Do not capitulate ! all is recapitulated :

To finish with heat transfer, let's establish the link between convection and conduction seen in the first part of these articles. Remember, the thermal power leaves the surface of the CPU, goes to the base of the cooler through the interface between these two surfaces with the corresponding contact resistance R_c , to arrive at the upper surface of the base with also corresponding resistances, pure conduction R'_c and spreading R_s.
R_cd , the sum of all these resistances, contributes to the effects of thermal conduction up to here :

Then the thermal power is absorbed by the fluid, with thermal resistance R_cv . It is still added to R_cd to finally give the total resistance R between the CPU and the fluid. This total resistance is defined by :

Where T_cpu is the CPU's temperature, T_f that of the fluid (pratically the temperature at the entry of the cooler) and P the thermal power given by the CPU to the cooler. The temperature of this latter can also be written :

I point out the importance of thermal resistance, it is the only parameter which allows to measure the thermal performance of a cooling system and this independently of the thermal power (thus independently of the CPU provided it has the same surface area) and of the temperature of the fluid at the entry (thus independently of what is between the input and the output of the cooler considered).
This thermal resistance of a cooler will be roughly the same if the CPU is changed or if the inlet temperature changes. Note that the same cooler mounted on a CPU having a different surface area won't have the same thermal resistance R. This fact is owing to spreading and contact resistances, and on a bigger CPU, R is generally lower.

This chart shows what kind of curve can be obtained for thermal resistance R with an Innovacool Rev. 3 waterblock ( thanks to Bill Adams ) :

Knowing the thermal resistance of a cooling system is quite pretty, but that's not enough to know what its really worth ...