太阳能制氢腔式吸热器混合对流的数值模拟研究

Numerical Simulation of Mixed Convection in Solar Cavity Receiver for Hydrogen Production

混合对流热损失是影响太阳能与生物质超临界水气化耦合制氢腔式吸热器热效率的关键因素之一。本文以动力工程多相流实验室建成的生物质超临界水与太阳能聚集供热耦合制氢腔式吸热器为研究对象,对腔式吸热器混合对流换热进行了数值模拟研究。通过使用RNGkε湍流模型,研究了制氢吸热器在外界风吹掠环境下的混合对流热损失,获得了腔式吸热器在不同风速、风向吹掠下的混合对流换热准则Nusselt数。模拟结果表明,侧向风与侧迎向风对腔内对流热损失影响最大,当风速超过某一数值(Richardson数>1),外界风诱发的强制对流会在对流热损失中占主导作用,且随着风速增加,混合对流热损失随Re提高而增大。

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.