How it\'s made: heat sinks...

[Jan Panteltje]

On a sunny day (Sun, 17 Apr 2022 09:25:41 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
<thfo5ht952906bo9837snjolpjfd2lsc00@4ax.com>:

On Sun, 17 Apr 2022 09:10:41 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Sun, 17 Apr 2022 15:55:21 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Ricky <gnuarm.deletethisbit@gmail.com> wrote in
news:3f3e0e0f-175e-4d27-be95-401418cc7e54n@googlegroups.com:

The large surface area of the long, skinny fins are perfect
coupling between the low thermal resistance of the heat sink and
the relatively high thermal conductivity of the fin/air contact.

The word(s) for today is \"boundary layer\".

https://www.heatsinkcalculator.com/blog/wp-
content/uploads/2016/05/effect_of_boundary_laher_thickness.png

https://www.heatsinkcalculator.com/blog/top-3-mistakes-made-when-
selecting-a-heat-sink/

Slow air would pass right over a close fin spaced sink. High speed
forced air is required when the fins get that closely spaced.


Right. Viscous drag will keep air from flowing between tall, closely
spaced fins. It will have to be ducted and forced, or it will go
around.

The limiting case, more and more denser and thinner fins, volumetric
air flow will approach zero.

My general rule is that a heat sink should reduce the native air flow
by about half. Neither zero nor 100% does any cooling.

And of course, the tips of tall thin fins have a high thermal
resistance to the baseplate, so run at about inlet air temp, so
restrict air flow without contributing much coolong. My 50% number is
useless if the air flow is restricted without corresponding cooling.

There is no limit to how bad a heat sink you can design. A solid
aluminum brick is pretty bad.

This works great:
http://panteltje.com/pub/big_3kg_heatsink_IMG_3745.GIF

BTW that is a rubidum reference on top of it.

 

[server]

jlarkin@highlandsniptechnology.com wrote in
news:thfo5ht952906bo9837snjolpjfd2lsc00@4ax.com:

On Sun, 17 Apr 2022 09:10:41 -0700,
jlarkin@highlandsniptechnology.com wrote:

On Sun, 17 Apr 2022 15:55:21 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Ricky <gnuarm.deletethisbit@gmail.com> wrote in
news:3f3e0e0f-175e-4d27-be95-401418cc7e54n@googlegroups.com:

The large surface area of the long, skinny fins are perfect
coupling between the low thermal resistance of the heat sink
and the relatively high thermal conductivity of the fin/air
contact.

The word(s) for today is \"boundary layer\".

https://www.heatsinkcalculator.com/blog/wp-
content/uploads/2016/05/effect_of_boundary_laher_thickness.png

https://www.heatsinkcalculator.com/blog/top-3-mistakes-made-when-
selecting-a-heat-sink/

Slow air would pass right over a close fin spaced sink. High
speed
forced air is required when the fins get that closely spaced.


Right. Viscous drag will keep air from flowing between tall,
closely spaced fins. It will have to be ducted and forced, or it
will go around.

The limiting case, more and more denser and thinner fins,
volumetric air flow will approach zero.

My general rule is that a heat sink should reduce the native air
flow by about half. Neither zero nor 100% does any cooling.

And of course, the tips of tall thin fins have a high thermal
resistance to the baseplate, so run at about inlet air temp, so
restrict air flow without contributing much coolong. My 50% number
is useless if the air flow is restricted without corresponding
cooling.

There is no limit to how bad a heat sink you can design. A solid
aluminum brick is pretty bad.

I even saw some where they slice up each fin into little fingers
and the sink was \"bristling\" with them. Probably pretty good, but
again, the air movement over and through them is required. Air flow
means nothing if it does not intertwine with the heated elements to
get hot and then be carried off as more air is added to be heated and
moved. It\'s a bucket brigade.

 

[server]

Anthony William Sloman <bill.sloman@ieee.org> wrote in
news:006be91f-550a-4145-829b-2903eda74707n@googlegroups.com:

Only if you can get it to evaporate. Liquid water as a heat
transfer medium is okay, if you can dump the warm water down the
sink - and I have done that for a research set-up - but it isn\'t
practical for long term use.

My decades old idea about making steam deep down in the heart of a
slat dome (VERY hot) won\'t work either. However, pipes from the
sirface taken down there to a heat exchanger that then sends the heated
water back up would be easier to bring to a steam head than cooler
water at the surface. So it could be used to preheat steam boiler
water.

 

[server]

Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote in
news:t3hijn$cus$1@dont-email.me:

On a sunny day (Sun, 17 Apr 2022 09:25:41 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
thfo5ht952906bo9837snjolpjfd2lsc00@4ax.com>:

On Sun, 17 Apr 2022 09:10:41 -0700,
jlarkin@highlandsniptechnology.com wrote:

On Sun, 17 Apr 2022 15:55:21 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Ricky <gnuarm.deletethisbit@gmail.com> wrote in
news:3f3e0e0f-175e-4d27-be95-401418cc7e54n@googlegroups.com:

The large surface area of the long, skinny fins are perfect
coupling between the low thermal resistance of the heat sink
and the relatively high thermal conductivity of the fin/air
contact.

The word(s) for today is \"boundary layer\".

https://www.heatsinkcalculator.com/blog/wp-
content/uploads/2016/05/effect_of_boundary_laher_thickness.png

https://www.heatsinkcalculator.com/blog/top-3-mistakes-made-when
- selecting-a-heat-sink/

Slow air would pass right over a close fin spaced sink. High
speed
forced air is required when the fins get that closely spaced.


Right. Viscous drag will keep air from flowing between tall,
closely spaced fins. It will have to be ducted and forced, or it
will go around.

The limiting case, more and more denser and thinner fins,
volumetric air flow will approach zero.

My general rule is that a heat sink should reduce the native air
flow by about half. Neither zero nor 100% does any cooling.

And of course, the tips of tall thin fins have a high thermal
resistance to the baseplate, so run at about inlet air temp, so
restrict air flow without contributing much coolong. My 50% number
is useless if the air flow is restricted without corresponding
cooling.

