Has anybody ever stacked two CPU coolers?

Has anybody ever stacked two CPU coolers? First one fitted normally, then the second welded on top of it. Theoretically, you have twice the cooling, if it conducts through the first fast enough. I'm referring to the type with the fan on the side.

On 25 Jul 2020, Commander Kinsey wrote
(in article op.0oboc2f2wdg98l@glass):

Has anybody ever stacked two CPU coolers? First one fitted normally, then the
second welded on top of it. Theoretically, you have twice the cooling,

no, you won’t.

if it
conducts through the first fast enough. I'm referring to the type with the
fan on the side.

there are numerous sites out there which cover this; I first encountered this
idea in 2001. (Yes, 2001. Not a typo. And it wasn’t a new idea then, it was
just new to me.) It turns out that doubling the fans gives from -5% (that’s
_negative_ five percent, it can make things worse) to +65% airflow, depending
on numerous factors. (Size of fan, are the fans spinning in the same
direction or in opposite directions, fan speed, how fans are placed relative
to the heat exchanger, space inside the computer’s case, location of CPU
relative to sides of computer case, location of other items including hard
drives, RAM, power supplies, video and/or sound cards, type of case
especially with respect to vents, internal cabling, more.) However, airflow
and cooling do not necessarily scale together. Merely increasing the airflow
does not necessarily do much for the cooling, for that you need heat
exchangers attached to the CPU, heat exchangers attached to another heat
exchanger don’t do much, and airflow is a square effect while heat
exchangers are a cube effect. Airflow maxed out at around +65% for two fans;
cooling maxed out at about +45%. And it took considerable effort to get that
+45%, most systems were considerably lower than that. There would be a
_reason_ why liquid cooling is popular. It’s actually simpler and easier to
do. Most modern CPUs generate a whole lot less heat than CPUs dating from
2001 did, so a good way to get a cooler-running system is toi use a newer
CPU. And to stay way from the heat-producing monsters, notably IBM Power
CPUs, which have improved no end since then but which are still devices to
convert electricity into heat, something anyone who ever went near a G5- or a
G4- powered Mac could tell you. (One G4 Mac was called the Windtunnel because
of the noise level from the fans to keep the CPU cool; one G5 Mac shipped
with liquid cooling because Apple didn’t want to ship Windtunnel Mk 2...)
IBM is up to Power 8 or 9 or some such now, where G5s were Power 5s, and
they’re much better behaved, but still...

On Sat, 25 Jul 2020 21:52:31 +0100, Wolffan wrote:

On 25 Jul 2020, Commander Kinsey wrote
(in article op.0oboc2f2wdg98l@glass):

Has anybody ever stacked two CPU coolers? First one fitted normally, then the
second welded on top of it. Theoretically, you have twice the cooling,

no, you won’t.

if it
conducts through the first fast enough. I'm referring to the type with the
fan on the side.

there are numerous sites out there which cover this; I first encountered this
idea in 2001. (Yes, 2001. Not a typo. And it wasn’t a new idea then, it was
just new to me.) It turns out that doubling the fans gives from -5% (that’s
_negative_ five percent, it can make things worse) to +65% airflow, depending
on numerous factors. (Size of fan, are the fans spinning in the same
direction or in opposite directions, fan speed, how fans are placed relative
to the heat exchanger, space inside the computer’s case, location of CPU
relative to sides of computer case, location of other items including hard
drives, RAM, power supplies, video and/or sound cards, type of case
especially with respect to vents, internal cabling, more.) However, airflow
and cooling do not necessarily scale together. Merely increasing the airflow
does not necessarily do much for the cooling, for that you need heat
exchangers attached to the CPU, heat exchangers attached to another heat
exchanger don’t do much, and airflow is a square effect while heat
exchangers are a cube effect. Airflow maxed out at around +65% for two fans;
cooling maxed out at about +45%. And it took considerable effort to get that
+45%, most systems were considerably lower than that. There would be a
_reason_ why liquid cooling is popular. It’s actually simpler and easier to
do. Most modern CPUs generate a whole lot less heat than CPUs dating from
2001 did, so a good way to get a cooler-running system is toi use a newer
CPU. And to stay way from the heat-producing monsters, notably IBM Power
CPUs, which have improved no end since then but which are still devices to
convert electricity into heat, something anyone who ever went near a G5- or a
G4- powered Mac could tell you. (One G4 Mac was called the Windtunnel because
of the noise level from the fans to keep the CPU cool; one G5 Mac shipped
with liquid cooling because Apple didn’t want to ship Windtunnel Mk 2...)
IBM is up to Power 8 or 9 or some such now, where G5s were Power 5s, and
they’re much better behaved, but still...

