Archived from groups: alt.comp.hardware.homebuilt (
More info?)
On Mon, 14 Jun 2004 23:28:26 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:
>"kony" wrote in error:
>> Reduced flow rate means reduced thermal energy removal,
>
>
> Absolutely wrong. If the flow is laminar, the thermal
> energy transfer can be low for high flow rates. If the
> flow is turbulent, the thermal energy transfer can be
> high for low flow rates.
In a model, where there is initial reading, measured component, this can
be observed. In a more complex system, 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. 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.
>Turbulence increases the rate
> of heat transfer over that of laminar flow. It makes
> the flow more efficient. That was shown by the links
> that I posted earlier. Flow rate is only an indicator of
> heat transfer if one keeps the degree of turbulence constant.
You keep coming back to simplistic concepts in dissimilar situations. In
a dissimilar situation we could also note that colors, metal type, and
other factors have an effect on some dissimilar model, but we're
considering one specific situation... or rather, you aren't. You are
ASSUMING your theory applied to this specific situation because you are
stuck in argument mode and aren't considering all the issues.
>
>
>
>> Back here on earth, it's not a radical theory that [reduction in airflow
>> rate results in higher temps].
>
>
> That statement is only true for a given degree of turbulence (however
> it is that you measure turbulence). 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.
We already covered this but you ignored what you didn't understand.
>
>
> >You have yet to establish any data concluding that the turbulence
>> from the case holes will result in any measureable temp drop,
>
>
> All that I have stated is just established physics of fluid flow.
> And you're asking me to "prove" that. You would undoubtedly
> want me to prove f=ma and e=mc**2 as well. And why?
> What would you gain by eliminating all the holes in front of
> the case and leaving just one big hole? What would you gain?
No, you did not state established physics once you applied someone else's
theory to a dissimilar model. There is plenty of reason why this
dissimilar model will behave diffferently but you never bothered to
consider that. Theory with no testing is a waste of time.
>
>
>> yet practically all of us have first-hand knowledge
>> that reduced airflow rate does increase temps.
>
>
> That is because 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. Your "first-
> hand knowledge" is correct - but incomplete.
>
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.
>
>
>> Surely we can at least agree that when this turbulence is created
>> (no matter how little or much) it MUST reduce flow rate.
>
>
> Yes, it reduces flow rate. And that reduction is one measure
> of drag, which in turn is a measure of contact between the
> moving fluid and the surface over which it flows, and that
> degree of "contact" determines the rate of heat transfer.
> The very reduction in flow rate indicates increased heat
> transfer.
>
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.
>
>> Problem is, the flow rate stays lowered even if the turblence
>> disperses.
>
>
> Problem is, that "dispersed turbulence" has already transfered
> a lot of heat - it did its job.
Nope, you have yet to establish that it transferred a lot of heat, only
that it could in a dissimilar model.
>
>
>> Usefull turbulence is created by the surface of
>> the object needing cooled, NOT the chassis.
>
>
> The object "needing cooled" cares not a whit
> where the turbulence comes from - whether it
> be a fan blowing into the case, sharp edges of holes,
> or little men inside waving their arms.
It does matter where the turbulence comes from, because the entry point
into the system is where the flow rate is dropping. 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.
> the way
> to get a full degree of turbulence to the upstream
> components is to provide the turbulence pre-made,
> and the cheapest way to do that is with many holes
> in the front of 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.
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.
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.
Facebook
Twitter
Instagram