Nusselt number for the natural convection and surface thermal radiation in a square tilted open cavity

In this communication, the numeric results of the heat transfer by natural convection and surface thermal radiation in a tilted 2D open cavity are presented. This study has importance in the thermal design of receivers for solar concentrators. The opposite wall to the aperture in the cavity holds a constant temperature of 500 K, while the temperature of the surrounding fluid interacting with the aperture is 300 K. The other walls are kept insulated. The results in the steady state are obtained for a Rayleigh range from 10⁴ to 10⁷ and for an inclination angles range of the cavity from 0° to 180°. The results show that the Nusselt numbers increase with the Rayleigh number except the convective Nusselt number for 180°, where it stays almost constant. The convective Nusselt number changes substantially with the inclination angle of the cavity, while the radiative Nusselt number is insensitive to the orientation change of the cavity.