Turbulence-producing vent holes - Dell and an experiment

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Both Dell and an experminter have apparently found that
vent holes in a flat plate, such as at the front of an
electronic enclosure (i.e. PC case) produce turbulence
in the entering air. This turbulence can be used to aid
in bringing the air that flows through the case into better
contact with the surfaces of warm component inside the
case.


DELL SERVERS

Take a look at the Dell PowerEdge servers:

<http://www1.us.dell.com/content/products/productdetails.aspx/pedge_400sc?c=us&c
s=04&l=en&s=bsd&~tab=viewstab>

<http://www1.us.dell.com/content/products/productdetails.aspx/pedge_1600sc?c=us&
cs=04&l=en&s=bsd&~tab=viewstab>

If you prefer .pdf files and shorter links, here they are again:

<http://www.dell.com/downloads/global/products/pedge/en/400sc_specs.pdf>
<http://www.dell.com/downloads/global/products/pedge/en/1600sc_specs.pdf>


Those bezels (fascias) are plastic. Those circular vent holes weren't put
there
to maximize flow - there would be a smooth intake ramp for the air if minimal
air resistance were the goal. Those circular vent holes weren't sized to
minimize
escaping Electromagnetic Interference (EMI) because the bezels are *plastic*
and any EMI would go right through them regardless of the size or shape of the
holes. Those circular vent holes are there to maximize TURBULENCE of the
air entering the case.

Why don't all of Dell's desktop computers have a bank of circular vent
holes in their bezels? Because the turbulence emits white sound, i.e. noise.
Noise is more expected and tolerable coming from a server (which can be
in a dedicated closet) rather than from a workstation sitting on one's
work desk.


AN EXPERIMENTER'S EXPERIENCE

But what evidence is there at all that the turbulence produced by circuler
vent holes in a flat plate aid in cooling? How about this:

http://www.benchtest.com/way2cool3.html

In the above project, the author notices that with the front bezel off and
a box obstructing the front intake fan, the temperatures inside the case drop.
He later finds that 1/4" holes drilled on the edges of the bezel cause the
temperatures inside the case to be one-to-two degrees lower with the bezel
on than with bezel off!

The author has no clear idea why "obstructing" the air intake would lower
temperatures, but could it be turbulence? With the box, the air velocity is
increased parallel to the face of the chassis, forcing it to make a sharp right
angle turn as it enters the fan. With the holes drilled in the bezel, more
turbulence is generated in the incoming air than with no bezel in place. It
seems pretty clear that this author has discovered exactly what Dell and some
heatsink manufacturers have discovered - that turbulent air cools better than
smoothly flowing air.

*TimDaniels*

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Timothy Daniels wrote:

> Both Dell and an experminter have apparently found that
> vent holes in a flat plate, such as at the front of an
> electronic enclosure (i.e. PC case) produce turbulence
> in the entering air. This turbulence can be used to aid
> in bringing the air that flows through the case into better
> contact with the surfaces of warm component inside the
> case.
>
>
> DELL SERVERS
>
> Take a look at the Dell PowerEdge servers:
>
> <http://www1.us.dell.com/content/products/productdetails.aspx/pedge_400sc?c=us&c
> s=04&l=en&s=bsd&~tab=viewstab>
>
> <http://www1.us.dell.com/content/products/productdetails.aspx/pedge_1600sc?c=us&
> cs=04&l=en&s=bsd&~tab=viewstab>
>
> If you prefer .pdf files and shorter links, here they are again:
>
> <http://www.dell.com/downloads/global/products/pedge/en/400sc_specs.pdf>
> <http://www.dell.com/downloads/global/products/pedge/en/1600sc_specs.pdf>
>
>
> Those bezels (fascias) are plastic. Those circular vent holes weren't put
> there
> to maximize flow

Really? You figure no holes would "maximize flow?"

> - there would be a smooth intake ramp for the air if minimal
> air resistance were the goal.

As I've tried to explain to you, no design has 'one goal'. There are many
'goals' and tradeoffs.

The holes are sized for the amount of airflow the case is designed for, and
that is all that's needed (note that your 'experimenter' below is aware of
that hole 'total area' determination).

> Those circular vent holes weren't sized to
> minimize
> escaping Electromagnetic Interference (EMI) because the bezels are *plastic*
> and any EMI would go right through them regardless of the size or shape of the
> holes.

Correct. They're there to keep fingers out and look pretty without undue
cost. And it appears to me they met both 'goals'. Looks neato, don't ya think?

> Those circular vent holes are there to maximize TURBULENCE of the
> air entering the case.

There is absolutely NOTHING to support that claim. It is simply your
prejudice to see 'holes' and go "ah hah!"

>
> Why don't all of Dell's desktop computers have a bank of circular vent
> holes in their bezels? Because the turbulence emits white sound, i.e. noise.
> Noise is more expected and tolerable coming from a server (which can be
> in a dedicated closet) rather than from a workstation sitting on one's
> work desk.

That might be why fewer holes, and a downward/side entry, are used on home
cases rather than a LOT of BIG holes on the FRONT of the server to allow
more airflow.

