Radiation heat transfer is almost negligible in comparison to the convective heat transfer for the following reasons

1) Radiation within the fins spacing goes into other fins.

2) Only radiation from the tips of the fins’ surfaces reaches surrounding bodies.

3) Radiation is subject to exposed surface material and its emissivity.

4) Forced convective heat-transfer amplifies convection of the sink’s heat and diminishes the importance of the radiation heat transfer in

scope and magnitude.