So you want to understand how to cool your PC
Download this heat transfer textbook.
Yes, I'm too lazy to make that a link.
Left button copy, middle button paste into your browser
Ignore the first chapter if you don't have the math background to make sense of it.
Look at the form of the equations for convective heat transfer. Look at the chapter on heat sink design, and look up the info on fin efficiency.
That is all, for the moment.
I am not an expert, I just do it for a living.