Help!! Need an enclosure FAST...

[Bill Sloman]

On Wednesday, May 8, 2019 at 12:30:42 PM UTC+10, John Larkin wrote:

On Tue, 07 May 2019 20:13:32 GMT, Johnny B Good
johnny-b-good@invalid.ntlworld.com> wrote:

On Tue, 07 May 2019 08:05:30 -0700, John Larkin wrote:

On Tue, 7 May 2019 10:11:15 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 5/7/19 10:00 AM, John Larkin wrote:
On 7 May 2019 05:44:36 -0700, Winfield Hill <hill@rowland.harvard.edu
wrote:

mpm wrote...

Deadline approaching fast. Anybody know where we can get a
heat-sink style enclosure similar ...

If you are truly desperate, your best bet is to fins and purchase
some product that uses a case similar to what you have in mind,
dis-assemble it and use its case. 12V to 115Vac inverters come in
cases with external heatsink structure.

Do you think those stubby little heat sink bumps help much? I'm
thinking they don't.



Almost certainly not. They're too shallow and narrow for much chimney
effect, and they're oriented the wrong way. The fins are thicker, and
so will help conduct heat down the long axis of the box, but not as well
as if the fins weren't cut into it.

They may be useless, but they sure are hard to clean.

Cheers

Phil Hobbs

If there's a PCB inside, the bad path will be from board to box inside,
with still air and no convection and a small PCB surface area with hot
spots.

That's basic heat dissipation failure techniques 101. Seagate used it to
good (bad?) effect with their FreeAgent external hard drives to ensure
early failure, even going to the extreme of doctoring the spin down power
saving mode into an immutable 10 minute spin down in their "Specials",
thoughtfully denoted by the use, appropriately enough, of the suffix
letter "S" in the drive model numbers.

I think John Larkin's ex-intern (or someone equally clueless) must have
landed himself a job with Seagate's external drive storage division...
seriously!

I'm always happy to spread incompetence throughout the rest of the
industry.

Having a more or less inexhaustible supply conveniently to hand. Designed any special purpose transformers recently?

--
Bill Sloman, Sydney

 

On Wednesday, 8 May 2019 03:57:47 UTC+1, mpm wrote:

On Tuesday, May 7, 2019 at 9:19:36 PM UTC-4, R Collins wrote:
Many times asking this group a simple question is like asking Statler and Waldorf. I hope you find something. I've not seen any product this interesting for heat dissipation. Why is it you can't buy it from Takachi? ....

Takachi is located in Japan, and purchasing said there was some sort of national holiday. So, we won't know until tomorrow (maybe?) whether they even have these in stock. And the clock is still ticking...., and they still have to get here.

I've looked around quite a bit (domestically) and really haven't found anything that looks quite as nice as these Takachi boxes, short of rolling something custom that we just don't have time for. (And if you think that's bad, I haven't mentioned the stress getting the box internals done!)

R&D might have to initiate a new policy of NO NEW DESIGNS (or re-work) for upcoming trade shows. Period. (Note: Will never happen.)

You've avoided telling us what you're doing with it, so I don't know whether to mention other options or not.


NT

 

[Martin Riddle]

On Tue, 7 May 2019 20:07:30 -0700 (PDT), mpm <mpmillard@aol.com>
wrote:

On Tuesday, May 7, 2019 at 11:05:39 AM UTC-4, John Larkin wrote:
... If there's a PCB inside, the bad path will be from board to box
inside, with still air and no convection and a small PCB surface area
with hot spots.

You are a mind-reader.

This build will have 14 watts to dissipate (min).
Do-able, but not trivial.

Of course, the boss mentioned today he'd like the higher-power board installed.
It never ends....

isn't the rule 1 watt per square inch still valid? 14 square inches of
case should suffice.

