Total Heat imbalance even if solution 'converged'
 

Hi friends ,
I am simulating a gaseous combustion problem, and the solution seems 'converged' if the residuals (energy:<1e-09 and all other: <1e-07) and the 'total sensible heat transfer rate' across all surfaces ( imbalance < 0.1 Watt) is considered. But the Total heat transfer rate refuses to converge even after running an extra 100000 iterations after reporting the above values. I have made the walls of the reactor adiabatic (to simplify things) but the difference between total heat input thru the velocity inlet and the total heat outlet through the pressure outlet is still substantial. (The exit temperature of the straight channel combustor does not match with the adiabatic flame temperature at the same conditions) I have already done a lot of simulations since 8 months ensuring that the above criteria are met but ignoring the 'total heat transfer rate' balance and there is a disparity in all the results. This has brought the veracity of all my past simulations under question. I have attached a screenshot of the 'FluX REPORT'. Please can someone address this problem??!.
Also, heat seems to be losing near the velocity inlet , even though the thermal BC there is a constant 300K( and constant inlet velocity normal to inlet). Turning inlet diffusion off does not change the result much.

Can anyone help here??