heat sink cooling

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moe
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heat sink cooling

Post by moe » Tue Apr 03, 2018 5:40 am

I want to install a muffin fan on the heat sink of a stereo receiver, my question is in what direction should the air flow?
Blowing in the heat sink or sucking heat off the fins?
Thanks
Moe

sghioto
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Re: heat sink cooling

Post by sghioto » Tue Apr 03, 2018 6:11 am

I don't think it would make much difference if the chassis is ventilated properly. I would prefer to draw the heat out if possible.
SG

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haklesup
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Re: heat sink cooling

Post by haklesup » Tue Apr 03, 2018 1:33 pm

in isolation it doesn't much matter but pulling air out of the HS will tend to deposit more dust in the fins resulting in efficiency loss sooner. when blowing into the HS, the higher velocity will settle less dust. The shape of the cooler may also direct your thinking.

If there is an airflow pattern or ducting in the chassis, this may further direct your decision. you don't want to be drawing in warmed air from another nearby heat sink or power supply for example. Usually air is expelled from the chassis but there is no rule and often a thermodynamic analysis can answer which is actually better. Frequently it is based on dust and contamination control as much as heat removal.

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MrAl
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Re: heat sink cooling

Post by MrAl » Wed Apr 04, 2018 9:33 am

moe wrote:I want to install a muffin fan on the heat sink of a stereo receiver, my question is in what direction should the air flow?
Blowing in the heat sink or sucking heat off the fins?
Thanks
Moe
Hi,

In most cases it is better to have the fan blowing on the heat sink, as close as possible to the heat sink.
This is because the air flow is more controlled when it is directed at the heat sink.

The output flow of the fan is more laminar than several inches away from the fan so there is less spread of flow which means reduced air flow at a distance. Thus you will always see CPU fans blowing right on the heat sink.

There are special cases that will work either way such as in a very restricted air shaft, but even then the air flow is strongest when the fan blows directly on the heat sink and as close as possible to the heat sink.

Also, the fan size (cross section height and width) is also sized to match the heat sink fins spread. THus if you have a heat sink with 4x4 inch cross section (fins aligned with air flow) then a fan 4x4 or 5x5 or bigger is recommended.

As always you want the air flow to 'touch' every square inch of heat sink surface area so align the fins with the air flow so that the air flows freely through the heat sink, flowing past all fins.
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Janitor Tzap
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Re: heat sink cooling

Post by Janitor Tzap » Wed Apr 04, 2018 10:13 am

moe wrote:I want to install a muffin fan on the heat sink of a stereo receiver, my question is in what direction should the air flow?
Blowing in the heat sink or sucking heat off the fins?
Thanks
Moe
Hmmm.........................

First off........
Where is the heat sink that you want to cool on the stereo receiver?

I've worked on several stereo receivers that have the Heat Sink mounted on the back of the receiver,
and the 12Vdc Muffin Fan mounted on it, with the air flow blowing outward.

Some of the cooling schemes were rather elaborate.
Like a Heat Pipe/Heat Sink arrangement, that put the Cooling Radiator outside of the case with the muffin fan.

Some PC Cases have CPU Intake Tubes or Vents that direct air outside the case to the CPU/Fan Heatsink.
Image
Many HP's and Dell Computers use them to help keep the CPU Cooler, instead of adding an extra case fan.


Signed: Janitor Tzap

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spackler
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Re: heat sink cooling

Post by spackler » Tue Apr 10, 2018 1:33 pm

I've worked on computers for a while now and from what I've seen, fans are configured to draw in cool air from the outside, blow it across the heat sink, and out the other side of the machine.
Brian Jenkins
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