Cheers

 

[Bill Sloman]

On Wednesday, May 8, 2019 at 2:42:05 PM UTC+10, tabb...@gmail.com wrote:

On Wednesday, 8 May 2019 03:57:47 UTC+1, mpm wrote:
On Tuesday, May 7, 2019 at 9:19:36 PM UTC-4, R Collins wrote:
Many times asking this group a simple question is like asking Statler and Waldorf. I hope you find something. I've not seen any product this interesting for heat dissipation. Why is it you can't buy it from Takachi? ....

Takachi is located in Japan, and purchasing said there was some sort of national holiday. So, we won't know until tomorrow (maybe?) whether they even have these in stock. And the clock is still ticking...., and they still have to get here.

I've looked around quite a bit (domestically) and really haven't found anything that looks quite as nice as these Takachi boxes, short of rolling something custom that we just don't have time for. (And if you think that's bad, I haven't mentioned the stress getting the box internals done!)

R&D might have to initiate a new policy of NO NEW DESIGNS (or re-work) for upcoming trade shows. Period. (Note: Will never happen.)


You've avoided telling us what you're doing with it, so I don't know whether to mention other options or not.

NT

Not the most helpful response ever posted.

--
Bill Sloman, Sydney

 

[John Miles, KE5FX]

On Tuesday, May 7, 2019 at 7:57:47 PM UTC-7, mpm wrote:
> R&D might have to initiate a new policy of NO NEW DESIGNS (or re-work) for upcoming trade shows. Period. (Note: Will never happen.)

I'm using an AWP-series enclosure in a project right now. Their products
range from decent to great, but those serrated heat sink fins are SHARP.
If you ever get your hands on one, consider that a word to the wise.
I evaluated several of their enclosures including that one, and almost had
to get stitches after grabbing the heat sinks on the side of an HY chassis
at the wrong angle.

The fins might or might not be helpful, but the detailed serrations on them
are totally useless due to boundary-layer effects. They are just too small
and too densely organized to do anything other than slice fingers open.
I'll give them credit for publishing degs/W numbers in their brochures, though.

Another helpful tip when dealing with Takachi is that there is *always* some
kind of vacation, holiday, or other extracurricular business that makes
communication challenging. Plan ahead and give them plenty of time, emergency
orders aren't their thing.

It's crazy how few domestic manufacturers sell quality electronic enclosures
that you wouldn't be embarrassed to use in a commercial product. Lots of room
for competition in that business IMO.

-- john, KE5FX

 

On Tuesday, 7 May 2019 16:11:25 UTC+2, Phil Hobbs wrote:

On 5/7/19 10:00 AM, John Larkin wrote:
On 7 May 2019 05:44:36 -0700, Winfield Hill <hill@rowland.harvard.edu
wrote:

mpm wrote...

Deadline approaching fast. Anybody know where
we can get a heat-sink style enclosure similar ...

If you are truly desperate, your best bet is to
fins and purchase some product that uses a case
similar to what you have in mind, dis-assemble
it and use its case. 12V to 115Vac inverters
come in cases with external heatsink structure.

Do you think those stubby little heat sink bumps help much? I'm
thinking they don't.



Almost certainly not. They're too shallow and narrow for much chimney
effect, and they're oriented the wrong way. The fins are thicker, and
so will help conduct heat down the long axis of the box, but not as well
as if the fins weren't cut into it.

They may be useless, but they sure are hard to clean.

Our thermal specialist has a rule that dimensions below 6mm wont do any good, since the air wont "flow" in such small dimensions, just stay there

Cheers

Klaus

 

[John S]

On 5/8/2019 6:58 AM, Bill Sloman wrote:

On Wednesday, May 8, 2019 at 2:42:05 PM UTC+10, tabb...@gmail.com wrote:
On Wednesday, 8 May 2019 03:57:47 UTC+1, mpm wrote:
On Tuesday, May 7, 2019 at 9:19:36 PM UTC-4, R Collins wrote:
Many times asking this group a simple question is like asking Statler and Waldorf. I hope you find something. I've not seen any product this interesting for heat dissipation. Why is it you can't buy it from Takachi? ...

