"Al Dykes" wrote:
> Timothy Daniels wrote:
>> 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.
Boundary layers are small in depth, but their *effects* are not small.
They keep a protective, almost stagnant, layer of air in contact
with objects that hinders direct contact with flowing fluids. It's
like having a layer of Saran Wrap on the object - the Saran Wrap
is thin, but it hinders heat flow between the fluid and the object.
The more turbulent the air impinging on this "Saran Wrap", the
thinner the Saran Wrap becomes, thus causing less resistance
to heat flow between the fluid and the object. There is nothing that
requires the boundary layer to have physical dimensions similar to
the size of the turbulent vortices or the extent of the turbulent region
in order for the turbulence to affect the boundary layer.
On Mon, 9 Oct 2006 16:16:22 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:
> "Turbulence will make your cooling system more efficient"
> is a better summary.
Of your theory, yes.
Of truth as applicable to cooling a reasonably normal PC,
server, etc, no.
Once again I remind you that you only have vague notions,
versus the entire world who has built, tested, and sold
products.
No oversimplifed idea about turbulence allows ignorance of
the other varables. To resolve these variables into a
working model, you'll have to start (get ready for it....)
Testing
"kornball"wrote:
> "Timothy Daniels" wrote:
>
>
>> "Turbulence will make your cooling system more efficient"
>> is a better summary.
>
> Of your theory, yes.
>
> Of truth as applicable to cooling a reasonably normal PC,
> server, etc, no.
>
> Once again I remind you that you only have vague notions,
> versus the entire world who has built, tested, and sold
> products.
>
> No oversimplifed idea about turbulence allows ignorance of
> the other varables. To resolve these variables into a
> working model, you'll have to start (get ready for it....)
> Testing
Don't make me laugh, kornball. You've never tested for
the effect of turbulence because you just assumed that it was
bad. On the other hand, turbulence has been the subject
of scientific and engineering investigation for a century.
As you would have it, everyone would have to test for the
effects of gravity before YOU would believe it.
In article <brGdnQiixJXaRbfYnZ2dnUVZ_vidnZ2d@comcast.com>,
Timothy Daniels <TDaniels@NoSpamDot.com> wrote:
>
>"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"
The phrase "more efficient" is meaningless marketing crap.
More than one millimeter away from a air-solid interface there is no
longer a boundery layer.
--
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:
>> "Turbulence will make your cooling system more efficient"
>
> The phrase "more efficient" is meaningless marketing crap.
Then how about "cause more calories of heat removed per
second with the same bulk air flow"?
> More than one millimeter away from a air-solid interface there
> is no longer a boundery layer.
So? One millimeter away from a solid is "not in contact" with
that solid. Gaseous boundary layers thinner than that keep the
pistons in your car's engine from melting, too. That's why
"pinging" is so damaging to your engine - the turbulence
scrubs away the boundary layer to expose the metal to the
full heat and oxidation of the burning gases. Normally, the
persistant boundary layer protects the walls of the cylinder
and the crowns of the pistons enough to allow them to survive
the hundreds of ignitions and combustions per second -
which can be pretty amazing if you view a microscopically thin
sheath of burned gases to be "non-protective". Somehow you
have been led to believe that a fluidic boundary layer has to
be on the order of an inch to have any effect, which is very far
from the truth.
On Mon, 9 Oct 2006 22:55:57 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:
> So? One millimeter away from a solid is "not in contact" with
> that solid. Gaseous boundary layers thinner than that keep the
> pistons in your car's engine from melting, too. That's why
> "pinging" is so damaging to your engine - the turbulence
> scrubs away the boundary layer to expose the metal to the
> full heat and oxidation of the burning gases. Normally, the
> persistant boundary layer protects the walls of the cylinder
> and the crowns of the pistons enough to allow them to survive
> the hundreds of ignitions and combustions per second -
> which can be pretty amazing if you view a microscopically thin
> sheath of burned gases to be "non-protective". Somehow you
> have been led to believe that a fluidic boundary layer has to
> be on the order of an inch to have any effect, which is very far
> from the truth.
Seldom does someone go so wrong in a single paragraph.
In article <4cCdnTf5Kd1tqLbYnZ2dnUVZ_uWdnZ2d@comcast.com>,
Timothy Daniels <TDaniels@NoSpamDot.com> wrote:
>"Al Dykes" wrote:
>> Timothy Daniels wrote:
>>> "Turbulence will make your cooling system more efficient"
>>
>> The phrase "more efficient" is meaningless marketing crap.
>
>
> Then how about "cause more calories of heat removed per
> second with the same bulk air flow"?
>
>
>> More than one millimeter away from a air-solid interface there
>> is no longer a boundery layer.
>
>
> So? One millimeter away from a solid is "not in contact" with
> that solid. Gaseous boundary layers thinner than that keep the
> pistons in your car's engine from melting, too. That's why
> "pinging" is so damaging to your engine - the turbulence
> scrubs away the boundary layer to expose the metal to the
> full heat and oxidation of the burning gases. Normally, the
> persistant boundary layer protects the walls of the cylinder
> and the crowns of the pistons enough to allow them to survive
> the hundreds of ignitions and combustions per second -
> which can be pretty amazing if you view a microscopically thin
> sheath of burned gases to be "non-protective". Somehow you
> have been led to believe that a fluidic boundary layer has to
> be on the order of an inch to have any effect, which is very far
> from the truth.
>
>*TimDaniels*
*If* true, how does the design of an IC engine relate to the removal
of heat from a CPU die or a beige box?
> sheath of burned gases to be "non-protective". Somehow you
> have been led to believe that a fluidic boundary layer has to
> be on the order of an inch to have any effect, which is very far
Drivel and ignorance. I don't think you have a clue what a "boundary
layer" is.
"Al Dykes" asked:
> Timothy Daniels wrote:
>>"Al Dykes" wrote:
>>> More than one millimeter away from a air-solid interface there
>>> is no longer a boundery layer.
>>
>>
>> So? One millimeter away from a solid is "not in contact" with
>> that solid. Gaseous boundary layers thinner than that keep the
>> pistons in your car's engine from melting, too. That's why
>> "pinging" is so damaging to your engine - the turbulence
>> scrubs away the boundary layer to expose the metal to the
>> full heat and oxidation of the burning gases. Normally, the
>> persistant boundary layer protects the walls of the cylinder
>> and the crowns of the pistons enough to allow them to survive
>> the hundreds of ignitions and combustions per second -
>> which can be pretty amazing if you view a microscopically thin
>> sheath of burned gases to be "non-protective". Somehow you
>> have been led to believe that a fluidic boundary layer has to
>> be on the order of an inch to have any effect, which is very far
>> from the truth.
>>
>>*TimDaniels*
>
>
> *If* true, how does the design of an IC engine relate to the removal
> of heat from a CPU die or a beige box?
It has nothing to do specifically with the *design* of an internal
combustion engine, it has *all* to do with the persistance and
isolating effect of a boundary layer. It contradicts your assumption
that a boundary layer of one millimeter or less in depth is insigni-
ficant.
"The pinging sound of detonation is just these pressure waves
pounding against the insides of the combustion chamber and
piston top. Piston tops, ring lands and rod bearings are especially
exposed to damage from detonation. In addition, these pressure
fronts (or shock waves) can sweep away the unburned boundary
layer (see figure 2 above) of air-fuel mix near the metal surfaces
in the combustion chamber.
"The boundary layer is a thin layer of fuel-air mix just above the
metal surfaces of the combustion chamber (see figure 2, above).
Physical principles (aptly called boundary conditions) require that
under normal circumstances (i.e. equilibrium combustion, which
means "nice, slow and thermally well transmitted") this boundary
layer stays close to the metal surfaces. It usually is quite thin, maybe
a fraction of a millimeter to a millimeter thick. This boundary layer
will not burn even when reached by the flame front because it is in
thermal contact with the cool metal, whose temperature is always
well below the ignition temperature of the fuel-air mix.
