I thought they were extruded, but no!

<https://youtu.be/wwWIyHo3yJM>

Like carving a turkey dinner

On Fri, 15 Apr 2022 18:58:13 -0400, bitrex <user@example.net> wrote:

>I thought they were extruded, but no!
>
><https://youtu.be/wwWIyHo3yJM>
>
>Like carving a turkey dinner

Most heat sinks are extruded. Some are cast, like pin fins.

Some are machined.

There's also a process where the fins are pressed into slots

--

I yam what I yam - Popeye

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.

On Friday, April 15, 2022 at 6:58:20 PM UTC-4, bitrex wrote:
> I thought they were extruded, but no!
>
> <https://youtu.be/wwWIyHo3yJM>
>
> Like carving a turkey dinner

This gets you more fins for better transfer to the air. People focus on silly points like diamond heat sink grease, when they often lose far more performance at other points in the heat path. Ultimately there is a limit on how larger a heat sink you can attach to a CPU/GPU directly.

If size and cost are not an issue, heat pipes to connect the heat block on the CPU/GPU to a much larger thermal air interface. Bigger fins, bigger fan and much better performance.

Then water cooling can get even better performance, and the noisy bits can be somewhere else, even in another room. I remember discussing this with a guy who ran the tubes to a drum in his garage where he didn't even need to use an air interface. The thermal mass of the drum was good enough to absorb the heat for the time he ran the computer. Zero noise other than the power supply fan, I suppose he still had one of those.

--

Rick C.

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

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 yam what I yam - Popeye

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.

--

Rick C.

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

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?

> 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.

Also:

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

Horses for courses....

...... Phil

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.

--
Cheers, Carlos.

On Sat, 16 Apr 2022 18:22:46 -0700 (PDT), Phil Allison
<pallison49@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.

https://www.dropbox.com/s/0kszc4nltr1q8d3/P944_HS_2.jpg?raw=1

https://www.dropbox.com/s/iwkbuuoa4iq33a7/Mock1.jpg?raw=1

https://www.dropbox.com/s/bz6ueadispq6ril/CPU_Cooler_Washers.jpg?raw=1

--

I yam what I yam - Popeye

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 yam what I yam - Popeye

Cydrome Leader <presence@MUNGEpanix.com> wrote in
news:t3f6os$9d4$1@reader1.panix.com:

> 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.
>

<https://www.youtube.com/watch?v=Q7qVpWu2QYs>
Funny it looks like the same damn machine.

Ricky <gnuarm.deletethisbit@gmail.com> wrote in
news:87e310b7-17aa-4feb-9032-c2104f7d2fdcn@googlegroups.com:

> On Friday, April 15, 2022 at 6:58:20 PM UTC-4, bitrex wrote:
>> I thought they were extruded, but no!
>>
>> <https://youtu.be/wwWIyHo3yJM>
>>
>> Like carving a turkey dinner
>
> This gets you more fins for better transfer to the air.

But at that close spacing, due to boundary layer effects, it would
have to be strongly forced air. or it would simply "walk over top
of" the whole thing, doing less work in the end.

> People
> focus on silly points like diamond heat sink grease,
All that is needed is intimate, coplanar contact. The grease takes
up voids. What *should be* "micro-sized voids", but voides
nonetheless... errr without it the heat tranfer IS less. Those
voids contain the insulative gas "air".

> when they
> often lose far more performance at other points in the heat path.

The first series of AMD dual core CPUs back in oh... 1998 or so
would fry the CPU AND the motherbaord almost instantly if the heat
sink was not well coupled, and that included void filling paste.
> Ultimately there is a limit on how larger a heat sink you can
> attach to a CPU/GPU directly.

That is why contained flowing water was the choice for a long time.

I always wanted to make an entire PC immersed in dielectric fluid
<https://econtroldevices.com/shop/3m-fc-40-fluorinert-electronic-
liquid-20kg/>

But it too has to be moving to carry the heat away.

> If size and cost are not an issue, heat pipes to connect the heat
> block on the CPU/GPU to a much larger thermal air interface.
> Bigger fins, bigger fan and much better performance.

Still water is better.
>
> Then water cooling can get even better performance,

Oh... I see you are aware.

> and the noisy
> bits can be somewhere else, even in another room. I remember
> discussing this with a guy who ran the tubes to a drum in his
> garage where he didn't even need to use an air interface. The
> thermal mass of the drum was good enough to absorb the heat for
> the time he ran the computer. Zero noise other than the power
> supply fan, I suppose he still had one of those.
>

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.

It is not only about their condution from the heat source, it is
about how well it gets transferred to a MOVING air mass. That is why
most heats sinks had wadire fin spacing.

"Carlos E.R." <robin_listas@es.invalid> wrote in news:ot6tii-7un.ln1
@Telcontar.valinor:

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

Silly.

A strong air blast must have blown the only two firing neurons you
have between your ears to a new location.

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.

--

I yam what I yam - Popeye

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 yam what I yam - Popeye

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.

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.

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.

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.

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

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

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.

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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.

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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