Takachi is located in Japan, and purchasing said there was some sort of national holiday. So, we won't know until tomorrow (maybe?) whether they even have these in stock. And the clock is still ticking...., and they still have to get here.

I've looked around quite a bit (domestically) and really haven't found anything that looks quite as nice as these Takachi boxes, short of rolling something custom that we just don't have time for. (And if you think that's bad, I haven't mentioned the stress getting the box internals done!)

R&D might have to initiate a new policy of NO NEW DESIGNS (or re-work) for upcoming trade shows. Period. (Note: Will never happen.)


You've avoided telling us what you're doing with it, so I don't know whether to mention other options or not.

NT

Not the most helpful response ever posted.

Nor yours.

 

[Bill Sloman]

On Friday, May 10, 2019 at 4:53:52 AM UTC+10, John S wrote:

On 5/8/2019 6:58 AM, Bill Sloman wrote:
On Wednesday, May 8, 2019 at 2:42:05 PM UTC+10, tabb...@gmail.com wrote:
On Wednesday, 8 May 2019 03:57:47 UTC+1, mpm wrote:
On Tuesday, May 7, 2019 at 9:19:36 PM UTC-4, R Collins wrote:
Many times asking this group a simple question is like asking Statler and Waldorf. I hope you find something. I've not seen any product this interesting for heat dissipation. Why is it you can't buy it from Takachi? ...

Takachi is located in Japan, and purchasing said there was some sort of national holiday. So, we won't know until tomorrow (maybe?) whether they even have these in stock. And the clock is still ticking...., and they still have to get here.

I've looked around quite a bit (domestically) and really haven't found anything that looks quite as nice as these Takachi boxes, short of rolling something custom that we just don't have time for. (And if you think that's bad, I haven't mentioned the stress getting the box internals done!)

R&D might have to initiate a new policy of NO NEW DESIGNS (or re-work) for upcoming trade shows. Period. (Note: Will never happen.)


You've avoided telling us what you're doing with it, so I don't know whether to mention other options or not.

NT

Not the most helpful response ever posted.


Nor yours.

I don't know. NT makes a habit of posting responses that aren't worth reading - he's pretty much down there with skybuckflying for posting useful content - so a comment to that effect may be helpful at a higher level.

--
Bill Sloman, Sydney

 

On Thursday, 9 May 2019 19:53:52 UTC+1, John S wrote:

On 5/8/2019 6:58 AM, Bill Sloman wrote:
On Wednesday, May 8, 2019 at 2:42:05 PM UTC+10, tabby wrote:

You've avoided telling us what you're doing with it, so I don't know whether to mention other options or not.

NT

Not the most helpful response ever posted.


Nor yours.

A request for more relevant info is not helpful? Must be Planet Slowman.


NT

 

[Bill Sloman]

On Friday, May 10, 2019 at 10:18:52 PM UTC+10, tabb...@gmail.com wrote:

On Thursday, 9 May 2019 19:53:52 UTC+1, John S wrote:
On 5/8/2019 6:58 AM, Bill Sloman wrote:
On Wednesday, May 8, 2019 at 2:42:05 PM UTC+10, tabby wrote:

You've avoided telling us what you're doing with it, so I don't know whether to mention other options or not.

NT

Not the most helpful response ever posted.

Nor yours.

A request for more relevant info is not helpful? Must be Planet Sloman.

NT neglects to mention that he never does anything with the extra information he thinks he's asking for - he's a black hole when it comes to information.

He has been known to express demented opinions, so his idea of "relevant" isn't great either. Precisely what made his very unspecific request for extra information "relevant" escapes me, and I can be confident that I won't be any better informed if he bothers to respond.

--
Bill Sloman, Sydney

 

[Lasse Langwadt Christense]

onsdag den 8. maj 2019 kl. 05.32.15 UTC+2 skrev John Larkin:

On Tue, 7 May 2019 20:07:30 -0700 (PDT), mpm <mpmillard@aol.com
wrote:

On Tuesday, May 7, 2019 at 11:05:39 AM UTC-4, John Larkin wrote:
... If there's a PCB inside, the bad path will be from board to box
inside, with still air and no convection and a small PCB surface area
with hot spots.