"Only under the extreme conditions of detonation can this boundary
layer be "swept away" by the high-pressure shock front that occurs
during detonation. In that case, during these "far from equilibrium"
process of the pressure-induced shock wave entering the boundary
layer, the physical principles allured to above (the boundary conditions)
will be effectively violated. The degree of violation will depend on
(a) the pressure fluctuation caused by the shock front and (b) the
adhesive and cohesive strength of the boundary layer. These
boundary layers of air-fuel mix remain unburned during the normal
combustion process due to their close proximity to the cool metal
surfaces and act as an insulating layer and prevent a direct exposure
of metal to the flame. Since pressure waves created during detonation
can sweep away these unburned boundary layers of air-fuel mix, they
leave parts of the piston top and combustion chamber exposed to
the flame front. This, in turn, causes an immediate rise in the
temperature of these parts, often leading to direct failure or at least
to engine overheating."
>> Somehow you have been led to believe that a fluidic boundary
>> layer has to be on the order of an inch to have any effect...
>
> Drivel and ignorance. I don't think you have a clue what a "boundary
> layer" is.
>
> http://en.wikipedia.org/wiki/Boundary_layer
How does Wikipedia contradict anything that I've stated?
As for the importance of boundary layers inside internal combutsion
engines, it has been studie extensively. Here are just a couple
examples of the many very academic investigations:
"kornball" could only come up with:
> "Timothy Daniels" wrote:
>
>
>> So? One millimeter away from a solid is "not in contact" with
>> that solid. Gaseous boundary layers thinner than that keep the
>> pistons in your car's engine from melting, too. That's why
>> "pinging" is so damaging to your engine - the turbulence
>> scrubs away the boundary layer to expose the metal to the
>> full heat and oxidation of the burning gases. Normally, the
>> persistant boundary layer protects the walls of the cylinder
>> and the crowns of the pistons enough to allow them to survive
>> the hundreds of ignitions and combustions per second -
>> which can be pretty amazing if you view a microscopically thin
>> sheath of burned gases to be "non-protective". Somehow you
>> have been led to believe that a fluidic boundary layer has to
>> be on the order of an inch to have any effect, which is very far
>> from the truth.
>
>
>
> Seldom does someone go so wrong in a single paragraph.
"The pinging sound of detonation is just these pressure waves
pounding against the insides of the combustion chamber and
piston top. Piston tops, ring lands and rod bearings are especially
exposed to damage from detonation. In addition, these pressure
fronts (or shock waves) can sweep away the unburned boundary
layer (see figure 2 above) of air-fuel mix near the metal surfaces
in the combustion chamber.
"The boundary layer is a thin layer of fuel-air mix just above the
metal surfaces of the combustion chamber (see figure 2, above).
Physical principles (aptly called boundary conditions) require that
under normal circumstances (i.e. equilibrium combustion, which
means "nice, slow and thermally well transmitted") this boundary
layer stays close to the metal surfaces. It usually is quite thin, maybe
a fraction of a millimeter to a millimeter thick. This boundary layer
will not burn even when reached by the flame front because it is in
thermal contact with the cool metal, whose temperature is always
well below the ignition temperature of the fuel-air mix.
"Only under the extreme conditions of detonation can this boundary
layer be "swept away" by the high-pressure shock front that occurs
during detonation. In that case, during these "far from equilibrium"
process of the pressure-induced shock wave entering the boundary
layer, the physical principles allured to above (the boundary conditions)
will be effectively violated. The degree of violation will depend on
(a) the pressure fluctuation caused by the shock front and (b) the
adhesive and cohesive strength of the boundary layer. These
boundary layers of air-fuel mix remain unburned during the normal
combustion process due to their close proximity to the cool metal
surfaces and act as an insulating layer and prevent a direct exposure
of metal to the flame. Since pressure waves created during detonation
can sweep away these unburned boundary layers of air-fuel mix, they
leave parts of the piston top and combustion chamber exposed to
the flame front. This, in turn, causes an immediate rise in the
temperature of these parts, often leading to direct failure or at least
to engine overheating."
In article <oIadnboFza3PabbYnZ2dnUVZ_vidnZ2d@comcast.com>,
Timothy Daniels <TDaniels@NoSpamDot.com> wrote:
>"Al Dykes" asked:
>> Timothy Daniels wrote:
>>>"Al Dykes" wrote:
>>>> More than one millimeter away from a air-solid interface there
>>>> is no longer a boundery layer.
>>>
>>>
>>> So? One millimeter away from a solid is "not in contact" with
>>> that solid. Gaseous boundary layers thinner than that keep the
>>> pistons in your car's engine from melting, too. That's why
>>> "pinging" is so damaging to your engine - the turbulence
>>> scrubs away the boundary layer to expose the metal to the
>>> full heat and oxidation of the burning gases. Normally, the
>>> persistant boundary layer protects the walls of the cylinder
>>> and the crowns of the pistons enough to allow them to survive
>>> the hundreds of ignitions and combustions per second -
>>> which can be pretty amazing if you view a microscopically thin
>>> sheath of burned gases to be "non-protective". Somehow you
>>> have been led to believe that a fluidic boundary layer has to
>>> be on the order of an inch to have any effect, which is very far
>>> from the truth.
>>>
>>>*TimDaniels*
>>
>>
>> *If* true, how does the design of an IC engine relate to the removal
>> of heat from a CPU die or a beige box?
>
>
> It has nothing to do specifically with the *design* of an internal
> combustion engine, it has *all* to do with the persistance and
> isolating effect of a boundary layer. It contradicts your assumption
> that a boundary layer of one millimeter or less in depth is insigni-
> ficant.
I never said or assumed that *any* boundary layer was insignificant.
It's but one of several factors in the cooling of a computer.
You can't seperate them.
--
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
"kornball" wrote:
"Timothy Daniels" wrote:
>
>> You've never tested for
>> the effect of turbulence because you just assumed that it was
>> bad.
>
> Funny coming from someone who turned down an offer from me
> to custom fab a panel you think would help.
YOU?! Run an experiment? With one variable isolated?
And we're supposed to take your word for having done it
right? <LOL>
"Al Dykes" wrote:
> Timothy Daniels wrote:
>>"Al Dykes" asked:
>>> Timothy Daniels wrote:
>>>>"Al Dykes" wrote:
>>>>> More than one millimeter away from a air-solid interface there
>>>>> is no longer a boundery layer.
>>>>
>>>>
>>>> So? One millimeter away from a solid is "not in contact" with
>>>> that solid. Gaseous boundary layers thinner than that keep the
>>>> pistons in your car's engine from melting, too. That's why
>>>> "pinging" is so damaging to your engine - the turbulence
>>>> scrubs away the boundary layer to expose the metal to the
>>>> full heat and oxidation of the burning gases. Normally, the
>>>> persistant boundary layer protects the walls of the cylinder
>>>> and the crowns of the pistons enough to allow them to survive
>>>> the hundreds of ignitions and combustions per second -
>>>> which can be pretty amazing if you view a microscopically thin
>>>> sheath of burned gases to be "non-protective". Somehow you
>>>> have been led to believe that a fluidic boundary layer has to
>>>> be on the order of an inch to have any effect, which is very far
>>>> from the truth.
>>>>
>>>>*TimDaniels*
>>>
>>>
>>> *If* true, how does the design of an IC engine relate to the removal
>>> of heat from a CPU die or a beige box?
>>
>>
>> It has nothing to do specifically with the *design* of an internal
>> combustion engine, it has *all* to do with the persistance and
>> isolating effect of a boundary layer. It contradicts your assumption
>> that a boundary layer of one millimeter or less in depth is insigni-
>> ficant.
