"kornball" spake:
> "Timothy Daniels" wrote:
>
>>Here are more examples of and advice regarding
>>turbulence and forced draft cooling:
>>
>> http://www.overclockers.com/tips90/ -
>>
>> "Turbulent air cools better. Say, for sake of argument,
>> you have a simple tube with a fan in the middle. The fan pulls
>> air from one side of the tube, and blows into the other. If you
>> have a hot component on the exhaust side of the fan, it will
>> be more efficiently cooled than on the intake side.
>
>
> Say for example, that you have a computer system, not a
> dissimilar situation, and instead of having a reduced flow
> rate from the component no matter which side it's on, you
> have a higher flow rate until you try to test your idea.
That's not English, kornball. Try a course in expository
writing. But if you want to elaborate, be my guest.
Your English is always good for a laugh.
"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'."
"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."
"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."
"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."
"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."
"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."
"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."
"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."
"kornball" wrote:
>"Timothy Daniels" wrote:
>> Cool air that contacts the components per
>> unit time is what is important.
>
> Yes, as I've said all along.
>
>> Whether the turbulence that
>> promotes that is caused by design or by accident is not
>> important to the heated parts.
>
>
> This is where you are wrong. You cannot resolve the fact
> that "by design" necessarily means a reduction in flow rate.
Not at all. The turbulence can be generated by many means.
Many current designs generate turbulence with a fan.
> The goal is to maximize flow rate to the part, and away from
> the part. The turbulence that is by design or accident is
> only useful when occuring ON the surface of the part being
> cooled.
You've mistakenly substitued "occurring" for "impinging".
It matters not at all WHERE the turbulence is GENERATED.
But it does matter that it IMPINGES ON THE PART to be cooled -
directly on the part and enegentically enough to penetrate
and scrub away the part's boundary layer of air.
> A perforated grill over anything hot would help if your theory
> were true, but it does not.
It works on my Dell computer! The hard drive is mounted
vertically with its circuit board right behind the holes stamped
in the front of the metal case. Although it would receive the
same amount of cooled air if mounted 6" to 8" back, it is
put right behind the holes - where the turbulence is greatest.
Furthermore, that placement creates more turbulence in the
downstream air, something to be avoided according to you.
But lo and behold, my hard drive and the rest of the system
runs cool, and it has had no failures in 7 1/2 years. Maybe
Dell designers know something about cooling?
> Once again you try to fixate on only one variable...
Such as you have fixated on "smooth flow"?
Please consider that many others recognize turbulent flow
for its value in cooling:
"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'."
"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."
"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."
"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."
"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."
"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."
"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."
"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."
"kornball" wrote:
> "Timothy Daniels" wrote:
> It is known that turbulence ON the hot part helps.
Uhh... you mean "impinging on" the hot part.
That means that it doesn't matter where the
turbulence is generated, certainly not just the
"self-turbulence" that you restrictively conceded
in past "discussions".
> IF we could have increased turbulence, created prior
> to reaching the part such that there was then even more
> turbulence ON the hot part, that too would help.
Finally! An admission that turbulence doesn't have
to be generated AT the surface of the part, but that it
could even be generated upstream and still help to cool
the part. CONGRATULATIONS, kornball!
> The problem is, we cannot get that increased turbulence
> prior to the part without a decrease in airflow.
Let me help you. You mean to say that any turbulence
generated upstream of a part to be cooled must be at
the expense of bulk air flow rate because it takes energy
to generate turbulence, and the energy to generate that
turbulence is at the expense of bulk flow rate.
There are two FALLACIES here:
1) That the bulk air flow rate reduction matters more
than the increase in turbulence, and
2) That all turbulence can only be generated by the
same energy that causes the bulk air flow.
Let's perform a gedanken experiment for 1):
Laminar flow depends on careful placement of the
hot parts. They must be directly in the path of the
flowing air because the nature of laminar flow is
that it does not "spread out" well - it just goes in as
straight a line as it can from entrance to exit. So
it is easy to imagine that a hot part, not placed directly
in the flow, or suffering from deflection of the flow by
another part, would overheat, regardless of the intensity
of the bulk air flow. The introduction of turbulence,
however, would smear and spread the air flow all
around in the case, and some of it would impinge
the hot part, cooling it. But, you would say, "That
turbulence was at the expense of the laminar flow rate!"
