# Alt: CFM calculator to get rid of HEAT (TDP or WATTS)

Discussion in 'Asus' started by Skybuck Flying, May 18, 2011.

1. ### Skybuck FlyingGuest

miss it ! =D

Important topic ! =D

Hello,

I'm curious if it's possible to build a powerfull PC/iCore/GPU/Cuda PC
without getting into heat problems !

For example CPU has about 30 TDP (which is close to watts, otherwise find
watts listing) and GPU could have as much as 200 to 300 TDP (watts) (top
model for maximum bandwidth).

Additional watts for memory( 20 watt ? just guessing ) /motherboard (10
watt ?)/4 harddisk (60 watt*4=240)

Let's say 800 watts.

How much CFM would be needed to get rid of all that heat ?!?

A CFM heat (PC) calculator would be most handy... maybe somebody can
make/program it.

What would be good formula's to use ?!?

Bye,
Skybuck =D

Skybuck Flying, May 18, 2011

2. ### PaulGuest

Skybuck Flying wrote:
> miss it ! =D
>
> Important topic ! =D
>
> Hello,
>
> I'm curious if it's possible to build a powerfull PC/iCore/GPU/Cuda PC
> without getting into heat problems !
>
> For example CPU has about 30 TDP (which is close to watts, otherwise find
> watts listing) and GPU could have as much as 200 to 300 TDP (watts) (top
> model for maximum bandwidth).
>
> Additional watts for memory( 20 watt ? just guessing ) /motherboard (10
> watt ?)/4 harddisk (60 watt*4=240)
>
> Let's say 800 watts.
>
> How much CFM would be needed to get rid of all that heat ?!?
>
> A CFM heat (PC) calculator would be most handy... maybe somebody can
> make/program it.
>
> What would be good formula's to use ?!?
>
> Bye,
> Skybuck =D
>

CFM = 3.16 * Watts / Delta_T_degrees_F

Say room temperature is 72F, case air temperature target is 90F,
computer watts is 200 watts.

CFM = 3.16 * 200 / (90 - 72) = 35CFM

You can get around three times that airflow rating from a fan like this,
but you don't want to be sitting next to this. The fan draws
12V @ 1A and should not be connected to the motherboard header.
You can run this off a Molex drive connector.

http://www.circuittest.com/cfa1212038mb-12vdc-120-x-38mm-121-cfm-ball-bearing.html

DDR3 memory DIMMs are around 2W. Hard drives are less than 12W. Your
800W number needs to be reworked.

Paul

Paul, May 18, 2011

3. ### Skybuck FlyingGuest

Re: CFM calculator to get rid of HEAT (TDP or WATTS)

Hmmm... could be really simple...

Wikipedia shows conversion chart:

http://en.wikipedia.org/wiki/Conversion_of_units#Power_or_heat_flow_rate

1 atmosphere-cubic foot per minute = 47.820 074 682 24 W

Which is probably close to 48 Watts.

But this is atm-cfm and not cfm hmm... not sure if that is same thing... but
for now I'll go with it

So (800 * 60) / 48 = 1000 CFM needed ! =D

Let's see if antec case is sufficient lol:

http://www.antec.com/pdf/manuals/1200_EN manual.pdf

So there is no way that the antec 1200 case would be able to cool such a
system sufficiently.

Yes perhaps the graphics card would output a little bit of air as well...
but it's waaayyyy too little.

And this manual probably assumes at maximum operating fan speed... so let's
divide 240 by 2 is 120 CFM... and let's divide it one more time because of
dust is only 60 CFM.

Yeah...

Well it's pretty clear where this is going:

OVERHEAT DAMAGE ! =D

Bye,
Skybuck

"Skybuck Flying" <> wrote in message
news:3319\$4dd397df\$54192c06\$1.nb.home.nl...
> some miss it ! =D
>
> Important topic ! =D
>
> Hello,
>
> I'm curious if it's possible to build a powerfull PC/iCore/GPU/Cuda PC
> without getting into heat problems !
>
> For example CPU has about 30 TDP (which is close to watts, otherwise find
> watts listing) and GPU could have as much as 200 to 300 TDP (watts) (top
> model for maximum bandwidth).
>
> Additional watts for memory( 20 watt ? just guessing ) /motherboard (10
> watt ?)/4 harddisk (60 watt*4=240)
>
> Let's say 800 watts.
>
> How much CFM would be needed to get rid of all that heat ?!?
>
> A CFM heat (PC) calculator would be most handy... maybe somebody can
> make/program it.
>
> What would be good formula's to use ?!?
>
> Bye,
> Skybuck =D
>
>
>
>
>

Skybuck Flying, May 18, 2011
4. ### Skybuck FlyingGuest

It might seem "we computer people" are getting fooled/scammed by
specifications ((unrealistic)CFM).

