Heat Transfer between Particle Phases

What happens when a multiphase flow has more than one particle component?

The multiphase flow model can handle multiple phases. The simplest example is the case with the fluid carrier as (phase-1) and the particle is (phase-2). In this case, the interaction between the phase-1 and phase-2 is very easy because the carrier fluid and particle phase. However, care must be taken when there are two or more particle phases.

Please see the attached pdf file below to understand the solution with theoretical example.