turbulent flow not bad for cooling

[Timothy Daniels]

Some people believe religiously in smooth laminar flow
of fluid past an object to cool that object. But turbulence
actually acts to scrub away the boundary layer of air (or
other fluid) that surrounds the object to make closer contact
between the object and the passing fluid. It is the blind
belief of many with non-technical educations that flow should
be laminar (i.e. "smooth") because fluid flows fastest and
unimpeded by the drag that turbulent flow suffers. But it is
the very nature of the contact between the flowing fluid and
an object that causes both the drag and the transfer of heat.
In other words, drag goes hand in hand with heat transfer,
and drag against a surface to be cooled is a measure of
the success one will have in cooling that surface.

Below are random FALLACIOUS arguments for laminar flow:

1) A layer composed of air does not oppose other air.
Laminar flow past a boundary layer will not leave that
boundary layer undisturbed even if #2 isn't true.

Laminar flow is by definition flow over and past a
boundary layer. If a fluid were to flow normal (i.e. in a
"perpendicular" direction) to the surface, it wouldn't
be laminar flow

2) The surface being cooled is radiating heat even without
ANY airflow, your boundary layer is no layer at all, it is
already moving air with no addt'l chassis airflow added.

Well, it's hard to argue with nonsense grammar,
but in a PC case, almost ALL the heat removed is
by forced convection, e.g. air moved by a fan, not
by radiation.

Even ON the surface being cooled, while creation of
turbulence is of benefit, it can't be done without consider-
ation of the reduction in airflow rate.

Reduction in flow rate as fluid flows across a surface
is one measure of the contact between the fluid and the
part. If the fluid does not slow down, it is because it didn't
actually contact the part.

Which ones?

Here are some interesting discussions and comments:

http://www.thermaflo.com/crosscut.shtml

"Turbulent air breaks the stagnant air boundary layers
around the pins and, as a result, enhances the heat sink's
thermal performance."

http://www.frostytech.com/articleview.cfm?articleID=2001

"To induce turbulence within the fins and improve thermal
transmission between the air and metal, Thermalright have
modified the aluminum fins by adding 'proprietary bent winglets'."

http://sound.westhost.com/heatsinks.htm

"Simple convection is not as effective (even for the same rate
of flow of air), because of the "laminar" flow of air (where the
air at the surface of the heatsink moves slower than that further
away). This effect can be easily seen on a windy day. If you stay
close to a wall or other large area (lying on the ground works too),
it will be noticed that it is less windy than out in the open. Exactly
the same thing happens with heatsinks (but on a somewhat
reduced scale). Creating turbulence is an excellent way to defeat
this process, but this requires fans, and fans are noisy."

http://www.fischerelektronik.de/fischer2002/fischer/Fachb-Act_Rep/kuehlkonzepte/KKoneng_e.htm

"The heat transfer towards the flowing air that can be achieved
with plain fins is relatively restricted. The laminar air flow that
emerges is not sufficient to carry off the heat. Therefore, attempts
are being made to improve heat transfer (fins to air) by producing
more turbulent flow using an appropriate fin geometry."

http://www.hilltech.com/products/uv_components/UV_irradiators.html

"Optimizing cooling efficiency in an LIA is achieved by using
a heatsink-based aluminum reflector, where the material has
a high thermal conductivity and the design maximizes the effects
of surface area and turbulence. Within reason, the more surface
area the better the lamp cooling. Also important is turbulence,
because of the skin effect in cooling. A thin layer of air surrounding
a cooling surface acts as a thermal insulator impeding the effect
of forced air-cooling. This layer needs to be disrupted by turbulent
airflow, which can be created by providing irregular fins and fin
geometries."

http://www.freepatentsonline.com/6729383.html

"at least some said protrusions affect said streaming of said
fluid so as to enhance the turbulence of said streaming of said
fluid, thereby enhancing convective heat transfer from said
object to said fluid."

two words: thermal gradient.
You have to get the heated air away from the part,
efficiently if you don't want a high noise:airflow ratio.

"Thermal gradient" is a measure of the change in
temperature per unit of length. The closer that a
passing fluid gets to an object of a differing temperature,
i.e. the thinner the boundary layer, the greater the gradient
in the direction normal (i.e. "perpendicular") to the surface.
That means that the more turbulence, and the resulting
thinning of the boundary layer, results in a higher temperature
gradient and a faster transfer of heat. That's what a high
temperature gradient does.