But so WHAT? It cooled the part, didn't it?
Furthermore, what proof have you that in the general case,
all increase in cooling by turbulent flow is overcome by
the reduction in cooling by laminar flow?
And furthermore than that, what engineering or scientific
basis do you have in claiming that energy expended to
generate turbulence AT THE PART is any less than the
energy expended to generate turbulence UPSTREAM
of the part?
And even furthermore, there are heatsinks that are
designed such that the air is forced to follow a zig-zag
path between "fingers" so as to increase the turbulence
at fingers immediately downstream. Why not place all
the fingers in rows so that turbulence is minimized?
Doesn't the increased turbulence decrease air flow rate?
Of course it does, but the designers calculated that the
increase in cooling more than compensated for it.
As for 2):
There are other ways to generate turbulence than by
using the translational energy of the flowing air itself
to generate turbulence. You can always just use a
fan that is internal to the case to do that. In fact, that is
exactly what CPU and GPU fans do - they increase
the turbulence - the localized flow, as opposed to
the overall bulk flow - that impinges the hot part's
surface (or extended surface, which is what a heatsink
is). This increase in turbulence is NOT at the expense
of the bulk flow rate, and recent PC designs use the
technique extensively.
> This much we see all around us in existing products.
Refutation of your kornball theory are all around you but
you see it not.
On Fri, 6 Oct 2006 22:33:30 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:
>"kony" wrote:
>> "Timothy Daniels" wrote:
>>> And so what if bulk flow rate reduces but the
>>> increased turbulence compensates?
>>
>> So you now concede that flow rate reduces.
>
>
> Do you actually understand English?
> "And so what if" doesn't concede *anything*.
> It's a hypothetical phrase.
Problem is, EVERYTHING you dream up is only hypothetical,
never tested. We're done Tim, no point to this argument.
On Fri, 6 Oct 2006 22:40:35 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:
>"kornball" ignores evidence:
>> "Timothy Daniels" wrote:
>>> Here are some interesting discussions and comments:
>>
>>
>> You still don't get it Tim, there is a flow rate reduction
>> that does matter.
>
>
> Why, then, do manufacturers of industrial cooling systems
> design turbulence production into their systems?
They don't, unless they care not about noise.
Different scenario, different approach to cooling.
On Fri, 6 Oct 2006 22:56:06 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:
>"kornball" gives up:
>> Unfortunately you continually ignore that heated air also
>> has to be removed from the system...
>
>
> Are you implying that trubulent air is hard to remove
> from the system?
No, rather that it is KNOWN it reduces flow rate.
That means you need more noise to move same amount of air,
but that the increased noise level could INSTEAD more even
more air.
Once again I point out the obvious- that when a system is
overheated, the proven solution is to increase airflow, not
increase turbulence.
There's nothing you can claim that changes this basic and
proven fact.
You will continue to think arguing or posting links somehow
mitigates this plan truth but it does not. Only Tim can't
see direct evidence like everyone else.
"kornball" continues like a running toilet:
>
> Problem is, EVERYTHING you dream up is only hypothetical,
> never tested. We're done Tim, no point to this argument.
You just got through saying:
"I'm done with the thread since you never do anything
but troll and pretend to cover something new that was
already covered multiple times- but never a test."
C'mon, kornball, say it a 3rd time for old times sake -
say you're done. <LOL>
"kornball" wrote:
> "Timothy Daniels" wrote:
>
>>"kornball" ignores evidence:
>>> "Timothy Daniels" wrote:
>>>> Here are some interesting discussions and comments:
>>>
>>>
>>> You still don't get it Tim, there is a flow rate reduction
>>> that does matter.
>>
>>
>> Why, then, do manufacturers of industrial cooling systems
>> design turbulence production into their systems?
>
> They don't, unless they care not about noise.
> Different scenario, different approach to cooling.
Awww, now you're introducing another variable to hide behind -
noise. Turbulence cools the parts, but it makes noise inside the
case. I guess noise bothers the dust balls. Konehead, I didn't know
you were so... so... CARING. <LOL>
"kornball" weaves and dances and brings in noise:
> "Timothy Daniels" wrote:
>
>>"kornball" gives up:
>>> Unfortunately you continually ignore that heated air also
>>> has to be removed from the system...
>>
>>
>> Are you implying that trubulent air is hard to remove
>> from the system?
