The energy equation for the mixture takes the following form:

(14–125)

where is enthalpy of species in phase , is the diffusive flux of species in phase , and is the effective conductivity calculated as:

(14–126)

where is the turbulent thermal conductivity defined according to the turbulence model being used.

The first three terms on the right-hand side of Equation 14–125 represent energy transfer due to conduction, species diffusion, and viscous dissipation, respectively. The last term includes volumetric heat sources that you have defined but not the heat sources generated by finite-rate volumetric or surface reactions since species formation enthalpy is already included in the total enthalpy calculation as described in Energy Sources Due to Reaction.

In Equation 14–125,

(14–127)

for a compressible phase, and for an incompressible phase, where is the sensible enthalpy for phase .