Laminar natural convection is studied in a square cavity filled with air whose
two vertical sides are subject to a temperature difference, while the other two
horizontal sides are adiabatic. The hot and cold wall temperatures are kept
constant. We have presented a dynamic and thermal study of pure natural
convection for different values of the Rayleigh number. The numerical simulation
was carried out for Rayleigh numbers ranging from 102, 103, …, 105 and
the Prandtl number is Pr = 0.71. We used the COMSOL Multiphysic 5.1
software, which allows us to simultaneously solve the coupled physical phenomena
in a square enclosure containing air under the Boussinesq approximation.
For the coupling of natural convection with radiation from radiative
surfaces, both horizontal faces are subjected to radiative flux, and the emissivity
of the surfaces varies from Ԑ = 0.1 to 0.8. We have seen that a circulation
process is involved. The fluid that is subjected to a high temperature near
the hot wall rises to the ceiling and the fluid near the cold wall sinks. This
movement continues until the fluid reaches thermal equilibrium. In a natural
convection-surface radiation coupling, simulation results indicate that radiative
exchange decreases as a function of the Rayleigh number. Surface radiation
reduces the flow in the cavity.

Natural Convection Square Cavity Radiation Coupling