(Solved): n-Octane gas (C8H18) is burned with 80 percent excess air in a constant pressure burner. ...

n-Octane gas $\left({\mathrm{C}}_8{\mathrm{H}}_{18}\right)$ is burned with 80 percent excess air in a constant pressure burner. The air and fuel enter this burner steadily at standard conditions and the products of combustion leave at $217\mathrm{deg}C$. An engineering team suggested that the heat leaving the surface of the combustion chamber at an average temperature of $142\mathrm{deg}C$ be used in another process in the power plant. They calculated that the exergy of the heat leaving the body of the combustion chamber must exceed $20000\mathrm{kJ}/\mathrm{kg}$ of ${\mathrm{C}}_8{\mathrm{H}}_{18}$ to be used in a subsequent process. Calculate the exergy value of the heat transfer, in $\mathrm{kJ}/\mathrm{kg}$ of ${\mathrm{C}}_8{\mathrm{H}}_{18}$, during the combustion process and indicate whether the heat can be used for the subsequent process. [reference temperature $25\mathrm{deg}\mathrm{C}$ ] You may use the following table: