| In order to properly understand the transport mechanisms present in the study case, a dimensionless analysis under work conditions of the set of used equations has been developed. Dimensionless equations corresponding to mass, momentum and energy balances are as follows:
The order of magnitude of the dimensionless groups was estimated taking physical-chemical properties values for supercritical CO2 under the simulation conditions. SRK equation of state was used to estimate density and heat capacity of the fluid, Lucas method was used to
estimate the viscosity, and thermal excess method was used to estimate the thermal conductivity. Results are shown in table 11.
Dimensionless analysis allows identifying the problem as natural convection heat transfer in laminar flow. Buoyancy terms and pressure drop are found to be relevant for the calculations. Turbulence terms are negligible in calculations. The mesh should be properly defined near to the surface of the spheres, in order to properly capture the boundary layer problem involved. In order to simulate contact points between particles, the spheres drawn have been overlapped in a 1 % of their diameters.
Table 11: Dimensionless numbers of the studied case
The boundary conditions of the model equations are as follows:
- Constant temperature and mass flow rate of the fluid at the inlet [330 K; 1 x 10-4 kg/s].
- Constant temperature at the particles surface [340 K].
- Adiabatic reactor’s wall.
- Constant operating pressure [1 x 107 Pa]. |