Doubling the size of the heatsink (and also the number of fans, which won't blow towards each other) must make a considerable difference. It will be twice the cooling effect, minus the lack of conduction through the first heatsink, which I assume will conduct well, being metal and all that.

On 25 Jul 2020, Commander Kinsey wrote
(in article op.0obycr1swdg98l@glass):

On Sat, 25 Jul 2020 21:52:31 +0100, wrote:

On 25 Jul 2020, Commander Kinsey wrote
(in article op.0oboc2f2wdg98l@glass):

Has anybody ever stacked two CPU coolers? First one fitted normally, then
the
second welded on top of it. Theoretically, you have twice the cooling,

no, you won’t.

if it
conducts through the first fast enough. I'm referring to the type with the
fan on the side.

there are numerous sites out there which cover this; I first encountered
this
idea in 2001. (Yes, 2001. Not a typo. And it wasn’t a new idea then, it
was
just new to me.) It turns out that doubling the fans gives from -5%
(that’s
_negative_ five percent, it can make things worse) to +65% airflow,
depending
on numerous factors. (Size of fan, are the fans spinning in the same
direction or in opposite directions, fan speed, how fans are placed relative
to the heat exchanger, space inside the computer’s case, location of CPU
relative to sides of computer case, location of other items including hard
drives, RAM, power supplies, video and/or sound cards, type of case
especially with respect to vents, internal cabling, more.) However, airflow
and cooling do not necessarily scale together. Merely increasing the airflow
does not necessarily do much for the cooling, for that you need heat
exchangers attached to the CPU, heat exchangers attached to another heat
exchanger don’t do much, and airflow is a square effect while heat
exchangers are a cube effect. Airflow maxed out at around +65% for two fans;
cooling maxed out at about +45%. And it took considerable effort to get that
+45%, most systems were considerably lower than that. There would be a
_reason_ why liquid cooling is popular. It’s actually simpler and easier
to
do. Most modern CPUs generate a whole lot less heat than CPUs dating from
2001 did, so a good way to get a cooler-running system is toi use a newer
CPU. And to stay way from the heat-producing monsters, notably IBM Power
CPUs, which have improved no end since then but which are still devices to
convert electricity into heat, something anyone who ever went near a G5- or
a
G4- powered Mac could tell you. (One G4 Mac was called the Windtunnel
because
of the noise level from the fans to keep the CPU cool; one G5 Mac shipped
with liquid cooling because Apple didn’t want to ship Windtunnel Mk 2...)
IBM is up to Power 8 or 9 or some such now, where G5s were Power 5s, and
they’re much better behaved, but still...

Doubling the size of the heatsink (and also the number of fans, which won't
blow towards each other) must make a considerable difference. It will be
twice the cooling effect, minus the lack of conduction through the first
heatsink, which I assume will conduct well, being metal and all that.

You’re not going to get anywhere close to double the cooling. Instead of
kludging together two fans, just buy one of the properly-designed dual fan
units out there. (which don’t get twice the cooling of similar single-fan
designs from the same company, pros can’t get double the cooling either.
Not even close. Look at the specs for yourself.) Or, if you’re serious
about cooling, use liquid cooling.

What you _will_ get with a dual-fan system is twice the noise. Especially if
you use small-diameter fans.

