Flow characteristics simulation of spiral coil reactor used in the thermochemical energy storage system

According to environmental and energy issues, renewable energy has been vigorously promoted. Now solar power is widely used in many areas but it is limited by the weather conditions and cannot work continuously. Heat storage is a considerable solution for this problem and thermochemical energy storage is the most promising way because of its great energy density and stability. However, this technology is not mature enough to be applied to the industry. The reactor is an important component in the thermochemical energy storage system where the charging and discharging process happens. In this paper, a spiral coil is proposed and used as a reactor in the thermochemical energy storage system. The advantages of the spiral coil include simple structure, small volume, and so on. To investigate the flow characteristics, the simulation was carried out based on energy-minimization multi-scale model (EMMS) and Eulerian two-phase model. CaCO3 particles were chosen as the reactants. Particle distribution was shown in the results. The gas initial velocity was set to 2 m.s(-1), 3 m.s(-1), and 4 m.s(-1). When the particles flowed in the coil, gravity, centrifugal force and drag force influenced their flow. With the Reynold numbers increasing, centrifugal and drag force got larger. Accumulation phenomenon existed in the coil and results showed with the gas velocity increasing, accumulation moved from the bottom to the outer wall of the coil. Besides, the accumulation phenomenon was stabilized when phi > 720 degrees. Also due to the centrifugal force, a secondary flow formed, which means solid particles moved from the inside wall to the outside wall. This secondary flow could promote turbulence and mixing of particles and gas. In addition, when the particle volume fraction is reduced from 0.2 to 0.1, the accumulation at the bottom of the coil decreases, and the unevenness of the velocity distribution becomes larger. (C) 2021 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.

Automated summary

Renewable energy, specifically solar power, has been widely promoted but is limited by weather conditions. Thermochemical energy storage, utilizing a spiral coil reactor, is a promising solution due to its energy density and stability. This study simulated the flow characteristics and found that gas velocity and particle volume fraction affect the flow behavior.