This website about thermal design of electronics is excellent: Link: http://akemalhammar.fr/ Lots of really good calculators for things like heatsinks (both online and downloadable) and a load of other useful resources and info. All free! I really recommend you check it out. It's been a big help to me. Many thanks to the genius behind it, Dr Ake MÃ¤lhammar for kindly making it all available.