... and subsequently, not so useful to cool anything else in
the system,....

The goal of cooling an object is to transfer its heat to
something else. If the cooling fluid gets hot, it's because
it drew away heat - just what you want.

In short, the goal of PC component cooling is not to just get the
largest volume of air into and out of the case per unit time, it's
to get the largest volume of air IN CONTACT WITH THE HEATED
PARTS per unit time, the turbulent flow in the vicinity of those
parts, regardless of how that turbulence is generated, is more
important.

*TimDaniels*

 

[kony]

Some people believe religiously in smooth laminar flow
of fluid past an object to cool that object.

Oh?

Who?

I believe in reducing turbulence PRIOR to the part, and
AFTER the part. The part itself when properly designed, has
sufficient 'sinking for this and the system designer needs
only sufficient airflow rate.

But turbulence
actually acts to scrub away the boundary layer of air (or
other fluid) that surrounds the object to make closer contact
between the object and the passing fluid. It is the blind
belief of many with non-technical educations that flow should
be laminar (i.e. "smooth") because fluid flows fastest and
unimpeded by the drag that turbulent flow suffers. But it is
the very nature of the contact between the flowing fluid and
an object that causes both the drag and the transfer of heat.
In other words, drag goes hand in hand with heat transfer,
and drag against a surface to be cooled is a measure of
the success one will have in cooling that surface.

You again demonstrate that you read something, didn't test
it, and want to, but can't, apply it to your proposed
environment and cooling needs of typical parts.


Pity that Tim doesn't understand that if any of these parts
needed some extra thought on his part, it would be
mentioned, and people not taking this half-baked concept and
employing it would have overheating parts- which they do
not.

As suggested previously, the next time you read of someone
with a part overheating, suggest to them that they not try
to increase airflow, rather leaving chassis airflow alone
and only increasing turbulence prior to that hot part.

Show us even one example of someone who found relief, a cool
temp resultant from doing this. Did you think turbulence
was a SECRET? Apparently so, otherwise there would surely
be at least one example of a computer part overheating that
was brought down in temp by implementation of your
incomplete idea.

You have no evidence Tim, only a limited grasp of one
variable opposing another 3 important variables:

1) Air temp
2) Flow rate
3) Fan noise

Until you address all three and TEST THIS, you're wasting
your time.

 

[Timothy Daniels]

"kornball" continues to dodge and equivacate:

Oh?

Who?

YOU, kornball konehead.

I believe in reducing turbulence PRIOR to the part, and
AFTER the part. The part itself when properly designed,
has sufficient 'sinking for this and the system designer needs
only sufficient airflow rate.

Riiiight. The ol' cockamammy "Self-Turbulence" concept
of yours. You'd just put on a bigger and bigger and BIGGER
heatsink until - by brute size alone - enough heat would bleed
through the boundary layer to cool the part. Then you'd sit
back and say "See, all it needed was "proper design".
Meanwhile, you could've gotten the same result with a smaller
heatsink and some improved turbulence.

*TimDaniels*

 

[Timothy Daniels]

...turbulence
actually acts to scrub away the boundary layer of air (or
other fluid) that surrounds the object to make closer contact
between the object and the passing fluid.

Ignored examples of turbulence within a PC case
actually cooling a part without an increase in overall
air flow through the case is turbulence that is mechanically
produced by a fan. CPUs and Graphic Processing Units
have gotten hot enough in recent years to require a
fan to blow the air that is inside the case against the CPU's
and the GPU's heatsinks. No longer is the bulk flow across
the interior of the case enough to keep those parts cool.
But instead of drawing in more air per minute, the designers
increase the local air circulation to put more of that air into
contact with the heatsink. It is what some nutheads would
call "stale air" or "pre-heated air" that cools the CPU's and
GPU's heatsinks. It works by re-circulating the local air
against the heatsink until more of the heat has been extracted
than by a single pass of the air. This localized re-circulation
speed increase is also accompanied by increased turbulence.
Indeed, it is one form of turbulence, as there results no increase
in the bulk flow rate, just an increase in localized air movement,
as with all turbulence. That this increases the amount of calories
that the bulk air flow is able to remove per minute is a measure
of efficiency of turbulence is ignored and unseen by various
computer modders who would call themselves "designers".

*TimDaniels*

 

[kony]

"kornball" continues to dodge and equivacate:


YOU, kornball konehead.

