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# how to calculate THEORETICAL C/W for WC?

in a WC loop, is there a way using water amount, water flow and pressure, sp. Heat of water, W of CPU to ESTIMATE (i know how to measure) C/W?

what i am thinking is Kg/s (water flow rate)* spH

Q=mcT

so C/W is T/Q=1/(mc)
Q is joules but W is Q/s, but since the m is kg/s thats fine.

but thats too easy...AND its assuming like I am just pouring water on the BARE CPU LOL!!!

i know that other factors will make it less efficient, so how efficient is the water cooling it? 70%? thats my guess, so maybe its 1/(.7mc)

but then do i have to take into account the copper waterblock? thats what makes things hard; so the heat transfer from water to copper waterblock (this brings up another unrelated question; why dont ppl use fans for waterblock? wont it get hot absorbing heat from water/cpu? if it doesnt, then why do you need a copper waterblock?? i know heat from water is not much since water spH is high but still, i would think it would benefit from a fan creating more temp differental...anyway back on topic ) can be counted; so like m1c1T1=m2c2T2 - inefficiency where T1 and T2 are delta T's

then for the radiator, calculate surface area of aluminum and copper, and do some conserv. of heat.

for all these calculations, what efficiency do i assume? thats what i cannot figure out.

sorry if all my questions about WC are annoying you guys, im really curious about it thats all. since i saw a \$150 kit which was based on the parts i was getting (except it had a MCP350) and it had a 320 rad instead of heatercore and it had an apogeeGT and it cools WORSE than my BT (lower C/W!!!)
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i forgot: i have posted these parts before but this is for my CPU: hydor l35, apogee GT, heatercore.

edit: what if i had flexible aluminum tubing? lower temps ?? i have a brazing torch. also i have tons of heatsinks sitting around, any way to use them?
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There are too many variables to calculate C/W. For just a CPU loop, you would need to know:
flow rate
ambient temperature
CPU power usage
Pump heat into loop
radiator performance with the specifc fans and temperature delta
Waterblock efficency
Thermal paste inefficency

You can calculate C/W from temperature delta and CPU power usage.
C/W = ((CPU temp) - (Ambient temp))/(TDP of CPU)
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thanks, i was wondering if i could calculate before i buy the parts (after i get the parts i know how to calculate using temp differentials and such) using surface area's and weight and spH's and estimated inefficiency
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Quote:
 Originally Posted by amd_hardsoftware thanks, i was wondering if i could calculate before i buy the parts (after i get the parts i know how to calculate using temp differentials and such) using surface area's and weight and spH's and estimated inefficiency
I count at least 10 variables. If you could find nine of them, then I am pretty sure you can calculate it then. However, getting the data for the variables would require setting up a few loops in the first place.
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ok so using as a reference
MCP350
ApogeeGT
MCR120
which is in a kit i found says C/W is 0.134

with the same waterblock, a Heatercore rad thats prolly better, and a pump that pumps 358 more GPH; but 6.75ft less of head (vertical displacement of tubing is at most + or - 3 inches, so i dont think head matters)

so flow rate is about 4X as much for the pump, but for the system which will acheive a higher system flow rate if i have 2ft of tubing and everything super close to each other (which i am planning out with building my case)? in this case i THINK, again i THINK that the l35 will seriously outperform but i could be mistaken

wait maybe head does matter; just read duckie's faq; but how much does it matter?

wait i see now, so flow rate is DIRECTLY proportional to head and NOT to GPH rating...unless your using it for an aquarium
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If your doing a CPU only loop with a non restrictive cpu block a pump with over 6' of head is fine...Head is energy it is what moves the water through your loop...
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Quote:
 Originally Posted by amd_hardsoftware wait i see now, so flow rate is DIRECTLY proportional to head and NOT to GPH rating...unless your using it for an aquarium
If you know your head and restriction, then you know your flow-rate. The three are intertwined. Head is 100% restriction and max flow rate is 0% restriction. You will always be somewhere in between.
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Quote:
 Originally Posted by amd_hardsoftware thanks, i was wondering if i could calculate before i buy the parts (after i get the parts i know how to calculate using temp differentials and such) using surface area's and weight and spH's and estimated inefficiency
Even theoretically it would be a huge mess. If you're looking for real-world values it's never gonna happen without a few degrees and a few hours on a supercomputer
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Quote:
 Originally Posted by amd_hardsoftware edit: what if i had flexible aluminum tubing? lower temps ?? i have a brazing torch. also i have tons of heatsinks sitting around, any way to use them?