Some of you may remember my earlier discussions on case cooling and CPU
temps. My concern was my Athlon 2700+ system in which the mobo sensor
(which I will refer to as case temp) indicated about 35C and the CPU temp
about 47C at idle (with a good heatsink) in a 22C room. This case is tall
and narrow, has no side vents, one intake and one exhaust fan and a volume
of amout 1848 cubic inches.
I recently moved the CPU to another system: very similar (same vendor,
layout and chipset) mobo, same video, same drives. This system has a
shorter, wider (and deeper) case with a total volume of 2061 cu. in. It has
only a single exhaust fan but has vents on the side panel above the CPU and
the PCI slots. At the same ambient temp, the Athlon 2700+ with stock AMD
heatsink/fan runs 35C with 26C case temp which is line with what I'd expect
and like to see.
So my question is: is it the larger volume, the side panel vents or the
combination that results in the dramatic reduction in both CPU and case
temps?
One other confusing fact, even removing the side panel of the smaller
(hotter) case drops the CPU temp only about 5C and case temp (as reported by
the mobo sensor) only 1C or so. So maybe there's something else that makes
this system run hotter.
> So my question is: is it the larger volume, the side panel vents or the
> combination that results in the dramatic reduction in both CPU and case
> temps?
No.
In air cooling, what makes more efficient cooling is more efficient
movement of air over/ across/ thru'/ in-out to dissipate the heat by
carrying it away in heated air from what needs to be cooled to somewhere
else.
A well designed 'closed' directional case airflow will be more efficient
at cooling than a poorly designed open case situation. A spinning case
fan 'over yonder' or another one 'over yonder' which isn't contributing to
any useful directional airflow in an open case which has no airflow
configuration isn't going to be doing any good except both of them making
noise.
On Thu, 29 May 2008 18:44:22 -0700, Mike Easter wrote:
> Lee M. wrote:
>
>> So my question is: is it the larger volume, the side panel vents or the
>> combination that results in the dramatic reduction in both CPU and case
>> temps?
>
> No.
>
> In air cooling, what makes more efficient cooling is more efficient
> movement of air over/ across/ thru'/ in-out to dissipate the heat by
> carrying it away in heated air from what needs to be cooled to somewhere
> else.
>
> A well designed 'closed' directional case airflow will be more efficient
> at cooling than a poorly designed open case situation. A spinning case
> fan 'over yonder' or another one 'over yonder' which isn't contributing to
> any useful directional airflow in an open case which has no airflow
> configuration isn't going to be doing any good except both of them making
> noise.
Yes, the basic aim is to get cool air in and warm air out without mixing
them too much or having conflicting streams which work against each other.
The requirement is for sufficient volumetric rate over the relevant areas;
flow (velocity) isn't everything and, if too much, could be
counterproductive as it won't allow the CPU fan to do it's job. Having said
that, too low a flow won't change the air quickly enough.
Now this is where a smaller case could help, as the through-flow wil be
more focussed across the board. Air doesn't have a high thermal capacity so
quite a high rate of change is needed /in the correct area/ - the bigger
case might have the throughput but a lot of it might miss the board.
--
Peter.
You don't understand Newton's Third Law of Motion?
It's not rocket science, you know.
On May 29, 7:30 pm, "Lee M." <lmacmil@forget_it.com> wrote:
> Some of you may remember my earlier discussions on case cooling and CPU
> temps. My concern was my Athlon 2700+ system in which the mobo sensor
> (which I will refer to as case temp) indicated about 35C and the CPU temp
> about 47C at idle (with a good heatsink) in a 22C room. This case is tall
> and narrow, has no side vents, one intake and one exhaust fan and a volume
> of amout 1848 cubic inches.
