Using a static magnetic field to control the rate of latent energy storage and release of phase-change materials

Abstract

Latent energy storage, using phase change materials (PCMs), has the potential to improve energy system efficiency, help reduce the energy supply and demand gap, and to contribute significantly to energy savings. However, the dynamics of the phase-change process affects the system's efficiency. Coordination between the melting and solidification duration and the increase in energy demand is essential to exploit the full potential of PCMs. This study deals with an experimental investigation of the use of a static magnetic field (SMF) generated by magnets to control the melting and solidification of Octadecane as a PCM. It is then supported using heat transfer scaling laws. Experimental results demonstrate that a magnetic field of 240 mT can delay the phase change process by up to 23 % if applied opposite to the buoyancy force across the entire surface of the enclosure. The used scaling laws show that an extremely high magnetic field can suppress the convection effect, thus, extremely slowing down the phase change process since the PCMs have relatively low thermal conductivity. Also, it is found that PCMs with a low Prandtl number and high electrical conductance are more sensitive to the magnetic field effect and, thereby, are advocated for future studies. Finally, this work aims at the development of techniques that allow the control of the rate at which energy should be stored or released in a latent heat system with PCMs and coordinate it with the subjected temperature variations.