turbulent flow not bad for cooling

[kony]

Not at all. I merely point out that turbulence, contrary to
those effete nabobs of negativism, is not bad for cooling.

Nobody claimed it was.
We have claimed you cannot ignore the detriment to airflow
and cannot assume actively trying to cause turbulence except
on, at the point of the parts' surface, will improve
cooling in a computer.

As a matter of fact, it's GOOD for cooling.

As a matter of what Tim? Sorry but FACT is what your posts
have been sorely lacking all along, because you have done no
testing.

That's not
"fixation".

Yes it is, but if you'd prefer us calling it "stuck"...

Steadfastly denying 100 years of scientific
investigation into fluid flow is fixation.

Nobody has denied anything, except that you cannot apply an
idea about turbulence to a dissimilar situation while
ignoring airflow rate changes.

 

[kony]

How did we get from talking about air at near-normal STP to talking
about the conditions inside a firing engine cylinder?

Tim likes pretending he has some advanced new insight into
common things, but as always when it comes right down to
demonstrating any benefit from his theories, he goes into
troll mode.

 

[David Maynard]

Turbulence is turbulence.
Nothing "micro" and "macro"
about it, except that they are neat terms.

Nope and you should have read it all before knee jerk replying.

You fashion your "facts" to your conclusion. The primary concern
*for YOU* is getting the most volume of air into and out of the case.
And you assume that by doing that, you are getting the maximum
amount of cooling for the heated parts.

I am not "assuming" anything. You are.

But merely running air past
a part does not bring it into close contact with the part. There is
still
the boundary layer of air around the part with which to contend.

Local turbulence is already taken care of by the part itself. Just try to
get 'laminar' flow over one. It's almost, if not, impossible.

Simply running a greater volume of air past a part is a brute force
approach to cooling. Adding turbulence to the fluid (in this case air)
that passes the heated part aids the fluid to scrub away that boundary
layer and makes the passage of fluid more efficient in carrying away
calories - if "efficiency" is measured in calories/volume of
fluid-per-second.

Simply untrue.

Your assumption that the addition of turbulence is a "waste of energy"
is presumptuous.

Just a fact.

To put it a better way, the air has to get there and be put into
close contact with the heated part in order to cool the part
efficiently. If the air has merely laminar flow, it will not
effectively
or efficiently contact the part, but merely pass by it, with the
part's boundary layer still insulating the part.

It won't have laminar flow over the part no matter how hard you try to do
it. The 'turbulence' don't need your 'help' on the other side of the case.

That is a good example of turbulence wasted to cool the wrong thing.
Clearly, the purpose of running cold air under the floor is not to cool
the underfloor cabling. Instead, the underfloor should be designed to
maximize laminar flow,

You're good up to here.

and the turbulence should be maximized as
the air approaches or enters the racks to be cooled.

Nope. Wasted energy.

"Extraneous" means "extra, unneeded".
Exactly.

So your description
is designed for your conclusion. But well-designed turbulence is
turbulence that impinges primarily the parts to be cooled.

Which isn't "6 inches" away.

You
could accomplish that by "turbulators" that induce the turbulence
at carefully selected upstream points.

Useless waste of energy.

This is a technique used
in aircraft design to control the point of stall onset in wings and
control surfaces. The slight reduction in lift or the slight increase
in drag is considered to be worth the added control predictability
for low speed handling.

We're not talking about airfoils and lift.

Similarly with PC case ventilation - the slight
increase in drag caused by turbulence generation can be offset by
the increase in cooling capacity. But if that makes you worry, you
can actively add turbulence with an internal fan - such as is currently
done to cool CPU heatsinks and GPU heatsinks, and there will be
NO increased drag due to energy used to generate that turbulence.

Hey, pal. The extra fan ain't 'free energy'. Nor is it there for 'turbulence.

But if you're willing to design for passive turbulence, you could
position
parts to minimize the increase in drag which would occur from the
passive generation of that turbulence. Since turbulence can be produced
by sharp-edged holes in flat plates, the opportunity arises to use the
inevitable turbulence

You should ponder your own words, there, "inevitable turbulence" when
looking at the physical components.

produced at the average case's air intake holes -
which are almost always just holes punched in metal sheets.

