Gas phase:

(9–3)

is the mean gas density and is the mean gas heat capacity at constant pressure. and are the temperature and the volume of the gas mixture and is the enthalpy of gas species at gas-phase temperature . is the total number of bulk phases. is the total heat addition to the gas phase from external sources and is the heat transfer rate from the bulk-phase to the gas phase. Note that the latter also includes the enthalpy brought into the gas-phase from bulk-phase due to the interphase interactions which are assumed to be happening at the temperature of the bulk phase (see Heat Transfer ). The first summation term corresponds to the effective inflow rate of the gas-phase enthalpy where , , and indicate mass-inflow rate, enthalpy at the inlet temperature, and enthalpy at the gas-phase temperature in the reactor of gas-phase species , respectively. Note that the summation over all the inlets (when/if there are multiple inlets) is implied. This summation term is non-zero (applicable) only for the open reactor model.

Bulk phase:

(9–4)

In Equation 9–4, molar basis is used and the ~ accent indicates that the quantities are in molar units. The first summation on the right-hand side of the equation corresponds to the effective inflow rate of enthalpy for bulk-phase and summation over multiple inlets is implied. is the total number of bulk phases, whereas is the temperature and the volume of the bulk-phase . The enthalpy of bulk species in bulk-phase at temperature is indicated by . is the total heat addition to the bulk phase from external sources. is the heat transfer rate from the bulk phase to the bulk phase . As in the case for the gas phase, the interphase heat transfer includes the enthalpy gain/loss due to mass transfer. This mass transfer is assumed to be occurring at a corresponding phase temperature (see Heat Transfer ).). In this release of Ansys Chemkin, the effect of dPdt term (in the case of the given volume closed reactor) and enthalpy inflow term due to surface species attached to the bulk phase (in the case of open reactor) is ignored.