There is, however, absolutely nothing to support your theory other than
your single minded myopic desire to attribute the 'purpose' of 'turbulence'
to any hole or case feature you run across.


> AN EXPERIMENTER'S EXPERIENCE
>
> But what evidence is there at all that the turbulence produced by circuler
> vent holes in a flat plate aid in cooling? How about this:
>
> http://www.benchtest.com/way2cool3.html
>
> In the above project, the author notices that with the front bezel off and
> a box obstructing the front intake fan, the temperatures inside the case drop.

True

> He later finds that 1/4" holes drilled on the edges of the bezel cause the
> temperatures inside the case to be one-to-two degrees lower with the bezel
> on than with bezel off!

Not so. He never achieved a temperature lower with the bezel on, regardless
of the drilled holes, than with the bezel off. And I quote "To make a long
story short, I have not been able to get the case temperature to drop below
what it is with no cover installed in all situations."


> The author has no clear idea why "obstructing" the air intake would lower
> temperatures, but could it be turbulence?

Hardly, and, interestingly enough, you ignore HIS theory that it was LESS
turbulence.

> With the box, the air velocity is
> increased parallel to the face of the chassis, forcing it to make a sharp right
> angle turn as it enters the fan.

Whatever 'attributes' the air had entering the fan becomes pretty much moot
after it's been beat to hell and back by the fan blades.

> With the holes drilled in the bezel,

He got more airflow as the holes originally in the bezel were minimal and
insufficient for the fan he hacked into the case.

> more
> turbulence is generated in the incoming air than with no bezel in place.

He never achieved the same results with the bezel holes. Which, again, are
pretty much moot for the intake fan 'turbulence' as it's beat to hell and
back by the fan blades.

> It
> seems pretty clear that this author has discovered exactly what Dell and some
> heatsink manufacturers have discovered - that turbulent air cools better than
> smoothly flowing air.

No, what's clear is you'll attribute ANY thing to turbulence without even
considering any other explanation.

Unfortunately, he doesn't provide enough pictures to know what the entire
case looks like, however, as serendipity would have it, I just happen to
possess that exact same case (found abandoned). It will hold a 'full sized'
ATX motherboard and a side mounted PSU, as you can see from the picture
with his top "squirrel cage" fan. The case itself is littered with holes:
front bottom vent holes that conform to no fan pattern (typical case
problem that allows the fan intake to circular steal air from inside the
case), rear vents across the side of the card slot covers, vent holes
'above' the motherboard adjacent to the PSU (where he stuck the rear
exhausting squirrel cage fan), holes in every front panel opening cover
plate (the knockouts), and vent holes across the entire bottom of the left
side metal case cover. It is, therefore, extremely problematic to talk
about case airflow patterns as air can literally come and go from damn near
anywhere.

Nevertheless, one possible explanation for his observed temperature
'anomaly' is that, with the front fan (as he put it) 'pressurizing' the
entire case, no mean feat with all those holes, it's short circuiting the
PSU to that air rather than letting it draw from the motherboard area where
the 'case' sensor is usually located. Lower the inlet airflow and the PSU
then draws air more locally, as it was intended, and that cools the
motherboard mounted sensor better.

Or the 'pressurized' case causes warmer heatsink air, already blowing
downward, to transverse over the motherboard directly to the rear case
vents 'right there' rather than being pulled 'upward' into the PSU.

Or a combination of the two (likely), or some other alteration of the
airflow pattern.

There is, however, no evidence whatsoever to justify attributing it to
'intake hole turbulence'.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Wed, 14 Jul 2004 13:49:07 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:

>Both Dell and an experminter have apparently found that
>vent holes in a flat plate, such as at the front of an
>electronic enclosure (i.e. PC case) produce turbulence
>in the entering air. This turbulence can be used to aid
>in bringing the air that flows through the case into better
>contact with the surfaces of warm component inside the
>case.

LOL, it was "this year's" design. They change the fronts over
and over again, next time it won't have the holes. <- Mark my
words.


> Those bezels (fascias) are plastic. Those circular vent holes weren't put
>there
>to maximize flow

You are assuming this based only upon your prior assumption,
without even bothering to test. A house of cards built on
quicksand.


> - there would be a smooth intake ramp for the air if minimal
>air resistance were the goal. Those circular vent holes weren't sized to
>minimize
>escaping Electromagnetic Interference (EMI) because the bezels are *plastic*
>and any EMI would go right through them regardless of the size or shape of the
>holes. Those circular vent holes are there to maximize TURBULENCE of the
>air entering the case.

Nice try but no cigar. If they were meant to increase turbulence
they'd have sharp edges as you already, previously argued was the
intentional design of the stamped-metal holes... you can't have
it both ways.


> Why don't all of Dell's desktop computers have a bank of circular vent
>holes in their bezels? Because the turbulence emits white sound, i.e. noise.
>Noise is more expected and tolerable coming from a server (which can be
>in a dedicated closet) rather than from a workstation sitting on one's
>work desk.

