cooling fans help

dunn2010 · 14 Sep 2012 at 14:52

Hey guys,

below is a picture of my case (not with fans in)

theres two fans on front for intake, one at bottom for intake. the PSU blows air in. The green arrow in the middle is to represent intake from the fan that is fitted onto the side panel of the case.

there is then two fans on top as exhuasts, one on rear as an exhaust. and since this photo i have turned the fan round on the heatsink. so the fan now sits on the other side of heatsink, and blows air through heatsink and out to the top of the case.

Is this a good setup for cooling efficiently? should i put side panel as an exhaust? Does blowing air through heatsink allow it to cool better or was it better way before?

Also now i have fitted all fans as shown in picture however at the bottom, my PSU now has a molex connection cable coming out of it. and there is a fair few wires that stick just above the fan. im assuming this will effect its airflow in some way.

any help greatly appreciated thanks.

EDIT** Should have mentioned they are all 120 mm bitfenix spectre fans

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Apem · 14 Sep 2012 at 16:05

The psu doesnt blow air into the case its used to cool the psu so its a intake fan. Layout looks ok but I would have the cpu cooler facing the rear exhaust.

BarKeep · 14 Sep 2012 at 17:49

Apem said:
I would have the cpu cooler facing the rear exhaust.

Why?

To the OP, as Apem said the PSU should be seen as an exhaust.

dunn2010 · 14 Sep 2012 at 17:53

BarKeep said:
Why?

To the OP, as Apem said the PSU should be seen as an exhaust.

Thats exactly what i originally thought. manual says it exhaust, it made sense for it to exhuast, however if i hold my hand above it, it feels like its blowing really cool air into my tower?

tonschk · 16 Sep 2012 at 09:16

dunn2010 said:
Also now i have fitted all fans as shown in picture however at the bottom, my PSU now has a molex connection cable coming out of it. and there is a fair few wires that stick just above the fan. im assuming this will effect its airflow in some way.

I am happy I avoid as hell the modular PSU, all those connectors cables sticking out of the modular PSU are ugly and develop problems, the non-modular version dont have this problem

BarKeep · 16 Sep 2012 at 16:25

dunn2010 said:
Thats exactly what i originally thought. manual says it exhaust, it made sense for it to exhuast, however if i hold my hand above it, it feels like its blowing really cool air into my tower?

Hold a tissue over the rear of the PSU (where the switch is). Intake will stick to the PSU, exhaust will blow away.

j.col · 16 Sep 2012 at 20:44

Apem said:
The psu doesnt blow air into the case its used to cool the psu so its a intake fan. Layout looks ok but I would have the cpu cooler facing the rear exhaust.

this tbh, if your case has an air grill under the psu, then turn it over, so the psu fan faces down, if no air grill then leave it.

regarding the cpu cooler orientation, personally i would have it facing the rear of the case, as the way u have it set up now, the cpu is sucking warm air from your gpu and psu through your cooler,
if u had it set up so its blowing to the rear, it would get more cooler air from the front of the case.

here is a pic, from a different forum, by a very well respected fan reviewer, its a bit ott, but u get the meaning

foster grant · 16 Sep 2012 at 21:09

A question please while your all here discussing cooling fans...if i have all my case fans connected via molex to the PSU and none of them into the motherboard will those fans be running at " full speed" all the time ?

j.col · 16 Sep 2012 at 21:40

iirc yes, molex will run them at full speed

foster grant · 17 Sep 2012 at 00:13

j.col said:
iirc yes, molex will run them at full speed

yeah i thought so thanx

doyll · 17 Sep 2012 at 07:34

j.col said:
this tbh, if your case has an air grill under the psu, then turn it over, so the psu fan faces down, if no air grill then leave it.

he cpu is sucking warm air from psu through your cooler,

Sucking warm air from PSU?
Every PSU I've seen expels air out the back.

Cooler up / cooler back.... dependent on how you layout your airflow
PSU sucking from inside case / below case.... Not much difference.

Most stock cases (including this one) set too close to floor for bottom fans to work efficiently. 20mm is about half the minimum face clearance a fan needs for unrestricted airflow.

Simple math; area of fan should be equal to or less than intake area. Circumference of fan times clearance equal intake area. 140mm fan has 154cm square area. 20mm bottom clearance is 88cm square... just over half the area of fan.

More complicated math; area of fan blades.. 140mm fan minus 40mm motor equals 141cm square fan area versus 88cm square intake area.

2 fans side by side on bottom need 25% more because they share a common intake face that neither can draw air from.

We don't need more complication involving fiction and air direction change in the equation.

I raised my case to 50mm clearance on casters. My HSF exhausts out top. 3x intake and 1x exhaust in R2 with i7 920 @ 3.55GHz 58c @ 1000rpm ambient of 22c. Idle @ 37c @ 600rpm. GPU is HD5770 Silent Cell (passive cooling) Only cooling issues are NB @ 50c and HDDs @ 30-45c if i try idling below 600rpm Case exhaust is 3-7c above ambient dependent on GPU and HDD load. . And I have 7x HDDs running.