On 25/07/2020 23:01, Wolffan wrote:
On 25 Jul 2020, Commander Kinsey wrote
(in article op.0obycr1swdg98l@glass):

On Sat, 25 Jul 2020 21:52:31 +0100, wrote:

On 25 Jul 2020, Commander Kinsey wrote
(in article op.0oboc2f2wdg98l@glass):

Has anybody ever stacked two CPU coolers? First one fitted normally, then
the
second welded on top of it. Theoretically, you have twice the cooling,

no, you won’t.

if it
conducts through the first fast enough. I'm referring to the type with the
fan on the side.

there are numerous sites out there which cover this; I first encountered
this
idea in 2001. (Yes, 2001. Not a typo. And it wasn’t a new idea then, it
was
just new to me.) It turns out that doubling the fans gives from -5%
(that’s
_negative_ five percent, it can make things worse) to +65% airflow,
depending
on numerous factors. (Size of fan, are the fans spinning in the same
direction or in opposite directions, fan speed, how fans are placed relative
to the heat exchanger, space inside the computer’s case, location of CPU
relative to sides of computer case, location of other items including hard
drives, RAM, power supplies, video and/or sound cards, type of case
especially with respect to vents, internal cabling, more.) However, airflow
and cooling do not necessarily scale together. Merely increasing the airflow
does not necessarily do much for the cooling, for that you need heat
exchangers attached to the CPU, heat exchangers attached to another heat
exchanger don’t do much, and airflow is a square effect while heat
exchangers are a cube effect. Airflow maxed out at around +65% for two fans;
cooling maxed out at about +45%. And it took considerable effort to get that
+45%, most systems were considerably lower than that. There would be a
_reason_ why liquid cooling is popular. It’s actually simpler and easier
to
do. Most modern CPUs generate a whole lot less heat than CPUs dating from
2001 did, so a good way to get a cooler-running system is toi use a newer
CPU. And to stay way from the heat-producing monsters, notably IBM Power
CPUs, which have improved no end since then but which are still devices to
convert electricity into heat, something anyone who ever went near a G5- or
a
G4- powered Mac could tell you. (One G4 Mac was called the Windtunnel
because
of the noise level from the fans to keep the CPU cool; one G5 Mac shipped
with liquid cooling because Apple didn’t want to ship Windtunnel Mk 2...)
IBM is up to Power 8 or 9 or some such now, where G5s were Power 5s, and
they’re much better behaved, but still...

Doubling the size of the heatsink (and also the number of fans, which won't
blow towards each other) must make a considerable difference. It will be
twice the cooling effect, minus the lack of conduction through the first
heatsink, which I assume will conduct well, being metal and all that.

You’re not going to get anywhere close to double the cooling. Instead of
kludging together two fans, just buy one of the properly-designed dual fan
units out there. (which don’t get twice the cooling of similar single-fan
designs from the same company, pros can’t get double the cooling either.
Not even close. Look at the specs for yourself.) Or, if you’re serious
about cooling, use liquid cooling.

What you _will_ get with a dual-fan system is twice the noise. Especially if
you use small-diameter fans.

Why are you talking down to a Computer Science graduate, Wolffan?

Apple *FAN* BOISE have no experience of such matters. :-P

You are way out of your league here.

Commander Kinsey wrote:
Has anybody ever stacked two CPU coolers? First one fitted normally,
then the second welded on top of it. Theoretically, you have twice the
cooling, if it conducts through the first fast enough. I'm referring to
the type with the fan on the side.

Call me, when your solution uses heatpipes.

Look at the Zalman completely-passive cooling
computer case, if you want to see how to do it.
It moves heat from one place to another with
heatpipes. The exterior of the case is the
final destination.

https://www.quietpc.com/tnn500af

Only with heatpipes, can you move heat from
the origin, to the second heatsink, and expect
to get improved performance.

That's why heatpipes are used, between baseplate
and top-of-fins, so that an excessively-long fin
does some work for you.

It's also why a 50mm tall 40mm square heatsink,
is no more effective than a 25mm tall 40mm square heatsink.
Those are used on chipsets. The upper portion of the
taller unit, has insufficient thermal conduction
for the top of the fins to remove heat. It means
making fins longer and longer (without heatpipes),
is asymptotic. At some point, a longer fin adds
nothing to the solution.

