CPU Fan vs. Case Fan

[Deleted]

So a year ago i built my first own PC and a while ago i changed my PSU, CPU cooler, and because the CPU cooler was too huge also the case.
Don't understand me wrong, everything works preety well and i have no problems with it.
But i've been wondering now for a while does a CPU fan draw air to the CPU or away from it?
I'm no expert in things like this but someone i know stated it blows ffesh air directly onto the CPU, which might not be good for my build since i use a CM Storm enforcer case and a CPU cooler with a 120mm fan which is positioned directly half-1cm away from the case fan...
So my question is; do i need to put the fan to another side of the heatsink or is it ok this way?

http://s23.postimg.org/k6ransaxn/201...4_10_40_19.jpg <- picture of what i'm toying around with

[Gorehowl]

you can have it drawing air in from the back like that, or the front, i would personally have it on the front and pushing air over the fins then have the back case fan drawing the hot air out of the case instead of the fan pushing the air directly onto the case fan.

[Saithes]

Yours is actually in a very bad setup.. The fan below is pulling out of the case while the fan on the heatsink is pulling air through the heatsink. They're basically pulling air away from one another when the heatsink fan should actually be reversed and be pushing air into the case fan.

[Deleted]

That's exactly what i've been wondering

So i should place the fan on the front side of the heatsink if i read this right?

[Neave]

I would put it on the other side. the small gap between the CPU fan and exhaust fan gives the acceleration of wind speed (therefore more cooling) where there is nothing to be cooled.

Put the fan on the other end, blowing towards the other fan and you will have a "push-pull' cooling (one fan pushs air, the other pulls the air)

[Saithes]

So i should place the fan on the front side of the heatsink if i read this right?

It should go like this..



Grey = Case
Red = Heatsink
Blue = Fans
Green = Airflow


The exhaust (aka the part of the fan with the brackets on it above) should be facing the inside of the heatsink and the case fan that is behind this should also be facing the same direction.

[chazus]

There are two methods of air cooling. Intel stock coolers, and many others, push air down onto the heatsink, and away. Better aftermarket coolers push over the heatsink, towards the back and out. Regardless, they both 'push' the air over the fins. Some heatsinks (Noctua) have two fans. One to push the air, one to pull the air, for better flow.

This is also one of the reasons the XBox 360 had an AWFUL thermal design... Because it had a heatsink with no fan attached... and only a 'pull' solution at the back. It's like having a hot day, getting a fan, turning it on, and facing it away from you, hoping it would help.

[Deleted]

BTW it's a Thermalright HR-02 Macho Rev.A heatsink
Like seen on the picture on the link it has 1 fan i can place on either the front or the back.

EDIT; oh thanks Saithes, that kind of answers my question perfectly; Looks like it's playing time again xD

[Kalas]

Regarding what Saithes said, look closely at the shape of the bottom fan blades in the pic. You'll notice it's aligned properly to vent air from the case so you're wrong about the airflow unless the CPU fan is backwards. And the CPU fan isn't visible in the pic so we can't conclusively say either way but I'm inclined to say the setup is fine as OP hasn't had temp issues.
All you have to do really is just stick your hand behind the exhaust. If air is coming out it's working fine, if not your CPU fan (not case fan) is backwards but that's incredibly unlikely without seeing some very high temps in normal use.
FYI you never ever want your CPU heatsink blowing air into the case as that heats up all other components.

[Saithes]

Regarding what Saithes said, look closely at the shape of the bottom fan blades in the pic. You'll notice it's aligned properly to vent air from the case so you're wrong about the airflow unless the CPU fan is backwards. And the CPU fan isn't visible in the pic so we can't conclusively say either way but I'm inclined to say the setup is fine as OP hasn't had temp issues.
All you have to do really is just stick your hand behind the exhaust. If air is coming out it's working fine, if not your CPU fan (not case fan) is backwards but that's incredibly unlikely without seeing some very high temps in normal use.
FYI you never ever want your CPU heatsink blowing air into the case as that heats up all other components.

In the picture you can partially make out a bright orange/yellow(the fan attached to the heatsink) which I would assume is the fan wire. This would mean that the fan is exhausting the opposite direction of the case fan. From my understanding of his original post he's simply wondering the most optimal setup for airflow which is what I provided. Having 2 fans blowing in opposite directions is not optimal.

[Deleted]

Yup Saithes, you understood me quite well.
I made a little google image search of my heatsink and on most of the images the fan is on the other side than in my build so i'm doing it that way too.
like for instance; http://prohardver.hu/dl/upc/2012-09/28688_imgp5644.jpg
heck some guy even turned the thing upside-down,... just noone did it the way i did so i guess i did it preety wrong

[Saithes]

Yup Saithes, you understood me quite well.
I made a little google image search of my heatsink and on most of the images the fan is on the other side than in my build so i'm doing it that way too.
like for instance; http://prohardver.hu/dl/upc/2012-09/28688_imgp5644.jpg
heck some guy even turned the thing upside-down,... just noone did it the way i did so i guess i did it preety wrong

Honestly the difference will likely be a few degrees Celsius difference but hey every little bit helps in the end right?