Actually the white noise from the holes is trivial compared to
any other part of system, mainly because the amount of turbulence
is also trivial. If you've ever heard one of those (have you?)
you'll realize that the vast majority of noise is due to higher
flow rate, RPM, of the rear exhaust fan.


>AN EXPERIMENTER'S EXPERIENCE
>
> But what evidence is there at all that the turbulence produced by circuler
>vent holes in a flat plate aid in cooling? How about this:
>
> http://www.benchtest.com/way2cool3.html
>
> In the above project, the author notices that with the front bezel off and
>a box obstructing the front intake fan, the temperatures inside the case drop.
>He later finds that 1/4" holes drilled on the edges of the bezel cause the
>temperatures inside the case to be one-to-two degrees lower with the bezel
>on than with bezel off!


The clueless author also shows how he reversed a fan on a power
supply that already had the fan pointed the correct direction to
exhaust. At first I though he was just inexperienced, but that
incredible blunder pretty well clarifies the whole situation.

>
> The author has no clear idea why "obstructing" the air intake would lower
>temperatures, but could it be turbulence?

It could be because his attempts at "improving" things created
anything but an efficient cooling. Hell, if he can't manage to
cool a K6 @ 290MHz with a single fan he's in really bad shape
these days.


>With the box, the air velocity is
>increased parallel to the face of the chassis, forcing it to make a sharp right
>angle turn as it enters the fan. With the holes drilled in the bezel, more
>turbulence is generated in the incoming air than with no bezel in place. It
>seems pretty clear that this author has discovered exactly what Dell and some
>heatsink manufacturers have discovered - that turbulent air cools better than
>smoothly flowing air.
>
>*TimDaniels*

So let's summarize what the auther did:

1) Toyed around with a fan cage marveling over it instead of
just ripping out the cage like everyone else does if they don't
need it for full-legth card support.

2) Took power supplies with correct fan orientation and put fans
in backwards. (Yes, I am aware that original ATX spec called for
fan intake on PSU instead of exhaust, but not on that PSU, which
can also be seen in the picture).

3) Installed AC fan with ludicrous noise level to cool basic
~290MHz system. Today's systems at over 8X the speed don't need
to be that loud. The following quote is a pretty good indicator
of the skill involved:

"I ended up attaching the fan directly to the grill, which is no
more than an array of holes punched in the case's metal frame.
This allowed the fan to draw only outside air and not recirculate
the warm air in the case. A good solution, I thought. The only
drawback I could see to this setup was that the metal fan housing
against the metal case frame tended to transmit a fair amount of
noise."

So already we can see that author has incredibly poor grasp of
case cooling, but soon thereafter we witness two distinct
blunders within the same sentence:

"At this point I wasn't sure that this was exactly what I wanted,
thinking a "free flowing" air exchange (where the case exhausted
as much air as it took in) would allow for more air to be
replaced in the case in the same period of time. "

A) It was exactly what he _should_ have wanted, a pressurized
case.

B) If case did not exhaust as much air as it took in, it would
explode. I suppose he was too inexperienced to realize that
having exactly equal (or trying to attain that) intake and
exhaust rate from the two fans could only be a negative thing,
creating dead-spots in the case.

C) The attitude that the front fan was a "problem" in itself due
to higher flow rate, rather than recognizing that his exhaust fan
wasn't effective and was the point needing addressed.

Now let's pause for a moment and consider that there was no
mention of how case temp was obtained (or did I overlook it?).
Author wrote:

"The oversized holes added to the openings already created by
removing the drive blanks... First, it is possible that the fan
is intaking too much air and bypassing the "chimney" between the
drives in the front of the box and the cards in the rear of the
box.... It is also where the case temperature sensor resides. By
partially blocking the fan, I could be slowing down the air flow
enough to allow it to travel up the chimney. "


Reread that if necessary, so that you realize the extent of it.
When the air intake (of external air) was reduced, the fan is
pulling (recirculating) more air though the chamber created by
the front bezel, though the area previously blocked by the
blanks. This isn't turbulence at work, nor the direct effect of
a change in flow rate, but a significant deviation in flow
concentration. Air wasn't traveling UP the chimney, as he
already mentioned the case had positive pressure so air was
traveling DOWN the chimney, and past that case temp sensor.

In other words, author had poor exhaust, heated air wasn't being
effectively removed from heatsink area, so this alternate air
path was moving heated air away from heatsink and case sensor.
The sad part is that most likely all the author needed was to
cutout the PS rear grill, remove front fan, and cut a slot along
the bottom edge of the plastic bezel... would be MUCH quieter,
look less ghetto, and avoid putting AC devices into the chassis
beyond PSU itself.

Summary - Turbulence didn't help, reducing the intake rate enough
that the front fan pulled more air from the top half of the bezel
down to the bottom again, did. Considering the modest
performance, heat generation of that system the result wasn't too
good, particularly considering the additional noise generated by
the two added fans.

Franly I'm amazed that you thought that article was an example of
intake holes helping, because the trivial amount of turbulence
created by the holes is both eliminated and greatly eclipsed by
the turbulence the fan creates when it pushes the air into the
chassis.