Once you lace the parts together with heatpipes,
then we'll talk. There's a limit to how many
heatpipes can be fitted, and some thought has to be
put into where the heatpipe is moving the heat.

You place the heatpipe at the source, as only if
the heatpipe is in intimate contact, does its 1000x
better performance, work. Just ramming a pipe into
a block with 3 inches of aluminum between the
baseplate and the pipe, that would be useless too.
As the 3 inches of aluminum is a huge thermal
resistance, and the zero resistance of the heatpipe
on top cannot then help. The heatpipes always start
in the baseplate, touching the CPU.

This is why we buy a larger heatsink, like a Noctua.
Instead of impishly welding stuff together, the
heatpipes on the properly-designed unit, have been
selected for the perfect location to get the
best effect. While the unit may be designed with
two fans, it works quite well with only the
central fan fitted.

Heatpipes have non-linear behavior. If you pump too
much heat into them, the liquid-vapor phase transfer
stops because all the materials remain in the vapor
phase. The manufacturer will usually suggest a max
power as a practical limit (before the pipes saturate
and the degree-of-cooling ends up actually reduced).
If you put six pipes in parallel, as soon as one
pipe saturates, the other five carry the load and
then they drop in quick succession.

Paul

On Sat, 25 Jul 2020 23:33:54 +0100, Paul wrote:

Commander Kinsey wrote:
Has anybody ever stacked two CPU coolers? First one fitted normally,
then the second welded on top of it. Theoretically, you have twice the
cooling, if it conducts through the first fast enough. I'm referring to
the type with the fan on the side.

Call me, when your solution uses heatpipes.

It does. Two coolers, each with their own 4 heatpipes.

Look at the Zalman completely-passive cooling
computer case, if you want to see how to do it.
It moves heat from one place to another with
heatpipes. The exterior of the case is the
final destination.

https://www.quietpc.com/tnn500af

No no and no. I once bought a "silent power supply" that threw it's heat out the back with a sticky out heatsink. It went bang after a few months.

Only with heatpipes, can you move heat from
the origin, to the second heatsink, and expect
to get improved performance.

And both the heatsinks have heatpipes running through them.

That's why heatpipes are used, between baseplate
and top-of-fins, so that an excessively-long fin
does some work for you.

It's also why a 50mm tall 40mm square heatsink,
is no more effective than a 25mm tall 40mm square heatsink.
Those are used on chipsets. The upper portion of the
taller unit, has insufficient thermal conduction
for the top of the fins to remove heat. It means
making fins longer and longer (without heatpipes),
is asymptotic. At some point, a longer fin adds
nothing to the solution.

I can't believe that, metal is a very good conductor. The top of tall ones can still be hot to touch.

Once you lace the parts together with heatpipes,
then we'll talk. There's a limit to how many
heatpipes can be fitted, and some thought has to be
put into where the heatpipe is moving the heat.

I would have 4 heatpipes running through the bottom half, and 4 through the top half. There would only be a short interface of normal metal to join the two.

You place the heatpipe at the source, as only if
the heatpipe is in intimate contact, does its 1000x
better performance, work. Just ramming a pipe into
a block with 3 inches of aluminum between the
baseplate and the pipe, that would be useless too.
As the 3 inches of aluminum is a huge thermal
resistance, and the zero resistance of the heatpipe
on top cannot then help. The heatpipes always start
in the baseplate, touching the CPU.

Doesn't have to. The top of the existing heatsink is too hot to touch. So the heatpipes on the new heatsink will take heat away from there.

This is why we buy a larger heatsink, like a Noctua.
Instead of impishly welding stuff together, the
heatpipes on the properly-designed unit, have been
selected for the perfect location to get the
best effect. While the unit may be designed with
two fans, it works quite well with only the
central fan fitted.

Heatpipes have non-linear behavior. If you pump too
much heat into them, the liquid-vapor phase transfer
stops because all the materials remain in the vapor
phase. The manufacturer will usually suggest a max
power as a practical limit (before the pipes saturate
and the degree-of-cooling ends up actually reduced).
If you put six pipes in parallel, as soon as one
pipe saturates, the other five carry the load and
then they drop in quick succession.

