The analysis in this work is based on a sodium cooled, billboard type receiver adopted in CSP plant for Jemalong (Australia) Solar Thermal Station. It is aimed to evaluate the convective heat losses for the irrational surface of the receiver by using 3D computational fluid dynamics (CFD). The computational results for free convection are first being analyzed when imposing different uniform surface temperature for the receiver and a correlation procedure based on dimensionless Nusselt number on dependency of Rayleigh number is conducted. Then simulations for pure forced convection under different wind direction and intensity are being set up with gravity off and directional wind effect on heat losses has been analyzed.