[Deleted]

True. From what i've actualy seen the fan barely needs to spin anyway since the airflow the case provides is quite immense on it's own.
And also it solves the trouble i was having managing the power cable from the psu for the heatsink. it is a quite tight situation the way it is right now xD

[Kalas]

BTW it's a Thermalright HR-02 Macho Rev.A heatsink
Like seen on the picture on the link it has 1 fan i can place on either the front or the back.

EDIT; oh thanks Saithes, that kind of answers my question perfectly; Looks like it's playing time again xD

Did you move the fan to the other side of the heatsink or is this photo inaccurate? If you did like the 2 photos seem to indicate then did you flip the fan or leave it with the same facing? Since the fan is on the opposite side of the heatsink vs all photos I can't tell which way it's blowing without that little detail.
Also, a quick way to skip all this quibbling over details is to simply unplug the case fan and see if you feel air blowing out the back still. If so you needn't read a single other part of this post because you're good to go.

In the picture you can partially make out a bright orange/yellow(the fan attached to the heatsink) which I would assume is the fan wire. This would mean that the fan is exhausting the opposite direction of the case fan. From my understanding of his original post he's simply wondering the most optimal setup for airflow which is what I provided. Having 2 fans blowing in opposite directions is not optimal.

I presume you mean this case fan connector with black, red, and yellow wires. (May appear different on your monitor.) The colors of a fan's wires or the type of connector used has all of dick nothing to do with which way it blows air. All that matters is the shape of the blades and the direction it spins, which you can always tell by the blades as all modern PC fan blades are shaped (slightly convex on 1 side, slightly concave on the other) so that they're far more efficient when blowing in the intended direction. (That fact combined with many fans having diodes to prevent reversing voltage makes it safe to assume they'll always blow in the intended direction. OP would have to manually rewire the connector to do otherwise even if it had no diode.)
It's a bit more complex than this but it can be boiled down to the general rule: the side of a fan blade which collects the most dust is the side in which air is forced 99% of the time. I'm probably just not doing a good job conveying the visual pictures of this, good thing I'm not a teacher.

[Saithes]

I presume you mean this case fan connector with black, red, and yellow wires. (May appear different on your monitor.) The colors of a fan's wires or the type of connector used has all of dick nothing to do with which way it blows air. All that matters is the shape of the blades and the direction it spins, which you can always tell by the blades as all modern PC fan blades are shaped (slightly convex on 1 side, slightly concave on the other) so that they're far more efficient when blowing in the intended direction. (That fact combined with many fans having diodes to prevent reversing voltage makes it safe to assume they'll always blow in the intended direction. OP would have to manually rewire the connector to do otherwise even if it had no diode.)
It's a bit more complex than this but it can be boiled down to the general rule: the side of a fan blade which collects the most dust is the side in which air is forced 99% of the time. I'm probably just not doing a good job conveying the visual pictures of this, good thing I'm not a teacher.

Yes it does.. the side the wire comes out of is the direction airflow goes :P and inbetween the heatsink and the fan there is yellow/red/etc which as I said I assumed would be a wire.

Red circle:
http://i.imgur.com/27TM2pp.jpg

You can also see the bracket that holds the fan motor. This indicates that this is the direction of airflow which means its pulling away from the case fan that's behind it. Thus, it is going against airflow. Yay industry standards!

As I said before the case fan is fine... you're just being an idiot and seemingly picking a fight over something completely unrelated to what I'm referring to.

[Deleted]

yes, the fan is blowing the right way; i was just wondering about the optimal placement of it and i got my answer to that; thank you.
No need to get into fights here guys... this will be fixed in half a minute without usage of any tools so it's realy not worth it.
Thank you again for the input

[yurano]

i was just wondering about the optimal placement of it and i got my answer to that; thank you.

Push is better than pull.

http://martinsliquidlab.org/2012/01/...ud-testing-v2/

[kegz]

Usually if you look on the side of the fan it has an arrow pointing in the direction which the air will travel...

[vesseblah]

Not all fans are built that way. The airflow direction depends on the shapes of the blades, not which side the motor is on. Concave side of the blades is where the air is pushed to and convex side is where it's pulled from.

All PC fans are supposed to have two arrows on one of the four sides which is the easiest way to figure out the direction of the fan. One arrow points the direction of airflow and other points the direction where the blades are turning, like this...

[Drunkenvalley]

Not all fans are built that way.

It's a generic rule of thumb, and if you find an example of fans where this doesn't apply I would very much like to know which.