Because it's *cheap*. Try looking up the 'big boy' stuff and see what they
say about intake filter turbulence. Hint, you won't find a single one
bragging at how much it creates but, rather, how little.

There is
lots of turbulence there and downstream of it, so by putting hot
parts in
that turbulence, one could make maximum use of it before it gets
dissipated by drag from contact with other parts in the case.

You put the (hot) parts in front of it because it's cool intake air with
lots of flow before it gets dispersed into the whole case volume.

Such an opportunity occurs for cooling the main hard drive, as in my
Dell computer. The intake holes are the standard holes punched in the
face of the metal case.

Because it's *cheap*.

Since the hard drive is mounted vertically
immediately behind these holes with its circuit board facing the holes,
the hard drive gets the maximum benefit of the inevitable intake
turbulence.
Despite the considerable freedom to position the hard drive elsewhere
in the bottom of the case, the designer put it where it is and
oriented it as
he did. Elsewhere low in the case would have gotten the same amount
of fresh air flow, but turbulence would have been cut down by the air's
drag against other parts and with the case wall.

Nope. Airflow is maximum at the intake.

If you're willing
(and have
the room) to install ducting or tunnels within the case to carry
intake air
directly to regions of the case, you could postpone the turbulence prod-
uction until just upstream of a part to be cooled.

Too much drag from the ducting and tunnels. Try it and you'll find out.

The air could
then be put
through a sieve consisting of holes in a flat plate, or it could be
given a
swirl by carefully designed vanes or "dragon's teeth" as is done in
aircraft
design. By virtue of the ducting, the air would be forced against
the sieve
or turbulating vanes, and it would not just go around those
"turbulators".

More drag and wasted energy.

Except for very hot and critical parts, are ducting and "turbulators"
necessary? Quite probably not. By careful positioning and use of
heatsink fans, just "getting the air in and out" has mostly sufficed.
But should one do anything to maximize laminar flow?

You aren't going to get 'laminar flow' so stop worrying about it. What you
do is cut down on the wasted turbulence as much as possible.

Unless that
laminar flow is going only past parts that don't need cooling, NO -
leave the air turbulent. Should one maximize turbulent flow if most
of that turbulence will impinge heated parts? YES.

That's a nice "if" but nothing you've talked about will improve 'heated
parts' turbulence one bit.

Yes, I agree with that. If one were relying on passive generation
of turbulence, one would have laminar flow until just upstream of
the part to be cooled, and a resumption of laminar flow just
downstream of it. The part itself should be bathed with turbulence.
But how does one revert turbulent flow to laminar flow without just
passively relying on time and viscosity to do it? Practically, the
best one can do is to just keep other parts out of the way of the
turbulence as it comes off the heated parts. The placement of the
CPU's heatsink near the exhaust vent of the case makes that easy.
The placement of the typical GPU heatsink makes it a little harder.

You're still thinking *way* too macro. The heat of a part will, itself,
create boundary layer turbulence. You can't avoid it unless using super
high velocities that scrub past it. For 'problem' parts the designer might
include surface 'bumps', or some other mechanism, but the point is there's
nothing you have to do about it 'in the case' except get a reasonable
amount of air in and out.

Again I agree. I mention "recirculation" to describe what happens,
NOT to indicate the PURPOSE of internal fans. The purpose of
internal fans, such as those which blow air directly against the fins
of a heatsink, is to increase volume/second of the local air flow.
Right.

Both the increased speed and the increased turbulence work to
increase the amount of heat transferred from the hot part to the air
flowing past it. The increased speed increases the velocity gradient
of the boundary layer of air - "thinning it" in effect to increase the
transport of heat across that boundary layer - and the increased
turbulence helps to disrupt and cut through that boundary layer.

Look at the CFM specifications for any forced air heatsink. You will not
see a 'turbulence' factor. It is strictly CFM.

