Summary
An innovative design of a mobile thermal battery resembling the solar receiver is presented. A ternary salt mixture consisting of 52% KNO3, 18% NaNO3, and 30% LiNO3 by wt% is used as the thermal energy storing medium inside the thermal battery. Since the thermal conductivity of the ternary salt mixture is low, aluminum meshes are introduced to create a thermal conduction tree inside the thermal energy storing medium. The actual field data are used in the simulations to resemble the solar irradiation emanating from the parabolic trough and focusing onto the thermal battery outer surface. To improve the uniform heating at the outer surface, the thermal battery rotation along the centerline of the trough is considered. The temperature parameter is introduced to assess the uniform‐like temperature distribution inside the ternary salt mixture. It is found that the use of aluminum meshes improves the heat diffusion in the phase change material of the ternary salt mixture; in which case, it acts like a thermal conduction tree inside the thermal battery. The rotation of the thermal battery results in uniform‐like temperature distribution across the thermal battery cross section and suppresses the excessive temperature rise because of the local heating in the close region of the thermal battery outer surface.
Thermal characteristics of a mobile thermal battery, consisting of a steel tube, metallic meshes, and the phase change material, are investigated. Concentrated solar heating of the steel tube is considered and the governing equations of heat transfer and the flow field, due to the natural convection, are solved numerically. Lithium nitrate is used as a phase change material due to its high latent heat of melting and aluminum is used as the metallic mesh material. The maximum and minimum temperature difference in the tube is predicted and the temperature parameter is introduced to assess the thermal storage performance of the mobile thermal battery. The numerical code is validated with the data reported in the early study and findings revealed that both results are in good agreement. It is found that temperature predictions agree well with the previous data. The use of metallic meshes inside the steel tube significantly improves the heat conduction in the phase change material. In this case, almost uniform temperature distribution is achieved inside the tube during the cycle of thermal energy storage. Sensible heating in the liquid phase of the phase change material results in the increase in the localized excessive temperature, which has an adverse effect on achieving a uniform temperature distribution inside the thermal battery.
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