>
> I recently moved the CPU to another system: very similar (same vendor,
> layout and chipset) mobo, same video, same drives. This system has a
> shorter, wider (and deeper) case with a total volume of 2061 cu. in. It has
> only a single exhaust fan but has vents on the side panel above the CPU and
> the PCI slots. At the same ambient temp, the Athlon 2700+ with stock AMD
> heatsink/fan runs 35C with 26C case temp which is line with what I'd expect
> and like to see.
>
> So my question is: is it the larger volume, the side panel vents or the
> combination that results in the dramatic reduction in both CPU and case
> temps?
>
> One other confusing fact, even removing the side panel of the smaller
> (hotter) case drops the CPU temp only about 5C and case temp (as reported by
> the mobo sensor) only 1C or so. So maybe there's something else that makes
> this system run hotter.
After getting the above case -- all the confusion disappeared into a
wind tunnel. Everything is now one gigantic suck and blow operation,
which essentially means I run a vacuum cleaner and computer
simultaneously. Fans turned into monsters at 120mm, which the rear
one an updated Dynaflow or something Newegg was giving away on an open-
box item. And I really do mean it sucks dust really hard. I've seen
them go for as low as $50 on discounted sales.
"Mike Easter" wrote:
> Lee M. wrote:
>
>> So my question is: is it the larger volume, the side panel vents or the
>> combination that results in the dramatic reduction in both CPU and
>> case temps?
>
> No.
>
> In air cooling, what makes more efficient cooling is more efficient
> movement of air over/ across/ thru'/ in-out to dissipate the heat by
> carrying it away in heated air from what needs to be cooled to
> somewhere else.
>
> A well designed 'closed' directional case airflow will be more efficient
> at cooling than a poorly designed open case situation. A spinning case
> fan 'over yonder' or another one 'over yonder' which isn't contributing
> to any useful directional airflow in an open case which has no airflow
> configuration isn't going to be doing any good except both of them
> making noise.
>
> --
> Mike Easter
I've had this discussion before with Korny Kornhole, and it's not
simply the "efficient" movement of air through the case which does
the cooling. It's also the velocity and turbulence of the air along the
surfaces of components which need cooling. Everything is cloaked
with a very thin layer of stagnant air which is called the "boundary"
layer in aerodynamics. This layer is adhesive, and it acts to insulate
the underlying object. It's effect can be reduced by thinning it with
high velocity air passing over it and by turbulence. But since turbulence
can act to reduce the "efficiency" of getting air in and out of the case,
proper component cooling is an art of balancing the two conflicting
needs - turbulence impinging the hot components, but then moving on
without impinging the cool components or diverting air that is headed
for other hot components. CPU coolers and graphic card coolers
solve this by putting a fan right up against a hot heatsink to get
localized air speed and turbulence without impacting the bulk flow of
air through the case. But what about other components which need
cooling, such as the hard drives? Some case designs put small fans
immediately upstream of the hard drives, but that usually adds noise
that escapes through the case inlets. Most middle-ground desktop
manufacturers put the hard drives just downstream of the case's air
intake holes - able to bathe in the cool incoming air that has been
"turbulated" by the sharp un-aerodynamic edges of the air intake
holes. Power supplies also have dedicated fans that pull air through
sharp-edged holes to bathe the power components with turnbulated
air. (Have you ever seen a high-end power supply designed with
smoothly constricting and smoothly expanding air holes that reduce
the turbulence entering the power supply?) Considering these factors,
especially the fans that are dedicated to individual components, simply
getting air into and out of the case "efficiently" is not the ultimate goal
in providing cooling - as non-intuitive and non-"green" as that may
sound.
On Fri, 30 May 2008 09:20:05 -0700, Timothy Daniels wrote:
> Considering these factors,
> especially the fans that are dedicated to individual components, simply
> getting air into and out of the case "efficiently" is not the ultimate goal
> in providing cooling - as non-intuitive and non-"green" as that may
> sound.
A classic example of 'noise' improving 'signal'.
The 'adhesive' layer of air is useful for other purposes: fluid logic and
the Coander effect is one.