But
the fan does not increase the bulk air flow through the case. It merely
increases the local air speed - which is another way of saying that
it increases the turbulence because the air is kinetically energized
without any increase in overall translational speed. In other words,
the fan is a "turbolator". It's an active turbulator because it
receives
electrical power, but it is a turbulator nonetheless.

Nope. It's more velocity, nothing else.

By pointing out that the air is "pre-heated" or "used", I am NOT
condoning such pre-heating or use, it is to point out that the
re-circulation which occurs is INCONSEQUENTIAL to cooling.

But it isn't 'inconsequential'.

*Konehead* is the one who calls air "pre-heated" or "stagnant"
if it has contacted a heated part multiple times. Re-read the thread,
and you will see that. What I point out is that DESPITE such
"pre-heating" or pre-use or re-circulation, internal fans that blow
against heated parts (such as a heatsink fan) still aid in cooling
those parts.

They do despite the problem of it being preheated.

If by "it" you mean a fan which blows against a heatsink,
Correct.

"it's" purpose is to increase the local air flow through the
heatsink. You said that in a statement just above.

Correct. Which is 'directed airflow'.

Sorry, there are too many "its" in your sentence. Perhaps
you could restate it without the "its". As for the effects of
an internal fan, the effects are identical to turbulence - to
increase the probability of contact between each air
molecule and the heated surface.

The 'it' is your attempt to equate directed airflow to 'turbulence'.

Please explain why turbulence generated 1/8" upstream
is different in effect from turbulence generated 1/4" upstream
which is different in effect from turbulence generated 6"
upstream. Why should the turbulence care where it was
generated?

Entropy

Your '6 inch away' turbulence might as well be on the moon.

"Turbulence", as I have been using the term, is localized increase
in fluid flow without an increase in bulk fluid flow. The granularity
that I have assumed for the turbulence ranges from microscopic
to vortices measuring up to an inch in diameter.

For a 1 inch long surface, like an IC, that 1 inch diameter 'turbulence' is
dern near laminar and at the micro scale, where it matters, it's downright
gargantuan.

By "bulk", I mean
volumes on the order of one or two cubic feet. Most of the energy
of the turbulence generated at the case's air intake holes are
probably in vortices measuring 1/32" to 1/4" across.

And gone almost as soon as they pass through.

Judging by
the persistence of vortices in such things as smoke rings or
blown candle smoke,

A smoke ring is not 'turbulence'. It's the shape left after it's creation.

these vortices probably last for a few to many
seconds - long enough to traverse the interior of a PC case. Thus,
turbulence generated at the intake vent holes would persist during
the air's transit of the case.
Nope.


You apparently assume that turbulence decays during the one
to five seconds that it takes air to travel across the case from
the vent holes. Why do you believe air to be so viscous?

What makes you think they last, other than 'smoke rings'? Which, if it
really was so turbulent as you think would vanish immediately.. from the
turbulence disrupting the shape.

How "cold you feel" is a function of how much the cooling is
aided by the air speed and ambient humidity. Disregarding
humidity, the chilling effect of air speed on people is exactly
the chilling effect on inanimate objects.

If you want to muster the power to blow a hurricane through the thing then
you could afford all that turbulence you like so much.

WHY?

I've told you through this whole thing.

Read again. The hard drive's placement wasn't to "create case
turbulence" - it was to take advantage of it.

It was to take advantage of the cold air coming in where it's of maximum
velocity.

"Of importance" does NOT mean "primary importance" or
"most important". Getting air in and out is "of importance".
Correct.

So is maintaining turbulence "of importance".

But nothing you need worry about.

And striving
for laminar flow throughout the case in to be avoided.

You can't *get* laminar flow. The best you can do is reduce the wasted
turbulence.

That
is the point - turbulence is not bad for cooling. In fact, it's
good for cooling.

Yes, right at the surface. Everything else is a waste of energy.

Turbulence is not bad for cooling - that's the subject of the thread,
and that's my point.

No, your point has been that any and all turbulence, regardless of where,
is a 'good thing' and that's simply not correct.

