What is the bottleneck of CPU liquid coolers?

[absorb333]

In all in one liquid coolers, what is the slowest part of heat transfer?

1) The transfer between the cpu hotplate onto the liquid coolant through the copper plate.

2) The Transfer of the heated liquid through the tubing and onto the radiator.
or
3) The exchange of heat from the radiator to the surrounding air through the use of fans.

Where does the bottleneck reside in such a system?

 

[modernwar99]

Correct me if I'm wrong, but I am going to make a guess based on my personal knowledge. Probably extracting the heat out of the coolant and into the radiator. Water has a very high thermal capacity which means it is great at absorbing massive amounts of heat, but the downside of that is it also takes more energy to remove the heat from the water.