Thermal performance augmentation of inner spiral finned tube for linear fresnel solar reflector

Optimizing the thermo-hydraulic behavior of solar receiver tubes has become a worldwide concern. An inner spiral finned tube is applied to enhance the heat transfer of a solar receiver tube to improve the energy utilization of Linear Fresnel Solar Reflector in this study. Non-uniform heat flux is applied on the receiver tube through the user-defined function to simulate the inhomogeneous solar radiation in real situation. The influences of spiral fin parameters (height-to-diameter ratio h/w and spiral pitch p) on the fluid flow and heat transfer characteristics are analyzed with the Finite Volume Method. Correlations of Nu, f, and JF with variables of Re, h/w, and p are fitted. The results demonstrate that the spiral fin can increase the fluid temperature and enhance the photothermal conversion efficiency of the receiver. Compared with the smooth tube, Nu of the receiver tube is increased by 29 %, and the turbulent kinetic energy inside the tube is also significantly increased. The thermal performance factor is improved by 116 % at h/w = 0.36 and p = 390 mm. The installation of spiral fin increases the heat transfer efficiency of solar receiver tube and provides theoretical guidance to improve the utilization of solar energy.