A theoretical model of exergy analysis, based on availability transfer and flow availability, in the process of spray combustion has been developed to evaluate the total thermodynamic irreversibility and second law efficiency of the process at various operating conditions. The velocity, temperature and concentration fields in the combustor, required for the evaluation of the availabilities and irreversibilities, have been computed numerically from a two phase separated flow model of the spray along with a suitable reaction kinetics for the gas phase reaction. The thermodynamic irreversibilities associated with the gas phase processes in the combustor have been obtained from the entropy transport equation, while that due to the interphase transport processes have been obtained as a difference of gas phase irreversibilities from the total irreversibility. The thermodynamic irreversibilities associated with different processes and a comparative picture of the variation of second law efficiency at various operating conditions have been made to throw light on the trade-off between the effectiveness of combustion and the lost work in a spray combustion process.