What temperature should the CPU be for optimal heatpipe cooling?

On 25/07/2020 23:47, Commander Kinsey wrote:
On Sat, 25 Jul 2020 23:33:54 +0100, Paul wrote:

Commander Kinsey wrote:
Has anybody ever stacked two CPU coolers? First one fitted normally,
then the second welded on top of it. Theoretically, you have twice the
cooling, if it conducts through the first fast enough. I'm referring to
the type with the fan on the side.

Call me, when your solution uses heatpipes.

It does.* Two coolers, each with their own 4 heatpipes.

SNIP FOR BREVITY ONLY

In my opinion, Commander, you are now talking to one of the most
intelligent and experienced Usenet advisers.

Be nice - and heed what he tells you! :-D

--
Surrogate dad!
Send photos please!

On Sun, 26 Jul 2020 00:17:04 +0100, David_B wrote:

On 25/07/2020 23:47, Commander Kinsey wrote:
On Sat, 25 Jul 2020 23:33:54 +0100, Paul wrote:

Commander Kinsey wrote:
Has anybody ever stacked two CPU coolers? First one fitted normally,
then the second welded on top of it. Theoretically, you have twice the
cooling, if it conducts through the first fast enough. I'm referring to
the type with the fan on the side.

Call me, when your solution uses heatpipes.

It does. Two coolers, each with their own 4 heatpipes.

SNIP FOR BREVITY ONLY

In my opinion, Commander, you are now talking to one of the most
intelligent and experienced Usenet advisers.

Be nice - and heed what he tells you! :-D

He told me to use what I was already using.

On Sat, 25 Jul 2020 23:08:09 +0100, David_B wrote:

On 25/07/2020 23:01, Wolffan wrote:
On 25 Jul 2020, Commander Kinsey wrote
(in article op.0obycr1swdg98l@glass):

On Sat, 25 Jul 2020 21:52:31 +0100, wrote:

On 25 Jul 2020, Commander Kinsey wrote
(in article op.0oboc2f2wdg98l@glass):

Has anybody ever stacked two CPU coolers? First one fitted normally, then
the
second welded on top of it. Theoretically, you have twice the cooling,

no, you won’t.

if it
conducts through the first fast enough. I'm referring to the type with the
fan on the side.

there are numerous sites out there which cover this; I first encountered
this
idea in 2001. (Yes, 2001. Not a typo. And it wasn’t a new idea then, it
was
just new to me.) It turns out that doubling the fans gives from -5%
(that’s
_negative_ five percent, it can make things worse) to +65% airflow,
depending
on numerous factors. (Size of fan, are the fans spinning in the same
direction or in opposite directions, fan speed, how fans are placed relative
to the heat exchanger, space inside the computer’s case, location of CPU
relative to sides of computer case, location of other items including hard
drives, RAM, power supplies, video and/or sound cards, type of case
especially with respect to vents, internal cabling, more.) However, airflow
and cooling do not necessarily scale together. Merely increasing the airflow
does not necessarily do much for the cooling, for that you need heat
exchangers attached to the CPU, heat exchangers attached to another heat
exchanger don’t do much, and airflow is a square effect while heat
exchangers are a cube effect. Airflow maxed out at around +65% for two fans;
cooling maxed out at about +45%. And it took considerable effort to get that
+45%, most systems were considerably lower than that. There would be a
_reason_ why liquid cooling is popular. It’s actually simpler and easier
to
do. Most modern CPUs generate a whole lot less heat than CPUs dating from
2001 did, so a good way to get a cooler-running system is toi use a newer
CPU. And to stay way from the heat-producing monsters, notably IBM Power
CPUs, which have improved no end since then but which are still devices to
convert electricity into heat, something anyone who ever went near a G5- or
a
G4- powered Mac could tell you. (One G4 Mac was called the Windtunnel
because
of the noise level from the fans to keep the CPU cool; one G5 Mac shipped
with liquid cooling because Apple didn’t want to ship Windtunnel Mk 2...)
IBM is up to Power 8 or 9 or some such now, where G5s were Power 5s, and
they’re much better behaved, but still...

