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Correct waterblock sequence

divbyzero said:
That's the problem with the statement. The loop isn't thermally closed (heat enters the loop from the CPU waterblock and heat leaves the loop through the radiator), so Zeroth's Law does not apply. What's more, work is done within the loop to the system(pump).

I can see that you're an intelligent person. I think there is just a little confusion as to how the laws apply. The only way that the loop could have the same temperature everywhere was if there was no heat transfer occuring to or from the loop and no work was being done by or to the loop.

EDIT

It has been some time since I've been in school, but I believe the ideal thermal system to apply Zeroth's Law to is when you have blocks A, B, and C at different temperatures, T1, T2, and T3, and you place them in contact with eachother in a vacuum (thermally closed). At some time t, all three blocks will be some temperature T123' based on their mass, initial temperatures, and thermal conductivities(affects only time), assuming no heat transfer to or from the vacuum.
Click to expand...

What do you mean when you say the zeroth law doesn't apply? Of course if applies. The relative state of a thermodynamic system has no bearing on when you can and cannot apply the laws of thermodynamics. Besides that, I completly agree with you that the loop isn't thermally closed. If it were, there would be no heat exchange and the processor would fry. My comment was simply meant to be interperated that all thermal systems that do not exchange mass (i.e. a pseudo-closed loop) must and will attempt to reach a stable thermal equilibrium. If this didn't happen, then all hell would break loose in the nuclear plant where you work because the heat would never leave the reactor side of the loop. I've said numerous times that a watercooling loop doesn't have the exact same temperatures at every point in the loop (except for my first post, which was done to quickly answer the question so no confusion could be made about waterblock ordering. The resulting blowback has brought the posting to this...). I have explained that because of the temperature differentials and continious heat being added to the loop, that the water simply can not reach a common temperature, but always tries to according to the laws governing the exchange of thermal energy and the zeroth law. I'll pull my textbooks out again and check, but after many years studying physics, I'm pretty sure it right. Even the added 'work' done by the pump is considered added energy to the water which is dissapated and subject to the same laws.

I think we are talking about the same thing, but getting there in a rather strange manner.

EDIT:

I see what you are saying about the Zeroth law, in that because there is an outside heat source (waterblocks) then the overall use to describe the loop is pointless. I couldn't agree more. The laws of thermal energy transfer within thermodynamics specifically say this, but allow for relative thermal equilibrium to be reached among adjacent sections and transfer heat to allow for a stable temperature.
 
Pardon for flogging a tired horse, but what then is the consensus regarding component placement?

As I understand it, the WC loop is not a thermally closed system. While I will agree that the loop can reach thermal equilibrium assuming constant energy input/output, equilibrium does not imply constant temperature throughout the system. Equilibrium refers only to state. Therefore there can still be temperature gradations throughout the loop. As long as the gradations remain constant or more precisely the temperature at each point does not change with respect to time, the loop is in thermal equilibrium. With the principle that temperature differential facilitates rate of heat transfer, does it not behoove one to then place the radiator immediately before the CPU block (assuming that is the most critical component to be cooled) given constant flow? Would this serve to shift the thermal function along the y-axis (but remain parallel)? Forgive my fuzzy math.
 
We figured that because of the small temperature gradients, it really doesn't matter if you go
pump->radiator->CPU->reservoir->pump
or
pump->CPU->radiator->reservoir->pump

Do whichever gives you the shortest tubing length.
 
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