How to choose right heatsink!?

Stabist

Member
2002-09-22 10:56 am
Slovenia
Hi!

I have some problems with designing the chassis for my Zen v4.

The thing is - I can get a heatsink a with 300x300x40 mesaurements - or the same one but cut on two identical halfs - that's 300x150x40. BUT now - if i check out the K/W diagram - the curve is more and more horizontal aproaching 150mm height (that's the point where the diagram ends) - at that point the K/W is around 0.32; I guess that at 300mm height it is somewhere 0.22-0.25K/W
So - if I use the lower one for just one channel - if Zen v4 has cca 100W disipation - that's 32°C over temp ..
If I use the big one for both (2x100W dissipation) - somewhere around 45-50°C over temp ... :(

Is that conslusion correct or not?!?

OK - so the solution is to make 15cm high chassis - but unfortenly the min. is at least 23cm because other demands :(
And also another thing - I would like to place heatsinks exclusively as a FRONT panel.
SO - my solution - if I place two 300x150 both on front - BUT leave between them cca 2cm of space - so the front panel would be 300x320 - will that improve cooling enough or not?!? Or are just my conslusions about cooling efficiency wrong and 300x300 will do his job just fine??
Same heatsinks Marijan (the picture and description of his amp is in passdiy/gallery) had used for his A2 monoblocks - two 300x200 for each monoblock. And he's quite satisfied with the result ... And as far as I know - each heatsink had to cool down 150W dissipation ...
Any sugestions very welcomed!


Another question - A3 and Zen v4 - can for both be used the same chassis with same heatsinks?? I think that dissipation is similar in both cases or am I wrong?
 
Skaara - your sugestion has only one failure - it increases the costs for the chassis for cca 85% of the price :(

And also - I would really like to make an amp with only front panel as heatsink ...

OK, there is also another solution that I might put as an option - front panel 300x300 heatsink - for main 4 mosfets ..
In the rear 300x50 heatsink as the top 5 cm of back panel for other 2 mosfets ...
That should be more than enough!
 
Stabist said:



SO - my solution - if I place two 300x150 both on front - BUT leave between them cca 2cm of space - so the front panel would be 300x320 - will that improve cooling enough or not?!? Or are just my conslusions about cooling efficiency wrong and 300x300 will do his job just fine??

I think that leaving the space between sinks in that arrangement won't change much. The drawback here is uneccessary complexity of the chassis in return for dubious results.
 
Peter - I assume the problem is in temperature of the air - it is allready warmer and altough I would separate heatsinks - the cooling efficiency cannot be improved - am I correct?

Btw - what about my comparison - if same model of the heatsink, just 200mm high is enough for 150W of A2 - then 300mm high surely must be enough for 200W of my stereo v4??
Because concerning that K/W diagram Marjan couldn't reach heatsink temp at around 60°C (around 35°C over temperature) -but he did it without problems!