Cooling effects on the heat transfer characteristics of a rectangular thermosyphon with PCM suspension fluid

A numerical and experimental study is presented to explore the effects of cooling (the section on subcooling and phase-change material (PCM) supercooling) on the thermal performance of a rectangular thermosyphon containing PCM suspensions. In the numerical simulation, a continuum mixture flow model is used for the buoyancy-driven circulation flow of the PCM suspensions together with an approximate enthalpy model to detail the solid-liquid phase change process of the PCM particles in the loop. Parametric simulations are conducted in the following ranges: heat input at the heating section = 12 W, average temperature of the outer wall of the cooling section = 10–25 °C, and PCM mass concentration = 0–15%. The results show that in the configuration of this study, the downward flow of the high-density fluid in the cooling section became the main driving force of the circulation loop. Therefore, the cooling effects affected the overall thermal performance. To allow the proper melting/freezing of PCM particles, it is critical to control the wall temperature at the cooling section to achieve an appropriate subcooling effect.