[abhik.banerjee]

I am trying to simulate steady state methane combustion in a single port of a glass melting furnace.I am using eddy dissipation model along with realizable ke model for species transport and turbulence in combustion space.i am using Do radaition model with emissivity of all surface set at 0.6.The bottom surface has a heat flux boundary condition(it is a heat sink) ,for air inlet and fuel inlet i have used mass flo BC,the air is at a very high temp.1300K so methane gets auto ignited.the exhaust is modelled as pressure oulet as distance from the air inlet to exhaust is around 10m .all other surfaces are considered as adiabatic.
The problem is that the mass flux imbalance is satisfactory(order of 10^-4) but the heat transfer rate imbalance is around 9000 W.Can anyone suggest me ways to reduce the the heat transfer rate imbalance.