Quote Originally Posted by ci2kla View Post
Interesting post.
I was first wonderin if I could get a better cooling performance (in terms of lower CPU temperature) by slowing down the water flow to the radiator using a res. Looks like I will get a disappointing result
That is not necessarily true. Again, it is going to be based on the balance equation (basically, your first law of thermodynamics)

h*A*(T2-T1) = mdot*Cp*(T2-T1)

h is your convective heat transfer coefficient, which is a function of how fast you the fluid is moving (in the radiator's case the fluid is air). So, if you increase the fan speed your h will go up. A (surface area) will always be the same unless you change radiators or it gets clogged with a lot of dust etc.
mdot is the water mass flow rate, Cp is constant.
So, if you slow down mdot and increase h more than the balance requires the water temperature change has to increase.