Can someone explain C/W to me

[ThePunkGeek]

Well i was reading reviews on CPU temptures and C/W kept being talked about. I was some what lost because i dont know what it stands for?
Could someone tell me please thx!

[KILLorBE]

Delta = CPU temp - Ambient Temp
C/W = Delta / CPU Watts

Interpreting C/W: For every watt the CPU radiates, the heatsink will cool the core by the (C/W x watts) plus ambient temp. For example, at an ambient temp of 25 C, a C/W of 0.25 with a CPU radiating 50 watts means that the CPU temp will be 50 x 0.25 = 12.5 C over ambient temp, or 37.5 C. The lower the C/W, the better.


Does that help?

[ThePunkGeek]

sorta but i still dunno what it stands for

[jbell]

what it stands for is not as important as what it does - you can call it what ever you want - it doesn't matter one lick!


:)

[PsYko420]

LoL i love thjat avatar i kept watching it for 5 min waiting for it to loop then i got it... =]

[Grande Juan]

Ah now I understand is a C/W of 45 good? It seems to be the best currently available for my piece of crap. In particularly the Swiftech MCX478. :beer:

[Grande Juan]

Am I wrong or is it the same as how quik a HS can exchange heat transfer to ambient temps.:confused:

[ButcherUK]

Originally posted by Grande Juan
Ah now I understand is a C/W of 45 good? It seems to be the best currently available for my piece of crap. In particularly the Swiftech MCX478. :beer:

45 is very very bad (50W cpu, 45C/W would mean 2250C over ambient, the cpu in free air is around 8-10 C/W). If you meant 0.45 that's OK, nothing special but not bad for air cooling.

[BillA]

from a thread on Tekheads (http://www.tekheads.co.uk/forum/posts.php?threadId=3670) titled "C/W Confusion", I wrote:

suspect that my confusion stems in part from the C/W term
don't know the genesis of the term, but Joe Citarella of overclockers.com describes it thusly:

Delta = CPU temp - Ambient Temp
C/W = Delta / CPU Watts
Interpreting C/W: For every watt the CPU radiates, the heatsink will cool the core by the (C/W x watts) plus ambient temp. For example, at an ambient temp of 25 C, a C/W of 0.25 with a CPU radiating 50 watts means that the CPU temp will be 50 x 0.25 = 12.5 C over ambient temp, or 37.5 C. The lower the C/W, the better.

so speaking loosely, the C/W is a measure of a device's cooling effectiveness

so, looking at a wb:
should the C/W change as the flow rate changes ?
should the C/W change as the heat load changes ?

of course the C/W decreases with increased flow, and increases with an increased heat load

I'm coming to the conclusion that C/Ws serve only as a relative basis for comparison between IDENTICAL systems and conditions
which is to say that C/Ws are describing a device's interaction with the system's conditions, rather than any characteristic, per se, of the device itself

as grist for the mill,
there is a characteristic of a wb which does not seem to be dependant on the flow or heat load, the CPU/wb bp temperature differential
(of course this includes the thermal interface of the goop layer - but assuming this to be a constant...)

When the wb inlet temperature is held constant (+ or - 0.00^C, all the accuracy I can hold), the temperature difference between a TC embedded within the 10x10mm heat die, and a TC embedded within the wb over the die area; divided by the applied heat load - results in the same value (which is not sensitive to the flow rate).

any thoughts on this ?
have I totally missed the "point" of C/Ws ?

be cool

[Grande Juan]

Ok butcher that is 0.45 and air cooled sorry, but I'm looking for better than OK any suggestions. Also Billa does this mean how quik a HS can transfer heat?

[BillA]

well, the "problem" as I see it is that C/Ws are a relative comparison - NOT a measurement

what that means is that JoeC's numberes can only be compared to his test results on other units
NOT to C/Ws generated by other people with different setups and test methods

(and I think JoeC's are the most accurate)

be cool