I sure hope that's not the case because then all of your calculations are
wrong...

and with "your" I mean everybody that used CFM.

You might want to read up on this stuff:

http://en.wikipedia.org/wiki/Actual_cubic_feet_per_minute

"real cfm"

For now after a quick glance I am thinking my atmosperic calculations might
actually be closer to the truth

Time will tell ! =D

Bye,
Skybuck.

"Paul" <> wrote in message
news:ir0621\$kvj\$...
> Skybuck Flying wrote:
>> some miss it ! =D
>>
>> Important topic ! =D
>>
>> Hello,
>>
>> I'm curious if it's possible to build a powerfull PC/iCore/GPU/Cuda PC
>> without getting into heat problems !
>>
>> For example CPU has about 30 TDP (which is close to watts, otherwise find
>> watts listing) and GPU could have as much as 200 to 300 TDP (watts) (top
>> model for maximum bandwidth).
>>
>> Additional watts for memory( 20 watt ? just guessing ) /motherboard (10
>> watt ?)/4 harddisk (60 watt*4=240)
>>
>> Let's say 800 watts.
>>
>> How much CFM would be needed to get rid of all that heat ?!?
>>
>> A CFM heat (PC) calculator would be most handy... maybe somebody can
>> make/program it.
>>
>> What would be good formula's to use ?!?
>>
>> Bye,
>> Skybuck =D
>>

>
> CFM = 3.16 * Watts / Delta_T_degrees_F
>
> Say room temperature is 72F, case air temperature target is 90F,
> computer watts is 200 watts.
>
> CFM = 3.16 * 200 / (90 - 72) = 35CFM
>
> You can get around three times that airflow rating from a fan like this,
> but you don't want to be sitting next to this. The fan draws
> 12V @ 1A and should not be connected to the motherboard header.
> You can run this off a Molex drive connector.
>
> http://www.circuittest.com/cfa1212038mb-12vdc-120-x-38mm-121-cfm-ball-bearing.html
>
> DDR3 memory DIMMs are around 2W. Hard drives are less than 12W. Your
> 800W number needs to be reworked.
>
> Paul

Skybuck Flying, May 18, 2011
5. ### Skybuck FlyingGuest

Another nice website:

http://www.truetex.com/aircompressors.htm

Mentions pressure must be added to the equation of "CFM"

Manual of antec1200 mentions "static pressure".

(it's something like 0.something ! yeah ! lol)

Gonna look that up

Bye,
Skybuck.

Skybuck Flying, May 18, 2011
6. ### Skybuck FlyingGuest

Skybuck Flying, May 18, 2011
7. ### RobGuest

On 18/05/2011 11:23, Skybuck Flying wrote:
> It might seem "we computer people" are getting fooled/scammed by
> specifications ((unrealistic)CFM).
>
> I sure hope that's not the case because then all of your calculations are
> wrong...
>
> and with "your" I mean everybody that used CFM.
>
> You might want to read up on this stuff:
>
> http://en.wikipedia.org/wiki/Actual_cubic_feet_per_minute
>
> "real cfm"
>
> For now after a quick glance I am thinking my atmosperic calculations might
> actually be closer to the truth
>
> Time will tell ! =D
>
> Bye,
> Skybuck.
>
> "Paul"<> wrote in message
> news:ir0621\$kvj\$...
>> Skybuck Flying wrote:
>>> some miss it ! =D
>>>
>>> Important topic ! =D
>>>
>>> Hello,
>>>
>>> I'm curious if it's possible to build a powerfull PC/iCore/GPU/Cuda PC
>>> without getting into heat problems !
>>>
>>> For example CPU has about 30 TDP (which is close to watts, otherwise find
>>> watts listing) and GPU could have as much as 200 to 300 TDP (watts) (top
>>> model for maximum bandwidth).
>>>
>>> Additional watts for memory( 20 watt ? just guessing ) /motherboard (10
>>> watt ?)/4 harddisk (60 watt*4=240)
>>>
>>> Let's say 800 watts.
>>>
>>> How much CFM would be needed to get rid of all that heat ?!?
>>>
>>> A CFM heat (PC) calculator would be most handy... maybe somebody can
>>> make/program it.
>>>
>>> What would be good formula's to use ?!?
>>>
>>> Bye,
>>> Skybuck =D
>>>

