Study on laminar flow heat transfer characteristics of phase change microencapsule suspension based on OpenFOAM-DEM

Microencapsulated phase change materials (MPCM) have the advantages of high energy storage density and small volume expansion rate. A novel heat transfer working medium, microencapsulated phase change materials suspension, can be obtained by mixing MPCM with single-phase heat transfer working medium and adding nanoparticles. It has the advantages of faster heat transfer rate, higher thermal conductivity and lower pumping power, and has broad application prospects in the field of heat energy storage and transport. In this work, the solid-liquid two-phase flow and heat transfer of microencapsulated phase change materials suspension in a long straight tube are numerically simulated based on OpenFOAM-DEM model. The effects of particle mass fraction, wall heat flux and Re number on the flow and heat transfer characteristics are discussed. The result show that, due to the boundary layer effect, the particle concentration is dense near the wall and sparse in the main stream area, and the uneven distribution of particles in the main stream area gradually increases with the increase of particle mass fraction. When the particle mass fraction is 10wt%, the uneven particle distribution is the most obvious. Because of melting heat absorption and particle perturbation, the particle mass fraction has a significant effect on the temperature distribution and heat transfer enhancement of the suspension. With the increase of the wall heat flux, the change trend of the low temperature region of the suspension in the tube is opposite to that of the particle mass fraction, and the low temperature region is gradually shrinking. In other words, the heat flux has a great influence on the melting rate of the phase change materials. The increase of local Nux number in pipe is not synchronized with the increase of Re number, so the synergistic effect of heat flux, flow rate and particle mass fraction should be considered comprehensively in practical engineering applications.