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Old 5th March 2012, 10:32 PM   #1111
fjpolo is offline fjpolo  Argentina
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Default ZV1

Sorry, can't seem to edit or eliminate my last post,and pics can't be seen :/
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Old 6th March 2012, 06:38 AM   #1112
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Originally Posted by Tiroler View Post
Your very well planned and finely crafted F4 looks great from any angle! This is DIY at a truly high level, I like it much!
Martin
Martin, I have been looking at your Picasa albums yesterday. It leaves a bittersweet feeling - most impressive in terms of skills, tools, process and result , depressing in terms of the realization that one will never ever get to that level, not in 100 years…. Thanks for sharing, anyway.

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Old 6th March 2012, 08:24 AM   #1113
Tiroler is offline Tiroler  Austria
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Sven, thanks. These things required hard work and I put a lot of time an dedication into these projects. I think it is the goal and the will to reach it, that can drive people to new levels. In my albums I wanted to share ideas with an instructive aspect about how to make things and overcome difficulies. Hope that it is much more inspiring than depressing!
Martin
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Old 7th March 2012, 08:54 AM   #1114
CENTRAL is offline CENTRAL  Greece
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I think it's inspiring!!!

It's always good to know that an inspired, skilled and dedicated individual can outperform the industrial giants at their own game.
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Old 7th March 2012, 11:51 AM   #1115
EUVL is offline EUVL  Europe
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> the heat sinks are 300x150mm (Fischer KL-271).

Do correct me if I am wrong, but I believe Fischer uses the prefix SK exclusively for their high power extrusions.

Judging from your photos, I belive the extrusions you have are Seifert KL271, which is 300mm wide and 83.5mm deep. It has 21 fins at 14.7mm pitch, and the base plate thickness is 15.5mm.

The closest equivalent from Fischer is SK157, which is also 300x83.5. However it is not 100% compatible, as it has 23 fins at 13.4mm pitch, and a base plate thickness of 12mm.

At 150mm extrusion length, Seifert quotes a Rth of 0.12K/W, and Fischer almost double at 0.25K/W. But in my experience with Seifert Rth figures, they tend to be extremely optimistic. Even the Fischer figures are only true when dT = 80 degC. But I guess most of you would want to operate at dT < 40 degC.

So realistically, one can dissipate about 135W per heatsink, placed vertical and black anodised.


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Patrick
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Old 7th March 2012, 11:58 AM   #1116
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So realistically, one can dissipate about 135W per heatsink, placed vertical and black anodised.

Regards,
Patrick
Does anodising the heatsink black helps in dissipating heat?
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Old 7th March 2012, 12:00 PM   #1117
EUVL is offline EUVL  Europe
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Yes, by about 15%, depending on dT.


Patrick
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Old 7th March 2012, 12:08 PM   #1118
EUVL is offline EUVL  Europe
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I did a quick simulation for both sinks based on the published geometries by the manufacturer.

At 40 degC temperature rise, the SK157 will dissipate 145W, and the KL271 135W.
Given the accuracy of the simulation probably identical, perhaps slight advantage to the Fischer due to larger dissipation surfaces (more fins).


Patrick


PS for this particular sink size, the optimum fin pitch is 10mm.

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Last edited by EUVL; 7th March 2012 at 12:19 PM.
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Old 7th March 2012, 12:23 PM   #1119
AndrewT is offline AndrewT  Scotland
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40C @ 140W is equivalent to 0.29C/W @ dt=40C

Using a DF factor of 1.2 to convert to dt=75C then Rth s-a comes out at ~0.24C/W

It would seem that the Rth s-a of a 150mm length of this heatsink is not well represented by either manufacturer.
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Old 7th March 2012, 12:26 PM   #1120
EUVL is offline EUVL  Europe
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Fischer did quote 0.25K/W (read from a graph).
I thought that is pretty close to the 0.24C/W that you mentioned above ??

Seifert is of course way out.


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