Apparently you alreay know your thread is nothing but a
trolling attempt, else why start it if you can't accept
disagreement- because you already knew there was some and
your thread was a pathetic attempt to get someone to agree
with you, even when you still did not face facts- when
someone has a cooling problem, the advice and solution is
never "try to create more turbulence upstream of the part",
it's always "increase airflow", unless a particularly unique
problem like very high ambient temps in which case it may
call for other changes too like a better heatsink or climate
control for the room.

Riiiight. The ol' cockamammy "Self-Turbulence" concept
of yours.

Argue with th entire industry Tim, because that's how parts
are designed to be cooled.

You'd just put on a bigger and bigger and BIGGER
heatsink until - by brute size alone - enough heat would bleed
through the boundary layer to cool the part.

Clueless one, I don't decide what heatsink gets put on
products you buy at Newegg, or any other major retailer.
Independant companies make the same conclusions year after
year, and disagree with you.

Then you'd sit
back and say "See, all it needed was "proper design".

I'd say, "you're the only one that keeps trying to claim
everything is difficult and only you have a secret solution,
nevermind these systems you claim need help, work fine".

Nobody cares about your silly idea until it is demonstrated
to actually make a difference.

Silly claims without ANY examples of it making that
difference are utter stupidity.

 

[Andrew Smallshaw]

as with all turbulence. That this increases the amount of calories
that the bulk air flow is able to remove per minute is a measure
of efficiency of turbulence is ignored and unseen by various
computer modders who would call themselves "designers".

Quite right - there's an awful lot spoken about heatsinks by people
who clearly do not understand the basics - that's all I would claim
to understand, but you know something is amiss if you simply _look_
at the heatsinks sold to case modders and overclockers.

How many _shiny_, _silver_ (or copper coloured for that matter)
heatsinks have you seen, for instance? They may look very nice
but it's basic physics - the best colour is matt black. Similarly
I've seen passively cooled sinks with their fins arranged horizontally,
again a no-no for anyone who's done even the slightest study into
the things.

It's long been my suspicion that a lot of sinks sold to end users
are designed with cosmetics (simply _looking_ impressive) in mind
rather than actual efficiency.

 

[Timothy Daniels]

Argue with th entire industry Tim, because that's how parts
are designed to be cooled.

No part is designed to be cooled by laminar flow or designed
to be cooled by turbulent flow. They are merely designed to
be cooled. The system assembler has the job of choosing
cooling methods. The part designer just designs for the lowest
common denominator - YOU.

Clueless one, I don't decide what heatsink gets put on
products you buy at Newegg, or any other major retailer.
Independant companies make the same conclusions year after
year, and disagree with you.

Name some. And leave out those ridiculous hobbyist-owned
websites.

I'd say, "you're the only one that keeps trying to claim
everything is difficult...

Provide a LINK to where I said "everything is difficult" or
that I had a "secret solution".

Nobody cares about your silly idea until it is demonstrated
to actually make a difference.

I just provided lots of links to manufacturers who say that
their product or design promotes cooling by increasing
turbulence.

Silly claims without ANY examples of it making that
difference are utter stupidity.

Utter stupidity leads people such as yourself to not
read the links that I just supplied at the start of this thread.

*TimDaniels*

 

[Timothy Daniels]

Here are some interesting discussions and comments:

http://www.thermaflo.com/crosscut.shtml

"Turbulent air breaks the stagnant air boundary layers
around the pins and, as a result, enhances the heat sink's
thermal performance."

http://www.frostytech.com/articleview.cfm?articleID=2001

"To induce turbulence within the fins and improve thermal
transmission between the air and metal, Thermalright have
modified the aluminum fins by adding 'proprietary bent winglets'."

http://sound.westhost.com/heatsinks.htm

"Simple convection is not as effective (even for the same rate
of flow of air), because of the "laminar" flow of air (where the
air at the surface of the heatsink moves slower than that further
away). This effect can be easily seen on a windy day. If you stay
close to a wall or other large area (lying on the ground works too),
it will be noticed that it is less windy than out in the open. Exactly
the same thing happens with heatsinks (but on a somewhat
reduced scale). Creating turbulence is an excellent way to defeat
this process, but this requires fans, and fans are noisy."

http://www.fischerelektronik.de/fischer2002/fischer/Fachb-Act_Rep/kuehlkonzepte/KKoneng_e.htm