>>
>> From http://www.motorcycle.com/mo/mcrob/rt-fuel2.html ,
>> here is pretty thorough explanation of how "pinging" affects
>> engine overheating due to its effects on the boundary layer:
>>
>> "The pinging sound of detonation is just these pressure waves
>> pounding against the insides of the combustion chamber and
>> piston top. Piston tops, ring lands and rod bearings are especially
>> exposed to damage from detonation. In addition, these pressure
>> fronts (or shock waves) can sweep away the unburned boundary
>> layer (see figure 2 above) of air-fuel mix near the metal surfaces
>> in the combustion chamber.
>>
>> "The boundary layer is a thin layer of fuel-air mix just above the
>> metal surfaces of the combustion chamber (see figure 2, above).
>> Physical principles (aptly called boundary conditions) require that
>> under normal circumstances (i.e. equilibrium combustion, which
>> means "nice, slow and thermally well transmitted") this boundary
>> layer stays close to the metal surfaces. It usually is quite thin, maybe
>> a fraction of a millimeter to a millimeter thick. This boundary layer
>> will not burn even when reached by the flame front because it is in
>> thermal contact with the cool metal, whose temperature is always
>> well below the ignition temperature of the fuel-air mix.
>>
>> "Only under the extreme conditions of detonation can this boundary
>> layer be "swept away" by the high-pressure shock front that occurs
>> during detonation. In that case, during these "far from equilibrium"
>> process of the pressure-induced shock wave entering the boundary
>> layer, the physical principles allured to above (the boundary conditions)
>> will be effectively violated. The degree of violation will depend on
>> (a) the pressure fluctuation caused by the shock front and (b) the
>> adhesive and cohesive strength of the boundary layer. These
>> boundary layers of air-fuel mix remain unburned during the normal
>> combustion process due to their close proximity to the cool metal
>> surfaces and act as an insulating layer and prevent a direct exposure
>> of metal to the flame. Since pressure waves created during detonation
>> can sweep away these unburned boundary layers of air-fuel mix, they
>> leave parts of the piston top and combustion chamber exposed to
>> the flame front. This, in turn, causes an immediate rise in the
>> temperature of these parts, often leading to direct failure or at least
>> to engine overheating."
>>
>>
>> Somehow you have been led to believe that a fluidic boundary
>> layer has to be on the order of an inch to have any effect...
>
>
> I never said or assumed that *any* boundary layer was insignificant.
> It's but one of several factors in the cooling of a computer.
> You can't seperate them.
I see. So which factors have I tried to "seperate" [sic] and please
tell us why separating them is bad.
"kornball" wrote:
> "Timothy Daniels" wrote:
>
>> "lornball wrote:
>>> Seldom does someone go so wrong in a single paragraph.
>>
>>
>> Oh? Here's more "wrong" stuff:
>>
>> From http://www.motorcycle.com/mo/mcrob/rt-fuel2.html ,
>> here is pretty thorough explanation of how "pinging" affects
>> engine overheating due to its effects on the boundary layer:
>>
>> "The pinging sound of detonation is just these pressure waves
>> pounding against the insides of the combustion chamber and
>> piston top. Piston tops, ring lands and rod bearings are especially
>> exposed to damage from detonation. In addition, these pressure
>> fronts (or shock waves) can sweep away the unburned boundary
>> layer (see figure 2 above) of air-fuel mix near the metal surfaces
>> in the combustion chamber.
>>
>> "The boundary layer is a thin layer of fuel-air mix just above the
>> metal surfaces of the combustion chamber (see figure 2, above).
>> Physical principles (aptly called boundary conditions) require that
>> under normal circumstances (i.e. equilibrium combustion, which
>> means "nice, slow and thermally well transmitted") this boundary
>> layer stays close to the metal surfaces. It usually is quite thin, maybe
>> a fraction of a millimeter to a millimeter thick. This boundary layer
>> will not burn even when reached by the flame front because it is in
>> thermal contact with the cool metal, whose temperature is always
>> well below the ignition temperature of the fuel-air mix.
>>
>> "Only under the extreme conditions of detonation can this boundary
>> layer be "swept away" by the high-pressure shock front that occurs
>> during detonation. In that case, during these "far from equilibrium"
>> process of the pressure-induced shock wave entering the boundary
>> layer, the physical principles allured to above (the boundary conditions)
>> will be effectively violated. The degree of violation will depend on
>> (a) the pressure fluctuation caused by the shock front and (b) the
>> adhesive and cohesive strength of the boundary layer. These
>> boundary layers of air-fuel mix remain unburned during the normal
>> combustion process due to their close proximity to the cool metal
>> surfaces and act as an insulating layer and prevent a direct exposure
>> of metal to the flame. Since pressure waves created during detonation
>> can sweep away these unburned boundary layers of air-fuel mix, they
>> leave parts of the piston top and combustion chamber exposed to
>> the flame front. This, in turn, causes an immediate rise in the
>> temperature of these parts, often leading to direct failure or at least
>> to engine overheating."
>>
>> *TimDaniels*
>
>
> Yes
Your rationale, such as it is, is irrefutable. <LOL>
In article <oIadnboFza3PabbYnZ2dnUVZ_vidnZ2d@comcast.com>,
Timothy Daniels <TDaniels@NoSpamDot.com> wrote:
>"Al Dykes" asked:
>> Timothy Daniels wrote:
>>>"Al Dykes" wrote:
>>>> More than one millimeter away from a air-solid interface there
>>>> is no longer a boundery layer.
>>>
>>>
>>> So? One millimeter away from a solid is "not in contact" with
....
>> Drivel and ignorance. I don't think you have a clue what a "boundary
>> layer" is.
>>
>> http://en.wikipedia.org/wiki/Boundary_layer
>
>
> How does Wikipedia contradict anything that I've stated?
>
> As for the importance of boundary layers inside internal combutsion
> engines, it has been studie extensively. Here are just a couple
> examples of the many very academic investigations:
>
> http://cat.inist.fr/?aModele=afficheN&cpsidt=17554037
>
> Here's one that investigates the effect of turbulence to
> enhance the flow of heat through the cylinder wall:
>
> http://www.emeraldinsight.com/Insigh...ton%20crown%22
>
>
>*TimDaniels*
>
How did we get from talking about air at near-normal STP to talking
about the conditions inside a firing engine cylinder? There is lots
of math in common, but the parameters and coefficients used in each
case make all the difference in the world.
It's like comparing a R/C flyer to a supersonic fighter. An
aerodynamicist may see some things in common but the hard aspects of
the problem are completely different, in practice.
We should take Tim's Google driving license away.
--
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 <7pGdnSr5LZK2pLHYnZ2dnUVZ_tCdnZ2d@comcast.com>,
Timothy Daniels <TDaniels@NoSpamDot.com> wrote:
>"Al Dykes" wrote:
>> Timothy Daniels wrote:
>>>"Al Dykes" asked:
>>>> Timothy Daniels wrote:
>>>>>"Al Dykes" wrote:
>>>>>> More than one millimeter away from a air-solid interface there
>>>>>> is no longer a boundery layer.
>>>>>
>>>>>
>>>>> So? One millimeter away from a solid is "not in contact" with
>>>>> that solid. Gaseous boundary layers thinner than that keep the
>>>>> pistons in your car's engine from melting, too. That's why
>>>>> "pinging" is so damaging to your engine - the turbulence
>>>>> scrubs away the boundary layer to expose the metal to the
>>>>> full heat and oxidation of the burning gases. Normally, the
>>>>> persistant boundary layer protects the walls of the cylinder
>>>>> and the crowns of the pistons enough to allow them to survive
>>>>> the hundreds of ignitions and combustions per second -
>>>>> which can be pretty amazing if you view a microscopically thin
>>>>> sheath of burned gases to be "non-protective". Somehow you
>>>>> have been led to believe that a fluidic boundary layer has to
>>>>> be on the order of an inch to have any effect, which is very far
>>>>> from the truth.
