Here is link from the university of Cairo to the full fundamentals of momentum, mass, and heat transfer textbook by James R. Welty.

http://www.unimasr.net/ums/upload/files/2012/Sep/UniMasr.com_919e27ecea47b46d74dd7e268097b653.pdf

Thanks, I wanted something more specific. I wanted to know if convection heat transfer is important in this case. If someone has studied this case. In my system Ra is aproximatly 41.  

To see experimentally if convection is occurring in your system. Set up a Schlieren optics system. Schlieren technique allows visualization of different densities due to their different indices of refraction.

Actually in the end I found a way to do it using a thermal probe. The convection in this case is indeed important.