thermal condition for combustor wall
 

problem description
I want to make simulation by fluent 6.3 for cubic combustor 9*16*16 cm3 .
I choose mixed thermal condition, but i don't know how calculate the heat transfer coefficient, and heat generation rate, and what does "free stream temperature" mean ?

details about the used fuel in combustor it is syn gas produced from gasification
the mass of species that inter to comb. is 0.012183514 kg/s, and
Cp=1.2648 kj/kg.k, inlet syn gas temp =668k,