>
> No, rather that it is KNOWN it reduces flow rate.
> That means you need more noise to move same amount of air,
> but that the increased noise level could INSTEAD more even
> more air.
Always another factor, huh, kornball? Now it's "noise".
What will be next? Bad luck? Will turbulence produce
bad luck? <LOL>
> Once again I point out the obvious- that when a system is
> overheated, the proven solution is to increase airflow, not
> increase turbulence.
MmmmHmmmm. And increased airflow doesn't produce
noise? Tell us about it, kornball.
> There's nothing you can claim that changes this basic and
> proven fact.
Yeah, I can. Well-planned turbulence would obviate the
need for your brute-force "solution".
> You will continue to think arguing or posting links somehow
> mitigates this plan truth but it does not. Only Tim can't
> see direct evidence like everyone else.
"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'."
"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."
"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."
"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."
"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."
"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."
"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."
"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."
"kornball" gasped:
> "Timothy Daniels" wrote:
>
>
>> That's not English, kornball.
>
> You're wasting your time Tim.
The reason you can't write English, kornball, is the
same reason you think you're an aerodynamicist
and a thermodynamicist - you think you know everything.
"kornball" tries his best joke:
> "Timothy Daniels" wrote:
>
>> Not at all. The turbulence can be generated by many means.
>> Many current designs generate turbulence with a fan.
>
>
> Still wasting time.
"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'."
"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."
"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."
"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."
"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."
"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."
"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."
"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."
"kornball" wrote:
> "Timothy Daniels" wrote:
>
>> Uhh... you mean "impinging on" the hot part.
>
> Trying to restate what I meant is yet again,
> wasting time.
Only kornball knows WTF kornball means.
The rest of us are always forced to guess.
"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'."
"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."
"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."
"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."
"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."
"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."
"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."
"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."
On Sat, 7 Oct 2006 19:13:23 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:
>"kornball" continues like a running toilet:
>>
>> Problem is, EVERYTHING you dream up is only hypothetical,
>> never tested. We're done Tim, no point to this argument.
>
>
> You just got through saying:
>
> "I'm done with the thread since you never do anything
> but troll and pretend to cover something new that was
> already covered multiple times- but never a test."
>
> C'mon, kornball, say it a 3rd time for old times sake -
> say you're done. <LOL>
Yes, and I am. I've given you all the help you need to
figure out why you find ATX a problem and where your cooling
idea went wrong.
Each time you posted nonsense, I tried to remind you that
your grand theory needed testing.
I am done Tim, done trying to help you learn the basics.
On Sun, 8 Oct 2006 03:45:27 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:
>"kornball" bleated:
>> I am done Tim, done trying to help you learn the basics.
>
>
> You're done all right. You're completely out of weasel room.
> The basics are part of science, and you flunked science.
All the evidence is against you.
Not dissimilar things which confused you, but real, running
systems... that don't overheat like yours.
"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'."
"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."
"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."
"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."
"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."
"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."
"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."
"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."
"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'."
"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."
"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."
"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."
"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."
"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."
"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."
"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."
"kornball konehead" wrote:
> It is known that turbulence ON the hot part helps. Nobody
> has argued against this.
YOU did! Starting way back on July 10, 2004, in
alt.comp.hardware.homebuilt you argued:
"Those links were examples of what we've been saying all
along, that turbulence should be created on the surface being,
needing cooled."
You said "CREATED ON THE SURFACE", not impinging on
the surface, not aimed at the surface, not directed to the surface.
That was the start of your "Self-Generated Turbulence" theory,
which was a way then to weasel out of your position that turbulence
was just plain bad. Now you're claiming that you meant all along
that the turbulence must be ON the hot part, not necessarily generated
AT the hot part. What a weasel you are!
*TimDaniels*
IF we could have increased
> turbulence, created prior to reaching the part such that
> there was then even more turbulence ON the hot part, that
> too would help. The problem is, we cannot get that
> increased turbulence prior to the part without a decrease in
> airflow.
On Sun, 8 Oct 2006 11:32:19 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:
>"kornball konehead" wrote:
>> It is known that turbulence ON the hot part helps. Nobody
>> has argued against this.
>
>
> YOU did! Starting way back on July 10, 2004, in
> alt.comp.hardware.homebuilt you argued:
>
> "Those links were examples of what we've been saying all
> along, that turbulence should be created on the surface being,
> needing cooled."