There is no limit to how bad a heat sink you can design. A solid
aluminum brick is pretty bad.

This works great:
http://panteltje.com/pub/big_3kg_heatsink_IMG_3745.GIF

BTW that is a rubidum reference on top of it.

That is a very poor heat sink. Essentialy it conduction cools the
device it is mounted to, but not much gets radiated away. More like
a homogenizer.

There is a reason that motorcycle air cooled cylinder jugs and
heads are NOT painted.

 

[Ricky]

On Saturday, April 16, 2022 at 9:22:50 PM UTC-4, palli...@gmail.com wrote:

TRicky Dickhead wrote:

======================

Those long skinny fins don\'t look efficient to me. And they would need
a huge air blast.

Does anyone know what he is talking about?

** Think so.

I know I\'m wasting my time trying to explain anything to you, but I\'m willing to give you the benefit of the doubt.

The large surface area of the long, skinny fins are perfect coupling between
the low thermal resistance of the heat sink and the relatively high thermal conductivity
of the fin/air contact.
** How well does heat travel via a thin plate?

Very well compared to the interface between the plate and the air. That\'s the point. Even a thin plate has lots of conductivity compared to the metal-air interface unless that interface area is large.

But you seem to have missed another aspect. The important thermal conductivity in the metal, is the *aggregate* thermal conductivity of the many plates. That would be similar to thicker fins spaced further apart.

It\'s the extruded heat sinks with much fewer fins and a lot less surface area,
that require a lot more air flow to get the same thermal conductivity.
** The scived idea relies on having very many fins.
Fewer but thicker ones, spaced widely, works just as well or better.

Zero evidence of that. The thick fins are spaced widely and much of the air flowing between them does little to cool the fins because it is not turbulent enough to come into contact with the fins.

Also:

Scived heatsinks suffer the disadvantage of being limited to internal use.
Extruded and cast ones are often structural parts of a case.

If you need a case, that\'s great, but that\'s not whats being discussed here.


> Horses for courses....

That\'s always true in engineering.

--

Rick C.

-- Get 1,000 miles of free Supercharging
-- Tesla referral code - https://ts.la/richard11209

 

[Ricky]

On Saturday, April 16, 2022 at 11:19:01 PM UTC-4, bill....@ieee.org wrote:

On Sunday, April 17, 2022 at 10:10:35 AM UTC+10, Ricky wrote:
On Saturday, April 16, 2022 at 6:23:26 PM UTC-4, jla...@highlandsniptechnology.com wrote:
On Sat, 16 Apr 2022 19:51:56 -0000 (UTC), Cydrome Leader
pres...@MUNGEpanix.com> wrote:

bitrex <us...@example.net> wrote:
I thought they were extruded, but no!

https://youtu.be/wwWIyHo3yJM

Like carving a turkey dinner

Skiving is real slow. The only value is you get thinner fins than can be
extruded. More machining is needed if you want holes though any of that.

Those long skinny fins don\'t look efficient to me. And they would need
a huge air blast.

Does anyone know what he is talking about?

The large surface area of the long, skinny fins are perfect coupling between the low thermal resistance of the heat sink and the relatively high thermal conductivity of the fin/air contact. Lots of surface area gives a low thermal resistance at the point of contact. That\'s the point of using them.

It\'s the extruded heat sinks with much fewer fins and a lot less surface area, that require a lot more air flow to get the same thermal conductivity.
The question hangs on how much heat you have to get rid of.

The heat capacity of air is well defined. If you need to move a lot of heat you have to heat up a lot of air and move it away as soon as it has got hot.

Fewer fins with lots of space between them let you blast a lot more air past them than you can squeeze between the thin fins of a skived heat sink.
If you don\'t need to get rid of as much heat, a slower air flow will serve, and you can get away with a less voluminous heat sink

\"Blasting air\" is only useful if it contacts the heat sink enough for the heat to transfer. Simply blowing between fins doesn\'t necessarily transfer the heat.

All aspects of the design need to be balanced.

--

Rick C.

-+ Get 1,000 miles of free Supercharging
-+ Tesla referral code - https://ts.la/richard11209

 

[Ricky]

On Sunday, April 17, 2022 at 10:48:36 AM UTC-4, jla...@highlandsniptechnology.com wrote:

On Sat, 16 Apr 2022 18:22:46 -0700 (PDT), Phil Allison
palli...@gmail.com> wrote:

TRicky Dickhead wrote:

======================

Those long skinny fins don\'t look efficient to me. And they would need
a huge air blast.

Does anyone know what he is talking about?


** Think so.

The large surface area of the long, skinny fins are perfect coupling between
the low thermal resistance of the heat sink and the relatively high thermal conductivity
of the fin/air contact.

** How well does heat travel via a thin plate?
The sheet thermal resistance of a thin plate can be high, especially
aluminum alloys that skive well.

If you blow air at a thin, tall, dense array of fins, it will
naturally prefer to go around, not through, the fins. And you\'ll get
most of the air flow at the tips of the fins, not near the baseplate,
so the thermal resistances hurt. Short skived copper fins are good if
the air is really blasted into the fins from above, like in a CPU
cooler.

I\'ve measured a lot of this stuff lately. That trumps theories.

Yes, but nothing relevant. I don\'t see any images of skived heatsinks.

--

Rick C.

+- Get 1,000 miles of free Supercharging
+- Tesla referral code - https://ts.la/richard11209

 

[Ricky]

On Sunday, April 17, 2022 at 1:26:23 PM UTC-4, Jan Panteltje wrote:

On a sunny day (Sun, 17 Apr 2022 09:25:41 -0700) it happened
jla...@highlandsniptechnology.com wrote in
thfo5ht952906bo98...@4ax.com>:
On Sun, 17 Apr 2022 09:10:41 -0700, jla...@highlandsniptechnology.com
wrote:

On Sun, 17 Apr 2022 15:55:21 -0000 (UTC),
DecadentLinux...@decadence.org wrote:

Ricky <gnuarm.del...@gmail.com> wrote in
news:3f3e0e0f-175e-4d27...@googlegroups.com:

The large surface area of the long, skinny fins are perfect
coupling between the low thermal resistance of the heat sink and
the relatively high thermal conductivity of the fin/air contact.