--
Peter.
You don't understand Newton's Third Law of Motion?
It's not rocket science, you know.
>> In air cooling, what makes more efficient cooling is more efficient
>> movement of air over/ across/ thru'/ in-out to dissipate the heat by
>> carrying it away in heated air from what needs to be cooled to
>> somewhere else.
> Everything is cloaked
> with a very thin layer of stagnant air which is called the "boundary"
> layer in aerodynamics. This layer is adhesive, and it acts to insulate
> the underlying object. It's effect can be reduced by thinning it with
> high velocity air passing over it and by turbulence. But since
> turbulence can act to reduce the "efficiency" of getting air in and out
> of the case, proper component cooling is an art of balancing the two
> conflicting needs
That sounds good to me. Thanks for expressing it so well.
> GUEST wrote:
> Some of you may remember my earlier discussions on case cooling and
CPU
> temps. My concern was my Athlon 2700+ system in which the mobo
sensor
> (which I will refer to as case temp) indicated about 35C and the
CPU temp
> about 47C at idle (with a good heatsink) in a 22C room. This case
is tall
> and narrow, has no side vents, one intake and one exhaust fan and a
volume
> of amout 1848 cubic inches.
>
> I recently moved the CPU to another system: very similar (same
vendor,
> layout and chipset) mobo, same video, same drives. This system has
a
> shorter, wider (and deeper) case with a total volume of 2061 cu.
in. It has
> only a single exhaust fan but has vents on the side panel above the
CPU and
> the PCI slots. At the same ambient temp, the Athlon 2700+ with
stock AMD
> heatsink/fan runs 35C with 26C case temp which is line with what
I'd expect
> and like to see.
>
> So my question is: is it the larger volume, the side panel vents
or the
> combination that results in the dramatic reduction in both CPU and
case
> temps?
>
> One other confusing fact, even removing the side panel of the
smaller
> (hotter) case drops the CPU temp only about 5C and case temp (as
reported by
> the mobo sensor) only 1C or so. So maybe there's something else
that makes
> this system run hotter.
I agree, great description. I never
thought about it that way, but now I'm going to open up my case and
see if I can "balance these two needs"
"PeterC" wrote:
> Timothy Daniels wrote:
>
>> Considering these factors,
>> especially the fans that are dedicated to individual components, simply
>> getting air into and out of the case "efficiently" is not the ultimate goal
>> in providing cooling - as non-intuitive and non-"green" as that may
>> sound.
>
> A classic example of 'noise' improving 'signal'.
>
> The 'adhesive' layer of air is useful for other purposes: fluid logic and
> the Coander effect is one.
Hmmm... "fluid logic". Care to explain "fluid logic" and the
"Coander effect" and how they would be used to control cooling ?
On Fri, 30 May 2008 22:27:02 -0700, Timothy Daniels wrote:
> "PeterC" wrote:
>> Timothy Daniels wrote:
>>
>>> Considering these factors,
>>> especially the fans that are dedicated to individual components, simply
>>> getting air into and out of the case "efficiently" is not the ultimate goal
>>> in providing cooling - as non-intuitive and non-"green" as that may
>>> sound.
>>
>> A classic example of 'noise' improving 'signal'.
>>
>> The 'adhesive' layer of air is useful for other purposes: fluid logic and
>> the Coander effect is one.
>
> Hmmm... "fluid logic". Care to explain "fluid logic" and the
> "Coander effect" and how they would be used to control cooling ?
>
> *TimDaniels*
I did say 'for other purposes', i.i. not meaning cooling.
[Pneumatic] Fluid logic is similar to electronic logic in some ways. The
Coander effect is simole: when a stream of air is 'attached' to a surface
it will stay attached until changed by an input pulse of air.
--
Peter.
You don't understand Newton's Third Law of Motion?
It's not rocket science, you know.
Do you think case volume affects cooling? 
Linear Mode