Turbulence may reduce bulk air flow if the
turbulence is generated passively, but it increases cooling
enough to make engineers design it into their systems (see
the numerous links that I've provided).

Your links are all surface micro turbulence examples.

You don't see them
designing it OUT of their cooling or heating systems except
in long ductways where the purpose is to transport the air,
not to apply the air for heat transfer. Where the heat transfer
is to take place, they always want turbulence.

Yes, and that isn't 6 inches away nor at the intake vents.

Turbulence is good where heat transfer is to take place.

Which is the thermal surface.

Where it's generated is inconsequential to its task of heat
transfer.
Wrong.

That's because turbulence doesn't care where it
is - it works the same "here" as "there".

Then why don't you just use all that natural 'turbulence' mother nature put
in the atmosphere, since it matters not 'where'?

If all the water flows to the same fire, it doesn't matter whether
the water enters the hose from the fire hydrant next to the fire or a
block away - the water still gets to the fire. Similarly for
turbulence -
if the distance isn't great enough so that the time of transit isn't
so long that viscosity dissipates the turbulence, it doesn't matter
where the source is.

It doesn't 'all go there' in either case.

Implicit in all your objections is that turbulence
dissipates in milliseconds and that it cannot traverse a significant
portion of the case before dissipating. Everyday experience
contradicts that.

No, the point is that the turbulence of use is micro turbulence at the
surface boundary layer and that your macro 'turbulence', because it's
'turbulent' only when compared to the case volume, or the room, or the
planet, looks just like your dreaded 'laminar flow' at the micro surface level.

Tell that to those PC users who have repeatedly failing hard drives.

Not enough un preheated air flow/

If the simple placement and orientation of a hard drive can take
advantage of intake turbulence for cooling, why not use it?

I think it's a good idea. It's just that your understanding of why is
incorrect.

Why
strive for "smooth air flow" if it's detrimental?

Because it isn't.

Again, the subject of
the thread is "turbulent flow is NOT BAD for cooling".

The problem is your interpretation of it.

 

[Al Dykes]

....

Somehow I sense that Tim has no clue about when turbulence is good,
when it's bad and when it's just a big "don't care".

 

[Timothy Daniels]

Here's a little hint Tim- I've made plenty of case parts
including intakes out of sheet aluminum. You're still in
the reading is fundamental stage of learning. Sooner or
later you will have to get up, take a case, and actually DO
IT. Otherwise, even _IF_ you /were/ right, you were still
foolish to put so much time into an idea without any
fruitful outcome.

And where is the description and the results of your "tests"?
C'mon, fakeball, present 'em.

*TimDaniels*

 

[Timothy Daniels]

Nobody claimed it was.

You have said that turbulence should be minimized or reduced.

We have claimed you cannot ignore the detriment to airflow
and cannot assume actively trying to cause turbulence except
on, at the point of the parts' surface, will improve
cooling in a computer.



As a matter of what Tim? Sorry but FACT is what your posts
have been sorely lacking all along, because you have done no
testing.

As I have said, you would have us all testing for the existence
of gravity. On the other hand, there exists a plethora of clues
for even boneheads like you that turbulence helps in heat
transfer:

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."

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."

 

[Timothy Daniels]

"kornball"wrote:

Tim likes pretending he has some advanced new insight into
common things, but as always when it comes right down to
demonstrating any benefit from his theories, he goes into
troll mode.

Here's "troll mode":

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."

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*

 

[Timothy Daniels]

Nope and you should have read it all before knee jerk replying.

"Nope" is not angument, Maynard.

I am not "assuming" anything. You are.

So what's your point?

Local turbulence is already taken care of by the part itself.
Just try to get 'laminar' flow over one. It's almost, if not, impossible.

Is this your "OFF/ON" theory of turbulence? Turbulence occurs
in degrees just as laminar flow does.

Simply untrue.

Is "simply untrue" the extent of your reasoning?

Just a fact.

Is "just a fact" the extent of your reasoning?