The word(s) for today is \"boundary layer\".

https://www.heatsinkcalculator.com/blog/wp-
content/uploads/2016/05/effect_of_boundary_laher_thickness.png

https://www.heatsinkcalculator.com/blog/top-3-mistakes-made-when-
selecting-a-heat-sink/

Slow air would pass right over a close fin spaced sink. High speed
forced air is required when the fins get that closely spaced.


Right. Viscous drag will keep air from flowing between tall, closely
spaced fins. It will have to be ducted and forced, or it will go
around.

The limiting case, more and more denser and thinner fins, volumetric
air flow will approach zero.

My general rule is that a heat sink should reduce the native air flow
by about half. Neither zero nor 100% does any cooling.

And of course, the tips of tall thin fins have a high thermal
resistance to the baseplate, so run at about inlet air temp, so
restrict air flow without contributing much coolong. My 50% number is
useless if the air flow is restricted without corresponding cooling.

There is no limit to how bad a heat sink you can design. A solid
aluminum brick is pretty bad.
This works great:
http://panteltje.com/pub/big_3kg_heatsink_IMG_3745.GIF

BTW that is a rubidum reference on top of it.

Convection cooled, right? For convection you need minimal obstruction of the air flow since the pressure is very, very low. It has to be *very* large relative to other designs to provide the same heat flow.

--

Rick C.

++ Get 1,000 miles of free Supercharging
++ Tesla referral code - https://ts.la/richard11209

 

[server]

On Sun, 17 Apr 2022 17:50:59 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote in
news:t3hijn$cus$1@dont-email.me:

On a sunny day (Sun, 17 Apr 2022 09:25:41 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
thfo5ht952906bo9837snjolpjfd2lsc00@4ax.com>:

On Sun, 17 Apr 2022 09:10:41 -0700,
jlarkin@highlandsniptechnology.com wrote:

On Sun, 17 Apr 2022 15:55:21 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Ricky <gnuarm.deletethisbit@gmail.com> wrote in
news:3f3e0e0f-175e-4d27-be95-401418cc7e54n@googlegroups.com:

The large surface area of the long, skinny fins are perfect
coupling between the low thermal resistance of the heat sink
and the relatively high thermal conductivity of the fin/air
contact.

The word(s) for today is \"boundary layer\".

https://www.heatsinkcalculator.com/blog/wp-
content/uploads/2016/05/effect_of_boundary_laher_thickness.png

https://www.heatsinkcalculator.com/blog/top-3-mistakes-made-when
- selecting-a-heat-sink/

Slow air would pass right over a close fin spaced sink. High
speed
forced air is required when the fins get that closely spaced.


Right. Viscous drag will keep air from flowing between tall,
closely spaced fins. It will have to be ducted and forced, or it
will go around.

The limiting case, more and more denser and thinner fins,
volumetric air flow will approach zero.

My general rule is that a heat sink should reduce the native air
flow by about half. Neither zero nor 100% does any cooling.

And of course, the tips of tall thin fins have a high thermal
resistance to the baseplate, so run at about inlet air temp, so
restrict air flow without contributing much coolong. My 50% number
is useless if the air flow is restricted without corresponding
cooling.

There is no limit to how bad a heat sink you can design. A solid
aluminum brick is pretty bad.

This works great:
http://panteltje.com/pub/big_3kg_heatsink_IMG_3745.GIF

BTW that is a rubidum reference on top of it.


That is a very poor heat sink. Essentialy it conduction cools the
device it is mounted to, but not much gets radiated away. More like
a homogenizer.

There is a reason that motorcycle air cooled cylinder jugs and
heads are NOT painted.

Radiation cooling goes as the 4th power of the temp difference between
the sink and the universe. Since semiconductors can\'t be allowed to
get very hot above ambient, rad cooling is usually minor. Inside a
metal box, a lot of the radiation is trapped and reflects back.



--

I yam what I yam - Popeye

 

[Phil Hobbs]

jlarkin@highlandsniptechnology.com wrote:

On Sun, 17 Apr 2022 17:50:59 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote in
news:t3hijn$cus$1@dont-email.me:

On a sunny day (Sun, 17 Apr 2022 09:25:41 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
thfo5ht952906bo9837snjolpjfd2lsc00@4ax.com>:

On Sun, 17 Apr 2022 09:10:41 -0700,
jlarkin@highlandsniptechnology.com wrote:

On Sun, 17 Apr 2022 15:55:21 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Ricky <gnuarm.deletethisbit@gmail.com> wrote in
news:3f3e0e0f-175e-4d27-be95-401418cc7e54n@googlegroups.com:

The large surface area of the long, skinny fins are perfect
coupling between the low thermal resistance of the heat sink
and the relatively high thermal conductivity of the fin/air
contact.

The word(s) for today is \"boundary layer\".

https://www.heatsinkcalculator.com/blog/wp-
content/uploads/2016/05/effect_of_boundary_laher_thickness.png

https://www.heatsinkcalculator.com/blog/top-3-mistakes-made-when
- selecting-a-heat-sink/

Slow air would pass right over a close fin spaced sink. High
speed
forced air is required when the fins get that closely spaced.


Right. Viscous drag will keep air from flowing between tall,
closely spaced fins. It will have to be ducted and forced, or it
will go around.

The limiting case, more and more denser and thinner fins,
volumetric air flow will approach zero.

My general rule is that a heat sink should reduce the native air
flow by about half. Neither zero nor 100% does any cooling.

And of course, the tips of tall thin fins have a high thermal
resistance to the baseplate, so run at about inlet air temp, so
restrict air flow without contributing much coolong. My 50% number
is useless if the air flow is restricted without corresponding
cooling.

