with the filters nearly nothing gets inside.

so just a quick wipe down,rinse the filters and a few blasts from a can of air inside and done.

Posted: Wed Dec 21, 2011 5:34 pm

imouse wrote:

My question arises as my old pc had fans covering just about every orifice sucking air into the chassis, but remains very hot in normal everyday usage. Speccy states 55c on the hdd's (3.0Ghz P4 4Gb ram, 250Gb x2 ATA)

If all your fans are sucking in you are creating positive air pressure inside the chassis and that's not good, you need to have equal in and out flow. Flip 1/2 of them around and you will be running cooler, and the fans will not be fighting against each other.

My preference on fans really depends on how the hardware fits inside the case as to wear and how many fans I use. Like I just recently scored a cheap I7 machine. It's a dell xps 435 mini tower and The only PCIE slot is right next to the bottom of the chassis and my Nvidia graphics card was not getting the air it needed so I had to improvise. I got a squirrel cage blower out of a projector and mounted that to my graphics card. Now it sucks air through the cooling fins and blows it out the back of the computer. I'm now a big fan (PUN) of the squirrel cage blower . Their like a mini leaf blower Laughing

Posted: Thu Dec 22, 2011 11:28 am

james hotwire has told you about "flowthrough", or throughput flow.
there are other concepts in the sport of "thermal relief"
here are some concept for the "ideal" situation
-heat rises in a gravitaional field, and produces convectional flow, so if the greatest source of radiation is placed highest in the chassis a flow can be created whithout fans(not to say you should do that with your computer!)
- shared thermal relief chain is the placement of the hottest element closest to the exhaust, and the coldest closest to the intake, and the intermediates somewhere, in the flow in order of heat production so each component is being washed in air of a cooler temperature than itself. IDEALLY this is in vertical array.
- a global flow should be used to immediately remove heat from components then displace it from the chassis
a chassis may include a gallery to collect the chassis flow into one area and immediately exhaust to outside the chassis so each component that is an extreme generator has a dedicated displacment mechanism, such as a thermal conductive sink, and or a fan.
and the chassis has an arrangement to pool the thermal output of these into a flow path, and convective assist may be used here.

for components, heat sinks have a rating called "theta" and have a desireable orientation for maximization of theta. thermal paste is used between component and heat sink, sink elemenst should be kept clean, and free of dust or objects
cables should be out of the flow path
for the chassis flow, an unrestricted intake plenum rather than a fan is best, and the exhaust fan should be highest CFM rating in the chassis

Wink

Posted: Thu Dec 22, 2011 1:55 pm

http://en.wikipedia.org/wiki/Computer_cooling

Edit: i need help. does anyone know how to dismantle Acer Z5 PC? my computer keeps shutting down by itself and i need to clean out any dust the fan has collected. i have unscrewed all the screws, yet i am still having trouble removing the exoskeleton.

Edit again: Hoorah! i've finally figured it out. the innards of my PC have been thoroughly vacuumed, dusted, and wiped clean of any dirt.

Posted: Wed Jan 04, 2012 9:30 pm

Quote:

If all your fans are sucking in you are creating positive air pressure inside the chassis and that's not good, you need to have equal in and out flow.

I'll second that.

On another note, addressing imouse's temps from the first post; your Pentium 4, even when clocked up around the same as you C2duo, has a higher voltage which is likely the cause of your higher temps (83w vs 65w) according to the Intel website:
P4 3.0
Core2 Duo 3.06
Not that airflow isn't important, but you gotta see all angles eh,

Posted: Thu Jan 05, 2012 12:10 am

If you are going to have top fans then make them take out the heat because the heat always rises up
A fan at the back to get the heat outside
Front and side getting air in

My setting with HAF X (i7 2600K)
Front big fan getting air in
Left side big fan getting air in
4 normal fans at top pulling heat(Corsair H100 fans)
1 normal fan at the back pulling heat

Posted: Thu Jan 05, 2012 1:15 am

I think you mean hot air rises, heat radiates outwards Wink

. For genereating airflow inside your case you only really need an exhaust fan, direction is irrelevant just put it near to a heat source so hot air doesn't circulate over all the other components.