Ceramic heat spreaders

Diamonds are a thermal engineers best friend.

If the TO3P package is metalization up, then attaching a heat sink is fairly easy. You're looking for a block of aluminum with the largest surface area available. Pins do best, but if you have most any reasonable shape (fins, drilled holes, Swiss cheese, etc) will also work. You've got 50 x 50 mm space but no clue as to height. I'll guess(tm) 20 mm. I'm lazy, so I'll just grovel through the Mouser catalog, find a similar heatsink, and declare the thermal resistance to be close to what you should get. TO3P is similar to TO247. (30 minutes later...) Looks like a BGA or CPU pin heat sink will fit. I kinda like using a recycled Pentium CPU heat sink like this: Just drill a hole in the flat part and bolt the xsistor to the heatsink.

Wakefield 649-51AB on Pg 21 looks good. 47.2 x 47.2 x 13mm. From the illegible graph, I would guess(tm) a thermal resistance of

Looks like the Wakefield 669 and 661 series (Pg 21) will also work and is a bit higher. You'll find them on old 486 motherboards.

Roughly, if you ambient temp is 180C and you want to keep the case under 200C, you can dissipate: (200C - 180C) / 10C/W = 2.0 watts Please adjust my numerical guesswork to your situation. (Note that this does not include the thermal resistance of the xsistor junction or the thermal resistance of the heat sink to xsistor thermal goo).

Good luck.

I also want my PC boards to be IGOS.

The BeO samples that I get are pure white. AlN is a tad grey.

Philippine fig trees? Intergovernmental organizations? International Guillain-Barre Syndrome Outcome Study?

Cheers

Phil Hobbs

Just checked my files--we were looking at a 250W heater, and (on reasonably conservative estimates) expected to get 15W of cooling power with a 25C cold plate and a 175 C ambient.

Cheers

Phil

That's pretty cool (NPI). So the heater makes sound with something like a Rijke tube?

I assume no one built a prototype. You'd think the down hole guys would be all over it. (Or perhaps it was tried and failed?)

George H.

On Mon, 18 Apr 2016 09:17:50 -0700, John Larkin Gave us:

Call the guy you get them from and ask him why he strayed from the norm with his process. The reason it is done is so that they are immediately recognized for what they are.

He is probably as bad as you are though. You do not like the space programs, and he does not like following mil specs.

The mechanism is heat deposited in the ceramic honeycomb/tubes/whatever inside the steel casing. The thermoacoustic instability occurs when the P-V heat deposited in the hot end of the tube on one half cycle is enough to drive the other half cycle. Heat is taken up and deposited in the honeycomb walls. That's basically how propane-powered boat refrigerators work.

Nope, not AFAIK. They tried free-piston Stirling coolers, and (surprise surprise) the pistons and seals beat themselves to death under the tender ministrations of the roughnecks. TECs aren't good at high delta-T, and they're very vulnerable to shear stress, so if you put any mass on the cold plate, they won't survive handling either.

Cheers

Phil Hobbs

Immerson Gold On Superconductor.

Which mil spec specifies purple BeO?

Gold is an insulator in superconducting circuits. ;)

Cheers

Phil Hobbs

(who built his first and only supercurrent switch about 35 years ago, based on that principle.)

Well (pun!) 5 feet is quite a bit, especially if you want to run a toolstring with several instruments. But still, there could be applications.

I don't readily see the need to cool to 25'C though, 125'C would cover nearly everything.

Cheers

It could probably be made smaller then, since the cooling requirement would be fairly modest. Our length budget was about 6 feet, so we decided to use most of it for the first unit. You know about oscillators that don't oscillate..... ;)

There's basic design software available for the job.

Cheers

Phil Hobbs

OK I know they use this to liquefy natural gass too...Here's a link,

(Figure 5 is NOT going to fit in a 3" hole :^)

OK how about a magnetic frig... Gadolinium has a Curie point near room temperature... Is there something that's closer to 100-150 C?

Maybe a Ferro-electric. I never heard of a ferro-electric frig... we could be the first. :^)

George H.

(too late, as usual0)

Yes, as l "This material, when in the form of fine dust or vapour and inhaled into the lungs, can cause a respiratory disease. In solid form ,as used here, it can be handled quite safely although it is prudent to avoid handling conditions which promote dust formation by surface abrasion.

Because of this you are advised to be very careful in removing and disposing of these components. Do not put them in the general industrial or domestic waste or dispatch them by post. They should be separately and securely packed and clearly identified to show the nature of the hazard and then disposed of in a safe manner by an authorised toxic waste contractor."

Well anything where you require a "toxic waste contractor" sounds expensive, if companies actually bother with that. Beryllia isn't banned under RoHS which lends credibility to the idea that it could be in consumer things, but I would be surprised.

Yes, that's when I learn things. It will be boring when nothing surprises me anymore. Maybe I'll have forgotten by then and I can be surprised again by the same things.

Metallic beryllium (2%) is widely used as an allow with copper (98%). Many electrical connectors use it for their spring contacts. CuBe is really useful for electrical springs because it has good conductivity and can be shaped while it is in a soft or "half hard" state. It is then heated for around 15 minutes which precipitation hardens it. It develops large numbers of small particles of a Cu/Be compound which block the movement of dislocations.

John

Right. The Los Alamos group has done a lot of good stuff. I have Greg Swift's thermoacoustics book, and it's a good read.

Well, maybe if you could figure out a continuous cycle...but that usually requires mass motion of some sort. The cool thing about thermoacoustics is that only the gas needs to move--everything else is completely solid and will take a lot of punishment.

Cheers

Phil Hobbs