Edit: Sorry for all the rambling. Can't sleep have to do something.

tonschk · 17 Sep 2012 at 08:48

doyll said:
PSU sucking from inside case / below case.... Not much difference.

The problem with the PSU fan pointing upwards (PSU sucking from inside case) is that the PSU fan suck air downwards into the PSU, and is more likely the dust will build up easier inside the PSU, therefore i think is better the fan of PSU pointing downwards

doyll · 17 Sep 2012 at 09:16

tonschk said:
The problem with the PSU fan pointing upwards (PSU sucking from inside case) is that the PSU fan suck air downwards into the PSU, and is more likely the dust will build up easier inside the PSU, therefore i think is better the fan of PSU pointing downwards

Honestly PSU would probably suck more dust fan facing down than fan facing up. Most cases now have filters on air intakes so air in case has little dust. Even assuming case bottom PSU intake is filtered the dustiest air is near floor level...

tonschk · 17 Sep 2012 at 20:50

doyll said:
Honestly PSU would probably suck more dust fan facing down than fan facing up. Most cases now have filters on air intakes so air in case has little dust. Even assuming case bottom PSU intake is filtered the dustiest air is near floor level...

The airflow has two components: the speed of the airflow and the temperature of the airflow, the dust travel together with the air molecules, when the speed of the airflow decrease enough, the dust cannot be keeped in suspension together with the air molecules and start to go landing downwands, the filters and grills help to decrease the velocity of the airflow, therefore I cut out the grills and eliminated the filters to keep the maximum possible amount of airflow velocity

doyll · 18 Sep 2012 at 07:32

Nice looking rig! What do you use for edging and to cut out your grills?

Your theory is flawed.

Most grilles are very restrictive. The simple wire ones should be used if grilles are needed.

Filters might be evil but dust in computer is much more evil. I will use more intakes and/or more powerful fans to compensate for their restriction. Removing most of the dust from intake air far out weights the restiction.

There are more components to the equation than air speed and temperature; humidity, composition of air, etc... and the particulate matter in the air comes is many flavors too.

The particulate matter in the air not only settles on itemes but also can adhere (stick) to surfaces it contacts (edges of fan blades, heatsink fins, etc. The air composition (smoke grease, oil, humidity, etc.) and size of particulate matter (dust, hair, etc.) dictates where it will collect and/or adhere. Places like leading edges of fan blades and heatsink fins, narrow gaps plugging with air and/or fussy stuff are result of air movement collection. Back side of fan blade collect because of the air turbulence/vacuum near the surface.

Not related but equally important:
Airflow to and from fans. Most case feet do not give enough bottom clearance for unrestricted airflow to bottom fans.

Your PSU intake and bottom vent are good examples fan & vent being greater than area they are able to draw from.

The distance between the feet times height of feet times 2 is area of intake versus Pi time radius squared minus fan motor area is area of fan. Same equation for vent area versus draw area.

tonschk · 19 Sep 2012 at 00:12

doyll said:
Nice looking rig! What do you use for edging and to cut out your grills?

.

This (cutting edging) was already made long time ago, the edging is a Edge Trim U Channel, I bought from chilledPC sold per meter, there are many ways/tools to cut out a grill

tonschk · 19 Sep 2012 at 00:16

doyll said:
Filters might be evil but dust in computer is much more evil. I will use more intakes and/or more powerful fans to compensate for their restriction. Removing most of the dust from intake air far out weights the restiction.

More powerful fans mean more noise

, the problem with the filters is that the reduction of airflow is by at least of about 40% (low restrictive filter) , but the problem dont finish there, with the build up of dust on the filter, the restriction increase day by day reducing even more the airflow and the cooling ability of the airflow

tonschk · 19 Sep 2012 at 00:22

doyll said:
There are more components to the equation than air speed and temperature; humidity, composition of air, etc... and the particulate matter in the air comes is many flavors too.

Yes the airflow has more components, but the most important components that affect the cooling ability of the airflow is the speed and the temperature and not the amount of dust coming in suspension with the airflow

tonschk · 19 Sep 2012 at 00:24

doyll said:
Not related but equally important:
Airflow to and from fans. Most case feet do not give enough bottom clearance for unrestricted airflow to bottom fans.

Your PSU intake and bottom vent are good examples fan & vent being greater than area they are able to draw from.

The distance between the feet times height of feet times 2 is area of intake versus Pi time radius squared minus fan motor area is area of fan. Same equation for vent area versus draw area.

I added a temporary way to lift the case 7cm to allow less restricted intake of air for the PSU

FRAGMAYO · 19 Sep 2012 at 00:34

Quick question while we are on topic then.

is it best to have the fans at the top of the case as an intake or an exhaust