Thermal Dissipation

Hey everyone.

So I have been working out math for some heatsinks I plan on developing, and I have some questions for calculating duty-cycle based off of heatsink size, etc.

So for my model, I am working on my 3/4in diameter 6061 aluminum rod heatsink with an Aixiz module sized hole in it. The heatsink will be one inch long, as well, for the sake of example.

So here are some equations:

W=(thermal conductivity*temperature difference (K) * contact area (m^2)) / depth (m^2)

So I worked it out and my heatsink should be able to dissipate 45.1W for a difference of 1 degree Kelvin... so the temperature difference between the two things will remain much less than one degree unless the power needed to be dissipated is 45.1W or so....

So the question is, then, how do I calculate how much heat is radiated/transferred away from the HEATSINK to the air?

Thanks. I want to maximize stuff.