[airspirit]

Let me lay some groundwork here that the thermodynamics and hands on people both can appreciate. My radiator provides little extra cooling between 2GPM and 4GPM. This means that after 2GPM, I've hit the point of diminishing returns. There is no real tangible advantage to pumping faster than that. This equates to 4xCPU blocks at .5GPM which is sh!t.

You will also notice that as you go from 2GPM to 4GPM the resistance provided by the radiator goes up dramatically. Since there is no real benefit to the heat transfer ability, there is no sense forcing flow through it.

By allowing a bypass, I will tune my system to allow for higher overall GPM in the system, to let the blocks move more efficiency. Since I've already tuned the radiator to the point of diminishing returns (2-2.5 GPM), I might as well allow the CPU blocks to work more effectively (more like 2 GPM EACH). That extra flow has to go somewhere, so I will need the bypass. What will happen in the system is that the overall water temperature will go up. This is a given, since the water will not all be circulating through the radiator. This will also raise the idle temps of all the CPUs in the array. This will also, since the temp. differential is going to be higher between ambient and the coolant, allow the radiator to be more efficient at its point of diminishing returns, flow-wise. Since the water will also act as a large buffer (there will be a total of over 5 gallons in the entire system, maybe more if I thread the internals of the cooling box exclusively with 1.5" PVC like I'm planning), and the higher flow through the blocks themselves make the BLOCKS more efficient at their jobs, I suspect the peak temps of all the CPUs will be lower than they would be if the rad was exclusively in series.

In the end my the dT between idle and peak will be lower, with the idle higher and the peak lower. Also, with the sheer water mass in the system, I could crank for quite a while before my water temps will rise appreciably. I'm thinking of putting a digital temperature display on my box for the water temps (measured in the res), but I don't know how to do this without generating leaks. This would also help me "tune" the system to its max efficiency. I suspect that in this particular case, with the original three CPUs on the array, that I will find peak efficiency with 3GPM through the rad and about 4GPM through the bypass. One thing to note is that I will probably use 3/8" blocks on my CPUs (Black Edge blocks from BECooling). Since the pump (1200) will have 3/4" output, I can use 4x3/8" easily.