On-demand intermittent ice slurry generation for subzero cold thermal energy storage: Numerical simulation and performance analysis

Abstract

Intermittent ice slurry generation is an innovative and realistic solution for obtaining on-demand ice slurry. In this article, solidification and multiphase transport phenomena during ice slurry generation in an intermittent ice slurry generator is numerically investigated. The numerical model considers multiphase convection, sedimentation and remelting of ice particles, drag on ice particles, permeability variation across the mushy zone, and slurry viscosity as a function of ice fraction. Prior to discussing the results of intermittent generator, ice slurry generation is analyzed in a cylindrical ice slurry generator (without any intermittency) in order to better understand the attendant transport phenomena. The evolution of ice fraction, temperature and concentration fields, and solid-liquid drift velocity is described. Thermal performance analysis is carried out to optimize the operational and design parameters. In the context of the present study, the optimum generation of ice slurry takes place for 0.75 aspect ratio (H:D), 0.1527 Stefan number and 24% depressant concentration. Using these optimized parameters, simulations are performed for intermittent ice slurry generator. The evolution of ice fraction in each cycle of intermittent ice slurry generation is described. For each cycle, the maximum extractable amount of ice slurry, the cold energy available and the effectiveness of the system are delineated. It is observed that in successive cycles, the total cold energy available in the system increases. On the other hand, the cold energy available from the ice slurry zone decreases because of widening of the immobile mushy zone.