It should evacuate it slowly through radiation and transfer to the air that will flow through it by convection.

Normally passive cooling like that can’t keep up with a typical modern desktop computer. But given how extremely heavy and large surface area it has, it might work. Provided that it is big enough and that the iron can conduct heat away from the source and spread it throughout its mass fast enough. Usually we use copper or aluminium for that for their better thermal conductivity.