Archived from groups: alt.comp.hardware.homebuilt (More info?)
"kony" wrote about turbulence:
> ....after meeting obstructions and
> cooling first component in path of air, it is already a reduced
> efficiency at cooling rest of system. Case holes are not creating
> a high turbulence, relatively speaking. You keep ignoring this
> but it doesn't change by omission. Before flow has reached
> end of system, it is a non-turbulent, slow moving, overheated
> stream... inferior in cooling.
Here you say flow becomes non-turbulent as it passes thru
the case.
> You keep getting confused that a theory of "laminar" flow is
> only a model, that once this flow enters a case and meets
> temp differentials, obstructions, it is no longer so laminar...
> turbulence is created just as it was in your theory, but
> created AFTER air enters case rather than at the entry point
> where the flow rate would be reduced most drastically.
Here you say flow becomes turbulent as it passes thru
the case.
Nice if it were both ways. But which is it?
> > For a given degree of turbulence,
> > a higher flow rate WILL increase heat transfer.
> > For a given flow rate, highter turbulence will
> > increase heat transfer.
>
> Yes, but it's NOT a "given" flow rate, the flow rate will always be
> lowered by the creation of the turbulence and the hole design in general.
You don't understand the concept of allowing only one variable
to change at a time. That is the basis of experimental research.
If more than one variable is allowed to vary, you can't possibly
know what the effect of each variable is. To determine the
individual effects of flow rate and turbulence on heat transfer,
you can't allow both flow rate and turbulence to vary simultaneously.
That is fundamental to any kind of lab work.
> > ...for a given degree of turbulence,
> > higher flow rate gives higher rate of heat transfer.
> > But if you keep the flow rate constant, more
> > turbulence would do the same thing....
>
> Flow rate will not remain constant, we already covered that.
> There are several variables and you only consider one, when
> it's already established that other variables are as, or more,
> significant.
To repeat: In scientific experiment (i.e. emperical research),
one must strive to keep all variables constant and to just vary
the parameter of interest. Otherwise, one cannot know the
influence of just that parameter. To study just the effect of flow
rate on heat transfer, one must vary the flow rate while keeping
turbulence constant. To study just the effect of turbulence on
heat transfer, one must vary the turbulence while keeping the
flow rate constant. Doing so is quite difficult, and that is why
flow rate, which is easy to measure, has become the focus of
amateur cooling designers such as yourself. Turbulence, on the
other hand, is hard to measure, and only true scientists attempt
to investigate its effects. Amateurs, on the other hand, just choose
to ignore it and deny its effects. But when educated engineers
apply the results of the true scientists in their cooling designs, e.g.
Dell, HP, Gateway, etc., they imbue the incoming air with turbulence.
And the cheapest way to do that is NOT with FANS blowing into
the case - it's with HOLES punched in the sheet metal of the case.
> Unfortunately you can't just claim a heat transfer without considering the
> rate at which that heat is removed from the chassis. Again, you want to
> apply a simple concept to an entire system, ignoring all variables that
> don't suit your argument.
>
> Further, this "drag" is going to be cooling the case holes themselves... I
> dont' recall ever hearing of anyone with a case-hole overheating problem.
> It is detrimental to create drag at a point in the system that doesn't do
> anything useful in itself, at that drag point.
The affect of turbulence on the temperature of the case holes
is irrelevant.
> It does matter where the turbulence comes from, because the entry point
> into the system is where the flow rate is dropping.
Unless you are creating or destroying matter somewhere in
the case, the time-averaged flow rate remains the same
throughout the case, i.e. air that comes in is air that goes out.
The rate of flow does not drop at the entry point.
> Again you try to claim turbulence helps cooling while ignoring
> that your theory drasitcally lowers flow rate,
> [...]
> and ignoring that this turbulence created at front of case
> is not going to persist, will be supplanted by other
> turbulence created inside the case, but at a lower rate
> because your theory reduced the overall flow rate.
Why do you believe that turbulence will dissipate
in the time that the air transits the case?
> You are not getting a full degreee of turbulence. You are
> creating a trival amount of turbulence that subsides,
> while lowering flow rate, which lowers turbulence created
> later inside the chassis. Holes are cheap, and they "can"
> be effective, but not because they're designed to create
> turbulence, rather to spread airflow.
On what do you base your theory that turbulence subsides
in the few seconds that it takes air to transit the case?
> You mentioned a smoke ring in prior replies. Certainly it's
> turbulent, but it travels in a single path, minimally effecting
> air around it. Compare it to smoke propelled with same
> amount of energy but not in a smoke ring, so it is necessarily
> at higher velocity or pressure... the smoke moves out and
> reaches multiple areas, disturbing more surrounding
> area, and in a chassis, would reduce dead spots.
That's why sharp-edged holes are used - they produce
vortices, which are long-lasting turbulence structures,
just as smoke rings are toroidal vortices and long-lasting.
> You came up with a concept that you can't prove, because
> you can't test it. You can't test it because the theory only
> applies in limited, dissimilar situations.
Tell it to the scientists who report their studies of the effects
of turbulence on heat transfer, and tell it to the engineers
who use those principle in designing heat exchange systems.
Because you yourself cannot measure turbulence and therefore
cannot know its effects is no reason to deny its value and function.