You are a mind-reader.

This build will have 14 watts to dissipate (min).
Do-able, but not trivial.

Of course, the boss mentioned today he'd like the higher-power board installed.
It never ends....


You need a lot of copper planes inside the board, spread out the hot
spots, and then use a gap-pad to move heat from the board to the box.
14 watts is, as you note, doable.

Better yet, heat sink the power semis directly to the inside of the
box.

and as I recently found out the thermal conductivity of the anodizing is absolutely horrible

 

[Rick C]

On Saturday, May 11, 2019 at 8:39:29 AM UTC-4, Lasse Langwadt Christensen wrote:

onsdag den 8. maj 2019 kl. 05.32.15 UTC+2 skrev John Larkin:
On Tue, 7 May 2019 20:07:30 -0700 (PDT), mpm <mpmillard@aol.com
wrote:

On Tuesday, May 7, 2019 at 11:05:39 AM UTC-4, John Larkin wrote:
... If there's a PCB inside, the bad path will be from board to box
inside, with still air and no convection and a small PCB surface area
with hot spots.

You are a mind-reader.

This build will have 14 watts to dissipate (min).
Do-able, but not trivial.

Of course, the boss mentioned today he'd like the higher-power board installed.
It never ends....


You need a lot of copper planes inside the board, spread out the hot
spots, and then use a gap-pad to move heat from the board to the box.
14 watts is, as you note, doable.

Better yet, heat sink the power semis directly to the inside of the
box.

and as I recently found out the thermal conductivity of the anodizing is absolutely horrible

Why would that matter? Anodizing is pretty thin. Nothing is a good thermal insulator if it is thin enough. What type of anodizing are you talking abougt? How bad is this supposed to be? I'm not familiar with the "horrible" spec.

--

Rick C.

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

 

[Lasse Langwadt Christense]

lørdag den 11. maj 2019 kl. 21.34.09 UTC+2 skrev Rick C:

On Saturday, May 11, 2019 at 8:39:29 AM UTC-4, Lasse Langwadt Christensen wrote:
onsdag den 8. maj 2019 kl. 05.32.15 UTC+2 skrev John Larkin:
On Tue, 7 May 2019 20:07:30 -0700 (PDT), mpm <mpmillard@aol.com
wrote:

On Tuesday, May 7, 2019 at 11:05:39 AM UTC-4, John Larkin wrote:
... If there's a PCB inside, the bad path will be from board to box
inside, with still air and no convection and a small PCB surface area
with hot spots.

You are a mind-reader.

This build will have 14 watts to dissipate (min).
Do-able, but not trivial.

Of course, the boss mentioned today he'd like the higher-power board installed.
It never ends....


You need a lot of copper planes inside the board, spread out the hot
spots, and then use a gap-pad to move heat from the board to the box.
14 watts is, as you note, doable.

Better yet, heat sink the power semis directly to the inside of the
box.

and as I recently found out the thermal conductivity of the anodizing is absolutely horrible

Why would that matter? Anodizing is pretty thin. Nothing is a good thermal insulator if it is thin enough. What type of anodizing are you talking abougt? How bad is this supposed to be? I'm not familiar with the "horrible" spec.

the usually grey anodizing on extruded alu enclosures with heat sink fins

I didn't do the measurements but milling off the anodizing where a transistor was bolted to the inside made a big difference

 

[John Miles, KE5FX]

On Saturday, May 11, 2019 at 12:34:09 PM UTC-7, Rick C wrote:

Why would that matter? Anodizing is pretty thin. Nothing is a good
thermal insulator if it is thin enough. What type of anodizing are
you talking abougt? How bad is this supposed to be? I'm not familiar
with the "horrible" spec.