>>
>> CFM = 3.16 * Watts / Delta_T_degrees_F
>>
>> Say room temperature is 72F, case air temperature target is 90F,
>> computer watts is 200 watts.
>>
>> CFM = 3.16 * 200 / (90 - 72) = 35CFM
>>
>> You can get around three times that airflow rating from a fan like this,
>> but you don't want to be sitting next to this. The fan draws
>> 12V @ 1A and should not be connected to the motherboard header.
>> You can run this off a Molex drive connector.
>>
>> http://www.circuittest.com/cfa1212038mb-12vdc-120-x-38mm-121-cfm-ball-bearing.html
>>
>> DDR3 memory DIMMs are around 2W. Hard drives are less than 12W. Your
>> 800W number needs to be reworked.
>>
>> Paul

Paul's calculation is correct. He knows what he is talking about.
--
Rob

Rob, May 18, 2011
8. ### PaulGuest

Rob wrote:
> On 18/05/2011 11:23, Skybuck Flying wrote:
>> It might seem "we computer people" are getting fooled/scammed by
>> specifications ((unrealistic)CFM).
>>
>> I sure hope that's not the case because then all of your calculations are
>> wrong...
>>
>> and with "your" I mean everybody that used CFM.
>>
>> You might want to read up on this stuff:
>>
>> http://en.wikipedia.org/wiki/Actual_cubic_feet_per_minute
>>
>> "real cfm"
>>
>> For now after a quick glance I am thinking my atmosperic calculations
>> might
>> actually be closer to the truth
>>
>> Time will tell ! =D
>>
>> Bye,
>> Skybuck.
>>
>> "Paul"<> wrote in message
>> news:ir0621\$kvj\$...
>>> Skybuck Flying wrote:
>>>> some miss it ! =D
>>>>
>>>> Important topic ! =D
>>>>
>>>> Hello,
>>>>
>>>> I'm curious if it's possible to build a powerfull PC/iCore/GPU/Cuda PC
>>>> without getting into heat problems !
>>>>
>>>> For example CPU has about 30 TDP (which is close to watts, otherwise
>>>> find
>>>> watts listing) and GPU could have as much as 200 to 300 TDP (watts)
>>>> (top
>>>> model for maximum bandwidth).
>>>>
>>>> Additional watts for memory( 20 watt ? just guessing )
>>>> /motherboard (10
>>>> watt ?)/4 harddisk (60 watt*4=240)
>>>>
>>>> Let's say 800 watts.
>>>>
>>>> How much CFM would be needed to get rid of all that heat ?!?
>>>>
>>>> A CFM heat (PC) calculator would be most handy... maybe somebody can
>>>> make/program it.
>>>>
>>>> What would be good formula's to use ?!?
>>>>
>>>> Bye,
>>>> Skybuck =D
>>>>
>>>
>>> CFM = 3.16 * Watts / Delta_T_degrees_F
>>>
>>> Say room temperature is 72F, case air temperature target is 90F,
>>> computer watts is 200 watts.
>>>
>>> CFM = 3.16 * 200 / (90 - 72) = 35CFM
>>>
>>> You can get around three times that airflow rating from a fan like this,
>>> but you don't want to be sitting next to this. The fan draws
>>> 12V @ 1A and should not be connected to the motherboard header.
>>> You can run this off a Molex drive connector.
>>>
>>> http://www.circuittest.com/cfa1212038mb-12vdc-120-x-38mm-121-cfm-ball-bearing.html
>>>
>>>
>>> DDR3 memory DIMMs are around 2W. Hard drives are less than 12W. Your
>>> 800W number needs to be reworked.
>>>
>>> Paul

>
> Paul's calculation is correct. He knows what he is talking about.

That's the only equation I know of, off hand. I'm not a thermal engineer,
and cribbed that off a web page that detailed how to put a computer
into an enclosure, and ensure it got enough cooling air. I expect
there is some room for using pressure curves for the fan, but I
don't know the first thing about that. I had an engineer at work,
who used to do that part for us. When you work in a big company,
you're generally "stuck in a silo".

Paul

Paul, May 18, 2011
9. ### Skybuck FlyingGuest

Skybuck Flying, May 18, 2011
10. ### Skybuck FlyingGuest

Skybuck Flying, May 18, 2011
11. ### Skybuck FlyingGuest

Skybuck Flying, May 18, 2011
12. ### Skybuck FlyingGuest

Most interesting part so far, and most interesting website so far:

http://www.aavidthermalloy.com/technical/papers/64bit.shtml

It mentions CFD analysis.

Why calculate one little simple fokking formula if you can simulate the
whole system ! LOL.

What hopefully CFD analysis software ! =D

CFD:

Csomething Fluid Dynamics LOL.

Bye,
Skyflow.

Skybuck Flying, May 18, 2011
13. ### Skybuck FlyingGuest

Skybuck Flying, May 18, 2011
14. ### Skybuck FlyingGuest

This one also seems kinda cool but a bit old, but that could be an
adventage, since I am on a PIII 450 mhz and best of all it's free, alas
only for MAC OS and Linux:

http://tetruss.larc.nasa.gov/

Could still be interesting though.