 

[Apollo]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Timothy Daniels <TDaniels@NoSpamDot.com> wrote:

What a load of bullshit, you a troll???

PLONK

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

"David Maynard" wrote:

> Correct. They're there to keep fingers out and look pretty
> without undue cost.


But those holes are big enough to *let* fingers and pencils
get in. - which dispenses with your theory that the bezel's
purpose is to keep such things out.


> Whatever 'attributes' the air had entering the fan becomes pretty much moot
> after it's been beat to hell and back by the fan blades.


You assume that the fan would somehow break up and
eliminate any turbulence that passed through it, which is
incorrect. Turbulence having dimensions smaller that the
opening of the fan and its blades would merely be swept
in along like bubbles of air - unimpeded and unaffected
by the fan.






>
> > With the holes drilled in the bezel,
>
> He got more airflow as the holes originally in the bezel were minimal and
> insufficient for the fan he hacked into the case.


You ignore the fact that he saw a higher temperature with the
bezel OFF.

The fact of the matter is that the author performed an experiment,
and the results suggest that turbulence caused by the non-
aerodynamically shaped intake holes lowered the temperature
at instrumented points inside the case. That is not enough to
convince you that turbulence had anything to do with it because
that is not enough to convince you. But that is not reason to
*disbelieve* that turbulence had something to do with it.

*TimDaniels*

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

I've cut huge chucks out if this message to make it more readable.

In article <k5idnZKrWtAKV2vd4p2dnA@comcast.com>,
Timothy Daniels <TDaniels@NoSpamDot.com> wrote:
>"kony" wrote:
>>
>> LOL, it was "this year's" design. They change the fronts over
>> and over again, next time it won't have the holes. <- Mark my
>> words.
>
> "Next year's designs" will probably have fans to force more
> air through the holes to create even *more* turbulence.
>
>> > Those bezels (fascias) are plastic. Those circular vent holes
>> > weren't put there to maximize flow
>>
>> You are assuming this based only upon your prior assumption,
>> without even bothering to test. A house of cards built on
>> quicksand.
>
>
> Any aerodynamicist can tell you that fluid flow through
> and aperture in a flat (or nearly flat) plate will produce
> turbulence. Even the car and motorcycle hotrodders
> know that. That is the reason for the "horn" shaped
> air intakes on engines.
>

Turbulance at the intakes is irrelivant, or a microcopic
downside to the extend that it increases backpreasure
or makes noice.


>
> Aerodynamically, those holes *are* sharply edged. Do you see
> any attempt at all to curve the edges?
>

Irrelivant. Manufacturing costs rule.


>
> Again, the author's success at cooling is irrelevant. His
> experiment is the important thing, and it shows a situation
> where what could be expected to increase temperature
> by "obstruction" of the air actually DECREASED the
> temperature by increasing the turbulence of the incoming
> air.
>
>

I say the case mods directed more air volume to the location
of the heat sensor. The turbulance of the air volume is
irrelavent.

--
Al Dykes
-----------
adykes at p a n i x . c o m

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

"Al Dykes" wrote:
> Turbulance at the intakes is irrelivant, or a microcopic
> downside to the extend that it increases backpreasure
> or makes noice.
>
>
> Irrelivant. Manufacturing costs rule.
>
>
>
> I say the case mods directed more air volume to the location
> of the heat sensor. The turbulance of the air volume is
> irrelavent.


Have you anything to back up your simple denials?

*TimDaniels*

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

In article <P9SdndkumqyGU2vdRVn-gg@comcast.com>,
Timothy Daniels <TDaniels@NoSpamDot.com> wrote:
>"David Maynard" wrote:
>
>> Correct. They're there to keep fingers out and look pretty
>> without undue cost.
>
>
> But those holes are big enough to *let* fingers and pencils
> get in. - which dispenses with your theory that the bezel's
> purpose is to keep such things out.
>
>
>> Whatever 'attributes' the air had entering the fan becomes pretty much moot
>> after it's been beat to hell and back by the fan blades.
>
>
> You assume that the fan would somehow break up and
> eliminate any turbulence that passed through it, which is
> incorrect. Turbulence having dimensions smaller that the
> opening of the fan and its blades would merely be swept
> in along like bubbles of air - unimpeded and unaffected
> by the fan.
>

You're in over your depth again,


--
Al Dykes
-----------
adykes at p a n i x . c o m

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

"Al Dykes" wrote:
> You're in over your depth again,


Then SAAAAVE me, oh exalted one!

*TimDaniels*

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Timothy Daniels wrote:

> "David Maynard" wrote:
>
>
>>Correct. They're there to keep fingers out and look pretty
>>without undue cost.
>
>
>
> But those holes are big enough to *let* fingers and pencils
> get in. - which dispenses with your theory that the bezel's
> purpose is to keep such things out.

And they line up with holes in the metal case?

Which, of course, still leaves pretty.

Frankly, it doesn't matter because your logic is inherently flawed to begin
with.