>>>>>
>>>>>*TimDaniels*
>>>>
>>>>
>>>> *If* true, how does the design of an IC engine relate to the removal
>>>> of heat from a CPU die or a beige box?
>>>
>>>
>>> It has nothing to do specifically with the *design* of an internal
>>> combustion engine, it has *all* to do with the persistance and
>>> isolating effect of a boundary layer. It contradicts your assumption
>>> that a boundary layer of one millimeter or less in depth is insigni-
>>> ficant.
>>>
>>> From http://www.motorcycle.com/mo/mcrob/rt-fuel2.html ,
>>> here is pretty thorough explanation of how "pinging" affects
>>> engine overheating due to its effects on the boundary layer:
>>>
>>> "The pinging sound of detonation is just these pressure waves
>>> pounding against the insides of the combustion chamber and
>>> piston top. Piston tops, ring lands and rod bearings are especially
>>> exposed to damage from detonation. In addition, these pressure
>>> fronts (or shock waves) can sweep away the unburned boundary
>>> layer (see figure 2 above) of air-fuel mix near the metal surfaces
>>> in the combustion chamber.
>>>
>>> "The boundary layer is a thin layer of fuel-air mix just above the
>>> metal surfaces of the combustion chamber (see figure 2, above).
>>> Physical principles (aptly called boundary conditions) require that
>>> under normal circumstances (i.e. equilibrium combustion, which
>>> means "nice, slow and thermally well transmitted") this boundary
>>> layer stays close to the metal surfaces. It usually is quite thin, maybe
>>> a fraction of a millimeter to a millimeter thick. This boundary layer
>>> will not burn even when reached by the flame front because it is in
>>> thermal contact with the cool metal, whose temperature is always
>>> well below the ignition temperature of the fuel-air mix.
>>>
>>> "Only under the extreme conditions of detonation can this boundary
>>> layer be "swept away" by the high-pressure shock front that occurs
>>> during detonation. In that case, during these "far from equilibrium"
>>> process of the pressure-induced shock wave entering the boundary
>>> layer, the physical principles allured to above (the boundary conditions)
>>> will be effectively violated. The degree of violation will depend on
>>> (a) the pressure fluctuation caused by the shock front and (b) the
>>> adhesive and cohesive strength of the boundary layer. These
>>> boundary layers of air-fuel mix remain unburned during the normal
>>> combustion process due to their close proximity to the cool metal
>>> surfaces and act as an insulating layer and prevent a direct exposure
>>> of metal to the flame. Since pressure waves created during detonation
>>> can sweep away these unburned boundary layers of air-fuel mix, they
>>> leave parts of the piston top and combustion chamber exposed to
>>> the flame front. This, in turn, causes an immediate rise in the
>>> temperature of these parts, often leading to direct failure or at least
>>> to engine overheating."
>>>
>>>
>>> Somehow you have been led to believe that a fluidic boundary
>>> layer has to be on the order of an inch to have any effect...
>>
>>
>> I never said or assumed that *any* boundary layer was insignificant.
>> It's but one of several factors in the cooling of a computer.
>> You can't seperate them.
>
>
> I see. So which factors have I tried to "seperate" [sic] and please
> tell us why separating them is bad.
You're fixated on turbulence.
--
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
Not at all. I merely point out that turbulence, contrary to
those effete nabobs of negativism, is not bad for cooling.
As a matter of fact, it's GOOD for cooling. That's not
"fixation". Steadfastly denying 100 years of scientific
investigation into fluid flow is fixation.
"Al Dykes" put forth:
> In article <oIadnboFza3PabbYnZ2dnUVZ_vidnZ2d@comcast.com>,
> Timothy Daniels <TDaniels@NoSpamDot.com> wrote:
>>"Al Dykes" asked:
>>> Timothy Daniels wrote:
>>>>"Al Dykes" wrote:
>>>>> More than one millimeter away from a air-solid interface there
>>>>> is no longer a boundery layer.
>
>
> How did we get from talking about air at near-normal STP to talking
> about the conditions inside a firing engine cylinder?
By your statement (see above) that "More than one millimeter away
from a air-solid interface there is no longer a boundery layer."
I pointed out that less than that thickness of a boundary layer
protects the insides of a combutsion chamber from meltdown.
> There is lots of math in common, but the parameters and coefficients
> used in each case make all the difference in the world.
If you want room temperature boundary layers, consider this:
"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 Tue, 10 Oct 2006 17:02:26 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:
>"kornball" wrote:
> "Timothy Daniels" wrote:
>>
>>> You've never tested for
>>> the effect of turbulence because you just assumed that it was
>>> bad.
>>
>> Funny coming from someone who turned down an offer from me
>> to custom fab a panel you think would help.
>
>
> YOU?! Run an experiment? With one variable isolated?
> And we're supposed to take your word for having done it
> right? <LOL>
Hmm, let's see what we should do to ...
- Pretend Tim is right when he actively argues against
testing, or
- Actually test the hypothesis
While the former aligns well with Tim's neverending ego, the
latter is the only way to get any validation.
Here's a little hint Tim- I've made plenty of case parts
including intakes out of sheet aluminum. You're still in
the reading is fundamental stage of learning. Sooner or
later you will have to get up, take a case, and actually DO
IT. Otherwise, even _IF_ you /were/ right, you were still
foolish to put so much time into an idea without any
fruitful outcome.
How is this not obvious? Do you really think you can
selectively ignore real testing? Really? C'mon Tim, this
is not a trick question, nor a trick test, it's up to you to
actually DO what you think will help, propose a specific
reproducible example of it helping.
On Tue, 10 Oct 2006 19:02:58 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:
>"Al Dykes" wrote:
>> You're fixated on turbulence.
>
>
> Not at all. I merely point out that turbulence, contrary to
> those effete nabobs of negativism, is not bad for cooling.
Nobody claimed it was.
We have claimed you cannot ignore the detriment to airflow
and cannot assume actively trying to cause turbulence except
on, at the point of the parts' surface, will improve
cooling in a computer.
> As a matter of fact, it's GOOD for cooling.
As a matter of what Tim? Sorry but FACT is what your posts
have been sorely lacking all along, because you have done no
testing.
> That's not
> "fixation".
Yes it is, but if you'd prefer us calling it "stuck"...
> Steadfastly denying 100 years of scientific
> investigation into fluid flow is fixation.
Nobody has denied anything, except that you cannot apply an
idea about turbulence to a dissimilar situation while
ignoring airflow rate changes.
On 10 Oct 2006 21:20:22 -0400, adykes@panix.com (Al Dykes)
wrote:
>How did we get from talking about air at near-normal STP to talking
>about the conditions inside a firing engine cylinder?
Tim likes pretending he has some advanced new insight into
common things, but as always when it comes right down to
demonstrating any benefit from his theories, he goes into
troll mode.
> "David Maynard" 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.
Nope and you should have read it all before knee jerk replying.
>> ...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.
I am not "assuming" anything. You are.
> But merely running air past
> a part does not bring it into close contact with the part. There is
> still
> the boundary layer of air around the part with which to contend.
Local turbulence is already taken care of by the part itself. Just try to
get 'laminar' flow over one. It's almost, if not, impossible.
> Simply running a greater volume of air past a part is a brute force
> approach to cooling. Adding turbulence to the fluid (in this case air)
> that passes the heated part aids the fluid to scrub away that boundary
> layer and makes the passage of fluid more efficient in carrying away
> calories - if "efficiency" is measured in calories/volume of
> fluid-per-second.