There is no limit to how bad a heat sink you can design. A solid
aluminum brick is pretty bad.

This works great:
http://panteltje.com/pub/big_3kg_heatsink_IMG_3745.GIF

BTW that is a rubidum reference on top of it.


That is a very poor heat sink. Essentialy it conduction cools the
device it is mounted to, but not much gets radiated away. More like
a homogenizer.

There is a reason that motorcycle air cooled cylinder jugs and
heads are NOT painted.

Radiation cooling goes as the 4th power of the temp difference between
the sink and the universe. Since semiconductors can\'t be allowed to
get very hot above ambient, rad cooling is usually minor. Inside a
metal box, a lot of the radiation is trapped and reflects back.

The emission from a black body goes like T**4, so the thermal coupling
between two surfaces goes like the difference, i.e. T1**4 - T2**4. For
small temperature differences, that\'s basically 4 * T**3 * delta T.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[server]

jlarkin@highlandsniptechnology.com wrote in
news:btro5hl6gr3pp1ph77olc2a2c8k5ihh017@4ax.com:

On Sun, 17 Apr 2022 17:50:59 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote in
news:t3hijn$cus$1@dont-email.me:

On a sunny day (Sun, 17 Apr 2022 09:25:41 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
thfo5ht952906bo9837snjolpjfd2lsc00@4ax.com>:

On Sun, 17 Apr 2022 09:10:41 -0700,
jlarkin@highlandsniptechnology.com wrote:

On Sun, 17 Apr 2022 15:55:21 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Ricky <gnuarm.deletethisbit@gmail.com> wrote in
news:3f3e0e0f-175e-4d27-be95-401418cc7e54n@googlegroups.com:

The large surface area of the long, skinny fins are perfect
coupling between the low thermal resistance of the heat sink
and the relatively high thermal conductivity of the fin/air
contact.

The word(s) for today is \"boundary layer\".

https://www.heatsinkcalculator.com/blog/wp-
content/uploads/2016/05/effect_of_boundary_laher_thickness.png

https://www.heatsinkcalculator.com/blog/top-3-mistakes-made-wh
en - selecting-a-heat-sink/

Slow air would pass right over a close fin spaced sink.
High speed
forced air is required when the fins get that closely spaced.


Right. Viscous drag will keep air from flowing between tall,
closely spaced fins. It will have to be ducted and forced, or
it will go around.

The limiting case, more and more denser and thinner fins,
volumetric air flow will approach zero.

My general rule is that a heat sink should reduce the native
air flow by about half. Neither zero nor 100% does any cooling.

And of course, the tips of tall thin fins have a high thermal
resistance to the baseplate, so run at about inlet air temp, so
restrict air flow without contributing much coolong. My 50%
number is useless if the air flow is restricted without
corresponding cooling.

There is no limit to how bad a heat sink you can design. A solid
aluminum brick is pretty bad.

This works great:
http://panteltje.com/pub/big_3kg_heatsink_IMG_3745.GIF

BTW that is a rubidum reference on top of it.


That is a very poor heat sink. Essentialy it conduction cools
the
device it is mounted to, but not much gets radiated away. More
like a homogenizer.

There is a reason that motorcycle air cooled cylinder jugs and
heads are NOT painted.

Radiation cooling goes as the 4th power of the temp difference
between the sink and the universe. Since semiconductors can\'t be
allowed to get very hot above ambient, rad cooling is usually
minor. Inside a metal box, a lot of the radiation is trapped and
reflects back.

All of the MIDS JTRS tactical transcievers in the US and ally
military are all populated with canned, conduction cooled cards.
Whether it is being slid into an F-18, or an F-35 or an F-22 they all
go on the same tray Which has the PS unit and the MIDS unit and the
RF amplifier unit. It is the most advanced SDR there is. ALL
conduction cooled \'cards\'. All temps get homogenized throughout the
init. The RF amp is the only part that has air passages ported
through it.

<https://www.dote.osd.mil/Portals/97/pub/reports/FY2010/dod/2010mids.
pdf?ver=2019-08-22-112846-223>

That is a micro sized VAX but way faster than a normal VAX.
It manages AEGIS targetting and all of the battlefield waveforms.
Mainly the still in use, still not crypto broken Link 16 waveform.

 

[Ricky]

On Sunday, April 17, 2022 at 4:49:48 PM UTC-4, Phil Hobbs wrote:

jla...@highlandsniptechnology.com wrote:
On Sun, 17 Apr 2022 17:50:59 -0000 (UTC),
DecadentLinux...@decadence.org wrote:

Jan Panteltje <pNaonSt...@yahoo.com> wrote in
news:t3hijn$cus$1...@dont-email.me:

On a sunny day (Sun, 17 Apr 2022 09:25:41 -0700) it happened
jla...@highlandsniptechnology.com wrote in
thfo5ht952906bo98...@4ax.com>:

On Sun, 17 Apr 2022 09:10:41 -0700,
jla...@highlandsniptechnology.com wrote:

On Sun, 17 Apr 2022 15:55:21 -0000 (UTC),
DecadentLinux...@decadence.org wrote:

Ricky <gnuarm.del...@gmail.com> wrote in
news:3f3e0e0f-175e-4d27...@googlegroups.com:

The large surface area of the long, skinny fins are perfect
coupling between the low thermal resistance of the heat sink
and the relatively high thermal conductivity of the fin/air
contact.

The word(s) for today is \"boundary layer\".

https://www.heatsinkcalculator.com/blog/wp-
content/uploads/2016/05/effect_of_boundary_laher_thickness.png

https://www.heatsinkcalculator.com/blog/top-3-mistakes-made-when
- selecting-a-heat-sink/

Slow air would pass right over a close fin spaced sink. High
speed
forced air is required when the fins get that closely spaced.


Right. Viscous drag will keep air from flowing between tall,
closely spaced fins. It will have to be ducted and forced, or it
will go around.

