Gas phase:

The conservation of the mass for gas species is given as

(9–5)

The first term, where represents the mass-fraction of the gas-phase species in the inlet, in the above equation is valid for the open reactor model. Note that summation over all inlets is implied.

Bulk phase:

The Multiphase Reactor model solves the bulk species moles instead of the mass fractions. The conservation equation is written as

(9–6)

where (in units of mol/s/cm³) and (in units of mol/s) are the net molar production rates of species due to the volumetric reactions within the -th bulk phase and the interphase reactions with other phases, respectively. The first term in parenthesis corresponds to the net molar flow rate of species in bulk-phase and is applicable only for the open reactor model. Note that summation over all inlets is implied.

Surface phase:

The surface site fractions are solved for the surface species that reside on a surface phase. In this release of Ansys Chemkin, the Multiphase Reactor models do not consider net surface area generation within the reactor volume to processes such as particle nucleation nor is there any specification such as volume-to-surface-area ratio. That is, the surface area for mass transfer is considered as a given (fixed) value. Thus

(9–7)

In the above equation, , , and are the site-fraction, occupancy, and net molar production rate of of the ^th surface species on the ^th surface phase whereas and indicate the surface area and site density of the surface phase .