It won't have laminar flow over the part no matter how hard you try to do it. The 'turbulence' don't need your 'help' on the other
side of the case.

If by "other side of the case" you mean "after contacting multiple
parts", the turbulence will have been reduced by drag against the
parts. If by "other side of the case" you mean "during the time of
transiting free space within the case", any turbulence generated
upstream will benefit the cooling of parts that it eventually impinges.

Nope. Wasted energy.

Is "Nope" the extent of your reasoning?

Which isn't "6 inches" away.

Transiting 6" probably takes the air one to two seconds.
So what makes you think turbulence will die out in that
period of time?

Useless waste of energy.

Is saying "useless waste of energy" the extent of your argument?

We're not talking about airfoils and lift.

Boundary layers and the effects of air flow apply universally,
especially in subsonic regimes.

Hey, pal. The extra fan ain't 'free energy'. Nor is it there for 'turbulence.

Who said turbulence was "free"? What an internal fan produces is
both turbulence and re-circulation. It does NOT increase bulk air flow.
Kornball has called re-circulated air "pre-heated" and "used" air -
which obviously isn't so bad if most PCs, especially of the gaming
variety - use internal fans.

You should ponder your own words, there, "inevitable turbulence" when looking at the physical components.

Read again. I wrote "Since turbulence can be produced by
SHARP-EDGED HOLES IN FLAT PLATES, the opportunity
arises to use the inevitable turbulence" That means that
the punched holes at the front of the case produce lots of
turbulence.

Because it's *cheap*.

And right in that turbulence, bathing in it, is where the
hard drive is put by Dell instead of other equally
available positions. It uses this "cheap" turbulence
to cool the hard drive.

Try looking up the 'big boy' stuff and see what they say about intake filter turbulence. Hint, you won't find a single one
bragging at how much it creates but, rather, how little.

Big Boy Stuff, if it's available to YOU, is for the Little Boys.

"Stuff", if it's available to YOU, will tout whatever will
impress YOU about their engineering and design prowess,
and it will not reveal any clever techniques which will
sound non-intuitive to Little Boys. Furthermore, all one
has to do is to inspect the product of the Big Boys,
and Dell, being a "Big Boy", utilizes turbulence in its
designs rather than trying to minimize it.

You put the (hot) parts in front of it because it's cool intake air with lots of flow before it gets dispersed into the whole case
volume.

"Before it gets DISPERSED into the whole case volume".
Hmmm... is that the "Little Balls" theory of air dispersal?
The intake air gets "DISPERSED"? First, it's concentrated,
then it gets "DISPERSED"? I thought you were designing
for laminar flow across the case. How would intake air get
dispersed?

Hey, I pointed out many times that there is free and direct
flow of intake air across an open cavity at the bottom of
Dell's case, and the hard drive would get the same air
anywhere in that cavity, but that some of the turbulence
would have been diminished by contact with the cavity's
walls. So Dell puts the hard drive flat against and close to
the turbulenvce generated by the passage of air through the
intake holes.

Because it's *cheap*.

First you claim that turbulence is a waste of energy, now you
say it's "cheap". Which is it?

Nope. Airflow is maximum at the intake.

And what goes in doesn't come out? <LOL>
Where does the air disappear to?
Is there an Air Destroyer in all your designs?

Too much drag from the ducting and tunnels. Try it and you'll find out.

Tell it to Apple Computers. I'm sure they're waiting to hear
from you.

More drag and wasted energy.

If you say so.

You aren't going to get 'laminar flow' so stop worrying about it. What you do is cut down on the wasted turbulence as much as
possible.

And how does one "cut down on the wasted turbulence"?
How does one even cut down on turbulence if not by drag
and viscosity - which would be a "useless waste of energy"?
You and kornball have these ideas about proper air flow
but no means to achieve what you recommend.

That's a nice "if" but nothing you've talked about will improve 'heated parts' turbulence one bit.