Simply untrue.
> Your assumption that the addition of turbulence is a "waste of energy"
> is presumptuous.
Just a fact.
>> 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.
It won't have laminar flow over the part no matter how hard you try to do
it. The 'turbulence' don't need your 'help' on the other side of the case.
>> 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,
You're good up to here.
> and the turbulence should be maximized as
> the air approaches or enters the racks to be cooled.
Nope. Wasted energy.
>> Similarly, creating extraneous turbulence inside the case simply
>> impedes airflow.
>
>
> "Extraneous" means "extra, unneeded".
Exactly.
> So your description
> is designed for your conclusion. But well-designed turbulence is
> turbulence that impinges primarily the parts to be cooled.
Which isn't "6 inches" away.
> You
> could accomplish that by "turbulators" that induce the turbulence
> at carefully selected upstream points.
Useless waste of energy.
> This is a technique used
> in aircraft design to control the point of stall onset in wings and
> control surfaces. The slight reduction in lift or the slight increase
> in drag is considered to be worth the added control predictability
> for low speed handling.
We're not talking about airfoils and lift.
> Similarly with PC case ventilation - the slight
> increase in drag caused by turbulence generation can be offset by
> the increase in cooling capacity. But if that makes you worry, you
> can actively add turbulence with an internal fan - such as is currently
> done to cool CPU heatsinks and GPU heatsinks, and there will be
> NO increased drag due to energy used to generate that turbulence.
Hey, pal. The extra fan ain't 'free energy'. Nor is it there for 'turbulence.
> But if you're willing to design for passive turbulence, you could
> position
> parts to minimize the increase in drag which would occur from the
> passive generation of that turbulence. Since turbulence can be produced
> by sharp-edged holes in flat plates, the opportunity arises to use the
> inevitable turbulence
You should ponder your own words, there, "inevitable turbulence" when
looking at the physical components.
> produced at the average case's air intake holes -
> which are almost always just holes punched in metal sheets.
Because it's *cheap*. Try looking up the 'big boy' stuff and see what they
say about intake filter turbulence. Hint, you won't find a single one
bragging at how much it creates but, rather, how little.
> There is
> lots of turbulence there and downstream of it, so by putting hot
> parts in
> that turbulence, one could make maximum use of it before it gets
> dissipated by drag from contact with other parts in the case.
You put the (hot) parts in front of it because it's cool intake air with
lots of flow before it gets dispersed into the whole case volume.
>
> Such an opportunity occurs for cooling the main hard drive, as in my
> Dell computer. The intake holes are the standard holes punched in the
> face of the metal case.
Because it's *cheap*.
> Since the hard drive is mounted vertically
> immediately behind these holes with its circuit board facing the holes,
> the hard drive gets the maximum benefit of the inevitable intake
> turbulence.
> Despite the considerable freedom to position the hard drive elsewhere
> in the bottom of the case, the designer put it where it is and
> oriented it as
> he did. Elsewhere low in the case would have gotten the same amount
> of fresh air flow, but turbulence would have been cut down by the air's
> drag against other parts and with the case wall.
Nope. Airflow is maximum at the intake.
> If you're willing
> (and have
> the room) to install ducting or tunnels within the case to carry
> intake air
> directly to regions of the case, you could postpone the turbulence prod-
> uction until just upstream of a part to be cooled.
Too much drag from the ducting and tunnels. Try it and you'll find out.
> The air could
> then be put
> through a sieve consisting of holes in a flat plate, or it could be
> given a
> swirl by carefully designed vanes or "dragon's teeth" as is done in
> aircraft
> design. By virtue of the ducting, the air would be forced against
> the sieve
> or turbulating vanes, and it would not just go around those
> "turbulators".
More drag and wasted energy.
> Except for very hot and critical parts, are ducting and "turbulators"
> necessary? Quite probably not. By careful positioning and use of
> heatsink fans, just "getting the air in and out" has mostly sufficed.
> But should one do anything to maximize laminar flow?
You aren't going to get 'laminar flow' so stop worrying about it. What you
do is cut down on the wasted turbulence as much as possible.
> Unless that
> laminar flow is going only past parts that don't need cooling, NO -
> leave the air turbulent. Should one maximize turbulent flow if most
> of that turbulence will impinge heated parts? YES.
That's a nice "if" but nothing you've talked about will improve 'heated
parts' turbulence one bit.
>> 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.
You're still thinking *way* too macro. The heat of a part will, itself,
create boundary layer turbulence. You can't avoid it unless using super
high velocities that scrub past it. For 'problem' parts the designer might
include surface 'bumps', or some other mechanism, but the point is there's
nothing you have to do about it 'in the case' except get a reasonable
amount of air in and out.
>>> ...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.
Right.
> Both the increased speed and the increased turbulence work to
> increase the amount of heat transferred from the hot part to the air
> flowing past it. The increased speed increases the velocity gradient
> of the boundary layer of air - "thinning it" in effect to increase the
> transport of heat across that boundary layer - and the increased
> turbulence helps to disrupt and cut through that boundary layer.
Look at the CFM specifications for any forced air heatsink. You will not
see a 'turbulence' factor. It is strictly CFM.
> But
> the fan does not increase the bulk air flow through the case. It merely
> increases the local air speed - which is another way of saying that
> it increases the turbulence because the air is kinetically energized
> without any increase in overall translational speed. In other words,
> the fan is a "turbolator". It's an active turbulator because it
> receives
> electrical power, but it is a turbulator nonetheless.
Nope. It's more velocity, nothing else.
>>> 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.
But it isn't 'inconsequential'.
> *Konehead* is the one who calls air "pre-heated" or "stagnant"
> if it has contacted a heated part multiple times. Re-read the thread,
> and you will see that. What I point out is that DESPITE such
> "pre-heating" or pre-use or re-circulation, internal fans that blow
> against heated parts (such as a heatsink fan) still aid in cooling
> those parts.
They do despite the problem of it being preheated.
>>> - 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,
Correct.
> "it's" purpose is to increase the local air flow through the
> heatsink. You said that in a statement just above.
Correct. Which is 'directed airflow'.
>> 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.
The 'it' is your attempt to equate directed airflow to 'turbulence'.
>>> It really doesn't matter whether this turbulence is
>>> generated an eighth of an inch or a quarter of an inch or six
>>> inches away - it's just turbulence,
>>
>>
>> And 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?
Entropy
Your '6 inch away' turbulence might as well be on the moon.
>> 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.
For a 1 inch long surface, like an IC, that 1 inch diameter 'turbulence' is
dern near laminar and at the micro scale, where it matters, it's downright
gargantuan.
> By "bulk", I mean
> volumes on the order of one or two cubic feet. Most of the energy
> of the turbulence generated at the case's air intake holes are
> probably in vortices measuring 1/32" to 1/4" across.
And gone almost as soon as they pass through.
> Judging by
> the persistence of vortices in such things as smoke rings or
> blown candle smoke,
A smoke ring is not 'turbulence'. It's the shape left after it's creation.
> these vortices probably last for a few to many
> seconds - long enough to traverse the interior of a PC case. Thus,
> turbulence generated at the intake vent holes would persist during
> the air's transit of the case.
Nope.
>>> 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?
What makes you think they last, other than 'smoke rings'? Which, if it
really was so turbulent as you think would vanish immediately.. from the
turbulence disrupting the shape.
>>> 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.
If you want to muster the power to blow a hurricane through the thing then
you could afford all that turbulence you like so much.
>>> 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?
I've told you through this whole thing.
>>> 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.
It was to take advantage of the cold air coming in where it's of maximum
velocity.
>>> 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".
Correct.
> So is maintaining turbulence "of importance".
