aluminum heatsink anodizing
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From: Rich Grise on 19 Dec 2008 19:41 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. >:-> Cheers! Rich
From: Eeyore on 19 Dec 2008 19:42 Phil Allison wrote: > "John Devereux" > > > Phil Hobbs explained it pretty well I think. > > ** But only from his blinkered point of view. > > > But really it is properly descibed as convection in both cases, > > ** You are making that same dumb, pedantic error yet again. > > There is no " properly " about it - that is just declaring yourself to be > RIGHT !! > > What is "proper" is purely a matter of what is common usage in some area of > technology or commerce. > > Where it is important to make a distinction between products that either do > or do not have internal fans - avoiding the word " convection " in the > former case avoids an obvious confusion. Absolutely. Here is an example of what would be called a 'convection cooled' amplifier. Note the fins at the side. http://behringer.com/A500/index.cfm?lang=ENG Whilst this WOULDN'T ! No visible fins. Cooling relies totally on forced airflow. http://behringer.com/EP2500/index.cfm?lang=ENG Graham
From: John Larkin on 19 Dec 2008 19:48 On Fri, 19 Dec 2008 22:26:49 +0000, 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? > > >> This is in a 17KW peak-output MRI gradient driver. > >And the dissipation in the devices is ? > About 300 watts peak each. We tested lots of fets to to destruction, find the ones with adequate margins. ftp://jjlarkin.lmi.net/ExFets.jpg Each fet has its own local opamp-closed-loop driver, to ensure precise current sharing regardless of gate thresholds. A microprocessor measures everything and runs a realtime dynamic simulation of junction temperatures, so we can push them precisely. The uP can also test each fet individually, at low available power supply energy, which helps a lot in production test. The amps sell for roughly $9K each and most people buy three at a time. John
From: Eeyore on 19 Dec 2008 19:51 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
From: John Larkin on 19 Dec 2008 19:53
On Thu, 18 Dec 2008 20:39:54 -0800, Capt. Cave Man <ItIsSoEasyACaveManCanDoIt(a)upyers.org> wrote: >On Fri, 19 Dec 2008 03:29:21 +0000, Eeyore ><rabbitsfriendsandrelations(a)hotmail.com> wrote: > >> >>Now do the sums kiddie ! Heatsinking is an expert area that clearly no-one else >>here has much of a clue about. I've been studying it for over 30 years. >> >>Graham > > > You're an idiot. My last large sink product was a 1500W supply for a >CAT scanner for Philips. We used a custom extrusion What's amazing is that you can tool up a die and buy a truckload of custom extrusion for nearly the price of the aluminum, which may be a fifth the price you'd pay for a similar stock extrusion from a "heatsink" company. Ditto sheet metal. We can do a custom chassis, exactly the way we want it, with all the pems and spacers and connector holes and vents in place, and have it fabbed for less than buying an unfinished "standard" chassis. Weird. John |