It turns out that anodizing makes a massive difference. Hard to appreciate
just how much until you play with a thermal camera. Emissivity of an
anodized surface is in the 0.9 range. The same enclosure with a conductive
alodine treatment will look essentially identical visually, but its infrared
emissivity will be a small fraction of that, maybe 0.2 or so.

The net effect is that an anodized enclosure will feel substantially cooler
to the touch but will appear quite a bit hotter on an IR camera. Thickness
of the surface treatment has nothing to do with it, another somewhat
unintuitive fact. It's all about the free electrons at the surface as I
understand it. There's some correlation between thermal conductivity and
electrical conductivity for similar reasons.

-- john, KE5FX

 

[Rick C]

On Saturday, May 11, 2019 at 5:02:38 PM UTC-4, John Miles, KE5FX wrote:

On Saturday, May 11, 2019 at 12:34:09 PM UTC-7, Rick C wrote:
Why would that matter? Anodizing is pretty thin. Nothing is a good
thermal insulator if it is thin enough. What type of anodizing are
you talking abougt? How bad is this supposed to be? I'm not familiar
with the "horrible" spec.

It turns out that anodizing makes a massive difference. Hard to appreciate
just how much until you play with a thermal camera. Emissivity of an
anodized surface is in the 0.9 range. The same enclosure with a conductive
alodine treatment will look essentially identical visually, but its infrared
emissivity will be a small fraction of that, maybe 0.2 or so.

The net effect is that an anodized enclosure will feel substantially cooler
to the touch but will appear quite a bit hotter on an IR camera. Thickness
of the surface treatment has nothing to do with it, another somewhat
unintuitive fact. It's all about the free electrons at the surface as I
understand it. There's some correlation between thermal conductivity and
electrical conductivity for similar reasons.

Two points... One, you are talking about radiation while Lasse is talking about conduction of the anodizing. Two, the emissivity effect you are talking about indicates the anodized enclosure is actually better for getting rid of the heat.

Or maybe I missed your point?

--

Rick C.

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

 

[Lasse Langwadt Christense]

søndag den 12. maj 2019 kl. 00.11.44 UTC+2 skrev Rick C:

On Saturday, May 11, 2019 at 5:30:22 PM UTC-4, Lasse Langwadt Christensen wrote:
lørdag den 11. maj 2019 kl. 21.34.09 UTC+2 skrev Rick C:
On Saturday, May 11, 2019 at 8:39:29 AM UTC-4, Lasse Langwadt Christensen wrote:
onsdag den 8. maj 2019 kl. 05.32.15 UTC+2 skrev John Larkin:
On Tue, 7 May 2019 20:07:30 -0700 (PDT), mpm <mpmillard@aol.com
wrote:

On Tuesday, May 7, 2019 at 11:05:39 AM UTC-4, John Larkin wrote:
... If there's a PCB inside, the bad path will be from board to box
inside, with still air and no convection and a small PCB surface area
with hot spots.

You are a mind-reader.

This build will have 14 watts to dissipate (min).
Do-able, but not trivial.

Of course, the boss mentioned today he'd like the higher-power board installed.
It never ends....


You need a lot of copper planes inside the board, spread out the hot
spots, and then use a gap-pad to move heat from the board to the box.
14 watts is, as you note, doable.

Better yet, heat sink the power semis directly to the inside of the
box.

and as I recently found out the thermal conductivity of the anodizing is absolutely horrible

Why would that matter? Anodizing is pretty thin. Nothing is a good thermal insulator if it is thin enough. What type of anodizing are you talking abougt? How bad is this supposed to be? I'm not familiar with the "horrible" spec.


the usually grey anodizing on extruded alu enclosures with heat sink fins

I didn't do the measurements but milling off the anodizing where a transistor was bolted to the inside made a big difference

I don't know what to tell you. Perhaps there was some other effect like the anodized surface not being very flat? Anodized layers are less than 1 mil up to 5 mils depending on type. It's pretty hard to get much insulating properties in 5 mils of thickness. How many watts? How large of a surface? What was the observed temperature change?