The limiting case, more and more denser and thinner fins,
volumetric air flow will approach zero.

My general rule is that a heat sink should reduce the native air
flow by about half. Neither zero nor 100% does any cooling.

And of course, the tips of tall thin fins have a high thermal
resistance to the baseplate, so run at about inlet air temp, so
restrict air flow without contributing much coolong. My 50% number
is useless if the air flow is restricted without corresponding
cooling.

There is no limit to how bad a heat sink you can design. A solid
aluminum brick is pretty bad.

This works great:
http://panteltje.com/pub/big_3kg_heatsink_IMG_3745.GIF

BTW that is a rubidum reference on top of it.


That is a very poor heat sink. Essentialy it conduction cools the
device it is mounted to, but not much gets radiated away. More like
a homogenizer.

There is a reason that motorcycle air cooled cylinder jugs and
heads are NOT painted.

Radiation cooling goes as the 4th power of the temp difference between
the sink and the universe. Since semiconductors can\'t be allowed to
get very hot above ambient, rad cooling is usually minor. Inside a
metal box, a lot of the radiation is trapped and reflects back.
The emission from a black body goes like T**4, so the thermal coupling
between two surfaces goes like the difference, i.e. T1**4 - T2**4. For
small temperature differences, that\'s basically 4 * T**3 * delta T.

Don\'t forget to use absolute temperature. I remember a discussion here about inflate-gate where it took four iterations on the calculations and a large number of posts before anyone got the math right, because both the temperature and the pressure had to be absolute, not relative. Basically, there are two independent mistakes that could be made and all three erroneous calculations were done before the correct calculation was stumbled upon.

--

Rick C.

--- Get 1,000 miles of free Supercharging
--- Tesla referral code - https://ts.la/richard11209

 

[Ricky]

On Sunday, April 17, 2022 at 6:23:37 PM UTC-4, DecadentLinux...@decadence.org wrote:

jla...@highlandsniptechnology.com wrote in
news:btro5hl6gr3pp1ph7...@4ax.com:
On Sun, 17 Apr 2022 17:50:59 -0000 (UTC),
DecadentLinux...@decadence.org wrote:

Jan Panteltje <pNaonSt...@yahoo.com> wrote in
news:t3hijn$cus$1...@dont-email.me:

On a sunny day (Sun, 17 Apr 2022 09:25:41 -0700) it happened
jla...@highlandsniptechnology.com wrote in
thfo5ht952906bo98...@4ax.com>:

On Sun, 17 Apr 2022 09:10:41 -0700,
jla...@highlandsniptechnology.com wrote:

On Sun, 17 Apr 2022 15:55:21 -0000 (UTC),
DecadentLinux...@decadence.org wrote:

Ricky <gnuarm.del...@gmail.com> wrote in
news:3f3e0e0f-175e-4d27...@googlegroups.com:

The large surface area of the long, skinny fins are perfect
coupling between the low thermal resistance of the heat sink
and the relatively high thermal conductivity of the fin/air
contact.

The word(s) for today is \"boundary layer\".

https://www.heatsinkcalculator.com/blog/wp-
content/uploads/2016/05/effect_of_boundary_laher_thickness.png

https://www.heatsinkcalculator.com/blog/top-3-mistakes-made-wh
en - selecting-a-heat-sink/

Slow air would pass right over a close fin spaced sink.
High speed
forced air is required when the fins get that closely spaced.


Right. Viscous drag will keep air from flowing between tall,
closely spaced fins. It will have to be ducted and forced, or
it will go around.

The limiting case, more and more denser and thinner fins,
volumetric air flow will approach zero.

My general rule is that a heat sink should reduce the native
air flow by about half. Neither zero nor 100% does any cooling.

And of course, the tips of tall thin fins have a high thermal
resistance to the baseplate, so run at about inlet air temp, so
restrict air flow without contributing much coolong. My 50%
number is useless if the air flow is restricted without
corresponding cooling.

There is no limit to how bad a heat sink you can design. A solid
aluminum brick is pretty bad.

This works great:
http://panteltje.com/pub/big_3kg_heatsink_IMG_3745.GIF

BTW that is a rubidum reference on top of it.


That is a very poor heat sink. Essentialy it conduction cools
the
device it is mounted to, but not much gets radiated away. More
like a homogenizer.

There is a reason that motorcycle air cooled cylinder jugs and
heads are NOT painted.

Radiation cooling goes as the 4th power of the temp difference
between the sink and the universe. Since semiconductors can\'t be
allowed to get very hot above ambient, rad cooling is usually
minor. Inside a metal box, a lot of the radiation is trapped and
reflects back.

All of the MIDS JTRS tactical transcievers in the US and ally
military are all populated with canned, conduction cooled cards.
Whether it is being slid into an F-18, or an F-35 or an F-22 they all
go on the same tray Which has the PS unit and the MIDS unit and the
RF amplifier unit. It is the most advanced SDR there is. ALL
conduction cooled \'cards\'. All temps get homogenized throughout the
init. The RF amp is the only part that has air passages ported
through it.

https://www.dote.osd.mil/Portals/97/pub/reports/FY2010/dod/2010mids.
pdf?ver=2019-08-22-112846-223

That is a micro sized VAX but way faster than a normal VAX.
It manages AEGIS targetting and all of the battlefield waveforms.
Mainly the still in use, still not crypto broken Link 16 waveform.

I wonder when it will support full self driving?

--

Rick C.

--+ Get 1,000 miles of free Supercharging
--+ Tesla referral code - https://ts.la/richard11209

 

[server]

On Sun, 17 Apr 2022 16:49:40 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Sun, 17 Apr 2022 17:50:59 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote in
news:t3hijn$cus$1@dont-email.me:

On a sunny day (Sun, 17 Apr 2022 09:25:41 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
thfo5ht952906bo9837snjolpjfd2lsc00@4ax.com>:

On Sun, 17 Apr 2022 09:10:41 -0700,
jlarkin@highlandsniptechnology.com wrote:

On Sun, 17 Apr 2022 15:55:21 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Ricky <gnuarm.deletethisbit@gmail.com> wrote in
news:3f3e0e0f-175e-4d27-be95-401418cc7e54n@googlegroups.com:

The large surface area of the long, skinny fins are perfect
coupling between the low thermal resistance of the heat sink
and the relatively high thermal conductivity of the fin/air
contact.