Doubling the size of the heatsink (and also the number of fans, which won't
blow towards each other) must make a considerable difference. It will be
twice the cooling effect, minus the lack of conduction through the first
heatsink, which I assume will conduct well, being metal and all that..

You’re not going to get anywhere close to double the cooling. Instead of
kludging together two fans, just buy one of the properly-designed dual fan
units out there. (which don’t get twice the cooling of similar single-fan
designs from the same company, pros can’t get double the cooling either.
Not even close. Look at the specs for yourself.) Or, if you’re serious
about cooling, use liquid cooling.

What you _will_ get with a dual-fan system is twice the noise. Especially if
you use small-diameter fans.

Why are you talking down to a Computer Science graduate, Wolffan?

Apple *FAN* BOISE have no experience of such matters. :-P

You are way out of your league here.

Are you not an Apple fan (can't call you a boy at your age) yourself?

On 25 Jul 2020, David_B wrote
(in article ):

On 25/07/2020 23:01, Wolffan wrote:
On 25 Jul 2020, Commander Kinsey wrote
(in article op.0obycr1swdg98l@glass):

On Sat, 25 Jul 2020 21:52:31 +0100, wrote:

On 25 Jul 2020, Commander Kinsey wrote
(in article op.0oboc2f2wdg98l@glass):

Has anybody ever stacked two CPU coolers? First one fitted normally, then
the
second welded on top of it. Theoretically, you have twice the cooling,

no, you won’t.

if it
conducts through the first fast enough. I'm referring to the type with
the
fan on the side.

there are numerous sites out there which cover this; I first encountered
this
idea in 2001. (Yes, 2001. Not a typo. And it wasn’t a new idea then, it
was
just new to me.) It turns out that doubling the fans gives from -5%
(that’s
_negative_ five percent, it can make things worse) to +65% airflow,
depending
on numerous factors. (Size of fan, are the fans spinning in the same
direction or in opposite directions, fan speed, how fans are placed
relative
to the heat exchanger, space inside the computer’s case, location of CPU
relative to sides of computer case, location of other items including hard
drives, RAM, power supplies, video and/or sound cards, type of case
especially with respect to vents, internal cabling, more.) However,
airflow
and cooling do not necessarily scale together. Merely increasing the
airflow
does not necessarily do much for the cooling, for that you need heat
exchangers attached to the CPU, heat exchangers attached to another heat
exchanger don’t do much, and airflow is a square effect while heat
exchangers are a cube effect. Airflow maxed out at around +65% for two
fans;
cooling maxed out at about +45%. And it took considerable effort to get
that
+45%, most systems were considerably lower than that. There would be a
_reason_ why liquid cooling is popular. It’s actually simpler and easier
to
do. Most modern CPUs generate a whole lot less heat than CPUs dating from
2001 did, so a good way to get a cooler-running system is toi use a newer
CPU. And to stay way from the heat-producing monsters, notably IBM Power
CPUs, which have improved no end since then but which are still devices to
convert electricity into heat, something anyone who ever went near a G5-
or
a
G4- powered Mac could tell you. (One G4 Mac was called the Windtunnel
because
of the noise level from the fans to keep the CPU cool; one G5 Mac shipped
with liquid cooling because Apple didn’t want to ship Windtunnel Mk
2...)
IBM is up to Power 8 or 9 or some such now, where G5s were Power 5s, and
they’re much better behaved, but still...

Doubling the size of the heatsink (and also the number of fans, which won't
blow towards each other) must make a considerable difference. It will be
twice the cooling effect, minus the lack of conduction through the first
heatsink, which I assume will conduct well, being metal and all that.

You’re not going to get anywhere close to double the cooling. Instead of
kludging together two fans, just buy one of the properly-designed dual fan
units out there. (which don’t get twice the cooling of similar single-fan
designs from the same company, pros can’t get double the cooling either.
Not even close. Look at the specs for yourself.) Or, if you’re serious
about cooling, use liquid cooling.

