aluminum heatsink anodizing
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From: Eeyore on 19 Dec 2008 20:15 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. Graham
From: Eeyore on 19 Dec 2008 20:22 Jim Thompson wrote: > Eeyore <rabbitsfriendsandrelations(a)hotmail.com> wrote: > >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. > > Graham, I think you've lost your Reynolds number ?:-) > > ...Jim Thompson Thanks for the advice but I got the same poo-pooing from a firm of consultants I once worked for. So we made 2 almost identical heatsinks. One 'conventional' and one with my 'trick'. Mine performed 20% better and weighed less. I think I could have improved on it too but since it met the spec, there was no need. Graham
From: John Fields on 19 Dec 2008 20:22 On Sat, 20 Dec 2008 00:41:23 GMT, Rich Grise <rich(a)example.net> wrote: >On Fri, 19 Dec 2008 10:47:18 -0800, Joel Koltner wrote: > >> "Rich Grise" <rich(a)example.net> wrote in message >> >>> I'm so enamoured of Dow Corning 340 grease that when I buy a new CPU and >>> heatsink kit, I clean off the goo that comes with the kit and use my own >>> personal (lifted from the USAF) DC-340. >> >> You realize that DC-340 stuff causes cancer, right? >> >> Just kidding. :-) > >I don't believe in carcinogens; I believe cancer is caused by denied >self-hatred. >:-> --- Interesting point. So, if one smokes tobacco, which is known to be carcinogenic, and one refuses to quit, then the wish for death relating to that weakness will be granted? JF
From: Eeyore on 19 Dec 2008 20:54 John Larkin wrote: > Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: > >Eeyore wrote: > > > >Conduction is important in the boundary layer, but you can't control > >that by waving a dead chicken over it. The best way to improve it is by > >making the fins out of mesh. > > I have an unproved theory that, given a fan-cooled box, the heatsink > fins should add enough air flow restriction to cut the free-flow air > volume about in half. Any less flow, there's not enough air moving > through the box to carry away the heat. Much more, and the air is > scooting past or around the heatsink fins. The air sort of scrapes the > heat off the fins. > > It's kind of like the maximum-power-transfer theorem. > > I haven't tried dead chickens yet. You could try doing something with the fins. And careful with placement of the heatsink in the enclosure, you can lose a lot to back pressure. I know, I've instrumented it. Which of these design(s) did I originally get the idea from ? http://www.surplussales.com/Heatsinks/HeatSink3.html Graham
From: John Larkin on 19 Dec 2008 23:04
On Sat, 20 Dec 2008 00:59:10 +0000, 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. > >Graham I drives NMR and MRI gradients, as it was designed to do. John |