The word(s) for today is \"boundary layer\".

https://www.heatsinkcalculator.com/blog/wp-
content/uploads/2016/05/effect_of_boundary_laher_thickness.png

https://www.heatsinkcalculator.com/blog/top-3-mistakes-made-when
- selecting-a-heat-sink/

Slow air would pass right over a close fin spaced sink. High
speed
forced air is required when the fins get that closely spaced.


Right. Viscous drag will keep air from flowing between tall,
closely spaced fins. It will have to be ducted and forced, or it
will go around.

The limiting case, more and more denser and thinner fins,
volumetric air flow will approach zero.

My general rule is that a heat sink should reduce the native air
flow by about half. Neither zero nor 100% does any cooling.

And of course, the tips of tall thin fins have a high thermal
resistance to the baseplate, so run at about inlet air temp, so
restrict air flow without contributing much coolong. My 50% number
is useless if the air flow is restricted without corresponding
cooling.

There is no limit to how bad a heat sink you can design. A solid
aluminum brick is pretty bad.

This works great:
http://panteltje.com/pub/big_3kg_heatsink_IMG_3745.GIF

BTW that is a rubidum reference on top of it.


That is a very poor heat sink. Essentialy it conduction cools the
device it is mounted to, but not much gets radiated away. More like
a homogenizer.

There is a reason that motorcycle air cooled cylinder jugs and
heads are NOT painted.

Radiation cooling goes as the 4th power of the temp difference between
the sink and the universe. Since semiconductors can\'t be allowed to
get very hot above ambient, rad cooling is usually minor. Inside a
metal box, a lot of the radiation is trapped and reflects back.

The emission from a black body goes like T**4, so the thermal coupling
between two surfaces goes like the difference, i.e. T1**4 - T2**4. For
small temperature differences, that\'s basically 4 * T**3 * delta T.

Cheers

Phil Hobbs

I wrote a little PowerBasic program to do the calc.

https://www.dropbox.com/s/6a70p72e9yltsj7/Radcool2.EXE?dl=0

It uses the equation from Reference Data for Radio Engineers.

It\'s still pretty small for semiconductors on heat sinks.




--

I yam what I yam - Popeye

 

[Phil Hobbs]

jlarkin@highlandsniptechnology.com wrote:

On Sun, 17 Apr 2022 16:49:40 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Sun, 17 Apr 2022 17:50:59 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote in
news:t3hijn$cus$1@dont-email.me:

On a sunny day (Sun, 17 Apr 2022 09:25:41 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
thfo5ht952906bo9837snjolpjfd2lsc00@4ax.com>:

On Sun, 17 Apr 2022 09:10:41 -0700,
jlarkin@highlandsniptechnology.com wrote:

On Sun, 17 Apr 2022 15:55:21 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Ricky <gnuarm.deletethisbit@gmail.com> wrote in
news:3f3e0e0f-175e-4d27-be95-401418cc7e54n@googlegroups.com:

The large surface area of the long, skinny fins are perfect
coupling between the low thermal resistance of the heat sink
and the relatively high thermal conductivity of the fin/air
contact.

The word(s) for today is \"boundary layer\".

https://www.heatsinkcalculator.com/blog/wp-
content/uploads/2016/05/effect_of_boundary_laher_thickness.png

https://www.heatsinkcalculator.com/blog/top-3-mistakes-made-when
- selecting-a-heat-sink/

Slow air would pass right over a close fin spaced sink. High
speed
forced air is required when the fins get that closely spaced.


Right. Viscous drag will keep air from flowing between tall,
closely spaced fins. It will have to be ducted and forced, or it
will go around.

The limiting case, more and more denser and thinner fins,
volumetric air flow will approach zero.

My general rule is that a heat sink should reduce the native air
flow by about half. Neither zero nor 100% does any cooling.

And of course, the tips of tall thin fins have a high thermal
resistance to the baseplate, so run at about inlet air temp, so
restrict air flow without contributing much coolong. My 50% number
is useless if the air flow is restricted without corresponding
cooling.

There is no limit to how bad a heat sink you can design. A solid
aluminum brick is pretty bad.

This works great:
http://panteltje.com/pub/big_3kg_heatsink_IMG_3745.GIF

BTW that is a rubidum reference on top of it.


That is a very poor heat sink. Essentialy it conduction cools the
device it is mounted to, but not much gets radiated away. More like
a homogenizer.

There is a reason that motorcycle air cooled cylinder jugs and
heads are NOT painted.

Radiation cooling goes as the 4th power of the temp difference between
the sink and the universe. Since semiconductors can\'t be allowed to
get very hot above ambient, rad cooling is usually minor. Inside a
metal box, a lot of the radiation is trapped and reflects back.

The emission from a black body goes like T**4, so the thermal coupling
between two surfaces goes like the difference, i.e. T1**4 - T2**4. For
small temperature differences, that\'s basically 4 * T**3 * delta T.

Cheers

Phil Hobbs

I wrote a little PowerBasic program to do the calc.

https://www.dropbox.com/s/6a70p72e9yltsj7/Radcool2.EXE?dl=0

It uses the equation from Reference Data for Radio Engineers.

It\'s still pretty small for semiconductors on heat sinks.