>>Whatever 'attributes' the air had entering the fan becomes pretty much moot
>>after it's been beat to hell and back by the fan blades.
>
> You assume that the fan would somehow break up and
> eliminate any turbulence that passed through it, which is
> incorrect. Turbulence having dimensions smaller that the
> opening of the fan and its blades would merely be swept
> in along like bubbles of air - unimpeded and unaffected
> by the fan.
>

I 'assume' nothing. I take from the established literature on the matter.
It is YOU who 'assume' that any hole on the planet must have been put there
for the purpose you imagine.

>
>>> With the holes drilled in the bezel,
>>
>>He got more airflow as the holes originally in the bezel were minimal and
>>insufficient for the fan he hacked into the case.
>
> You ignore the fact that he saw a higher temperature with the
> bezel OFF.

That is not true and I even quoted his summary of it that states so.

>
> The fact of the matter is that the author performed an experiment,
> and the results suggest that turbulence caused by the non-
> aerodynamically shaped intake holes lowered the temperature
> at instrumented points inside the case. That is not enough to
> convince you that turbulence had anything to do with it because
> that is not enough to convince you. But that is not reason to
> *disbelieve* that turbulence had something to do with it.

No, the fact of the matter is that you ignore any possible explanation, of
which I gave you two, other than the one you had chosen even before you
found the article and are doing precisely what you accuse others of.

>
> *TimDaniels*

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

kony wrote:

> On Thu, 15 Jul 2004 11:19:06 -0700, "Timothy Daniels"
> <TDaniels@NoSpamDot.com> wrote:
>
>
>>"kony" wrote:
>>
>>>LOL, it was "this year's" design. They change the fronts over
>>>and over again, next time it won't have the holes. <- Mark my
>>>words.

The 'dispute' over these 'holes' is as much a matter of flawed logic as it
is supposed 'science'.

He's looking at 'holes' after the fact, noting they appear to be consistent
with his 'theory' (not difficult in this case since darn near 'anything'
qualifies), and then claiming that MUST be the reason for them.

It simply doesn't follow. He'd have to prove there is NO OTHER reason they
could have been made that way in order for their existence to have any
'support' for his theory.

And note, that demanding someone else provide an alternate explanation, and
then contending that proves his theory if they can't, is the 'From
Ignorance" fallacy. Ignorance is not a proof of anything, other than the
person doesn't know, as exemplified in my Fire Breathing Dragon example:

Well, if a fire breathing dragon didn't kill poor old Fred, then what do
you say did? Huh? Huh? Huh?

Don't know.

Well, that PROVES it was a fire breathing dragon.
(obviously not)

Being able to provide a viable alternate DOES, however, positively destroy
the original 'it must be' contention. (Poor old Fred's fireplace, which
I've never seen him clean, may have flared, setting himself and the house
on fire.

<snip>

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Thu, 15 Jul 2004 13:17:05 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:

>"Al Dykes" wrote:
>> Turbulance at the intakes is irrelivant, or a microcopic
>> downside to the extend that it increases backpreasure
>> or makes noice.
>>
>>
>> Irrelivant. Manufacturing costs rule.
>>
>>
>>
>> I say the case mods directed more air volume to the location
>> of the heat sensor. The turbulance of the air volume is
>> irrelavent.
>
>
> Have you anything to back up your simple denials?

How about science?

Never heard of science have you?
It involves doing tests, not just citing examples that do not
isolate the variable you're looking to prove with the example.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Thu, 15 Jul 2004 13:17:05 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:

>"Al Dykes" wrote:
>> Turbulance at the intakes is irrelivant, or a microcopic
>> downside to the extend that it increases backpreasure
>> or makes noice.
>>
>>
>> Irrelivant. Manufacturing costs rule.
>>
>>
>>
>> I say the case mods directed more air volume to the location
>> of the heat sensor. The turbulance of the air volume is
>> irrelavent.
>
>
> Have you anything to back up your simple denials?


I do.
Case after case I modded.
I even offered to let you in on the details of one, but you
didn't want an opportunity to be proven wrong, apparently.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

"kony" wrote:
> "Timothy Daniels" wrote:
> > "Next year's designs" will probably have fans to force more
> > air through the holes to create even *more* turbulence.
>
> Nope.
> This time next year we'll see.


Check out Dell's new 1U servers and their new high end
laptops. They are sporting circular intake holes in their
front plates, now, too.


> You need a bigger monitor. If you had a big enough monitor you'd
> see that the holes do have curved edges, while NOT having those
> curved edges would result in higher turbulence. The design they
> choose was one creating less turbulence than would result from a
> simpler sharp-edged hole. They spent EXTRA time on it with an
> end result of less turbulence.


Sharp-edged holes are harder to mold AND they would present
the liability risk of cuts to fingers. As they are, though, they are
sharp-edged enough to produce turbulence.


> [...]
> Try focusing on the facts. The fact is that heatsink turbulence
> DOES help, when created at the heatsink surface. That does
> not decrease total chassis airflow rate, while front bezel holes do.


