Multi-scale modeling and investigation of thermo-fluidic performance of microencapsulated phase-change material slurry

摘要

Using the microencapsulated phase change material (MPCM) slurry is an effective measure to improve the balance between the supply and demand of energy with renewable and clean energy sources. However, most previous studies have neglected the nonlinear release of phase-change latent energy of the microcapsules and used an empirical modification of the heat transfer coefficient between the two phases to ensure that the simulation results were consistent with experimental data. In order to avoid the empirical modification of the heat transfer coefficient, a new multiscale model was developed by combining the heterogeneous multiscale method (HMM) framework and the correlative multi-scale methodology, whose numerical results are in good agreement with the experimental results in terms of the flow and heat transfer. By introducing the MPCM nonlinear phase change behavior into the thermal performance of the MPCM slurry, this multiscale model can be used to better understand the mechanism of the enhanced heat transfer of MPCM for the slurry. By the new model, the heat transfer performance of the MPCM slurry under various capsule sizes and concentrations is discussed by analyzing the slurry temperature distribution, liquid volume fraction of the PCM, and heat transfer coefficients. The results show that a smaller capsule size has the advantage of improving the heat transfer coefficient when the size is above 100 mu m. Furthermore, the average heat transfer coefficient first increases and then decreases as the concentration increases, and the value reaches a maximum of 106.84 W/(m(2).K) when the concentration is 20 vol%.