In our lab practice, we measured the rate of heat loss of a copper plate in atmospheric pressure and the rate of heat loss of the same plate in high vacuum ($\sim 10^5 torr$). So all I could find for heat loss in the internet is Newton's law of cooling, which is pretty much elementary (pressure doesn't appear as a variable). I was wondering if someone could give me a reference of where I can read something more profound about rate of heat loss for a metal plate involving radiation of course.