Put the heated parts near turbulent areas -
such as right behind vent holes instead of 2 or 3 or 4 or 6 inches
downstream. Make hot surfaces and surfaces just upstream of
them rough or undulating. (The dimples in a golf ball actually
*reduce* the drag on the golf ball by inducing turbulence). Design
heatsinks with labyrinth air passages rather than straight smooth
air paths. Install internal fans. Put small vanes in areas where
air must pass to induce a swirl. Do anything to put the air in
motion instead of calmly transiting the case.

You're still thinking *way* too macro. The heat of a part will, itself, create boundary layer turbulence. You can't avoid it
unless using super high velocities that scrub past it. For 'problem' parts the designer might include surface 'bumps', or some
other mechanism, but the point is there's nothing you have to do about it 'in the case' except get a reasonable amount of air in
and out.

The heat of a piston crown is very hot. Yet it is protected from
the heat of combustion flame by its boundary layer of unburned
gases.

Surface bumps are good for turbulence, even surface pits.
Little vanes are good, too. The problem with little vanes is
that the interior of a PC case varies considerably from one
case to another due to hardware options and cabling that
only a homebuilder can plan or implement detailed air flow.
But you guys are the homebuilders, aren't you?

As for easy ways to implement turbulence, internal fans are
easy to implement.

Look at the CFM specifications for any forced air heatsink. You
will not see a 'turbulence' factor. It is strictly CFM.

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."
In other words, the leading and trailing edges along either side
of the aluminum fins are bent 15° up and 15° down respectively."

Nope. It's more velocity, nothing else.

Velocity without any change in bulk air flow. That's what turbulence
accomplishes, and that's what fans accomplish. You get to choose,
as a designer, which device to use.

But it isn't 'inconsequential'.

What are the consequences, then?

They do despite the problem of it being preheated.

So you agree that re-circulation by fans is useful despite
the fact that no new air is being brought in to increase the
bulk air flow rate.




A fan INCREASES the rate of air flow - more cubic inches of
air per minute - without an increase in bulk air flow rate. That
implies that some of the air passes through the fan more than
once. Turbulence does the same thing to put more air molecules
in contact with a heated surface than laminar flow would. Dismiss
the commonality as "semantics" if you want, but the desirable
effect on cooling is the same. All that is different is that one takes
an active input of energy (the fan), and the other uses some of the
energy of the air flow.

Entropy

Entropy is the "randomness" of a system - which tends
to increase with time. Why does that make a difference
to where turbulence was generated? All that is important
is that the turbulence impinge the object to be cooled.

Your '6 inch away' turbulence might as well be on the moon.

AHHH! The heart of the matter - kornball's Molasses
Theory of Air Flow. You believe turbulence to be short-lived.
You believe turbulence to be a micro effect, effective only
over microscopic distances. Have you ever stirred your
coffee? Blown a smoke ring? Driven your car through
the rain? Blown out a candle? Does the turbulence disappear
immediately? You defy everyday experience!!

For a 1 inch long surface, like an IC, that 1 inch diameter 'turbulence' is dern near laminar and at the micro scale, where it
matters, it's downright gargantuan.

And that "gargantuan" swirl or eddy increases the velocity
of the air passing along the surface of the IC - thinning the
boundary layer. I can see that you belive that turbulence
is "jiggling of the molecules", whereas turbulence can actually
be planetary and galaxial in size. There is considerable study
into the boundary layer and turbulence of the plasma flow
past our planet from the sun. That is not "micro". And it's
effects are not "micro".

And gone almost as soon as they pass through.

Any pilot will tell you that vortices strong enough to upset
an aircraft can last on the order of minutes. Just blow a
smoke ring to see that. You defy everyday experience to
bolster your argument - such as it is.

A smoke ring is not 'turbulence'. It's the shape left after it's creation.

Any vortex, by definition, is not part of bulk air flow. It is
a description of translational energy BESIDE bulk air flow.
Call is a "shape", or call it increased kinetic enegy, the
effect is to bring more molecules of fluid per unit time into
contact with the surface its passing over.

Nope.

Is "Nope" the extent of your reasoning?