"The heat transfer towards the flowing air that can be achieved
with plain fins is relatively restricted. The laminar air flow that
emerges is not sufficient to carry off the heat. Therefore, attempts
are being made to improve heat transfer (fins to air) by producing
more turbulent flow using an appropriate fin geometry."

http://www.hilltech.com/products/uv_components/UV_irradiators.html

"Optimizing cooling efficiency in an LIA is achieved by using
a heatsink-based aluminum reflector, where the material has
a high thermal conductivity and the design maximizes the effects
of surface area and turbulence. Within reason, the more surface
area the better the lamp cooling. Also important is turbulence,
because of the skin effect in cooling. A thin layer of air surrounding
a cooling surface acts as a thermal insulator impeding the effect
of forced air-cooling. This layer needs to be disrupted by turbulent
airflow, which can be created by providing irregular fins and fin
geometries."

http://www.freepatentsonline.com/6729383.html

"at least some said protrusions affect said streaming of said
fluid so as to enhance the turbulence of said streaming of said
fluid, thereby enhancing convective heat transfer from said
object to said fluid."



The goal of cooling an object is to transfer its heat to something else.
If the cooling fluid gets hot, it's because it drew away heat - just what
you want.

In short, the goal of PC component cooling is not to just get the
largest volume of air into and out of the case per unit time, it's
to get the largest volume of air IN CONTACT WITH THE HEATED
PARTS per unit time, the turbulent flow in the vicinity of those
parts, regardless of how that turbulence is generated, is more
important.

*TimDaniels*

 

[kony]

No part is designed to be cooled by laminar flow or designed
to be cooled by turbulent flow.
Wrong.



They are merely designed to
be cooled.

Yes, WITH the nonsense considerations you're claiming are
needed.

However, you are the one trying to claim I'm the proponent
of "laminar airflow".

That is not what I argued. I argued for not making efforts
to increase turbulence, then you went off half-cocked like
always, trying to suggest I mean a purely, hypothetic
laminar airflow. For a moment or two I did go along with
it, within the context of it being the other alternative to
trying to change the airflow, but all the while recognizing
that it is never purely laminar, and all the while
mentioning the reasons- that creation of this turbulence
will increase noise:flow ration but more importantly,
decrease flow rate.

I do not suggest taking any measures to try and make the
airflow more laminar, either.

It would seem you need to try really HARD to screw your head
on and have intelligent discussions, because your idea of
argument is laughable.

The system assembler has the job of choosing
cooling methods. The part designer just designs for the lowest
common denominator - YOU.

Again you have a basic REQUIREMENT you have not met-

An example

Find someone, one single system that had overheating parts
and it was solved by increasing turbulence without any
additional airflow.

Again I remind you that you are only considering one
variable among many, and ignoring anything detrimental in
your idea. Show your idea works Tim, because so far as real
examples go, they all suggest otherwise.

 

[kony]

Here are some interesting discussions and comments:

Not as interesting as how clueless you have to be to get
stuck in a continual loop where you ignore every other
variable except for turbulence.

Again Tim, read this carefully:

I have never argued that turbulence ON the hot part should
be avoided.

I have argued that attempts to create turbulence before or
after the part(s) should be avoided.

You keep thinking in simpleton mode as if dwelling on
turbulence or boundary layers as abstract topics, are the
only factors. Until you accept that flow rate matters too,
you haven't any change of seeing why you are wrong.

Since it would seem you are never going to be able to
concede you hadn't considered all the variables, I'd
proposed a test, or any existing system that had already
resolved an overheating problem using your idea.

You have nothing, because you can't follow the scientific
method to test your idea. Repeating it over and over again
as an abstract idea, not applied to anything in particular,
is no proof it will help in particular cases when weighed
against other variables.

This is not rocket science Tim, how is it you can't even
fathom more than one variable?

 

[kony]

Name some. And leave out those ridiculous hobbyist-owned
websites.

Are you awake RIGHT NOW Tim?
Because if you were, I'd have thought Newegg was one.
How many do you need? It's not as though this will be hard,
everybody and their brother is an example seller of products
with heatsinks.

Provide a LINK to where I said "everything is difficult" or
that I had a "secret solution".

Tim, right now this entire argument is about your having
your head stuck so far up your ass that you can't even
accept there is no silly idea about creating turbulence
necessary to keep parts cool enough.

You are suggesting some extra thought is necessary to
address a problem that the rest of us don't have. It is
obvious that you find the things we do easily- difficult.