What you _will_ get with a dual-fan system is twice the noise. Especially if
you use small-diameter fans.

Why are you talking down to a Computer Science graduate, Wolffan?

For one thing, troll-boy, I have a masters. For another, I have 40 years
experience. For a thirds, you’re a drunken idiot.



Apple *FAN* BOISE have no experience of such matters. :-P

damn, but you’re stupid. (looks at heavily moded beige G3, at even more
heavily moded Windtunnel... and at the various Windows and Linux systems...)



You are way out of your league here.

nope.

On 25 Jul 2020, Commander Kinsey wrote
(in article op.0ob3ngs7wdg98l@glass):

On Sat, 25 Jul 2020 23:08:09 +0100, wrote:

On 25/07/2020 23:01, Wolffan wrote:
On 25 Jul 2020, Commander Kinsey wrote
(in article op.0obycr1swdg98l@glass):

On Sat, 25 Jul 2020 21:52:31 +0100, wrote:

On 25 Jul 2020, Commander Kinsey wrote
(in article op.0oboc2f2wdg98l@glass):

Has anybody ever stacked two CPU coolers? First one fitted normally,
then
the
second welded on top of it. Theoretically, you have twice the cooling,

no, you won’t.

if it
conducts through the first fast enough. I'm referring to the type with
the
fan on the side.

there are numerous sites out there which cover this; I first encountered
this
idea in 2001. (Yes, 2001. Not a typo. And it wasn’t a new idea then, it
was
just new to me.) It turns out that doubling the fans gives from -5%
(that’s
_negative_ five percent, it can make things worse) to +65% airflow,
depending
on numerous factors. (Size of fan, are the fans spinning in the same
direction or in opposite directions, fan speed, how fans are placed
relative
to the heat exchanger, space inside the computer’s case, location of
CPU
relative to sides of computer case, location of other items including
hard
drives, RAM, power supplies, video and/or sound cards, type of case
especially with respect to vents, internal cabling, more.) However,
airflow
and cooling do not necessarily scale together. Merely increasing the
airflow
does not necessarily do much for the cooling, for that you need heat
exchangers attached to the CPU, heat exchangers attached to another heat
exchanger don’t do much, and airflow is a square effect while heat
exchangers are a cube effect. Airflow maxed out at around +65% for two
fans;
cooling maxed out at about +45%. And it took considerable effort to get
that
+45%, most systems were considerably lower than that. There would be a
_reason_ why liquid cooling is popular. It’s actually simpler and
easier
to
do. Most modern CPUs generate a whole lot less heat than CPUs dating from
2001 did, so a good way to get a cooler-running system is toi use a newer
CPU. And to stay way from the heat-producing monsters, notably IBM Power
CPUs, which have improved no end since then but which are still devices
to
convert electricity into heat, something anyone who ever went near a G5-
or
a
G4- powered Mac could tell you. (One G4 Mac was called the Windtunnel
because
of the noise level from the fans to keep the CPU cool; one G5 Mac shipped
with liquid cooling because Apple didn’t want to ship Windtunnel Mk
2...)
IBM is up to Power 8 or 9 or some such now, where G5s were Power 5s, and
they’re much better behaved, but still...

Doubling the size of the heatsink (and also the number of fans, which
won't
blow towards each other) must make a considerable difference. It will be
twice the cooling effect, minus the lack of conduction through the first
heatsink, which I assume will conduct well, being metal and all that.

You’re not going to get anywhere close to double the cooling. Instead of
kludging together two fans, just buy one of the properly-designed dual fan
units out there. (which don’t get twice the cooling of similar single-fan
designs from the same company, pros can’t get double the cooling either.
Not even close. Look at the specs for yourself.) Or, if you’re serious
about cooling, use liquid cooling.

What you _will_ get with a dual-fan system is twice the noise. Especially
if
you use small-diameter fans.

Why are you talking down to a Computer Science graduate, Wolffan?

Apple *FAN* BOISE have no experience of such matters. :-P

You are way out of your league here.

Are you not an Apple fan (can't call you a boy at your age) yourself?

he’s an idiot.