For two black bodies at 300K, the thermal impedance of radiation is
about the same as 6 mm of air.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[server]

On Sun, 17 Apr 2022 21:24:40 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Sun, 17 Apr 2022 16:49:40 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Sun, 17 Apr 2022 17:50:59 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote in
news:t3hijn$cus$1@dont-email.me:

On a sunny day (Sun, 17 Apr 2022 09:25:41 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
thfo5ht952906bo9837snjolpjfd2lsc00@4ax.com>:

On Sun, 17 Apr 2022 09:10:41 -0700,
jlarkin@highlandsniptechnology.com wrote:

On Sun, 17 Apr 2022 15:55:21 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Ricky <gnuarm.deletethisbit@gmail.com> wrote in
news:3f3e0e0f-175e-4d27-be95-401418cc7e54n@googlegroups.com:

The large surface area of the long, skinny fins are perfect
coupling between the low thermal resistance of the heat sink
and the relatively high thermal conductivity of the fin/air
contact.

The word(s) for today is \"boundary layer\".

https://www.heatsinkcalculator.com/blog/wp-
content/uploads/2016/05/effect_of_boundary_laher_thickness.png

https://www.heatsinkcalculator.com/blog/top-3-mistakes-made-when
- selecting-a-heat-sink/

Slow air would pass right over a close fin spaced sink. High
speed
forced air is required when the fins get that closely spaced.


Right. Viscous drag will keep air from flowing between tall,
closely spaced fins. It will have to be ducted and forced, or it
will go around.

The limiting case, more and more denser and thinner fins,
volumetric air flow will approach zero.

My general rule is that a heat sink should reduce the native air
flow by about half. Neither zero nor 100% does any cooling.

And of course, the tips of tall thin fins have a high thermal
resistance to the baseplate, so run at about inlet air temp, so
restrict air flow without contributing much coolong. My 50% number
is useless if the air flow is restricted without corresponding
cooling.

There is no limit to how bad a heat sink you can design. A solid
aluminum brick is pretty bad.

This works great:
http://panteltje.com/pub/big_3kg_heatsink_IMG_3745.GIF

BTW that is a rubidum reference on top of it.


That is a very poor heat sink. Essentialy it conduction cools the
device it is mounted to, but not much gets radiated away. More like
a homogenizer.

There is a reason that motorcycle air cooled cylinder jugs and
heads are NOT painted.

Radiation cooling goes as the 4th power of the temp difference between
the sink and the universe. Since semiconductors can\'t be allowed to
get very hot above ambient, rad cooling is usually minor. Inside a
metal box, a lot of the radiation is trapped and reflects back.

The emission from a black body goes like T**4, so the thermal coupling
between two surfaces goes like the difference, i.e. T1**4 - T2**4. For
small temperature differences, that\'s basically 4 * T**3 * delta T.

Cheers

Phil Hobbs

I wrote a little PowerBasic program to do the calc.

https://www.dropbox.com/s/6a70p72e9yltsj7/Radcool2.EXE?dl=0

It uses the equation from Reference Data for Radio Engineers.

It\'s still pretty small for semiconductors on heat sinks.

For two black bodies at 300K, the thermal impedance of radiation is
about the same as 6 mm of air.

Cheers

Phil Hobbs

That\'s a fun number. That\'s a lot of thermal resistance, and the
insides of a metal box won\'t be a black body so things are worse in
real life.



--

I yam what I yam - Popeye

 

[Phil Hobbs]

jlarkin@highlandsniptechnology.com wrote:

On Sun, 17 Apr 2022 21:24:40 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Sun, 17 Apr 2022 16:49:40 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Sun, 17 Apr 2022 17:50:59 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote in
news:t3hijn$cus$1@dont-email.me:

On a sunny day (Sun, 17 Apr 2022 09:25:41 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
thfo5ht952906bo9837snjolpjfd2lsc00@4ax.com>:

On Sun, 17 Apr 2022 09:10:41 -0700,
jlarkin@highlandsniptechnology.com wrote:

On Sun, 17 Apr 2022 15:55:21 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Ricky <gnuarm.deletethisbit@gmail.com> wrote in
news:3f3e0e0f-175e-4d27-be95-401418cc7e54n@googlegroups.com:

The large surface area of the long, skinny fins are perfect
coupling between the low thermal resistance of the heat sink
and the relatively high thermal conductivity of the fin/air
contact.

The word(s) for today is \"boundary layer\".

https://www.heatsinkcalculator.com/blog/wp-
content/uploads/2016/05/effect_of_boundary_laher_thickness.png

https://www.heatsinkcalculator.com/blog/top-3-mistakes-made-when
- selecting-a-heat-sink/

Slow air would pass right over a close fin spaced sink. High
speed
forced air is required when the fins get that closely spaced.


Right. Viscous drag will keep air from flowing between tall,
closely spaced fins. It will have to be ducted and forced, or it
will go around.

The limiting case, more and more denser and thinner fins,
volumetric air flow will approach zero.

My general rule is that a heat sink should reduce the native air
flow by about half. Neither zero nor 100% does any cooling.

And of course, the tips of tall thin fins have a high thermal
resistance to the baseplate, so run at about inlet air temp, so
restrict air flow without contributing much coolong. My 50% number
is useless if the air flow is restricted without corresponding
cooling.

There is no limit to how bad a heat sink you can design. A solid
aluminum brick is pretty bad.

This works great:
http://panteltje.com/pub/big_3kg_heatsink_IMG_3745.GIF

BTW that is a rubidum reference on top of it.


That is a very poor heat sink. Essentialy it conduction cools the
device it is mounted to, but not much gets radiated away. More like
a homogenizer.

There is a reason that motorcycle air cooled cylinder jugs and
heads are NOT painted.

Radiation cooling goes as the 4th power of the temp difference between
the sink and the universe. Since semiconductors can\'t be allowed to
get very hot above ambient, rad cooling is usually minor. Inside a
metal box, a lot of the radiation is trapped and reflects back.

The emission from a black body goes like T**4, so the thermal coupling
between two surfaces goes like the difference, i.e. T1**4 - T2**4. For
small temperature differences, that\'s basically 4 * T**3 * delta T.

Cheers

Phil Hobbs

I wrote a little PowerBasic program to do the calc.

https://www.dropbox.com/s/6a70p72e9yltsj7/Radcool2.EXE?dl=0

It uses the equation from Reference Data for Radio Engineers.