Your proposed solution (to the problem that doesn't exist,
LOL !!) must be a "secret", since nobody else is doing this.

Either it's a secret, or others know about turbulence and
know it doesn't help, beyond that naturally occuring on the
parts' heatsinks as a result of a normal, adequate level of
chassis airflow.

Only Tim tries to pretend he's some expert with an advanced
idea that could only be useful if he demanded there was some
problem needing addressed.

Without this supposed problem, your entirely arguement is
folly. So show us that any of this is necessary, that you
aren't just a loon backed into a corner with no excuse for
all the nonsense.

 

[Timothy Daniels]

I'd have thought Newegg was one.
How many do you need? It's not as though this will be hard,
everybody and their brother is an example seller of products
with heatsinks.

Here are some interesting discussions and comments:

http://www.thermaflo.com/crosscut.shtml

"Turbulent air breaks the stagnant air boundary layers
around the pins and, as a result, enhances the heat sink's
thermal performance."

http://www.frostytech.com/articleview.cfm?articleID=2001

"To induce turbulence within the fins and improve thermal
transmission between the air and metal, Thermalright have
modified the aluminum fins by adding 'proprietary bent winglets'."

http://sound.westhost.com/heatsinks.htm

"Simple convection is not as effective (even for the same rate
of flow of air), because of the "laminar" flow of air (where the
air at the surface of the heatsink moves slower than that further
away). This effect can be easily seen on a windy day. If you stay
close to a wall or other large area (lying on the ground works too),
it will be noticed that it is less windy than out in the open. Exactly
the same thing happens with heatsinks (but on a somewhat
reduced scale). Creating turbulence is an excellent way to defeat
this process, but this requires fans, and fans are noisy."

http://www.fischerelektronik.de/fischer2002/fischer/Fachb-Act_Rep/kuehlkonzepte/KKoneng_e.htm

"The heat transfer towards the flowing air that can be achieved
with plain fins is relatively restricted. The laminar air flow that
emerges is not sufficient to carry off the heat. Therefore, attempts
are being made to improve heat transfer (fins to air) by producing
more turbulent flow using an appropriate fin geometry."

http://www.hilltech.com/products/uv_components/UV_irradiators.html

"Optimizing cooling efficiency in an LIA is achieved by using
a heatsink-based aluminum reflector, where the material has
a high thermal conductivity and the design maximizes the effects
of surface area and turbulence. Within reason, the more surface
area the better the lamp cooling. Also important is turbulence,
because of the skin effect in cooling. A thin layer of air surrounding
a cooling surface acts as a thermal insulator impeding the effect
of forced air-cooling. This layer needs to be disrupted by turbulent
airflow, which can be created by providing irregular fins and fin
geometries."

http://www.freepatentsonline.com/6729383.html

"at least some said protrusions affect said streaming of said
fluid so as to enhance the turbulence of said streaming of said
fluid, thereby enhancing convective heat transfer from said
object to said fluid."


The goal of cooling an object is to transfer its heat to something else.
If the cooling fluid gets hot, it's because it drew away heat - just what
you want.

In short, the goal of PC component cooling is not to just get the
largest volume of air into and out of the case per unit time, it's
to get the largest volume of air IN CONTACT WITH THE HEATED
PARTS per unit time, the turbulent flow in the vicinity of those
parts, regardless of how that turbulence is generated, is more
important.

*TimDaniels*

 

[Timothy Daniels]

"kornball" tries to dance his way out:

I have argued that attempts to create turbulence before or
after the part(s) should be avoided.

You keep thinking in simpleton mode as if dwelling on
turbulence or boundary layers as abstract topics, are the
only factors. Until you accept that flow rate matters too,
you haven't any change of seeing why you are wrong.

I have never denied that flow rate played a part in
cooling by forced draft. Indeed, the higher the flow
rate, the increased likelihood of generating turbulence.
It is your ignorant advice to minimize turbulence that
misleads readers of this newsgroup.

*TimDaniels*

 

[Timothy Daniels]

"kornnball" verbiates

However, you are the one trying to claim I'm the proponent
of "laminar airflow".

That is not what I argued. I argued for not making efforts
to increase turbulence, then you went off half-cocked like
always, trying to suggest I mean a purely, hypothetic
laminar airflow. For a moment or two I did go along with
it, within the context of it being the other alternative to
trying to change the airflow, but all the while recognizing
that it is never purely laminar, and all the while
mentioning the reasons- that creation of this turbulence
will increase noise:flow ration but more importantly,
decrease flow rate.

