Each processor will be different.
Running processor X at 100% capacity will generate an amount of heat, but running processor Y at 100% capacity will generate another amount of heat.
You can come up with an equation per processor, but there won't be one overall that you can just stick figures into.
As a side note:
Overclocking an older processor can produce more heat than running the newer dual / quad cores at normal operating specs. So no, heat dissipation isn't related to processor speed overall. Just that it increases with power consumption (as you ask the processor to do more).
As above, for individual processors you can come up with an equation (measure the temps at different operating points and plot them should give you something fairly simple for a processor).