What is the difference between turbulence generated at a
heatsink and turbulence generated at the air intake holes?
Turbulence at the heatsink helps to cool the heatsink. Unless
you're still subscribing to the Molasses Theory of turbulence
dissipation, why shouldn't turbulence in the air passing over
components without a dedicated heatsink not help to cool
those components as well?

*TimDaniels*

 

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"kony" wrote:
> "Timothy Daniels" wrote:
>
> > Have you anything to back up your simple denials?
>
>
> I do.
> Case after case I modded.
> I even offered to let you in on the details of one, but you
> didn't want an opportunity to be proven wrong, apparently.


Hey, don't let li'l ol' *me* stop you from sharing your skills
and experience with the world. Let's hear all about it.

*TimDaniels*

 

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On Wed, 21 Jul 2004 23:12:28 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:

>"kony" wrote:
>> "Timothy Daniels" wrote:
>>
>> > Have you anything to back up your simple denials?
>>
>>
>> I do.
>> Case after case I modded.
>> I even offered to let you in on the details of one, but you
>> didn't want an opportunity to be proven wrong, apparently.
>
>
> Hey, don't let li'l ol' *me* stop you from sharing your skills
> and experience with the world. Let's hear all about it.
>
>*TimDaniels*

Well I have a few OEM cases, lets consider one with the holes you
like so much, a Compaq mATX, one of those that has the
translucent blue bezels. Model number really isn't important but
I'm sure I have that around here somewhere too. There are many
holes on the bottom front face, next time I get a chance I'll
snap a pic of it then we can go from there describing the
experiment.

 

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"kony" wrote:
> Well I have a few OEM cases, lets consider one with the holes you
> like so much, a Compaq mATX, one of those that has the
> translucent blue bezels. Model number really isn't important but
> I'm sure I have that around here somewhere too. There are many
> holes on the bottom front face, next time I get a chance I'll
> snap a pic of it then we can go from there describing the
> experiment.


Let's do it!

*TimDaniels*

 

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On Wed, 21 Jul 2004 23:06:50 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:

>"kony" wrote:
>> "Timothy Daniels" wrote:
>> > "Next year's designs" will probably have fans to force more
>> > air through the holes to create even *more* turbulence.
>>
>> Nope.
>> This time next year we'll see.
>
>
> Check out Dell's new 1U servers and their new high end
> laptops. They are sporting circular intake holes in their
> front plates, now, too.

... and as I already mentioned, it is "this year's" style.

Are you suggesting that any models now made (and past, future
models) that don't have round holes have a poor cooling strategy?

I'm pretty sure my pasta strainer has round holes too, do you
think it keeps the sink cooler as a result?


> Sharp-edged holes are harder to mold

Quite wrong.


>AND they would present
> the liability risk of cuts to fingers.

Again, quite wrong.


> As they are, though, they are
> sharp-edged enough to produce turbulence.

.... as little as possible without detracting from the visual
appearance of the front.

>
>
>> [...]
>> Try focusing on the facts. The fact is that heatsink turbulence
>> DOES help, when created at the heatsink surface. That does
>> not decrease total chassis airflow rate, while front bezel holes do.
>
>
> What is the difference between turbulence generated at a
> heatsink and turbulence generated at the air intake holes?

The chassis flow rate is decreased by one but not the other.


> Turbulence at the heatsink helps to cool the heatsink. Unless
> you're still subscribing to the Molasses Theory of turbulence
> dissipation, why shouldn't turbulence in the air passing over
> components without a dedicated heatsink not help to cool
> those components as well?

It will to a limited extent, compared to same flow rate... flow
rate isn't the same though, that's where your argument has been
flawed all along.

 

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"kony" wrote:
> "Timothy Daniels" wrote:
> > What is the difference between turbulence generated at a
> > heatsink and turbulence generated at the air intake holes?
>
> The chassis flow rate is decreased by one but not the other.


If turbulence decreased flow rate and thus decreased cooling,
the turbulence at the fins of a heatsink would decrease the flow rate
through the fins of a heatsink and thus the cooling of the heatsink -
which doesn't happen.


> > Turbulence at the heatsink helps to cool the heatsink. Unless
> > you're still subscribing to the Molasses Theory of turbulence
> > dissipation, why shouldn't turbulence in the air passing over
> > components without a dedicated heatsink not help to cool
> > those components as well?
>
> It will to a limited extent, compared to same flow rate... flow
> rate isn't the same though, that's where your argument has been
> flawed all along.

It sounds really like you're saying "Turbulence added to a
flow rate cools better than the same flow rate without turbulence"
but that "the slightest decrease in flow rate by the addition of
any degree of turbulence causes a reduction in cooling effect".
Is that what you're saying?

*TimDaniels*

 

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kony wrote:

> On Wed, 21 Jul 2004 23:06:50 -0700, "Timothy Daniels"
> <TDaniels@NoSpamDot.com> wrote:

<snip>

>> What is the difference between turbulence generated at a
>> heatsink and turbulence generated at the air intake holes?
>
>
> The chassis flow rate is decreased by one but not the other.

