Thermo-fluidic characteristics of ice slurry flows in U-bend pipes for cold thermal energy storage

Abstract

Thermal energy storage plays an important role in improving the efficiency of refrigeration systems. Ice slurries have a high potential for thermal energy storage due to their high latent energy storage properties and almost uniform temperature field. Ice slurry flows in heat exchangers can assist in peak load conditions of refrigeration systems. In the present study, the thermo-hydraulic behavior of ice slurry in U-Bend pipes as a component of heat exchangers was investigated. Numerical simulations were perforfemd using multiphase two-fluid model. Kinetic theory of granular flows were used for modeling the viscosity of ice particles. The effect of geometry of U-Bend pipes on heat transfer rate, pressure drop and ice slurry phase change were investigated. Numerical results were in good agreement with the experimental data. The results showed that heat transfer coefficient and pressure drop increase with Reynolds number, ice volume fraction and ice particle diameter. Tripling the particle diameter leads to the Nusselt number increase by 76 %. It was also found that by reducing the radius ratio, the heat transfer coefficient and the average skin friction coefficient increase, but overally it improves the performance. With a 100 % increase in Reynolds number, the average Nusselt number increases by 80 %, and by decreasing the radius ratio to 50 %, the Nusselt number increases by <1 %.