Method for calculating latent heat thermal energy storage

Abstract

Application of phase change material (PCM) is a promising direction of thermal energy storage, including cold. Accumulation is carried out due to the latent heat of the phase transition (melting). The article describes the information about the numerical and analytical process models for PCM. It can be used to calculate the parameters of existing battery designs. Calculated data on the value of the heat flux during the discharge of spherical capsules containing PCM are presented. The paper proposes a technique for engineering calculation of cold accumulators at the stage of designing cooling systems for various types of PCM located in the form of spherical containers in a coolant. The method allows estimating the number of capsules needed to achieve given cooling capacity of the system. To calculate the discharge time, an analytical dependence is proposed that corresponds to the forced flow around the container surface. The initial data for the calculation are the physical properties of the PCM, the properties of the capsule material, and its geometric parameters, as well as the coefficient of heat transfer from the surface of the capsule to the coolant. Recommended dependencies for calculating the heat transfer coefficient with the arrangement of capsules with PCM in the form of packed bed are presented. The proposed analytical dependences are confirmed by comparison with the calculated data for a spherical container with an inner diameter of 64 mm, filled with n‑tetradecane. The discrepancy in calculating the defrosting time was no more than 3 %. The calculation method presented can be used in the design of latent heat thermal energy storage (LHTES) filled with spherical capsules. Such LHTES can additionally be used for air conditioning systems in buildings.