Heat transfer analysis of PCM slurry flow between parallel plates

• Performed direct simulations of slurry flows with particle melting and settling.
• Demonstrated a linear increase of average wall Nu with solid PCM fraction.
• Showed wall Nu increases 100% of the single-phase flow at 18% particle fraction.
• Showed particle diameter and initial arrangement not important for Nu calculation.
• Determined average particle Nu number as inputs for mixture-based CFD model.

A CFD analysis of melting of solid particles during sedimentation in their own melt is presented. The motion of the solid particles is determined using a Lagrangian approach, while hydrodynamics and heat transfer throughout the fluid are determined using a finite volume scheme. Particle and fluid motions are two-way coupled through moving solid–liquid interfaces, whose morphologies are determined from the local interfacial heat fluxes and tracked using a deforming grid. The accuracy of the model is verified using benchmark solutions of a single particle undergoing simultaneous melting and settling. The results show that the presence of solid-phase particles within the liquid enhances the heat transfer between the bulk fluid and the heating surfaces due to improved mixing, as well as the latent heat associated with phase change. Particle loadings corresponding to solid volume fractions of 3–18% have been considered here, and it is found that the average wall Nusselt number increases linearly with volume fraction. An enhancement in the average wall Nusselt number of 100% as compared to a single-phase flow is achieved using a slurry with 18% solid particles by volume. Initial particle arrangement is found to have a minimal effect on the overall heat transfer. Additionally, for a fixed solid volume fraction, it is found that particle diameter does not strongly influence heat transfer enhancement.