Jeff Liebermann wrote:

...
... The thermal resistance of the flange mount was too high for
one device to handle the load at the rated temperatures. However, 4
devices did the trick.

Barry L. Ornitz, PhD WA4VZQ

Yeah, all that, and then try to sink 5KW+ into a paint can ... 20 X 1000
ohm resistors is very minimum, in a tubular aluminum heat-sink-no less,
in my humble opinion ... as when you are in key-down, and your attention
is diverted, things can get warm, quickly, or so it seems!

Regards,
JS

In article ,
Jeff Liebermann wrote:

On Sat, 03 Jan 2009 18:53:59 -0800, Jeff Liebermann
wrote:

Thermal Conductivity Viscosity
W/mK cSt @20c
Water 0.6 0.9
AF (glycol) 0.24 2.0
Water+AF 0.8(?) 1.5 50%/50%
Silicon Oil 0.1 varies radically
Mineral Oil 0.138 34.5
Fluorinert FC-77 0.063 0.75

Air 0.025
Copper 370.
Diamond 1000.

Ok, I see why. Water has 1/5th of the thermal conductivity of mineral
oil. 50/50 water and antifreeze won't work. That raises the boiling
point but ruins the thermal conductivity. Pure ethylene glycol looks
tolerable. Other than the health and ecology issues, any reason that
100% antifreeze won't work?

Sorry, I goofed. Vicodin etc. It should be the higher the W/mK, the
better the thermal conductivity.

So why is Fluorinert favored for cooling when it has such a lousy
thermal conductivity?

High resistivity
High dielectric strength
Low maintenance
Low corrosion = very compatible with most materials
Leaks don't cause more damage
low viscosity
Wide useful temperature range

http://multimedia.3m.com/mws/mediawe...E5X46EVuQEcuZg
Vs6EVs6E666666--
Since it's usually circulated with a pump and involves direct
immersion, is it because of it's low viscosity and superior electrical
characteristics?

It would also appear that water has 5 times the thermal conductivity
than mineral oil. So, why use mineral oil?

DI water is very corrosive and requires stainless steel heat transfer
radiators among other components. It is difficult to keep uncontaminated
and you have to keep changing filters for example. Get a leak and it
usually causes additional damage.

Mineral oil makes a mess and is old technology.

I know of one ATE manufacture that used DI water for cooling in the
mainframe and test head. What a mistake that was. Every time they had a
leak in the test head expensive boards got damaged.

--
Telamon
Ventura, California

On Jan 4, 3:21*am, Telamon
wrote:
In article ,
*Jeff Liebermann wrote:





On Sat, 03 Jan 2009 18:53:59 -0800, Jeff Liebermann
wrote:

* * * * *Thermal Conductivity * * Viscosity
* * * * * * * * *W/mK * * * * * * * * cSt @20c
Water * * * * * * 0.6 * * * * * * * * *0..9
AF (glycol) * * * 0.24 * * * * * * * * 2.0
Water+AF * * * * *0.8(?) * * * * * * * 1.5 * 50%/50%
Silicon Oil * * * 0.1 * * * * * * * * *varies radically
Mineral Oil * * * 0.138 * * * * * * * *34.5
Fluorinert FC-77 *0.063 * * * * * * * *0.75

*Air * * * * * * * 0.025
*Copper * * * * *370.
*Diamond * * * *1000.

Ok, I see why. *Water has 1/5th of the thermal conductivity of mineral
oil. *50/50 water and antifreeze won't work. *That raises the boiling
point but ruins the thermal conductivity. *Pure ethylene glycol looks
tolerable. *Other than the health and ecology issues, any reason that
100% antifreeze won't work?

Sorry, I goofed. *Vicodin etc. *It should be the higher the W/mK, the
better the thermal conductivity. *

So why is Fluorinert favored for cooling when it has such a lousy
thermal conductivity?

High resistivity
High dielectric strength
Low maintenance
Low corrosion = very compatible with most materials
Leaks don't cause more damage
low viscosity
Wide useful temperature range

http://multimedia.3m.com/mws/mediawe...SLXTtnxTE5X46E....
Vs6EVs6E666666--
Since it's usually circulated with a pump and involves direct
immersion, is it because of it's low viscosity and superior electrical
characteristics?

It would also appear that water has 5 times the thermal conductivity
than mineral oil. *So, why use mineral oil?

DI water is very corrosive and requires stainless steel heat transfer
radiators among other components. It is difficult to keep uncontaminated
and you have to keep changing filters for example. Get a leak and it
usually causes additional damage.

Mineral oil makes a mess and is old technology.

I know of one ATE manufacture that used DI water for cooling in the
mainframe and test head. What a mistake that was. Every time they had a
leak in the test head expensive boards got damaged.

--
Telamon
Ventura, California- Hide quoted text -

- Show quoted text -


No kidding on how messy mineral oil can be. I had a leak in a
recirculating pump and it put about 20 gal of oil on the carpeted
floor of the radar site. We had to take up the carpet and the asphalt
tile. The floor is now bare concrete because carpet is forbidden
around oil and the concrete will not take adhesive to put down new
tile.

Jimmie

"Allodoxaphobia" wrote in message
...
On Fri, 02 Jan 2009 15:36:17 -0500, Billy Burpelson wrote:

I am a bit puzzled. IIRC, the silicone in women's breast implants
would/could/did leak and cause fairly serious health problems. Yet, Dr.
Ornitz says "Silicone oils are excellent from a health standpoint" and
Mr. Smith says: "food grade".

Could anyone take a shot at explaining this apparent dichotomy?

Plaintiffs' lawyers and defendants' lawyers....

