Isobaric, Isothermal combustion

As previously stated for internal energy, the change in enthalpy is solely a reflection of the initial and final states of the system. It does not matter whether the change is the result of one reaction or many intermediate reactions. For instance, the test tube combustion of glucose to carbon dioxide and water has the same enthalpy of reaction in an isothermic, isobaric, closed system as the algebraic sum of the enthalpies for all the reactions in the respiratory degradation of the sugar by cells in a similar system. This is an example of Hess s Law. 

A third way of combustion would be isothermal, isobaric as indicated in Figure 4. This reaction requires a heat reservoir... 

Figure 4. Enthalpy, entropy diagram with exergy for reactants e- and reaction products 2 after an isothermal, isobaric combustion Q4) The change of state from 1 to la is a release of heat at constant temperature, therefore the entropy decreases.

Only the ideal cases of an isothermal-isobaric combustion process will be assumed. This combustion is superior to the usual isobaric-adiabatic process. Such an assumption can be verified more easily than in a normal combustion process, since in the cases studied here the chemical reactions take place at the surface of the oxygen carriers. 

To sum up, the combustion in a diesel engine occurs in a turbulent flame, which is non-premixed, non-isothermal, non-isobaric, where there is vaporization of the liquids, heat exchanges, variable reaction volume, transient state, a complex and non-homogeneous reaction mixture. 

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