But nothing you need worry about.
> And striving
> for laminar flow throughout the case in to be avoided.
You can't *get* laminar flow. The best you can do is reduce the wasted
turbulence.
> That
> is the point - turbulence is not bad for cooling. In fact, it's
> good for cooling.
Yes, right at the surface. Everything else is a waste of energy.
>>> 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.
No, your point has been that any and all turbulence, regardless of where,
is a 'good thing' and that's simply not correct.
> Turbulence may reduce bulk air flow if the
> turbulence is generated passively, but it increases cooling
> enough to make engineers design it into their systems (see
> the numerous links that I've provided).
Your links are all surface micro turbulence examples.
> You don't see them
> designing it OUT of their cooling or heating systems except
> in long ductways where the purpose is to transport the air,
> not to apply the air for heat transfer. Where the heat transfer
> is to take place, they always want turbulence.
Yes, and that isn't 6 inches away nor at the intake vents.
>>> 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.
Which is the thermal surface.
> Where it's generated is inconsequential to its task of heat
> transfer.
Wrong.
> That's because turbulence doesn't care where it
> is - it works the same "here" as "there".
Then why don't you just use all that natural 'turbulence' mother nature put
in the atmosphere, since it matters not 'where'?
>>> 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.
It doesn't 'all go there' in either case.
> Implicit in all your objections is that turbulence
> dissipates in milliseconds and that it cannot traverse a significant
> portion of the case before dissipating. Everyday experience
> contradicts that.
No, the point is that the turbulence of use is micro turbulence at the
surface boundary layer and that your macro 'turbulence', because it's
'turbulent' only when compared to the case volume, or the room, or the
planet, looks just like your dreaded 'laminar flow' at the micro surface level.
>> 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.
Not enough un preheated air flow/
> If the simple placement and orientation of a hard drive can take
> advantage of intake turbulence for cooling, why not use it?
I think it's a good idea. It's just that your understanding of why is
incorrect.
> Why
> strive for "smooth air flow" if it's detrimental?
Because it isn't.
> Again, the subject of
> the thread is "turbulent flow is NOT BAD for cooling".
"kornball" wrote:
> Here's a little hint Tim- I've made plenty of case parts
> including intakes out of sheet aluminum. You're still in
> the reading is fundamental stage of learning. Sooner or
> later you will have to get up, take a case, and actually DO
> IT. Otherwise, even _IF_ you /were/ right, you were still
> foolish to put so much time into an idea without any
> fruitful outcome.
And where is the description and the results of your "tests"?
C'mon, fakeball, present 'em.
"kornball" wrote:
> "Timothy Daniels" wrote:
>> Not at all. I merely point out that turbulence, contrary to
>> those effete nabobs of negativism, is not bad for cooling.
>
> Nobody claimed it was.
You have said that turbulence should be minimized or reduced.
> We have claimed you cannot ignore the detriment to airflow
> and cannot assume actively trying to cause turbulence except
> on, at the point of the parts' surface, will improve
> cooling in a computer.
>
>
>> As a matter of fact, it's GOOD for cooling.
>
> As a matter of what Tim? Sorry but FACT is what your posts
> have been sorely lacking all along, because you have done no
> testing.
As I have said, you would have us all testing for the existence
of gravity. On the other hand, there exists a plethora of clues
for even boneheads like you that turbulence helps in heat
transfer:
"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:
> Tim likes pretending he has some advanced new insight into
> common things, but as always when it comes right down to
> demonstrating any benefit from his theories, he goes into
> troll mode.
"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:
>> Turbulence is turbulence. Nothing "micro" and "macro"
>> about it, except that they are neat terms.
>
> Nope and you should have read it all before knee jerk replying.
"Nope" is not angument, Maynard.
> I am not "assuming" anything. You are.
So what's your point?
> Local turbulence is already taken care of by the part itself.
> Just try to get 'laminar' flow over one. It's almost, if not, impossible.
Is this your "OFF/ON" theory of turbulence? Turbulence occurs
in degrees just as laminar flow does.
>> Simply running a greater volume of air past a part is a brute force
>> approach to cooling. Adding turbulence to the fluid (in this case air)
>> that passes the heated part aids the fluid to scrub away that boundary
>> layer and makes the passage of fluid more efficient in carrying away
>> calories - if "efficiency" is measured in calories/volume of fluid-per-second.
>
> Simply untrue.
Is "simply untrue" the extent of your reasoning?
>> Your assumption that the addition of turbulence is a "waste of energy"
>> is presumptuous.
>
> Just a fact.
Is "just a fact" the extent of your reasoning?
>>> 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.
>
> It won't have laminar flow over the part no matter how hard you try to do it. The 'turbulence' don't need your 'help' on the other
> side of the case.
If by "other side of the case" you mean "after contacting multiple
parts", the turbulence will have been reduced by drag against the
parts. If by "other side of the case" you mean "during the time of
transiting free space within the case", any turbulence generated
upstream will benefit the cooling of parts that it eventually impinges.
>> and the turbulence should be maximized as
>> the air approaches or enters the racks to be cooled.
>
> Nope. Wasted energy.
Is "Nope" the extent of your reasoning?
>> .. well-designed turbulence is
>> turbulence that impinges primarily the parts to be cooled.
>
> Which isn't "6 inches" away.
Transiting 6" probably takes the air one to two seconds.
So what makes you think turbulence will die out in that
period of time?
>> You
>> could accomplish that by "turbulators" that induce the turbulence
>> at carefully selected upstream points.
>
> Useless waste of energy.
Is saying "useless waste of energy" the extent of your argument?
>> This is a technique used
>> in aircraft design to control the point of stall onset in wings and
>> control surfaces. The slight reduction in lift or the slight increase
>> in drag is considered to be worth the added control predictability
>> for low speed handling.
>
> We're not talking about airfoils and lift.
Boundary layers and the effects of air flow apply universally,
especially in subsonic regimes.
>> Similarly with PC case ventilation - the slight
>> increase in drag caused by turbulence generation can be offset by
>> the increase in cooling capacity. But if that makes you worry, you
>> can actively add turbulence with an internal fan - such as is currently
>> done to cool CPU heatsinks and GPU heatsinks, and there will be
>> NO increased drag due to energy used to generate that turbulence.
>
> Hey, pal. The extra fan ain't 'free energy'. Nor is it there for 'turbulence.
Who said turbulence was "free"? What an internal fan produces is
both turbulence and re-circulation. It does NOT increase bulk air flow.
Kornball has called re-circulated air "pre-heated" and "used" air -
which obviously isn't so bad if most PCs, especially of the gaming
variety - use internal fans.
>> But if you're willing to design for passive turbulence, you could position parts to minimize the increase in drag which would
>> occur from the passive generation of that turbulence. Since
>> turbulence can be produced by sharp-edged holes in flat plates,
>> the opportunity arises to use the inevitable turbulence
>
> You should ponder your own words, there, "inevitable turbulence" when looking at the physical components.
Read again. I wrote "Since turbulence can be produced by
SHARP-EDGED HOLES IN FLAT PLATES, the opportunity
arises to use the inevitable turbulence" That means that
the punched holes at the front of the case produce lots of
turbulence.
>> produced at the average case's air intake holes -
>> which are almost always just holes punched in metal sheets.
>
> Because it's *cheap*.
And right in that turbulence, bathing in it, is where the
hard drive is put by Dell instead of other equally
available positions. It uses this "cheap" turbulence
to cool the hard drive.
> Try looking up the 'big boy' stuff and see what they say about intake filter turbulence. Hint, you won't find a single one
> bragging at how much it creates but, rather, how little.
Big Boy Stuff, if it's available to YOU, is for the Little Boys.
