Thermo-fluidic performance of microencapsulated phase change material slurry in thermal energy storage

Microencapsulated phase change material slurry (MPCS) is an efficient way to storage energy and transport heat in buildings. The motion of particles imposes significant influences on thermo-hydraulic performance of MPCS. However, most numerical studies regard it as a homogenous fluid neglecting the motion of particles. In this paper, to better understand the enhancement mechanism of particles’ motion on heat transfer performance of MPCS, a 3D model of MPCS flowing through a horizontal tube is built and the Euler-Euler model using the kinetic theory of granular flow is adopted. The numerical results are validated and in good agreement with the experimental results in terms of macro and micro performance. In addition, effects of particle scale on performance of MPCS are investigated. The results indicate smaller particles present a uniform distribution. As increasing particles size, the specific equilibrium position where most particles accumulate is observed and it shifts from Segre-Silberberg annulus towards the centre of tube. Furthermore, pressure drop of MPCS increases significantly with the increase of particles sizes and increases about by 31% when the particle diameter increases from 500 μm to 1000 μm. The comprehensive performance of MPCS reaches its maximum at the diameter of 5 μm and the value is 1660.9, which is 2.3 times that of water.