In the food industry, it is necessary to provide lubricants, coolants, etc.,
for the proper operation of equipment and preparation of product. The same
holds true in the pharmaceutical/medical device industries, where silicone
(medical grade 360) is used to lubricate rubber stoppers which are inserted
by machine into vials, etc.

There are at least 2 classifications: (1) product contact, and (2)
incidental product contact. These are essentially the same; just a matter
of degree.

They (silicones) are not a food ingredient.

HankG

"JB" wrote in message
news
Mineral Oil (available at your local drug store).

Just be prepared for some strange looks when you purchase a gallon of
mineral oil all at once. :-O

Is motor oil a conductor?

Might burn and sludge up your resistor. Lots of additives you just don't
need.

I had a cantenna for 20 years with light mineral oil. there was a little
seepage to the top of the lid through the vent. I actually had
transformer
oil but never used it because of the thought of that stuff seeping. It
really is a lot cleaner. Check feed stores, Vet supply stores, paint
stores, hardware. Check this out:
http://www.pugetsystems.com/submerged.php


When I was in the Navy, we had some gear that used a high power TWT. It was
immersed in a bath of a fluorocarbon called FC-75, trade name Fluorinert.
Good heat conductor, great insulator, totally inert. Supposedly, you could
drink it. It's still around. Google FC-75 and wikipedia will tell you all
about it. $68/ten gallons is a little pricey for my Cantenna but you might
not think so.

Here's a summary of that chemical family's characteristics for the curious:
http://www.acota.co.uk/products/fluo...tronic-liquids

"John Smith" wrote in message
...
Jeff Liebermann wrote:

...
... The thermal resistance of the flange mount was too high for
one device to handle the load at the rated temperatures. However, 4
devices did the trick.

Barry L. Ornitz, PhD WA4VZQ

Yeah, all that, and then try to sink 5KW+ into a paint can ... 20 X 1000
ohm resistors is very minimum, in a tubular aluminum heat-sink-no less, in
my humble opinion ... as when you are in key-down, and your attention is
diverted, things can get warm, quickly, or so it seems!


That's where the crisco comes in handy!



Regards,
JS

"HankG" wrote in message
...

"Allodoxaphobia" wrote in message
...
On Fri, 02 Jan 2009 15:36:17 -0500, Billy Burpelson wrote:

I am a bit puzzled. IIRC, the silicone in women's breast implants
would/could/did leak and cause fairly serious health problems. Yet, Dr.
Ornitz says "Silicone oils are excellent from a health standpoint" and
Mr. Smith says: "food grade".

Could anyone take a shot at explaining this apparent dichotomy?

Plaintiffs' lawyers and defendants' lawyers....

In the food industry, it is necessary to provide lubricants, coolants,
etc., for the proper operation of equipment and preparation of product.
The same holds true in the pharmaceutical/medical device industries, where
silicone (medical grade 360) is used to lubricate rubber stoppers which
are inserted by machine into vials, etc.

There are at least 2 classifications: (1) product contact, and (2)
incidental product contact. These are essentially the same; just a matter
of degree.

They (silicones) are not a food ingredient.


The crisco is!


HankG

"Billy Burpelson" wrote in message
...

"RF BURNS" wrote in message
...
"KC8QJP" wrote in message
. ..
a crisco can works well

http://www.radiobanter.com/showpost....73&postcount=1

Dave wrote:

leave the crisco in it and after tuning up you can fry your dinner!

...and fry your arteries with all the cholesterol!


We make deep fried fatback sandwiches with it.

Modern dielectric oil (aka transformer oil) is refined mineral oil
with an antioxidant (tocopherol, BHA, or BHT) added to retard
spoiling.

Shell Diala AX
ExxonMobil Univolt 65

are the two major kinds (there's one from Castrol,too)

Both are sold (in 5 gallon pails, typically, as a minimum quantity) by
"jobbers" which can be found on the mfr's website (you enter a zip
code and gives you the distributors within X miles), or by looking in
the yellow pages under Oil,Lubricants-Jobbers. Used to be in the $4-5/
gallon range, but I just was talking to someone who had to pay around
$50 for a 5gallon pail. (probably a hangover from $100/bbl crude
prices)

You *can* use USP White Mineral Oil (laxative) available in pints at
the drugstore, gallons at the feedstore (If you've got a colicky
horse, gallons are the quantity wanted), but it's
a) more expensive
b) not water content controlled

For HV dielectric purposes water content (in the ppm range) is
important. So is particulate contamination. For a dummy load,
probably not so much.

Another inexpensive source of mineral oil without many additives is
hydraulic oil (as used in, say, tractors, etc.).

Even "straight weight" motor oil without additives/detergents can work
(look for the SAE 10,15, or 20 viscosities).. it can be VERY cheap on
sale as a "loss leader" to get folks into the store (since nobody in
their right mind would actually run this in an engine)

For a dummy load, viscosity IS important, because convective flow is
important. (viscosity change with temperature, too...)

Silicone would be massive overkill, and we won't even get into
Fluorinert. BTW, if you spill mineral oil, it cleans up nicely with
detergent and water.. the same cannot be said of silicone or FC-xx..
Silicone oils are almost impossible to remove.

Jim, w6rmk

On Jan 1, 9:49*am, "KC8QJP" wrote:
"John Passaneau" wrote in message

... KC8QJP wrote:
a crisco can works well
Sometimes you can get empty paint cans at professional paint supplies
stores. They are nice as they are clean and shiny.

John W3JXP

Thanks for the tip!

Yes. I did that The new can had a plastic type coating on the inside
to prevent any possible leaks and corrosion, a great improvement over
cans of yesteryear that leaked on to the floor over time. Same story
for the lid., Cost me something like $3 and well worth it.
Art