What makes you think they last, other than 'smoke rings'? Which, if it really was so turbulent as you think would vanish
immediately.. from the turbulence disrupting the shape.

Ask any pilot or air controller about the persistance of turbulence
and then get back to us.

If you want to muster the power to blow a hurricane through the
thing then you could afford all that turbulence you like so much.

A degree of turbulence is all around us - no hurricane is necessary.
A degree of laminar flow is all around us as well. In cooling, though,
turbulence aids bulk air flow by scrubbing down through the
boundary layer that is around all objects to bring the passing fluid
into closer contact with the underlying object.



Is "Bad assumption" the extent of your argument?

I've told you through this whole thing.

All you've been doing is making terse denials.
You haven't explained your reasoning.

It was to take advantage of the cold air coming in where it's of
maximum velocity.

And the velocity reduces further into the case? Isn't it
"Air Out = Air In"? Where does the air go in the cases
that you design?

Yes, right at the surface. Everything else is a waste of energy.

That says *nothing* about WHERE the turbulence gets
generated. It could be generated anywhere upstream
of the part to be cooled. What is important is that it
IMPINGE the part - that it GETS TO the part.

No, your point has been that any and all turbulence,
regardless of where, is a 'good thing' and that's simply not correct.

No, the turbulence must IMPINGE the part to be cooled
to have an effect on the cooling of that part. I have been
saying that consistently throughout this thread.

Your links are all surface micro turbulence examples.

Back up that claim with details from the links, please.
Tell us what you consider to be a "micro" example
and what is a "macro" situation, and then tell us why
they don't interact.

Yes, and that isn't 6 inches away nor at the intake vents.

That's to reduce contact with the walls of the ducting
and with parts not needing cooling. Otherwise, the
turbulence could be generated anywhere.

Which is the thermal surface.


Wrong.

Is "Wrong" the extent of your argument?

Then why don't you just use all that natural 'turbulence'
mother nature put in the atmosphere, since it matters not 'where'?

Because the ducting would be too large.

No, the point is that the turbulence of use is micro turbulence at the surface boundary layer and that your macro 'turbulence',
because it's 'turbulent' only when compared to the case volume, or the room, or the planet, looks just like your dreaded 'laminar
flow' at the micro surface level.

Any velocity of a passing fluid helps to thin the boundary layer.
That velocity may be that of the bulk fluid flow, or it may be
the bulk fluid flow PLUS that of any turbulence. The action of
the two is better for cooling.

Not enough un preheated air flow/

What makes you think the air they got was "pre-heated"?

I think it's a good idea. It's just that your understanding of why is incorrect.

What is "incorrect" about my understanding?

Because it isn't.

"Smooth air flow" doesn't have turbulence, and you've
admitted turbulence was good for cooling.

The problem is your interpretation of it.

Interpretation of what? Could you be more specific?
What is to be "interpreted", and how have I done
that incorrectly?

*TimDaniels*

 

[kony]

And where is the description and the results of your "tests"?
C'mon, fakeball, present 'em.

*TimDaniels*

What good would it do at this point? Ever since you were
backed into a corner you have merely trolled and repeatedly
linked non-applicable scenarios.

It is obvious you have excuses for everything, so the only
valid test you can't dispute is the one you propose. Since
you seemingly won't accept anyone else doing it, that makes
you the tester.

Without the testing, you are just another loon with a
half-baked idea.

 

[kony]

You have said that turbulence should be minimized or reduced.

Yes, before or after the hot part, never did I claim ON the
part.

 

[kony]

"kornball"wrote:

Here's "troll mode"

Tim you don't have to announce Troll mode, with you it's
implied already.

Did it not occur to you that an applicable demonstration is
of what you are proposing, not of some other thing that
merely has turbulence as a variable?

 

[David Maynard]

Interpretation of what? Could you be more specific?
What is to be "interpreted", and how have I done
that incorrectly?

I've already explained it and I'm not going to go around in circles with
you. Boundary layer turbulence is dealt with at the component level and at
the case level the primary concern is minimizing flow restriction, not
creating 'turbulence' because, to repeat, that's dealt with at the
component level. Either learn it or cling to whatever amuses you.