What the hell is a "noise:flow ration"? And so what if
bulk flow rate reduces but the increased turbulence
compensates?

I do not suggest taking any measures to try and make the
airflow more laminar, either.

No, just trying to keep it laminar. That means trying to
keep it non-turbulent, konehead.

*TimDaniels*

 

[Timothy Daniels]

Here are more examples of and advice regarding
turbulence and forced draft cooling:

http://www.overclockers.com/tips90/ -

"Turbulent air cools better. Say, for sake of argument,
you have a simple tube with a fan in the middle. The fan pulls
air from one side of the tube, and blows into the other. If you
have a hot component on the exhaust side of the fan, it will
be more efficiently cooled than on the intake side.

"This is because the air on the exhaust side of the fan
is more turbulent. For lack of a better explanation, the loops
and whorls of turbulent air moving across the surface pick
up more heat. The effective surface area of the object is
increased. (Actually, it was explained to me by saying the
effective surface area of the air is increased.) The total
volume of airflow remains the same, but turbulent air just
cools better."

http://www.begellhouse.com/books/497d60632054f587,6ddfe1a32b58c789.html -

"Turbulent flow is the most common form of motion of liquids
and gases playing the role of the heat-transfer medium in thermal
systems. The complexity of turbulent flow and the importance of
hydrodynamics and heat transfer in practice inspired continuing
research for methods of efficient heat augmentation by the
Lithuanian Energy Institute. The solution of this problem was directly
linked with the determination of the reaction of flow in the boundary
layer to the effect of various factors and heat transfer rate under
given conditions. The investigated factors included elevated degree
of turbulence of the external flow as well as strong acceleration and
turbulization of flow near the wall by surface roughness. The material
in this volume shows that it is possible to control the efficiency of
turbulent transfer when the vortical structure of the turbulent flow is
known."

http://www.cougarlabs.com/cool2.html -

"For convective heat transfer to work well, we need to get the
heat energy out into the flowing coolant. Turbulence will do this
for us."

http://www.ceere.org/beep/docs/FY2002/Turbulent_Flow_in_Enclosure.pdf -

"Comparatively speaking, turbulent flows often lead to higher
transport rate of momentum, energy and mass than laminar flows.
These features are widely made use of in energy systems in industry.
For example, turbulence enhancers such as ribs are added to
cooling systems of turbine blades and microelectronic devices
to create more turbulent motions so that the overall heat transfer
efficiency can be improved."

*TimDaniels*

 

[Al Dykes]

Some people believe religiously in smooth laminar flow .....


In short, the goal of PC component cooling is not to just get the
largest volume of air into and out of the case per unit time, it's
to get the largest volume of air IN CONTACT WITH THE HEATED
PARTS per unit time, the turbulent flow in the vicinity of those
parts, regardless of how that turbulence is generated, is more
important.

*TimDaniels*

Not *you* again.

You are picking *one* aspect of the many that affectthe cooling parts
in a box. You also freely jump between the macro and micro effects.
What is optimal in one is occasionally sub-optimal in the other.

 

[Ed Medlin]

You are picking *one* aspect of the many that affectthe cooling parts

in a box. You also freely jump between the macro and micro effects.
What is optimal in one is occasionally sub-optimal in the other.

Finally..... Each layout and case is different. I built this system a year
or so ago and had problems with airflow across the CPU. It was also my first
S775 build. The CPU socket and HS are just slightly different in position
than my previous AMD and Intel boards. This case has a top "chimney" type
fan and it turned out that the turbulence from that fan (exhaust) was
causing a hot spot around the HS/Fan area of the board. By disabling the fan
I fixed the problem. I am sure there is a lot of turbulence in this box, but
also a basic laminar airflow overall. It really doesn't matter. Getting as
much outside (cooler) air to the critical components and getting as much hot
air back out is the goal. HS's by nature cause turbulence when cooling the
CPU, but as far as the case itself, it may take a bit of tweaking here and
there to get the best results, laminar airflow and/or turbulent airflow.

Ed

 

[Timothy Daniels]

"Andrew Smallshaw" observed:

It's long been my suspicion that a lot of sinks sold to end users
are designed with cosmetics (simply _looking_ impressive) in mind
rather than actual efficiency.

