Parallella with big heat sink, is it also requires fan?

While running Parallella with large heat sink, it was showing high temperature reading, from boot it easily reaches up to 80 C. Load such as compiling R increases the temperature to 83 C.
Surprisingly, focusing a wall fan into Parallella reduces temperature from 83 C to 57 C. So the large heat sink also requires fan, is in it?
Surprisingly, focusing a wall fan into Parallella reduces temperature from 83 C to 57 C. So the large heat sink also requires fan, is in it?