aluminum heatsink anodizing
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From: Eeyore on 20 Dec 2008 03:58 John Larkin wrote: > Eeyore <rabbitsfriendsandrelations(a)hotmail.com> wrote: > >John Larkin wrote: > >> Eeyore <rabbitsfriendsandrelations(a)hotmail.com> wrote: > >> >John Larkin wrote: > >> > > >> >> No insulators at all of course... the heatsink is hot to the load. > >> > > >> >Isn't that just what I recommended ? > >> > >> Was it? > > > >For optimum cooling, of course ! > > > > > >> >> This is in a 17KW peak-output MRI gradient driver. > >> > > >> >And the dissipation in the devices is ? > >> > >> About 300 watts peak each. > > > >Cheat ! Average figure please ? Which you damn well know is the important > >one unless your pulses are several seconds long. > > I drives NMR and MRI gradients, as it was designed to do. So you won't answer the question because it wouls show you up as a charlatan. Graham
From: Eeyore on 20 Dec 2008 04:00 John Larkin wrote: > Most power transistors do seem to be nicely flat. And it's not hard to > fly-cut an extrusion to a few 10's of microinches flatness. You can't do that in a consumer / low cost product. Graham
From: Eeyore on 20 Dec 2008 04:02 krw wrote: > rabbitsfriendsandrelations(a)hotmail.com says... > > krw wrote: > > > rabbitsfriendsandrelations(a)hotmail.com says... > > > > John Fields wrote: > > > > > Eeyore <rabbitsfriendsandrelations(a)hotmail.com> wrote: > > > > > >Phil Allison wrote: > > > > > >> "Adrian Tuddenham" > > > > > >> > > > > > > >> > A point not often appreciated is the possible heat gain when a heatsink > > > > > >> > is operated in bright sunshine. A surface finish which is a poor > > > > > >> > radiator/absorber of radiant heat will work better in those > > > > > >> > circumstances. > > > > > >> > > > > > >> ** Only a complete dope would not find some way to shade the heatsink from > > > > > >> direct sunlight on a hot day. > > > > > > > > > > > >There's no shortage of dopes. > > > > > --- > > > > > And you're the proof of the pudding. > > > > > > > > You're out of your depth. > > > > > > That's OK. You're out of your mind. > > > > How many of YOUR high power amplifiers are for sale in the shops and on ebay ? We've > > made tens of thousands of them. > > I don't do "high power amplifiers" nor am I silly enough to use sil- > pads on even high power processors (where we've made millions of > them). You're out of your mind. As I said, I moved to bolting the collector direct to the heatsink when we went past a certain power level. You don't even have a mind to be out of. Graham
From: Eeyore on 20 Dec 2008 04:07 Archimedes' Lever wrote: > Rich Grise <rich(a)example.net> wrote: > > > Plain aluminum has very poor emissivity. > > It varies with surface finish differences. > > Grit blasted matte finish and 36 grit rough polish emit pretty well > compared to average extrusion finishes. And when you're using conduction it matters very little. Graham
From: Eeyore on 20 Dec 2008 04:12
Archimedes' Lever wrote: > Eeyore <rabbitsfriendsandrelations(a)hotmail.com> wrote: > > snip > > >Which of these design(s) did I originally get the idea from ? > > snip > > You're an idiot. No, I make better heatsinks than it seems anyone else here can. And it's none of the extruded ones. It was an IERC app note that drew me to the technique. Graham |