"Stuff", if it's available to YOU, will tout whatever will
impress YOU about their engineering and design prowess,
and it will not reveal any clever techniques which will
sound non-intuitive to Little Boys. Furthermore, all one
has to do is to inspect the product of the Big Boys,
and Dell, being a "Big Boy", utilizes turbulence in its
designs rather than trying to minimize it.
> You put the (hot) parts in front of it because it's cool intake air with lots of flow before it gets dispersed into the whole case
> volume.
"Before it gets DISPERSED into the whole case volume".
Hmmm... is that the "Little Balls" theory of air dispersal?
The intake air gets "DISPERSED"? First, it's concentrated,
then it gets "DISPERSED"? I thought you were designing
for laminar flow across the case. How would intake air get
dispersed?
Hey, I pointed out many times that there is free and direct
flow of intake air across an open cavity at the bottom of
Dell's case, and the hard drive would get the same air
anywhere in that cavity, but that some of the turbulence
would have been diminished by contact with the cavity's
walls. So Dell puts the hard drive flat against and close to
the turbulenvce generated by the passage of air through the
intake holes.
>> Such an opportunity occurs for cooling the main hard drive, as in my
>> Dell computer. The intake holes are the standard holes punched in the
>> face of the metal case.
>
> Because it's *cheap*.
First you claim that turbulence is a waste of energy, now you
say it's "cheap". Which is it?
>> Since the hard drive is mounted vertically immediately behind
>> these holes with its circuit board facing the holes, the hard drive
>> gets the maximum benefit of the inevitable intake turbulence.
>> Despite the considerable freedom to position the hard drive
>> elsewhere in the bottom of the case, the designer put it where
>> it is and oriented it as he did. Elsewhere low in the case would
>> have gotten the same amount of fresh air flow, but turbulence
>> would have been cut down by the air's drag against other parts
>> and with the case wall.
>
> Nope. Airflow is maximum at the intake.
And what goes in doesn't come out? <LOL>
Where does the air disappear to?
Is there an Air Destroyer in all your designs?
>> 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 production until just upstream
>> of a part to be cooled.
>
> Too much drag from the ducting and tunnels. Try it and you'll find out.
Tell it to Apple Computers. I'm sure they're waiting to hear
from you.
>> The air could then be put through a sieve consisting of holes
>> in a flat plate, or it could be given a swirl by carefully designed
>> vanes or "dragon's teeth" as is done in aircraft design. By virtue
>> of the ducting, the air would be forced against the sieve
>> or turbulating vanes, and it would not just go around those "turbulators".
>
> More drag and wasted energy.
If you say so.
>> Except for very hot and critical parts, are ducting and "turbulators"
>> necessary? Quite probably not. By careful positioning and use of
>> heatsink fans, just "getting the air in and out" has mostly sufficed.
>> But should one do anything to maximize laminar flow?
>
> You aren't going to get 'laminar flow' so stop worrying about it. What you do is cut down on the wasted turbulence as much as
> possible.
And how does one "cut down on the wasted turbulence"?
How does one even cut down on turbulence if not by drag
and viscosity - which would be a "useless waste of energy"?
You and kornball have these ideas about proper air flow
but no means to achieve what you recommend.
>> Unless that laminar flow is going only past parts that don't need
>> cooling, NO - leave the air turbulent. Should one maximize
>> turbulent flow if most of that turbulence will impinge heated parts?
>> YES.
>
> That's a nice "if" but nothing you've talked about will improve 'heated parts' turbulence one bit.
Put the heated parts near turbulent areas -
such as right behind vent holes instead of 2 or 3 or 4 or 6 inches
downstream. Make hot surfaces and surfaces just upstream of
them rough or undulating. (The dimples in a golf ball actually
*reduce* the drag on the golf ball by inducing turbulence). Design
heatsinks with labyrinth air passages rather than straight smooth
air paths. Install internal fans. Put small vanes in areas where
air must pass to induce a swirl. Do anything to put the air in
motion instead of calmly transiting the case.
>> If one were relying on passive generation
>> of turbulence, one would have laminar flow until just upstream of
>> the part to be cooled, and a resumption of laminar flow just
>> downstream of it. The part itself should be bathed with turbulence.
>> But how does one revert turbulent flow to laminar flow without just
>> passively relying on time and viscosity to do it? Practically, the
>> best one can do is to just keep other parts out of the way of the
>> turbulence as it comes off the heated parts. The placement of the
>> CPU's heatsink near the exhaust vent of the case makes that easy.
>> The placement of the typical GPU heatsink makes it a little harder.
>
> You're still thinking *way* too macro. The heat of a part will, itself, create boundary layer turbulence. You can't avoid it
> unless using super high velocities that scrub past it. For 'problem' parts the designer might include surface 'bumps', or some
> other mechanism, but the point is there's nothing you have to do about it 'in the case' except get a reasonable amount of air in
> and out.
The heat of a piston crown is very hot. Yet it is protected from
the heat of combustion flame by its boundary layer of unburned
gases.
Surface bumps are good for turbulence, even surface pits.
Little vanes are good, too. The problem with little vanes is
that the interior of a PC case varies considerably from one
case to another due to hardware options and cabling that
only a homebuilder can plan or implement detailed air flow.
But you guys are the homebuilders, aren't you?
As for easy ways to implement turbulence, internal fans are
easy to implement.
> Look at the CFM specifications for any forced air heatsink. You
> will not see a 'turbulence' factor. It is strictly CFM.
"To induce turbulence within the fins and improve thermal
transmission between the air and metal, Thermalright have
modified the aluminum fins by adding "proprietary bent winglets."
In other words, the leading and trailing edges along either side
of the aluminum fins are bent 15° up and 15° down respectively."
>> But the fan does not increase the bulk air flow through the case.
>> It merely increases the local air speed - which is another way of
>> saying that it increases the turbulence because the air is kinetically
>> energized without any increase in overall translational speed. In
>> other words, the fan is a "turbolator". It's an active turbulator
>> because it receives electrical power, but it is a turbulator nonetheless.
>
> Nope. It's more velocity, nothing else.
Velocity without any change in bulk air flow. That's what turbulence
accomplishes, and that's what fans accomplish. You get to choose,
as a designer, which device to use.
>> By pointing out that the air is "pre-heated" or "used", I am NOT
>> condoning such pre-heating or use, it is to point out that the
>> re-circulation which occurs is INCONSEQUENTIAL to cooling.
>
> But it isn't 'inconsequential'.
What are the consequences, then?
>> *Konehead* is the one who calls air "pre-heated" or "stagnant"
>> if it has contacted a heated part multiple times. Re-read the thread,
>> and you will see that. What I point out is that DESPITE such
>> "pre-heating" or pre-use or re-circulation, internal fans that blow
>> against heated parts (such as a heatsink fan) still aid in cooling
>> those parts.
>
> They do despite the problem of it being preheated.
So you agree that re-circulation by fans is useful despite
the fact that no new air is being brought in to increase the
bulk air flow rate.
>>>> - 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.
A fan INCREASES the rate of air flow - more cubic inches of
air per minute - without an increase in bulk air flow rate. That
implies that some of the air passes through the fan more than
once. Turbulence does the same thing to put more air molecules
in contact with a heated surface than laminar flow would. Dismiss
the commonality as "semantics" if you want, but the desirable
effect on cooling is the same. All that is different is that one takes
an active input of energy (the fan), and the other uses some of the
energy of the air flow.
>> Please explain why turbulence generated 1/8" upstream
>> is different in effect from turbulence generated 1/4" upstream
>> which is different in effect from turbulence generated 6"
>> upstream. Why should the turbulence care where it was
>> generated?
>
> Entropy
Entropy is the "randomness" of a system - which tends
to increase with time. Why does that make a difference
to where turbulence was generated? All that is important
is that the turbulence impinge the object to be cooled.
