External Free Convection - BC Question

Craig Hildreth

Let's say I have a book size Al. plate sitting on an insulated surface with air above it. This plate has internal heat generation and is cooled by natural convection. I am trying to do a study to determine how big this outer volume of air needs to be to adequately model 'free conditions'. I was thinking of a process where I gradually increase the outer air volume's size until the temperature of the plate stops changing. Is the approach correct and what BCs might be appropriate on the air boundaries? Any help would be appreciated. I am a bit unsure how to approach this problem. Thanks!

Sincerely, Craig Hildreth