Cooling a Wedge

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fine-tune
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Cooling a Wedge

Post by fine-tune »

I've got to force some air into a wedge shaped gap. There is one hot spot. It can't be more
than two (maybe three) square inches. A stream of air from a four inch desk fan completely
swamps the problem, even though 95% of the air flow from a round desk fan does not enter
the gap.

As you can see in the diagram, the wedge is completely open at the rear and both sides.
If the wedge was a closed pocket cooling would almost be impossible. Water cooling or
even a power hogging thermoelectric cooler might be the only options.

I was thinking some kind of axial or squrriel cage blower. There is plenty of open space
behind the wedge, but the output end must concentrate the air stream into the gap, so
it can't be wider than 1-3/8". The final requirement is noise. Human ears will be close to
this gap, so it must run quietly. A gentle "whoosh" is ok.

Finding oddball fans or blowers is difficult. If what I need exists, it's probably a never used
surplus item or pulled from some other device. Years ago I remember seeing an array of
extremely tiny open frame cooling fans, mounted side by side in a bracket. Not exactly
ideal for this configuration, but it might work.
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Janitor Tzap
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Re: Cooling a Wedge

Post by Janitor Tzap »

You probably saw one of these.
Image
They fit in to the 5.25 bay of a computer case, and run off the 12Vdc supply.
This one is on ebay for $9.75.

Problem with these fans, is that they use a cheap Sleeve Bearing, and not Ball Bearing or Hydro-Bearing.
Sleeve Bearing Fans wear out faster than Ball, or Hydro-Bearing fans.

Sleeve Bearing Fans are quiet, at first.
But as they get dust in them, age, and wear.
They will buzz, and rattle.
Expect 2-3 years out of them.

Note: Sleeve Bearing Fans will last a bit longer when mounted horizontally, then Vertically.


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haklesup
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Re: Cooling a Wedge

Post by haklesup »

A TEC is not a good option for small volumes. it still has a hot side that's not far from the cold side you would have to remove even more heat from than you are removing from your hot spot. A TEC generally makes 4-5 times more heat on its hot side than it removes from the cold side. If you need to remove 10W of heat, you will end up radiating at least 50W from the TEC to do it. This is only a reasonable option if you need to closely control a region to a specific set point or need to set multiple set points lower than ambient.

Your quietest option is a heatsink incorporating heat pipes so that you can move the heat outside the small volume area and radiate it without a fan, there are many off the shelf products out there. If you lack area outside the wedge then a water block with recirculating pump to a passive radiator (no active cooling) would be relatively compact and there are many water blocks off the shelf in the internet.

Since the hot spot is small and the wedge is larger than it, you may also be able to apply a passive finned HS right to the area which allows you to use even lower volume air flow

Got a broken laptop. The heatsink for the CPU inside might be just what you need See this example
http://www.impactcomputers.com/p0003975 ... aQodNGQMcQ
fine-tune
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Re: Cooling a Wedge

Post by fine-tune »

Yes, I'm very familiar with all the passive and active cooling components used in computers.

My head hurts when I think too much about this, but I'll briefly explain why this wedge shaped
gap exists.

About six years ago I built a "hybrid" computer. It's a cross between a desktop and server.
I won't try to explain all the different ways it can be configured, because that would require
several pages! The tower was custom built to accommodate 12 hard drive bays. You get
the idea.

This monster is in my home office. Every step in the construction was carefully planned. I
made cardboard and wood mockups before I cut a single piece of metal or plastic. I never
said a word about this project to anyone.

I have very few living relatives. One day, my super bright cousin was visiting. I don't know
why, but he went to the back of my house and opened the office door. He saw the "monster"
and went slightly crazy.

After about an hour of saying "no" over and over I finally relented and gave him a set of
construction plans. I told him not to expect any help from me if he decided to build the thing.
My construction plans and notes are very detailed. If he followed them step by step, there
should be no problems.

Maybe you can guess the rest. He made dozens of changes to the design to suit his needs.
That's why there is a wedge shaped gap that needs cooling. My only regret is not locking
the office door before my cousin visited.
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Janitor Tzap
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Re: Cooling a Wedge

Post by Janitor Tzap »

:lol: :lol: :lol:

I actually see this a lot.

Someone gets a computer case that is designed for a certain motherboard, processor, and drive setup.
Then they start changing things inside the case, disrupting the air flow pattern in the case.
To keep everything still cool enough that they don't overheat.
They have too jury-rig something that will add extra cooling to the case.

This maybe is just adding an extra case fan, or adding fans to chipsets, video cards, and Hard Drives.

But some gamers tend to go crazy with there cooling setups.
Image
Image

Here's one that has the computer in a fish tank with mineral oil!
Image
Now that's Cool & Quiet! :lol:


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Lenp
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Re: Cooling a Wedge

Post by Lenp »

You might consider a transaxial or crossflow blower similar to this one.
http://www.galco.com/buy/ebm-papst-Inc. ... HwodqkYO6A
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)
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