Thermodynamic analysis and improvement of cascaded latent heat storage system using temperature-enthalpy diagram

摘要

In order to analyze and improve the cascaded latent heat storage (CLHS) system under the steady heat source, a novel method based on the temperature-enthalpy (T-H) diagram was developed. The heat storage and release processes can be intuitively described by the T-H diagram when the minimum temperature difference DTmin related to heat transfer capacity is defined, which is helpful to evaluate the CLHS performance and find heat transfer bottlenecks. The implementation steps of the proposed method were specified in detail, and three typical cases were presented to verify its feasibility. Moreover, an optimization model for the CLHS system was proposed. The optimal melting temperatures of PCMs can be obtained by solving the multivariate linear equations, and meanwhile, a general expression of the optimal melting temperature was derived. Furthermore, the main and interaction effects of the three model parameters were investigated. The results show that a larger stage number Ns, a smaller minimum temperature difference DTmin, and a heat capacity flow rate ratio R with a value slightly greater than 1 are recommended. In short, the novel method is primarily graphical and heuristic-based, which provides the benefits of being easy to understand and ready to be used in practice. (C) 2020 Elsevier Ltd. All rights reserved.