It\'s still pretty small for semiconductors on heat sinks.

For two black bodies at 300K, the thermal impedance of radiation is
about the same as 6 mm of air.


That\'s a fun number. That\'s a lot of thermal resistance, and the
insides of a metal box won\'t be a black body so things are worse in
real life.

Until convection gets going, right. That\'s also the reason that foam
and fibre-batt insulation isn\'t just immobilized air, as is often
said--you need to scatter the IR radiation every few millimetres at most.

Photon budgets are a lot easier to do when you have a bag full of
fun-fact numbers like that: spheres scatter light into 4 pi steradians;
if your feedback resistor drops more than 50 mV, you\'re in the shot
noise limit; and so on and so forth.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[server]

On Mon, 18 Apr 2022 10:17:21 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Sun, 17 Apr 2022 21:24:40 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Sun, 17 Apr 2022 16:49:40 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Sun, 17 Apr 2022 17:50:59 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote in
news:t3hijn$cus$1@dont-email.me:

On a sunny day (Sun, 17 Apr 2022 09:25:41 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
thfo5ht952906bo9837snjolpjfd2lsc00@4ax.com>:

On Sun, 17 Apr 2022 09:10:41 -0700,
jlarkin@highlandsniptechnology.com wrote:

On Sun, 17 Apr 2022 15:55:21 -0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Ricky <gnuarm.deletethisbit@gmail.com> wrote in
news:3f3e0e0f-175e-4d27-be95-401418cc7e54n@googlegroups.com:

The large surface area of the long, skinny fins are perfect
coupling between the low thermal resistance of the heat sink
and the relatively high thermal conductivity of the fin/air
contact.

The word(s) for today is \"boundary layer\".

https://www.heatsinkcalculator.com/blog/wp-
content/uploads/2016/05/effect_of_boundary_laher_thickness.png

https://www.heatsinkcalculator.com/blog/top-3-mistakes-made-when
- selecting-a-heat-sink/

Slow air would pass right over a close fin spaced sink. High
speed
forced air is required when the fins get that closely spaced.


Right. Viscous drag will keep air from flowing between tall,
closely spaced fins. It will have to be ducted and forced, or it
will go around.

The limiting case, more and more denser and thinner fins,
volumetric air flow will approach zero.

My general rule is that a heat sink should reduce the native air
flow by about half. Neither zero nor 100% does any cooling.

And of course, the tips of tall thin fins have a high thermal
resistance to the baseplate, so run at about inlet air temp, so
restrict air flow without contributing much coolong. My 50% number
is useless if the air flow is restricted without corresponding
cooling.

There is no limit to how bad a heat sink you can design. A solid
aluminum brick is pretty bad.

This works great:
http://panteltje.com/pub/big_3kg_heatsink_IMG_3745.GIF

BTW that is a rubidum reference on top of it.


That is a very poor heat sink. Essentialy it conduction cools the
device it is mounted to, but not much gets radiated away. More like
a homogenizer.

There is a reason that motorcycle air cooled cylinder jugs and
heads are NOT painted.

Radiation cooling goes as the 4th power of the temp difference between
the sink and the universe. Since semiconductors can\'t be allowed to
get very hot above ambient, rad cooling is usually minor. Inside a
metal box, a lot of the radiation is trapped and reflects back.

The emission from a black body goes like T**4, so the thermal coupling
between two surfaces goes like the difference, i.e. T1**4 - T2**4. For
small temperature differences, that\'s basically 4 * T**3 * delta T.

Cheers

Phil Hobbs

I wrote a little PowerBasic program to do the calc.

https://www.dropbox.com/s/6a70p72e9yltsj7/Radcool2.EXE?dl=0

It uses the equation from Reference Data for Radio Engineers.

It\'s still pretty small for semiconductors on heat sinks.

For two black bodies at 300K, the thermal impedance of radiation is
about the same as 6 mm of air.


That\'s a fun number. That\'s a lot of thermal resistance, and the
insides of a metal box won\'t be a black body so things are worse in
real life.

Until convection gets going, right. That\'s also the reason that foam
and fibre-batt insulation isn\'t just immobilized air, as is often
said--you need to scatter the IR radiation every few millimetres at most.

Photon budgets are a lot easier to do when you have a bag full of
fun-fact numbers like that: spheres scatter light into 4 pi steradians;
if your feedback resistor drops more than 50 mV, you\'re in the shot
noise limit; and so on and so forth.

Cheers

Phil Hobbs

I experimented with covers over heated blocks, namely with various
types of insulation. Given a pretty close fitting cover, the best
insulation is none.

https://www.dropbox.com/s/9v4dse1vv4vjs0w/P500_XO_Cover.jpg?raw=1



--

I yam what I yam - Popeye

 

[Carlos E.R.]

On 2022-04-17 16:49, jlarkin@highlandsniptechnology.com wrote:

On Sun, 17 Apr 2022 12:31:52 +0200, \"Carlos E.R.\"
robin_listas@es.invalid> wrote:

On 2022-04-17 00:23, jlarkin@highlandsniptechnology.com wrote:
On Sat, 16 Apr 2022 19:51:56 -0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:

bitrex <user@example.net> wrote:
I thought they were extruded, but no!

https://youtu.be/wwWIyHo3yJM

Like carving a turkey dinner

Skiving is real slow. The only value is you get thinner fins than can be
extruded. More machining is needed if you want holes though any of that.

Those long skinny fins don\'t look efficient to me. And they would need
a huge air blast.

I don\'t think so: a strong air blast would bend the fins.

That strong would destroy the enclosure and kill bystanders.

I don\'t think so, those fins are almost paper thin.

--
Cheers, Carlos.

 

[Commander Kinsey]

On Fri, 15 Apr 2022 23:58:13 +0100, bitrex <user@example.net> wrote:

I thought they were extruded, but no!

https://youtu.be/wwWIyHo3yJM

Like carving a turkey dinner

How does that even work? The bit at the end of each one where it magically bends up to the vertical.