>
> You said "CREATED ON THE SURFACE", not impinging on
> the surface, not aimed at the surface, not directed to the surface.
Yes Tim. jThat is ON the hot part.
The reason you still can't understand cooling is that you
can't resolve these finer details. This is not a dissimilar
situation as you're trying ot imply, it is cooling for an
entire system where there is more than one part, more
downstream of the first part cooled.
> "Al Dykes" wrote:
>
>> You are picking *one* aspect of the many that affectthe cooling parts
>> in a box. You also freely jump between the macro and micro effects.
>> What is optimal in one is occasionally sub-optimal in the other.
>
>
>
> I am picking "*one* aspect* to write about that is often denigrated
> by "experts" as being undesirable.
Kony is correct in that you are mixing micro and macro effects and then
assuming the tradeoffs are the same, but they're not.
> You can read countless
> "modder" sites that advise keeping the air flow "smooth" to cool
> the interior parts of a computer as much as possible.
That is because the primary concern in macro case flow is getting the most
volume of air in and out of the case, and to the parts to be cooled, with
the least wasted energy. Or, put another way, the air has to get there (and
then removed) before it can be used for cooling purposes.
Take an extreme example to illustrate the point, like an air-conditioned
computer center where the air-conditioning is floor ducted around the room
and then up into the individual racks for cooling. Clearly, 'turbulence' in
the floor ducting does nothing to 'improve cooling' but does lower the
overall airflow to the racks, or causes one to employ larger, more
powerful, nosier, more costly, fans to over come the resistance caused by
the useless turbulence.
Similarly, creating extraneous turbulence inside the case simply impedes
airflow.
> I merely
> point out that if a part is to be cooled by a forced flow of fluid past
> and over it (such as by forced draft of air), turbulent fluid flow cools
> the part better than laminar fluid flow.
That is in the immediate vicinity of the cooling surface.
> That it is putting the flow
> past the part to be cooled that is more important than merely
> getting bulk air in and out of the case
They're both important. It's of little use to get air in and out of the
case if it hasn't picked up the heat but it's just as useless to pick up
the heat and then not take it out of the case. And there's your clue for
what does what where and why. You want useful turbulence at the dissipating
surface but a low resistance path getting the air to it and back out.
> is evidenced by the transition
> to dedicated fans on the heatsinks of CPUs and GPUs.
For different reasons.
> The
> designers don't just put bigger fans or more fans on the walls of
> the case to get more air-per-minute in and to get more air-per-
> minute out of the case,
Right, because the other components don't need a gazillion CFM to cool them
so running a hurricane through the entire case is not efficient.
> they instead put interior re-circulating flow
> fans right at the heatsink.
It's not a 'recirculating' fan, per see. It's purpose is to increase the
speed of airflow at that point where it's needed because the alternative is
a gigantic heatsink, which creates it's own practical problems.
> That this causes "pre-heated" or "used"
> air to re-circulate against the heatsink in secondary
It's actually unfortunate, which is why exterior ducting is sometimes used,
and is why it's *purpose* is not to be a 'recirculating fan', per see.
You're 'stuck' with that aspect and hope the case designer gets the air in
and out fast enough to ameliorate the problem.
> - what is
> important is that air is brought into contact with the heatsink as
> much as possible, despite that the bulk flow through the case is
> unchanged. This increased air speed at the surface of the
> heatsink that does not affect the bulk flow of air is a form of
> turbulence.
Semantics. It's a means of directing airflow and while one can 'analogize'
it to 'turbulence' by making a stretch of comparing what 'laminar' flow
through the case would otherwise look like is to ignore the purpose of it.
> It really doesn't matter whether this turbulence is
> generated an eighth of an inch or a quarter of an inch or six
> inches away - it's just turbulence,
And there you are incorrect. It makes all the difference and, no, it's not
'just turbulence'.
'Turbulence' is a 'local thing'. Or, put on the other end of the extreme,
everything looks like 'turbulence' at the scale of the 'universe'
regardless of how laminar you think it is where you are. So saying "it's
just turbulence" means nothing unless you consider the scale and what
you're trying to accomplish.
> and it's effect is to scrub down
> through the thin boundary layer of air that surrounds all objects
> to make maximum contact with the object itself.