I didn't do the measurements, the surface is ~10mmx30mm, maybe 50watt

 

[Rick C]

On Saturday, May 11, 2019 at 5:30:22 PM UTC-4, Lasse Langwadt Christensen wrote:

lørdag den 11. maj 2019 kl. 21.34.09 UTC+2 skrev Rick C:
On Saturday, May 11, 2019 at 8:39:29 AM UTC-4, Lasse Langwadt Christensen wrote:
onsdag den 8. maj 2019 kl. 05.32.15 UTC+2 skrev John Larkin:
On Tue, 7 May 2019 20:07:30 -0700 (PDT), mpm <mpmillard@aol.com
wrote:

On Tuesday, May 7, 2019 at 11:05:39 AM UTC-4, John Larkin wrote:
... If there's a PCB inside, the bad path will be from board to box
inside, with still air and no convection and a small PCB surface area
with hot spots.

You are a mind-reader.

This build will have 14 watts to dissipate (min).
Do-able, but not trivial.

Of course, the boss mentioned today he'd like the higher-power board installed.
It never ends....


You need a lot of copper planes inside the board, spread out the hot
spots, and then use a gap-pad to move heat from the board to the box.
14 watts is, as you note, doable.

Better yet, heat sink the power semis directly to the inside of the
box.

and as I recently found out the thermal conductivity of the anodizing is absolutely horrible

Why would that matter? Anodizing is pretty thin. Nothing is a good thermal insulator if it is thin enough. What type of anodizing are you talking abougt? How bad is this supposed to be? I'm not familiar with the "horrible" spec.


the usually grey anodizing on extruded alu enclosures with heat sink fins

I didn't do the measurements but milling off the anodizing where a transistor was bolted to the inside made a big difference

I don't know what to tell you. Perhaps there was some other effect like the anodized surface not being very flat? Anodized layers are less than 1 mil up to 5 mils depending on type. It's pretty hard to get much insulating properties in 5 mils of thickness. How many watts? How large of a surface? What was the observed temperature change?

--

Rick C.

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

 

[Lasse Langwadt Christense]

søndag den 12. maj 2019 kl. 00.56.05 UTC+2 skrev Rick C:

On Saturday, May 11, 2019 at 6:22:32 PM UTC-4, Lasse Langwadt Christensen wrote:
søndag den 12. maj 2019 kl. 00.11.44 UTC+2 skrev Rick C:
On Saturday, May 11, 2019 at 5:30:22 PM UTC-4, Lasse Langwadt Christensen wrote:
lørdag den 11. maj 2019 kl. 21.34.09 UTC+2 skrev Rick C:
On Saturday, May 11, 2019 at 8:39:29 AM UTC-4, Lasse Langwadt Christensen wrote:

and as I recently found out the thermal conductivity of the anodizing is absolutely horrible

Why would that matter? Anodizing is pretty thin. Nothing is a good thermal insulator if it is thin enough. What type of anodizing are you talking abougt? How bad is this supposed to be? I'm not familiar with the "horrible" spec.


the usually grey anodizing on extruded alu enclosures with heat sink fins

I didn't do the measurements but milling off the anodizing where a transistor was bolted to the inside made a big difference

I don't know what to tell you. Perhaps there was some other effect like the anodized surface not being very flat? Anodized layers are less than 1 mil up to 5 mils depending on type. It's pretty hard to get much insulating properties in 5 mils of thickness. How many watts? How large of a surface? What was the observed temperature change?


