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Old 4th November 2007, 12:51 AM   #21
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Quote:
Originally posted by Magura


I greatly respect your input, but in this case you need to do the math....it's a plain matter of radiating surface area.

Hi,
How much surface area do you think a radiator has? You have several tubes, surrounded by fins. The water contacts the inner walls of the tubes, heat radiates out.
It doesn't take a very big radiator to out do the biggest heatsink.
No math required
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Old 4th November 2007, 12:53 AM   #22
Magura is offline Magura  Denmark
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Quote:
Originally posted by MJL21193



Hi,
How much surface area do you think a radiator has? You have several tubes, surrounded by fins. The water contacts the inner walls of the tubes, heat radiates out.
It doesn't take a very big radiator to out do the biggest heatsink.
No math required
If you compare apples to apples, you will see that if a radiator is not force cooled by a fan, it hardlt works, and is actually outnumbered by a regular heatsink.

Magura
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Old 4th November 2007, 12:56 AM   #23
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Quote:
Originally posted by Magura
Now all you need is to tell us what the actual difference is between a radiator and a heatsink when it comes to dissipating heat?
As a heat exchanger, a radiator is more effective because the temperature is close to constant at every location.
Which is not the case for a heatsink, the reason why thermal efficiency drops for a bigger heatsink.

Most heat in a car engine is generated in the heads, easier to take away the heat with watercooling, unless you make really big heads.
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Old 4th November 2007, 01:08 AM   #24
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Quote:
Originally posted by jacco vermeulen


As a heat exchanger, a radiator is more effective because the temperature is close to constant at every location.
Which is not the case for a heatsink, the reason why thermal efficiency drops for a bigger heatsink.

Most heat in a car engine is generated in the heads, easier to take away the heat with watercooling, unless you make really big heads.

I have actually spent a little time on this stuff a while ago, and if the heatsink has a reasonably massive backbone, the temperature differences for heatsinks in a size of interest to us, is neglectible. We are talking less than 1 degree C for a 180*180*60 heatsink, measured anywhere on the sink.

Again compare apples to apples, your theory only holds true if forced cooling is used. I dare to assume you don't want a fan in the size of the radiator running in your living room.

As for the car engine cooling, yes, watercooling is the way to go, due to a number of reasons, one is size of heatsinks required on the cylinder heads.......but we are not building car engines

Magura
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Old 4th November 2007, 01:13 AM   #25
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Quote:
Originally posted by Magura
if the heatsink has a reasonably massive backbone
Which most do not have.
A combination of passive and fluid cooling is highly effective : heatpipes.
If you use a regular domestic radiator it will be big,... and you'll be living nextdoor to Mr Rollins
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Old 4th November 2007, 01:15 AM   #26
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Whether you are using radiators or heat sinks, the use of slow running fans is probably desirable.

The PC world is full of slow running 120mm DC fans that are 15-20dba.

Under-volting fans from 12v to 7v is commonplace in trying to achieve a "quiet PC".

Another tactic I've considered is placing the heat sinks/radiator inside a pipe of say 10-20" long. My guess is that the fan noise would be reduced significantly and lowered in frequency.

From the PC world you can get four 120mm radiator systems pretty easily http://www.dangerden.com/store/produ...1&cat=5&page=1

The thing I wonder about is how you'd mate the water cooling system to your transistors? For PC's they make copper water blocks for easy connection to CPU's, GPU's, even hard drives.

Could you use a CPU water block?
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Old 4th November 2007, 01:21 AM   #27
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Quote:
Originally posted by jacco vermeulen


Which most do not have.

Now that is a fact

But that is just a matter of making people understand that it's actually an important factor.

Back when I desigened the heatsinks for the round boxes, I first tried myself to make a design, but quite soon I found out that the way to go was to simply adapt an existing design, or it would take a lot of math and most likely suffer in one way or the other anyway.

My conclusion back then was that this design (see image) is among the most versatile.

Magura
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Old 4th November 2007, 01:25 AM   #28
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When I was monkeying around with the alephX a couple of years ago. I had a heat sink about 6" high by 9" long by 1 1/2" deep that I wanted to use to test the board with after assembly. I was building an AlephX-100 so I knew the heat sink wasn't nearly enough. I found a surplus Cool plate on ebay. I took alot of thermal transfer goo and smeared it on the plate and bolted it to the heatsink. I then mounted the board to the cool plate. A good friend offered me a Zalman external water cooling system to use for 2 weeks (his son was being punished with no gaming for two weeks and this was one way to be sure his son didn't cheat). I filled the system with ethylene glycol and water. I was very surprised to find out that the combo of water cooler/heatsink worked well to keep the output transistors cool.

Here is what the cool plate I used looked like:

Click the image to open in full size.


I never used the aleph x as I sold the loaded boards here on the forum. I instead built an aleph5 using a conventional heatsinks. The solution for water cooling worked but too expensive for my tastes.
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Old 4th November 2007, 01:30 AM   #29
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Groovy...

I'm a DIY kind of guy, so...

I'm going the water route because I like to experiment. I've gone the diy aluminum heatsink route, which is also a blast, but want something more streamlined.

I have a 3/4 ton Ford F250 radiator that I saved for a project like this. I'll mount it outside, in the shade, on the back porch, just outside my brand-new hobby room. Eventually, I'll couple a fan to the radiator. I'm tired of worrying about heatsinks, capacity, etc. Water works well, and will relieve me of the hefty labor involved in fabricating my own heatsinks.

You guys sure know how to work up a discussion...I like it!
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Old 4th November 2007, 01:37 AM   #30
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Quote:
Originally posted by carpenter
Groovy...

I'm a DIY kind of guy, so...

I'm going the water route because I like to experiment. I've gone the diy aluminum heatsink route, which is also a blast, but want something more streamlined.

I have a 3/4 ton Ford F250 radiator that I saved for a project like this. I'll mount it outside, in the shade, on the back porch, just outside my brand-new hobby room. Eventually, I'll couple a fan to the radiator. I'm tired of worrying about heatsinks, capacity, etc. Water works well, and will relieve me of the hefty labor involved in fabricating my own heatsinks.

You guys sure know how to work up a discussion...I like it!
If watercooling must make any sense, this is sure that way to go about it.
One thing you should keep in mind is that you need to be able to control the flow in order to get the MOSFETs up to working temperature without having to heat half of your backyard up to the desired working temperature. If made reasonably simple with a thermostatic valve from a domestic radiator, you can even just set the working temp with the thermostat, and just leave it at that, amp working or not, rain or shine.

Magura
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