Advanced Thermodynamics for Engineers, 2nd Edition

12.12 CONCLUDING REMARKS

It has been shown that dissociation is an equilibrium process which seeks to minimise the Gibbs energy

of the mixture. In a combustion proce ss, dissociation always reduces the temperatures and pressures

achieved (except for very rich mixtures, see Chapter 13), and hence reduces the work output and

efficiency of a device.

The thermodynamic theory of dissociation has been rigorously developed, and it will be seen later

that this applies to fuel cells also (see Chapter 21).

Dissociation usually tends to break product molecules into intermediate reactant molecules (e.g.

CO

2

and H

2

O become CO, H

2

and O

2

). However, the same theory