> Your '6 inch away' turbulence might as well be on the moon.
AHHH! The heart of the matter - kornball's Molasses
Theory of Air Flow. You believe turbulence to be short-lived.
You believe turbulence to be a micro effect, effective only
over microscopic distances. Have you ever stirred your
coffee? Blown a smoke ring? Driven your car through
the rain? Blown out a candle? Does the turbulence disappear
immediately? You defy everyday experience!!
> For a 1 inch long surface, like an IC, that 1 inch diameter 'turbulence' is dern near laminar and at the micro scale, where it
> matters, it's downright gargantuan.
And that "gargantuan" swirl or eddy increases the velocity
of the air passing along the surface of the IC - thinning the
boundary layer. I can see that you belive that turbulence
is "jiggling of the molecules", whereas turbulence can actually
be planetary and galaxial in size. There is considerable study
into the boundary layer and turbulence of the plasma flow
past our planet from the sun. That is not "micro". And it's
effects are not "micro".
>> By "bulk", I mean
>> volumes on the order of one or two cubic feet. Most of the energy
>> of the turbulence generated at the case's air intake holes are
>> probably in vortices measuring 1/32" to 1/4" across.
>
> And gone almost as soon as they pass through.
Any pilot will tell you that vortices strong enough to upset
an aircraft can last on the order of minutes. Just blow a
smoke ring to see that. You defy everyday experience to
bolster your argument - such as it is.
>> Judging by
>> the persistence of vortices in such things as smoke rings or
>> blown candle smoke,
>
> A smoke ring is not 'turbulence'. It's the shape left after it's creation.
Any vortex, by definition, is not part of bulk air flow. It is
a description of translational energy BESIDE bulk air flow.
Call is a "shape", or call it increased kinetic enegy, the
effect is to bring more molecules of fluid per unit time into
contact with the surface its passing over.
>> these vortices probably last for a few to many
>> seconds - long enough to traverse the interior of a PC case. Thus,
>> turbulence generated at the intake vent holes would persist during
>> the air's transit of the case.
>
> Nope.
Is "Nope" the extent of your reasoning?
>> You apparently assume that turbulence decays during the one
>> to five seconds that it takes air to travel across the case from
>> the vent holes. Why do you believe air to be so viscous?
>
> What makes you think they last, other than 'smoke rings'? Which, if it really was so turbulent as you think would vanish
> immediately.. from the turbulence disrupting the shape.
Ask any pilot or air controller about the persistance of turbulence
and then get back to us.
> If you want to muster the power to blow a hurricane through the
> thing then you could afford all that turbulence you like so much.
A degree of turbulence is all around us - no hurricane is necessary.
A degree of laminar flow is all around us as well. In cooling, though,
turbulence aids bulk air flow by scrubbing down through the
boundary layer that is around all objects to bring the passing fluid
into closer contact with the underlying object.
>>>> 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.
Is "Bad assumption" the extent of your argument?
>> WHY?
>
> I've told you through this whole thing.
All you've been doing is making terse denials.
You haven't explained your reasoning.
>> The hard drive's placement wasn't to "create case turbulence" -
>> it was to take advantage of it.
>
> It was to take advantage of the cold air coming in where it's of
> maximum velocity.
And the velocity reduces further into the case? Isn't it
"Air Out = Air In"? Where does the air go in the cases
that you design?
>> turbulence is not bad for cooling. In fact, it's good for cooling.
>
> Yes, right at the surface. Everything else is a waste of energy.
That says *nothing* about WHERE the turbulence gets
generated. It could be generated anywhere upstream
of the part to be cooled. What is important is that it
IMPINGE the part - that it GETS TO the part.
> No, your point has been that any and all turbulence,
> regardless of where, is a 'good thing' and that's simply not correct.
No, the turbulence must IMPINGE the part to be cooled
to have an effect on the cooling of that part. I have been
saying that consistently throughout this thread.
>> Turbulence may reduce bulk air flow if the
>> turbulence is generated passively, but it increases cooling
>> enough to make engineers design it into their systems (see
>> the numerous links that I've provided).
>
> Your links are all surface micro turbulence examples.
Back up that claim with details from the links, please.
Tell us what you consider to be a "micro" example
and what is a "macro" situation, and then tell us why
they don't interact.
>> You don't see them designing it OUT of their cooling or
>> heating systems except in long ductways where the
>> purpose is to transport the air, not to apply the air for
>> heat transfer. Where the heat transfer is to take place,
>> they always want turbulence.
>
> Yes, and that isn't 6 inches away nor at the intake vents.
That's to reduce contact with the walls of the ducting
and with parts not needing cooling. Otherwise, the
turbulence could be generated anywhere.
>> Turbulence is good where heat transfer is to take place.
>
> Which is the thermal surface.
>
>> Where it's generated is inconsequential to its task of heat
>> transfer.
>
> Wrong.
Is "Wrong" the extent of your argument?
>> That's because turbulence doesn't care where it
>> is - it works the same "here" as "there".
>
> Then why don't you just use all that natural 'turbulence'
> mother nature put in the atmosphere, since it matters not 'where'?
Because the ducting would be too large.
> No, the point is that the turbulence of use is micro turbulence at the surface boundary layer and that your macro 'turbulence',
> because it's 'turbulent' only when compared to the case volume, or the room, or the planet, looks just like your dreaded 'laminar
> flow' at the micro surface level.
Any velocity of a passing fluid helps to thin the boundary layer.
That velocity may be that of the bulk fluid flow, or it may be
the bulk fluid flow PLUS that of any turbulence. The action of
the two is better for cooling.
>> Tell that to those PC users who have repeatedly failing hard drives.
>
> Not enough un preheated air flow/
What makes you think the air they got was "pre-heated"?
>> If the simple placement and orientation of a hard drive can take
>> advantage of intake turbulence for cooling, why not use it?
>
> I think it's a good idea. It's just that your understanding of why is incorrect.
What is "incorrect" about my understanding?
>> Why strive for "smooth air flow" if it's detrimental?
>
> Because it isn't.
"Smooth air flow" doesn't have turbulence, and you've
admitted turbulence was good for cooling.
>> Again, the subject of the thread is "turbulent flow is
>> NOT BAD for cooling".
>
> The problem is your interpretation of it.
Interpretation of what? Could you be more specific?
What is to be "interpreted", and how have I done
that incorrectly?
On Wed, 11 Oct 2006 09:17:24 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:
>"kornball" wrote:
>> Here's a little hint Tim- I've made plenty of case parts
>> including intakes out of sheet aluminum. You're still in
>> the reading is fundamental stage of learning. Sooner or
>> later you will have to get up, take a case, and actually DO
>> IT. Otherwise, even _IF_ you /were/ right, you were still
>> foolish to put so much time into an idea without any
>> fruitful outcome.
>
>
> And where is the description and the results of your "tests"?
> C'mon, fakeball, present 'em.
>
>*TimDaniels*
What good would it do at this point? Ever since you were
backed into a corner you have merely trolled and repeatedly
linked non-applicable scenarios.
It is obvious you have excuses for everything, so the only
valid test you can't dispute is the one you propose. Since
you seemingly won't accept anyone else doing it, that makes
you the tester.
Without the testing, you are just another loon with a
half-baked idea.
On Wed, 11 Oct 2006 09:23:15 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:
>"kornball" wrote:
>> "Timothy Daniels" wrote:
>>> Not at all. I merely point out that turbulence, contrary to
>>> those effete nabobs of negativism, is not bad for cooling.
>>
>> Nobody claimed it was.
>
>
> You have said that turbulence should be minimized or reduced.
Yes, before or after the hot part, never did I claim ON the
part.
Re: turbulent flow not bad for cooling 
Linear Mode