That's the reality of retail sales - ya gotta offer what people
will buy, and they will buy what looks "good" or what looks
"technical". A lot of these modder sites are the archtype of
retail sales, many selling cottage industry stuff and stuff that
was "designed" by a marketer, not by an engineer. How
much does it take to "design" a heatsink? Well, you call
down to your local Guongdong extrusion rep and order
some aluminum extrusions drilled with a certain pattern,
and voilà! You're a heatsink designer.

Similarly, what sounds "good", and what sounds "technical",
is "keep the cooling air flow smooth", i.e. laminar. Say that
and voilà! You're an ATX PC computer cooling expert, and
you can have a website giving modder advice, and you can
post on Usenet.

*TimDaniels*

 

[Timothy Daniels]

Each layout and case is different....
[......]
Getting as much outside (cooler) air to the critical components
and getting as much hot air back out is the goal. HS's by nature
cause turbulence when cooling the CPU, but as far as the case
itself, it may take a bit of tweaking here and there to get the best
results, laminar airflow and/or turbulent airflow.

Absolutely correct. Cool air that contacts the components per
unit time is what is important. Whether the turbulence that
promotes that is caused by design or by accident is not
important to the heated parts. And especially since each case
has its own heat generation distribution and its own hardware
combination and distribution and its own cabling arrangement,
air flow in different cases travels different routes with different
velocities at various points, and cooling requirements and
methods from one case to another can differ greatly.

As for HSes (heatsinks) causing turbulence by nature, there
are heatsinks that are *designed* to promote turbulence and
heatsinks that are *advertized* to minimize turbulence. You
can find both sold on the 'Net.

*TimDaniels*

 

[Timothy Daniels]

You are picking *one* aspect of the many that affectthe cooling parts
in a box. You also freely jump between the macro and micro effects.
What is optimal in one is occasionally sub-optimal in the other.

I am picking "*one* aspect* to write about that is often denigrated
by "experts" as being undesirable. You can read countless
"modder" sites that advise keeping the air flow "smooth" to cool
the interior parts of a computer as much as possible. I merely
point out that if a part is to be cooled by a forced flow of fluid past
and over it (such as by forced draft of air), turbulent fluid flow cools
the part better than laminar fluid flow. That it is putting the flow
past the part to be cooled that is more important than merely
getting bulk air in and out of the case is evidenced by the transition
to dedicated fans on the heatsinks of CPUs and GPUs. The
designers don't just put bigger fans or more fans on the walls of
the case to get more air-per-minute in and to get more air-per-
minute out of the case, they instead put interior re-circulating flow
fans right at the heatsink. That this causes "pre-heated" or "used"
air to re-circulate against the heatsink in secondary - what is
important is that air is brought into contact with the heatsink as
much as possible, despite that the bulk flow through the case is
unchanged. This increased air speed at the surface of the
heatsink that does not affect the bulk flow of air is a form of
turbulence. It really doesn't matter whether this turbulence is
generated an eighth of an inch or a quarter of an inch or six
inches away - it's just turbulence, and it's effect is to scrub down
through the thin boundary layer of air that surrounds all objects
to make maximum contact with the object itself. In weatherman's
terms, in increases the "chill factor".

In practical terms, I can give my Dell ATX case as an example
of a design that takes advantage of turbulence to cool. There is
volume of space at the bottom of the case in which fresh air
sweeps in the from the lower front, straight back to the lower part
of the motherboard and the expansion cards. The main hard
drive plastic cage could easily have been mounted anywhere in
that cavity, and its mounting cage could have been conveniently
attached at any number of places. But the HD is mounted vertically
with its circuit board facing the front and about !/2" from the vent
holes - despite that this impedes the incoming air. Not only
does this put the HD's circuit board in the field of maximum
turbulence caused by the vent holes stamped in the metal case,
but it causes more turbulence in the case immediately behind it.
If the designers were designing for maximum bulk air flow through
the case, they failed. If they were designing for optimal cooling,
they did quite well because in 7 1/2 yrs, I haven't had a HD (or any
other part) in the PC fail. In fact, when I touch the 7,200 rpm HD,
it feels no warmer than my body temperature.

That turbulence cools parts is evidenced in countless fields of
science and engineering. That turbulence alone can cool objects -
of course not! If that were true, there would just be fans inside
cases and the cases would be sealed shut. What I point out is
that turbulence is NOT BAD, and that turbulence is turbulence -
be it generated by friction of the flow against the part itself that
is to be cooled, or somewhere upwind of that part.

*TimDaniels*