On 7/25/2020 2:37 PM, Commander Kinsey wrote:

Doubling the size of the heatsink (and also the number of fans, which
won't blow towards each other) must make a considerable difference.Â* It
will be twice the cooling effect, minus the lack of conduction through
the first heatsink, which I assume will conduct well, being metal and
all that.

What you know about heat sinks one could stuff in a thimble, asshole!

On 7/25/20 4:17 PM, David_B wrote:
On 25/07/2020 23:47, Commander Kinsey wrote:
On Sat, 25 Jul 2020 23:33:54 +0100, Paul wrote:

Commander Kinsey wrote:
Has anybody ever stacked two CPU coolers? First one fitted normally,
then the second welded on top of it. Theoretically, you have twice the
cooling, if it conducts through the first fast enough. I'm referring to
the type with the fan on the side.

Call me, when your solution uses heatpipes.

It does.* Two coolers, each with their own 4 heatpipes.

SNIP FOR BREVITY ONLY

In my opinion, Commander, you are now talking to one of the most
intelligent and experienced Usenet advisers.

Be nice - and heed what he tells you! :-D


I had started a reply to note that, no, you would not get twice the
cooling -- but my response would have been FAR less detailed and
knowledgeable.

--
Personal attacks from those who troll show their own insecurity. They
cannot use reason to show the message to be wrong so they try to feel
somehow superior by attacking the messenger.

They cling to their attacks and ignore the message time and time again.

On 2020-07-25 5:33 p.m., Paul wrote:
Commander Kinsey wrote:
Has anybody ever stacked two CPU coolers? First one fitted normally,
then the second welded on top of it. Theoretically, you have twice the
cooling, if it conducts through the first fast enough. I'm referring
to the type with the fan on the side.

Call me, when your solution uses heatpipes.

Look at the Zalman completely-passive cooling
computer case, if you want to see how to do it.
It moves heat from one place to another with
heatpipes. The exterior of the case is the
final destination.

https://www.quietpc.com/tnn500af

Only with heatpipes, can you move heat from
the origin, to the second heatsink, and expect
to get improved performance.

That's why heatpipes are used, between baseplate
and top-of-fins, so that an excessively-long fin
does some work for you.

It's also why a 50mm tall 40mm square heatsink,
is no more effective than a 25mm tall 40mm square heatsink.
Those are used on chipsets. The upper portion of the
taller unit, has insufficient thermal conduction
for the top of the fins to remove heat. It means
making fins longer and longer (without heatpipes),
is asymptotic. At some point, a longer fin adds
nothing to the solution.

Once you lace the parts together with heatpipes,
then we'll talk. There's a limit to how many
heatpipes can be fitted, and some thought has to be
put into where the heatpipe is moving the heat.

You place the heatpipe at the source, as only if
the heatpipe is in intimate contact, does its 1000x
better performance, work. Just ramming a pipe into
a block with 3 inches of aluminum between the
baseplate and the pipe, that would be useless too.
As the 3 inches of aluminum is a huge thermal
resistance, and the zero resistance of the heatpipe
on top cannot then help. The heatpipes always start
in the baseplate, touching the CPU.

This is why we buy a larger heatsink, like a Noctua.
Instead of impishly welding stuff together, the
heatpipes on the properly-designed unit, have been
selected for the perfect location to get the
best effect. While the unit may be designed with
two fans, it works quite well with only the
central fan fitted.

Heatpipes have non-linear behavior. If you pump too
much heat into them, the liquid-vapor phase transfer
stops because all the materials remain in the vapor
phase. The manufacturer will usually suggest a max
power as a practical limit (before the pipes saturate
and the degree-of-cooling ends up actually reduced).
If you put six pipes in parallel, as soon as one
pipe saturates, the other five carry the load and
then they drop in quick succession.

** Paul

That case sure has a lot of good engineering put into it, I can see why
it has casters, it weighs about 70 lbs, I looked around a bit but
couldn't find a price on it yet.
It will be great for audio and such purposes.

I'm not in need of one because one of the perks of old age is a much
reduced sound perception (what did you say). :-)

Rene