 

[Timothy Daniels]

"David Maynard" backed down:

I've already explained it and I'm not going to go around in circles
with you.

All you've done is issue terse denials with no substantiating
reasoning or evidence. "Nope" and "you haven't a clue"
don't qualify as reasoning.

It's clear to me that you confuse "turbulence" with "boundary
layer turbulence", and since you think all boundary layers are
microscopic, you believe all turbulence is microscopic.

In fact, boundary layers can be quite large. On an airplane
wing, the boundary layer can be thicker than the cross-section
of the wing. The boundary layer in the plasma streaming from
the sun past Earth can be many times larger the planet. It is
your confused concept of a boundary layer which has blocked
your understanding of turbulence.

Boundary layer turbulence is dealt with at the component level

Why? You still haven't said why.
And who does this "dealing"? Passive Voice is poor reporting,
Maynard. Put it into the Active Voice. WHO deals with boundary
layer turbulence, and HOW and WHAT does he/she do?

and at the case level the primary concern is minimizing flow restriction,
not creating 'turbulence' because, to repeat, that's dealt with at the
component level.

WHOSE "primary concern"? Who is this smart guy and why
does he do what you claim he does? Who is this guy? Is he
just some "expert" that you made up?

To say "the primary concern is minimizing flow restriction" is
to beg the question about WHY the primary concern is to be
minimizing flow restriction. Obviously, you have been taking
this as a given all your life, and it hasn't occurred to you that
it might not be true. Think about WHY you believe such a
thing.

*TimDaniels*

 

[kony]

"David Maynard" backed down:

All you've done is issue terse denials with no substantiating
reasoning or evidence.

LOL

Tim tersely denies millions of ATX systems cooled fine
without any thought towards creating additional turbulence,
no substantiated reasoning why they aren't overheating.

Test, Tim. Get a working and reproducible model as proof.
That's called evidence.

 

[Timothy Daniels]

"kornball" tries to change the subject:

LOL

Tim tersely denies millions of ATX systems cooled fine

Please point out where I denied that millions of ATX
systems "cooled fine". I would add, though, that
millions of ATX systems could cool better if modders
didn't strive to reduce turbulence.

*TimDaniels*

 

[kony]

"kornball" tries to change the subject:


Please point out where I denied that millions of ATX
systems "cooled fine".

You suggested evidence contradicted by millions of ATX
systems without cooling problems. Several times. I'm not
going to link every single time, that'd take forever. Did
you ever learn how to use a newsreader so you can look back
through your posts?

I would add, though, that
millions of ATX systems could cool better if modders
didn't strive to reduce turbulence.

You can spew anything you want, because you're 100% FOS.

 

[David Maynard]

"David Maynard" backed down:



All you've done is issue terse denials with no substantiating
reasoning or evidence.

I went in great detail in the FIRST post and the second was only in
response to you repeating the same nonsense over and over again while
ignoring what was written. Which is why I'm not going to do it again, and
again, and again, and again.

<snip>

 

[Timothy Daniels]

I went in great detail in the FIRST post and the second was only in
response to you repeating the same nonsense over and over again while
ignoring what was written. Which is why I'm not going to do it again, and
again, and again, and again.

<snip>

I would like to understand your reasoning, Dave, if only
as a forensic exercise. But you really haven't presented
any of it.

*TimDaniels*

 

[Timothy Daniels]

"kornball" gets lamer by the minute:

You suggested evidence contradicted by millions of ATX
systems without cooling problems. Several times. I'm not
going to link every single time, that'd take forever. Did
you ever learn how to use a newsreader so you can look back
through your posts?

<LOL> You can't use a news reader to prove your claim
because your claim is false.

*TimDaniels*

 

[kony]

"kornball" gets lamer by the minute:


<LOL> You can't use a news reader to prove your claim
because your claim is false.

*TimDaniels*

I'm not the one who made the claim Tim, I only wrote
"millions" (and the rest) after you had already made a claim
you couldn't back up.