Suppose the substances which comprise the reactants and the products are not at 25C and 0. 1MPa If so, the expression that connects the reactants and products is ∑几e Ti, A and reference le, pe and reference conditions Equation(C 4.1)shows that we must compute the enthalpy difference Ah between the reference conditions and the given state if the inlet or exit conditions are not the reference pressure and temperature There are different levels of approximation for the computation: (a) assume the specific heat is constant over the range at some average value, (b)use the polynomial expressions (table A 6)in the integral, and(c)use tabulated values. The first is the simplest and the crudest Combustion processes often involve changes of a thousand degrees or more and, as Figure C-2 shows, the specific heat for some gases can change by a factor of two or more over this range although the changes for air are more modest. This means that, depending on the accuracy desired one may need to consider the temperature dependence of the specific heat in computing 4h Figure C-2: Specific heat as a function of temperature [from SB&vw Muddy points When doing cycle analysis, do we have to consider combustion products and their effect on specific heat ratio (y is not 1.4)?(MP 2C.6) 2C-6Suppose the substances which comprise the reactants and the products are not at 25o C and 0.1MPa. If so, the expression that connects the reactants and products is;          h o f + h Pi and reference conditions      ∆ { e      h o f + h Pe and reference conditions      ∆ { Q . (C.4.1) CV + ∑n = ∑n i R Between P Between Ti Te , , i e Equation (C.4.1) shows that we must compute the enthalpy difference ∆h between the reference conditions and the given state if the inlet or exit conditions are not the reference pressure and temperature. There are different levels of approximation for the computation: (a) assume the specific heat is constant over the range at some average value, (b) use the polynomial expressions (Table A.6) in the integral, and (c) use tabulated values. The first is the simplest and the crudest. Combustion processes often involve changes of a thousand degrees or more and, as Figure C-2 shows, the specific heat for some gases can change by a factor of two or more over this range, although the changes for air are more modest. This means that, depending on the accuracy desired, one may need to consider the temperature dependence of the specific heat in computing ∆h . Figure C-2: Specific heat as a function of temperature [from SB&VW] Muddy points When doing cycle analysis, do we have to consider combustion products and their effect on specific heat ratio (γ is not 1.4)? (MP 2C.6) 2C-6