Which is why it's essentially useless in a case, as you put it, "six inches
away" from what you want to cool.
> In weatherman's
> terms, in increases the "chill factor".
Mother nature is not concerned with the 'efficiency' of wind creation
relative to how cold you feel and is quite happy mustering global
thermonuclear war levels of power to do it. She doesn't have to pay the
electric bill and the 'fans' are 'free'.
> In practical terms, I can give my Dell ATX case as an example
> of a design that takes advantage of turbulence to cool. There is
> volume of space at the bottom of the case in which fresh air
> sweeps in the from the lower front, straight back to the lower part
> of the motherboard and the expansion cards. The main hard
> drive plastic cage could easily have been mounted anywhere in
> that cavity, and its mounting cage could have been conveniently
> attached at any number of places.
Bad assumption.
> But the HD is mounted vertically
> with its circuit board facing the front and about !/2" from the vent
> holes - despite that this impedes the incoming air. Not only
> does this put the HD's circuit board in the field of maximum
> turbulence caused by the vent holes stamped in the metal case,
> but it causes more turbulence in the case immediately behind it.
> If the designers were designing for maximum bulk air flow through
> the case, they failed. If they were designing for optimal cooling,
> they did quite well because in 7 1/2 yrs, I haven't had a HD (or any
> other part) in the PC fail. In fact, when I touch the 7,200 rpm HD,
> it feels no warmer than my body temperature.
All that proves is it does a good job of cooling the hard drive, not that
they put it there to 'create case turbulence'.
> That turbulence cools parts is evidenced in countless fields of
> science and engineering. That turbulence alone can cool objects -
> of course not! If that were true, there would just be fans inside
> cases and the cases would be sealed shut.
And that should give you a clue that how well one can get the air in and
out is of importance.
> What I point out is
> that turbulence is NOT BAD,
The problem is the broad sweeping generalization and, as the saying goes,
the devil is in the details.
> and that turbulence is turbulence -
But turbulence just anywhere is not necessarily a 'good thing', as has been
previously illustrated.
> be it generated by friction of the flow against the part itself that
> is to be cooled, or somewhere upwind of that part.
Nope. Just as pouring water on a wood fire at the lumber yard helps
extinguish it but pouring water over the whole state for the same fire
isn't an efficient use of resources even though, to analogize your logic,
'water is water'.
Component level turbulence pretty much takes care of itself, either by
nature or the component designer's intent, so the case designer is
primarily concerned with getting the air in, through (to all needed areas),
and out efficiently.
"kornball" wrote:
> All evidence is against you.
>
> No observation in a dissimilar closed system can be assumed
> applicable to another use. TESTING is what others have
> done but not Tim.
You probably don't believe in gravity, either.
But thermodynamics and aerodynamics show
your "arguments" to be fallacies:
"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'."
"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."
"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."
"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."
"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."
"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."
"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."
"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."
"kornball" wrote:
> "Timothy Daniels" wrote:
>
>>"kornball konehead" wrote:
>>> It is known that turbulence ON the hot part helps. Nobody
>>> has argued against this.
>>
>>
>> YOU did! Starting way back on July 10, 2004, in
>> alt.comp.hardware.homebuilt you argued:
>>
>> "Those links were examples of what we've been saying all
>> along, that turbulence should be created on the surface being,
>> needing cooled."
>>
>> You said "CREATED ON THE SURFACE", not impinging on
>> the surface, not aimed at the surface, not directed to the surface.
>
>
> Yes Tim. jThat is ON the hot part.
Riiiiiight. "CREATED ON" the hot part. Your "self-turbulence" again.
As if turbulence CREATED ON the hot part is the only effective
turbulence. A very... uh, "novel" idea. <LOL>
"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'."
"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."
"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."
"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."
"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."
"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."
"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."
"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."
"David Maynard" wrote:
> Kony is correct in that you are mixing micro and macro effects
> and then assuming the tradeoffs are the same, but they're not.
Turbulence is turbulence. Nothing "micro" and "macro"
about it, except that they are neat terms.
> ...the primary concern in macro case flow is getting the most
> volume of air in and out of the case, and to the parts to be cooled,
> with the least wasted energy.
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. 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.
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.
Your assumption that the addition of turbulence is a "waste of energy"
is presumptuous.
