Hi, I'm interested in the theory of an Aluminum sphere that is initially at some temperature that is hotter than its surroundings. The sphere is surrounded by air at some small radius, say one meter, and then the air and sphere are both enclosed by an infinite shell of Aluminum at some ambient temperature about 100K less than the inner sphere. I am also assuming there is a temperature gradient already established due to radiation, conduction, and forced convection (with vent). If I close the vents and turn off the forced convection mechanism, I'm then interested in the mechanisms which contribute to the model reaching equilibrium temperature, i.e. ambient. From what I gather I will have free convection, radiation, and conduction as my heat transfer mechanisms. My question is, where do start? In time, I will have a decreasing temperature gradient across my air boundary. I also do not know if free convection will really play a role, even though my current model has free convection dominating the energy transfer from the hot body when I close up all vents and turn off fan. Another question is, if free convection IS a mechanism in reaching the equilibrium state what do I use for my convective heat transfer coefficient? I am finding many values for this and am wondering if it too will change during the cool-down. I know I have a lot of questions here, please let me know if I have misstated or under-supplied info. Any help would be appreciated, thanks in advance.