No, they both decrease flow rate but by introducing only that amount useful
to the heatsink it has much much less of an effect on the total.

Same kind of reason as why you don't fill your entire car with grease
because the wheel bearings need some lub: it's a waste.

 

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In article <8L6dnbcRV_PlxGLd4p2dnA@comcast.com>,
Timothy Daniels <TDaniels@NoSpamDot.com> wrote:
>"kony" wrote:
>> "Timothy Daniels" wrote:
>> > "Next year's designs" will probably have fans to force more
>> > air through the holes to create even *more* turbulence.
>>
>> Nope.
>> This time next year we'll see.
>
>
> Check out Dell's new 1U servers and their new high end
> laptops. They are sporting circular intake holes in their
> front plates, now, too.
>

URL for the above paragraph, or did you just make it a conjecture. If
they come out with one it could just as easily be argued that it was a
marketing-look decision. Teh bottom line is that we don't know why
Dell choose that design until you find some supporting information.


>
>> You need a bigger monitor. If you had a big enough monitor you'd
>> see that the holes do have curved edges, while NOT having those
>> curved edges would result in higher turbulence. The design they
>> choose was one creating less turbulence than would result from a
>> simpler sharp-edged hole. They spent EXTRA time on it with an
>> end result of less turbulence.
>
>
> Sharp-edged holes are harder to mold AND they would present
> the liability risk of cuts to fingers. As they are, though, they are
> sharp-edged enough to produce turbulence.
>
>

LOL

It doesn't take a .25 inch radius edge to be child-proof. .050 would
do it, besides the holes are small enough that you could barely get
your pinly into it, let alone cut yourself. (I've worked with this
box)

FWIW a larger number of smaller holes, and larger raduis tends to
increase laminar flow, not increase turbulence. I don't use this
as one of my argurements.


>> [...]
>> Try focusing on the facts. The fact is that heatsink turbulence
>> DOES help, when created at the heatsink surface. That does
>> not decrease total chassis airflow rate, while front bezel holes do.
>
>
> What is the difference between turbulence generated at a
> heatsink and turbulence generated at the air intake holes?
> Turbulence at the heatsink helps to cool the heatsink. Unless
> you're still subscribing to the Molasses Theory of turbulence
> dissipation, why shouldn't turbulence in the air passing over
> components without a dedicated heatsink not help to cool
> those components as well?
>
>*TimDaniels*

The difference is that an air molecule adjacent to the HS surface
doesn't have a memory and doesn't know how it got there. All they
know is that a cool molecule will absorb and carry away more heat than
a warm one. Beyong the immediate air-HS interface turbulence is
irrelevant. Volume of air rules. (I'm doing horrible damage to the
vocabulary of heatflow here, but the concepts are right)


--
Al Dykes
-----------
adykes at p a n i x . c o m

 

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In article <HN6dnXGM0cYf5WLdRVn-rg@comcast.com>,
Timothy Daniels <TDaniels@NoSpamDot.com> wrote:
>"kony" wrote:
>> "Timothy Daniels" wrote:
>> > What is the difference between turbulence generated at a
>> > heatsink and turbulence generated at the air intake holes?
>>
>> The chassis flow rate is decreased by one but not the other.
>
>
> If turbulence decreased flow rate and thus decreased cooling,
> the turbulence at the fins of a heatsink would decrease the flow rate
> through the fins of a heatsink and thus the cooling of the heatsink -
> which doesn't happen.
>
>
>> > Turbulence at the heatsink helps to cool the heatsink. Unless
>> > you're still subscribing to the Molasses Theory of turbulence
>> > dissipation, why shouldn't turbulence in the air passing over
>> > components without a dedicated heatsink not help to cool
>> > those components as well?
>>
>> It will to a limited extent, compared to same flow rate... flow
>> rate isn't the same though, that's where your argument has been
>> flawed all along.
>
> It sounds really like you're saying "Turbulence added to a
> flow rate cools better than the same flow rate without turbulence"
> but that "the slightest decrease in flow rate by the addition of
> any degree of turbulence causes a reduction in cooling effect".
> Is that what you're saying?
>
>*TimDaniels*

Yes.

I'll support the last paragraph, and explain it by the basic fact that
the only way heat exits the box in by the warm are leaving, as shown
by these high school physics calculations;

Heat is measured in BTU.

BTU/hr = Watts x 3.4115 so a PC case drawing 200W is converting
electricity to heat at the rate of 680 BTU/hr.

One BTU is the quantity of heat required to raise the temperature of a
pound of water one degree Fahrenheit. So if you move water in and out
of the case at the rate of 680 pounds/hr the water leaving the case
will be one degree hotter than the inlet water. If you move 68
pounds/hr thru the case the temp at the out let will be 10Deg hotter.

The calculation is EXACTLY the same except that that I'd have to look
up the specific heat of air, and do the calcualtions of CuFt to pounds
for air. I could do the calculations in terms of pounds of air/hr but
that's more work and a punds of air doesn't make a good talking point.

The AVERAGE temperature of the case will be that of the outlet temp.