Bye,
Skybuck.

Skybuck Flying, May 18, 2011
15. ### Skybuck FlyingGuest

Skybuck Flying, May 18, 2011
16. ### RobGuest

On 18/05/2011 12:22, Paul wrote:
> Rob wrote:
>> On 18/05/2011 11:23, Skybuck Flying wrote:
>>> It might seem "we computer people" are getting fooled/scammed by
>>> specifications ((unrealistic)CFM).
>>>
>>> I sure hope that's not the case because then all of your calculations
>>> are
>>> wrong...
>>>
>>> and with "your" I mean everybody that used CFM.
>>>
>>> You might want to read up on this stuff:
>>>
>>> http://en.wikipedia.org/wiki/Actual_cubic_feet_per_minute
>>>
>>> "real cfm"
>>>
>>> For now after a quick glance I am thinking my atmosperic calculations
>>> might
>>> actually be closer to the truth
>>>
>>> Time will tell ! =D
>>>
>>> Bye,
>>> Skybuck.
>>>
>>> "Paul"<> wrote in message
>>> news:ir0621\$kvj\$...
>>>> Skybuck Flying wrote:
>>>>> some miss it ! =D
>>>>>
>>>>> Important topic ! =D
>>>>>
>>>>> Hello,
>>>>>
>>>>> I'm curious if it's possible to build a powerfull PC/iCore/GPU/Cuda PC
>>>>> without getting into heat problems !
>>>>>
>>>>> For example CPU has about 30 TDP (which is close to watts,
>>>>> otherwise find
>>>>> watts listing) and GPU could have as much as 200 to 300 TDP (watts)
>>>>> (top
>>>>> model for maximum bandwidth).
>>>>>
>>>>> Additional watts for memory( 20 watt ? just guessing )
>>>>> /motherboard (10
>>>>> watt ?)/4 harddisk (60 watt*4=240)
>>>>>
>>>>> Let's say 800 watts.
>>>>>
>>>>> How much CFM would be needed to get rid of all that heat ?!?
>>>>>
>>>>> A CFM heat (PC) calculator would be most handy... maybe somebody can
>>>>> make/program it.
>>>>>
>>>>> What would be good formula's to use ?!?
>>>>>
>>>>> Bye,
>>>>> Skybuck =D
>>>>>
>>>>
>>>> CFM = 3.16 * Watts / Delta_T_degrees_F
>>>>
>>>> Say room temperature is 72F, case air temperature target is 90F,
>>>> computer watts is 200 watts.
>>>>
>>>> CFM = 3.16 * 200 / (90 - 72) = 35CFM
>>>>
>>>> You can get around three times that airflow rating from a fan like
>>>> this,
>>>> but you don't want to be sitting next to this. The fan draws
>>>> 12V @ 1A and should not be connected to the motherboard header.
>>>> You can run this off a Molex drive connector.
>>>>
>>>> http://www.circuittest.com/cfa1212038mb-12vdc-120-x-38mm-121-cfm-ball-bearing.html
>>>>
>>>>
>>>> DDR3 memory DIMMs are around 2W. Hard drives are less than 12W. Your
>>>> 800W number needs to be reworked.
>>>>
>>>> Paul

>>
>> Paul's calculation is correct. He knows what he is talking about.

>
> That's the only equation I know of, off hand. I'm not a thermal engineer,
> and cribbed that off a web page that detailed how to put a computer
> into an enclosure, and ensure it got enough cooling air. I expect
> there is some room for using pressure curves for the fan, but I
> don't know the first thing about that. I had an engineer at work,
> who used to do that part for us. When you work in a big company,
> you're generally "stuck in a silo".
>
> Paul

I know what you mean Paul. I do have windows here, but they
have bars on them! )
It's easy to get hung-up about system cooling, especially with
heat being the biggest killer of hardware. I just configure
things so that hard drives have airflow over them, stay
below 40C and that everything else (particularly CPU and GPU)
stays within spec'd temps when pushed hard. Unless it's an
overclocked system, that normally just means a standard 120mm
fan drawing air in at the front and same extracting at the back,
with perhaps an extra fan directing air across the HDs if
they are poorly positioned within the case (as they often are.)
Because PSUs generally also have fans, I'd assume this leads
to a slight negative air pressure but that's not something
that seems to have any measureable effect in my experience
(eg I tried 3 intake fans as an experiment a few years ago
when I was overclocking those P4 Prescott roasting devices!)
Cooling has become much less of an issue with modern hardware -
even high-end GPUs dissipate much less power these days.
--
Rob

Rob, May 18, 2011