*TimDaniels*
"kony" wrote about turbulence:
> ....after meeting obstructions and
> cooling first component in path of air, it is already a reduced
> efficiency at cooling rest of system. Case holes are not creating
> a high turbulence, relatively speaking. You keep ignoring this
> but it doesn't change by omission. Before flow has reached
> end of system, it is a non-turbulent, slow moving, overheated
> stream... inferior in cooling.
Here you say flow becomes non-turbulent as it passes thru
the case.
> You keep getting confused that a theory of "laminar" flow is
> only a model, that once this flow enters a case and meets
> temp differentials, obstructions, it is no longer so laminar...
> turbulence is created just as it was in your theory, but
> created AFTER air enters case rather than at the entry point
> where the flow rate would be reduced most drastically.
Here you say flow becomes turbulent as it passes thru
the case.
Nice if it were both ways. But which is it?
> > For a given degree of turbulence,
> > a higher flow rate WILL increase heat transfer.
> > For a given flow rate, highter turbulence will
> > increase heat transfer.
>
> Yes, but it's NOT a "given" flow rate, the flow rate will always be
> lowered by the creation of the turbulence and the hole design in general.
You don't understand the concept of allowing only one variable
to change at a time. That is the basis of experimental research.
If more than one variable is allowed to vary, you can't possibly
know what the effect of each variable is. To determine the
individual effects of flow rate and turbulence on heat transfer,
you can't allow both flow rate and turbulence to vary simultaneously.
That is fundamental to any kind of lab work.
> > ...for a given degree of turbulence,
> > higher flow rate gives higher rate of heat transfer.
> > But if you keep the flow rate constant, more
> > turbulence would do the same thing....
>
> Flow rate will not remain constant, we already covered that.
> There are several variables and you only consider one, when
> it's already established that other variables are as, or more,
> significant.
To repeat: In scientific experiment (i.e. emperical research),
one must strive to keep all variables constant and to just vary
the parameter of interest. Otherwise, one cannot know the
influence of just that parameter. To study just the effect of flow
rate on heat transfer, one must vary the flow rate while keeping
turbulence constant. To study just the effect of turbulence on
heat transfer, one must vary the turbulence while keeping the
flow rate constant. Doing so is quite difficult, and that is why
flow rate, which is easy to measure, has become the focus of
amateur cooling designers such as yourself. Turbulence, on the
other hand, is hard to measure, and only true scientists attempt
to investigate its effects. Amateurs, on the other hand, just choose
to ignore it and deny its effects. But when educated engineers
apply the results of the true scientists in their cooling designs, e.g.
Dell, HP, Gateway, etc., they imbue the incoming air with turbulence.
And the cheapest way to do that is NOT with FANS blowing into
the case - it's with HOLES punched in the sheet metal of the case.
> Unfortunately you can't just claim a heat transfer without considering the
> rate at which that heat is removed from the chassis. Again, you want to
> apply a simple concept to an entire system, ignoring all variables that
> don't suit your argument.
>
> Further, this "drag" is going to be cooling the case holes themselves... I
> dont' recall ever hearing of anyone with a case-hole overheating problem.
> It is detrimental to create drag at a point in the system that doesn't do
> anything useful in itself, at that drag point.
The affect of turbulence on the temperature of the case holes
is irrelevant.
> It does matter where the turbulence comes from, because the entry point
> into the system is where the flow rate is dropping.
Unless you are creating or destroying matter somewhere in
the case, the time-averaged flow rate remains the same
throughout the case, i.e. air that comes in is air that goes out.
The rate of flow does not drop at the entry point.
> Again you try to claim turbulence helps cooling while ignoring
> that your theory drasitcally lowers flow rate,
> [...]
> and ignoring that this turbulence created at front of case
> is not going to persist, will be supplanted by other
> turbulence created inside the case, but at a lower rate
> because your theory reduced the overall flow rate.
Why do you believe that turbulence will dissipate
in the time that the air transits the case?
> You are not getting a full degreee of turbulence. You are
> creating a trival amount of turbulence that subsides,
> while lowering flow rate, which lowers turbulence created
> later inside the chassis. Holes are cheap, and they "can"
> be effective, but not because they're designed to create
> turbulence, rather to spread airflow.
On what do you base your theory that turbulence subsides
in the few seconds that it takes air to transit the case?
> You mentioned a smoke ring in prior replies. Certainly it's
> turbulent, but it travels in a single path, minimally effecting
> air around it. Compare it to smoke propelled with same
> amount of energy but not in a smoke ring, so it is necessarily
> at higher velocity or pressure... the smoke moves out and
> reaches multiple areas, disturbing more surrounding
> area, and in a chassis, would reduce dead spots.
That's why sharp-edged holes are used - they produce
vortices, which are long-lasting turbulence structures,
just as smoke rings are toroidal vortices and long-lasting.
> You came up with a concept that you can't prove, because
> you can't test it. You can't test it because the theory only
> applies in limited, dissimilar situations.
Tell it to the scientists who report their studies of the effects
of turbulence on heat transfer, and tell it to the engineers
who use those principle in designing heat exchange systems.
Because you yourself cannot measure turbulence and therefore
cannot know its effects is no reason to deny its value and function.
*TimDaniels*
Facebook
Twitter
Instagram