I didn't do the measurements, the surface is ~10mmx30mm, maybe 50watt

I did a quick calculation based on 30 W·m−1·K−1 3 cm^2 at 5 mil thickness (hard anodizing) would be about 70 W/K. That would seem to be less than one degree Kelvin from removing the anodized layer.

yes I also looked up aluminium oxide and saw 30 W·m−1·K−1 and thought no problem, but then I looked up numbers for anodizing and found multiple papers where they had measured it as more like 1 W·m−1·K−1

 

[Rick C]

On Saturday, May 11, 2019 at 6:22:32 PM UTC-4, Lasse Langwadt Christensen wrote:

søndag den 12. maj 2019 kl. 00.11.44 UTC+2 skrev Rick C:
On Saturday, May 11, 2019 at 5:30:22 PM UTC-4, Lasse Langwadt Christensen wrote:
lørdag den 11. maj 2019 kl. 21.34.09 UTC+2 skrev Rick C:
On Saturday, May 11, 2019 at 8:39:29 AM UTC-4, Lasse Langwadt Christensen wrote:

and as I recently found out the thermal conductivity of the anodizing is absolutely horrible

Why would that matter? Anodizing is pretty thin. Nothing is a good thermal insulator if it is thin enough. What type of anodizing are you talking abougt? How bad is this supposed to be? I'm not familiar with the "horrible" spec.


the usually grey anodizing on extruded alu enclosures with heat sink fins

I didn't do the measurements but milling off the anodizing where a transistor was bolted to the inside made a big difference

I don't know what to tell you. Perhaps there was some other effect like the anodized surface not being very flat? Anodized layers are less than 1 mil up to 5 mils depending on type. It's pretty hard to get much insulating properties in 5 mils of thickness. How many watts? How large of a surface? What was the observed temperature change?


I didn't do the measurements, the surface is ~10mmx30mm, maybe 50watt

I did a quick calculation based on 30 W·m−1·K−1 3 cm^2 at 5 mil thickness (hard anodizing) would be about 70 W/K. That would seem to be less than one degree Kelvin from removing the anodized layer..

--

Rick C.

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

 

[Rick C]

On Saturday, May 11, 2019 at 7:13:25 PM UTC-4, Lasse Langwadt Christensen wrote:

søndag den 12. maj 2019 kl. 00.56.05 UTC+2 skrev Rick C:
On Saturday, May 11, 2019 at 6:22:32 PM UTC-4, Lasse Langwadt Christensen wrote:
søndag den 12. maj 2019 kl. 00.11.44 UTC+2 skrev Rick C:
On Saturday, May 11, 2019 at 5:30:22 PM UTC-4, Lasse Langwadt Christensen wrote:
lørdag den 11. maj 2019 kl. 21.34.09 UTC+2 skrev Rick C:
On Saturday, May 11, 2019 at 8:39:29 AM UTC-4, Lasse Langwadt Christensen wrote:

and as I recently found out the thermal conductivity of the anodizing is absolutely horrible

Why would that matter? Anodizing is pretty thin. Nothing is a good thermal insulator if it is thin enough. What type of anodizing are you talking abougt? How bad is this supposed to be? I'm not familiar with the "horrible" spec.


the usually grey anodizing on extruded alu enclosures with heat sink fins

I didn't do the measurements but milling off the anodizing where a transistor was bolted to the inside made a big difference

I don't know what to tell you. Perhaps there was some other effect like the anodized surface not being very flat? Anodized layers are less than 1 mil up to 5 mils depending on type. It's pretty hard to get much insulating properties in 5 mils of thickness. How many watts? How large of a surface? What was the observed temperature change?


I didn't do the measurements, the surface is ~10mmx30mm, maybe 50watt

I did a quick calculation based on 30 W·m−1·K−1 3 cm^2 at 5 mil thickness (hard anodizing) would be about 70 W/K. That would seem to be less than one degree Kelvin from removing the anodized layer.


yes I also looked up aluminium oxide and saw 30 W·m−1·K−1 and thought no problem, but then I looked up numbers for anodizing and found multiple papers where they had measured it as more like 1 W·m−1·K−1

That seems pretty unrealistic. Are you perhaps not getting the right units, with the thickness already having been taken into account or something? That's what I would expect from a paper analyzing thermal conductivity of anodizing.

--

Rick C.

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