> Or, put another way, the air has to get there (and
> then removed) before it can be used for cooling purposes.
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.
> Take an extreme example to illustrate the point, like an air-conditioned
> computer center where the air-conditioning is floor ducted around the
> room and then up into the individual racks for cooling. Clearly,
> 'turbulence' in the floor ducting does nothing to 'improve cooling' but
> does lower the overall airflow to the racks, or causes one to employ
> larger, more powerful, nosier, more costly, fans to over come the
> resistance caused by the useless turbulence.
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, and the turbulence should be maximized as
the air approaches or enters the racks to be cooled.
> Similarly, creating extraneous turbulence inside the case simply
> impedes airflow.
"Extraneous" means "extra, unneeded". So your description
is designed for your conclusion. But well-designed turbulence is
turbulence that impinges primarily the parts to be cooled. You
could accomplish that by "turbulators" that induce the turbulence
at carefully selected upstream points. 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. 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.
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 produced at the average case's air intake holes -
which are almost always just holes punched in metal sheets. 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.
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. 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. 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. 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".
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? 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.
> You want useful turbulence at the dissipating surface but a low
> resistance path getting the air to it and back out.
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.
>> ...interior re-circulating flow fans right at the heatsink.
>
> It's not a 'recirculating' fan, per see. It's purpose is to increase the
> speed of airflow at that point where it's needed because the
> alternative is a gigantic heatsink, which creates it's own practical
> problems.
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.
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. 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.
>> That this causes "pre-heated" or "used" air to re-circulate
>> against the heatsink in secondary
>
> It's actually unfortunate, which is why exterior ducting is sometimes
> used, and is why it's *purpose* is not to be a 'recirculating fan', per see.
> You're 'stuck' with that aspect and hope the case designer gets the
> air in and out fast enough to ameliorate the problem.
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.
*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.
>> - what is
>> important is that air is brought into contact with the heatsink as
>> much as possible, despite that the bulk flow through the case is
>> unchanged. This increased air speed at the surface of the
>> heatsink that does not affect the bulk flow of air is a form of
>> turbulence.
>
> Semantics. It's a means of directing airflow
If by "it" you mean a fan which blows against a heatsink,
"it's" purpose is to increase the local air flow through the
heatsink. You said that in a statement just above.
> and while one can 'analogize' it to 'turbulence' by making a
> stretch of comparing what 'laminar' flow through the case
> would otherwise look like is to ignore the purpose of it.
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.
>> It really doesn't matter whether this turbulence is
>> generated an eighth of an inch or a quarter of an inch or six
>> inches away - it's just turbulence,
>
> And there you are incorrect. It makes all the difference...
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?
> and, no, it's not 'just turbulence'.
>
> 'Turbulence' is a 'local thing'. Or, put on the other end of the extreme,
> everything looks like 'turbulence' at the scale of the 'universe'
> regardless of how laminar you think it is where you are. So saying "it's
> just turbulence" means nothing unless you consider the scale and what
> you're trying to accomplish.
"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. 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. Judging by
the persistence of vortices in such things as smoke rings or
blown candle smoke, 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.
>> and it's effect is to scrub down through the thin boundary layer
>> of air that surrounds all objects to make maximum contact with
>> the object itself.
>
> Which is why it's essentially useless in a case, as you put it,
> "six inches away" from what you want to cool.
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?
>> In weatherman's terms, it increases the "chill factor".
>
> Mother nature is not concerned with the 'efficiency' of wind
> creation relative to how cold you feel...
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.
>> In practical terms, I can give my Dell ATX case as an example
>> of a design that takes advantage of turbulence to cool. There is
>> volume of space at the bottom of the case in which fresh air
>> sweeps in the from the lower front, straight back to the lower part
>> of the motherboard and the expansion cards. The main hard
>> drive plastic cage could easily have been mounted anywhere in
>> that cavity, and its mounting cage could have been conveniently
>> attached at any number of places.
>
> Bad assumption.
WHY?
>> But the HD is mounted vertically
>> with its circuit board facing the front and about !/2" from the vent
>> holes - despite that this impedes the incoming air. Not only
>> does this put the HD's circuit board in the field of maximum
>> turbulence caused by the vent holes stamped in the metal case,
>> but it causes more turbulence in the case immediately behind it.
