Heatsink

When a tube acts as a heatsink (or heat exchanger), heat transfer is radial. The rate of radial heat conduction (Q) through the thick wall of a cylinder is governed by the equation:

Where k is thermal conductivity, L is tube length, T represents the inner and outer temperatures, and r represents the inner and outer radii). Finned tubes manipulate this equation by drastically increasing the effective outer radius (r_o), allowing the tube to shed thermal energy rapidly.