Numerical simulation of mixed convection in solar cavity receiver for hydrogen production

Mixed convection heat loss is the key factor to determine the thermal efficiency of solar cavity receiver for hydrogen production by biomass gasification using concentrated solar energy. In this paper, the solar cavity receiver, built by State Key Laboratory of Multiphase Flow in Power Engineering, was numerically modeled to study the characteristics of mixed convection heat loss. The RNG k-ε turbulence model was adopted to investigate the flow pattern and mixed convection heat transfer characteristics around the solar cavity with external wind effect. The correlation for Nusselt number was obtained with various wind directions and wind velocity. The result showed that, the side towards wind and semi-side towards wind have the most significant effects on convection heat loss. When the wind velocity was big enough to make Richardson greater than 1, the forced convection drive by external wind is dominated, and mixed convection heat loss increases with augmentation of Re and the increase of wind velocity.