Turbulence does not enter into this analysis.

Please, please please either critic my analysis, or bring some
third-party evidence to support your claims.


--
Al Dykes
-----------
adykes at p a n i x . c o m

 

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On Thu, 22 Jul 2004 01:19:17 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:

> It sounds really like you're saying "Turbulence added to a
> flow rate cools better than the same flow rate without turbulence"

Yes, though we're talking about a very low amount of turbulence,
so it would make a very small difference.


> but that "the slightest decrease in flow rate by the addition of
> any degree of turbulence causes a reduction in cooling effect".
> Is that what you're saying?

Yes, the slightly decrease in flow rate from a slight addition in
turbulence would have almost immeasurable difference, but that
difference would be reduced cooling effectiveness. HOWEVER, the
larger issue is that without trying to constrict flow though
turbulent holes, there will be a larger intake area, so not only
is the turbulent hole ineffective, but it's removal, substutution
by another intake design allows higher flow rate than would be
seen even if the perfect theoretical hole with zero turbulent
effect were used. It artifically restricts airflow towards the
end of EMI reduction but if ignoring EMI issues then a larger
open area can be used.

This EMI issue is where OEMs are limited, they have to follow
those restrictions but once you have system in-home (or wherever)
your options are less limited to what your environment can
tolerate.

 

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"Al Dykes" wrote:
> Timothy Daniels wrote:
> > It sounds really like you're saying "Turbulence added to a
> > flow rate cools better than the same flow rate without turbulence"
> > but that "the slightest decrease in flow rate by the addition of
> > any degree of turbulence causes a reduction in cooling effect".
> > Is that what you're saying?
>
> Yes.


Then you contradict yourself. If all changes in cooling
were attributable to flow rate, there could be no
contribution at all by changes in turbulence.


> I'll support the last paragraph, and explain it by the basic fact
> that the only way heat exits the box in by the warm are leaving,


Yes, of course. All the heat that is removed by the air
is removed by the air. And the rate of heat transfer from
the warm components in the box is determined by factors
such as the temperature difference between the air and
the components, the rate of flow of air through the box,
and by the efficiency of the heat transfer. If you
increase the efficiency of heat transfer, the difference in
temperature can be lower for the same flow rate and
thus the temperature of the components can be lower.
One way to increase this efficiency is to add turbulence
to the air.


> as shown by these high school physics calculations;
>
> Heat is measured in BTU.


Heat energy is just energy. It doesn't matter whether
it's measured in BTU or calories or watt-hours or
pound-feet or joules. Let's just call it heat.


> BTU/hr = Watts x 3.4115 so a PC case drawing 200W is
> converting electricity to heat at the rate of 680 BTU/hr.


BTU/hr or 200W is just power. Let's just call it power.


> One BTU is the quantity of heat required to raise the temperature
> of a pound of water one degree Fahrenheit. So if you move water
> in and out of the case at the rate of 680 pounds/hr the water leaving
> the case will be one degree hotter than the inlet water. If you move 68
> pounds/hr thru the case the temp at the out let will be 10Deg hotter.


You neglect that transfer of heat requires time and that it
requires a difference of temperature. You assume that
heat will move into the cooler water instantly to equalize
the temperatures of the two masses. Just because water
has passed through the case is no reason to believe that
the water temperature has reached that of the warm surfaces.
Indeed, there remains a difference in temperature to attest
to the fact that there is still some heat to be carried away
Similarly, just because air has passed through the case is no
reason to believe that all heat in the case has transfered to the
air. Indeed, that is the reason for heatsinks - to increase the
efficiency of the transfer of heat to the air. And that is what
turbulence does - it increases the efficiency (i.e. the speed of
transfer) of heat from heated surfaces to the cooler air, allowing
less flow rate to accomplish the same degree of cooling.


> The AVERAGE temperature of the case will be that of the
> outlet temp.

The average temperature of the AIR in the case
will be the outlet temp. The air at the outlet will only
contain the heat that the air has been able to absorb
during its passage through the case, and thus the temp
will be limited by the efficiency of that absorption.
The greater the efficiency of that absorption, the higher
will be its outlet temperature for a given flow rate.
Since turbulence increases that efficiency, the temperature
of the outlet air will be higher for turbulent flow within
the case for a given flow rate, and it will be lower for
that same flow rate if there is laminar (or less-turbulent)
flow.


> Turbulence does not enter into this analysis.

That simply means is that you have not included
turbulence in your analysis.

*TimDaniels*

 

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"David Maynard" wrote:
> kony wrote:
>
> > "Timothy Daniels" wrote:
> >> What is the difference between turbulence generated at a
> >> heatsink and turbulence generated at the air intake holes?
> >
> >
> > The chassis flow rate is decreased by one but not the other.
>
> No, they both decrease flow rate but by introducing only that
> amount useful to the heatsink it has much much less of an effect
> on the total.


You assume that all cooling is desired at a heatsink. There
are many more components that need cooling than have
heatsinks. Those components can benefit from turbulence
just as well as those that have a heatsink.

*TimDaniels*