Design of High Temperature Thermal Energy Storage for High Power Levels

Kurzfassung

A latent heat storage unit for integration in a heat- and power cogeneration plant in Saarland, Germany has been simulated and designed for the production of superheated steam for an in-dustrial customer. The storage unit design is an extended finned tube design with sodium nit-rate as the storage medium and water/steam as the heat transfer fluid. The header design pro-vides for a very fast switch time from standby to discharging. Various fin designs and tube spacings were analyzed for the system requirements in an iterative design method. The main steps in the method include the design of the fin based on empirical as well as geometrical information and the heat transfer analysis of a single tube assembly. The heat transfer analysis is further divided into a heat transfer analysis of the cross-section of one tube, a transfer from the cross-section to a simplified one-dimensional radial phase change material (PCM) model and a two-dimensional axial and radial analysis coupling the axial steam flow in the tubes and the radial PCM model. The result for the full storage between headers is then obtained by multiplying the result of one tube with the number of tubes. The analysis method developed is described here.