>> If the designers were designing for maximum bulk air flow through
>> the case, they failed. If they were designing for optimal cooling,
>> they did quite well because in 7 1/2 yrs, I haven't had a HD (or any
>> other part) in the PC fail. In fact, when I touch the 7,200 rpm HD,
>> it feels no warmer than my body temperature.
>
> All that proves is it does a good job of cooling the hard drive, not that
> they put it there to 'create case turbulence'.
Read again. The hard drive's placement wasn't to "create case
turbulence" - it was to take advantage of it.
>> That turbulence cools parts is evidenced in countless fields of
>> science and engineering. That turbulence alone can cool objects -
>> of course not! If that were true, there would just be fans inside
>> cases and the cases would be sealed shut.
>
> And that should give you a clue that how well one can get the air in and
> out is of importance.
"Of importance" does NOT mean "primary importance" or
"most important". Getting air in and out is "of importance".
So is maintaining turbulence "of importance". And striving
for laminar flow throughout the case in to be avoided. That
is the point - turbulence is not bad for cooling. In fact, it's
good for cooling.
>> What I point out is that turbulence is NOT BAD,
>
> The problem is the broad sweeping generalization...
Turbulence is not bad for cooling - that's the subject of the thread,
and that's my point. 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). 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.
>> and that turbulence is turbulence -
>
> But turbulence just anywhere is not necessarily a 'good thing',
> as has been previously illustrated.
Turbulence is good where heat transfer is to take place.
Where it's generated is inconsequential to its task of heat
transfer. That's because turbulence doesn't care where it
is - it works the same "here" as "there".
>> be it generated by friction of the flow against the part itself that
>> is to be cooled, or somewhere upwind of that part.
>
> Nope. Just as pouring water on a wood fire at the lumber yard helps
> extinguish it but pouring water over the whole state for the same fire
> isn't an efficient use of resources even though, to analogize your logic,
> 'water is water'.
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. 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.
> Component level turbulence pretty much takes care of itself, either by
> nature or the component designer's intent, so the case designer is
> primarily concerned with getting the air in, through (to all needed areas),
> and out efficiently.
Tell that to those PC users who have repeatedly failing hard drives.
If the simple placement and orientation of a hard drive can take
advantage of intake turbulence for cooling, why not use it? Why
strive for "smooth air flow" if it's detrimental? Again, the subject of
the thread is "turbulent flow is NOT BAD for cooling".
In article <AdCdnUjZlKYfcLTYnZ2dnUVZ_vKdnZ2d@comcast.com>,
Timothy Daniels <TDaniels@NoSpamDot.com> wrote:
>"kornball" wrote:
>> All evidence is against you.
>>
>> No observation in a dissimilar closed system can be assumed
>> applicable to another use. TESTING is what others have
>> done but not Tim.
>
>
> You probably don't believe in gravity, either.
> But thermodynamics and aerodynamics show
> your "arguments" to be fallacies:
>
> 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."
So turbulant air solves your cooling problem if, and only if, boundry
layers are the bottleneck in your cooling system.
jeesh.
--
a d y k e s @ p a n i x . c o m
Harrison for Congress in NY 13CD www.harrison06.com
Don't blame me. I voted for Gore. A Proud signature since 2001
In article <ZpKdnVK8Icg0irfYnZ2dnUVZ_rCdnZ2d@comcast.com>,
Timothy Daniels <TDaniels@NoSpamDot.com> wrote:
>"David Maynard" wrote:
>> Kony is correct in that you are mixing micro and macro effects
>> and then assuming the tradeoffs are the same, but they're not.
>
>
> Turbulence is turbulence. Nothing "micro" and "macro"
> about it, except that they are neat terms.
>
but boundry layer aerodynamics *is* a small scale ("micro") effect.
You're clueless.
--
a d y k e s @ p a n i x . c o m
Harrison for Congress in NY 13CD www.harrison06.com
Don't blame me. I voted for Gore. A Proud signature since 2001
"Al Dykes" wrote:
> Timothy Daniels wrote:
>> 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."
>
> So turbulant air solves your cooling problem if, and only if,
> boundry layers are the bottleneck in your cooling system.
"Turbulence will make your cooling system more efficient"
is a better summary. Boundary layers will always be there.
Turbulence just "wears" them down to a thinner depth and
prevents their buildup to thicker depths.
Re: turbulent flow not bad for cooling 
Linear Mode
