Numerical Details of Convective Heat Transfer by Micro-Encapsulated PCM Case Study: Annular Slurry Flow

Due to the high latent heat value, using microencapsulated PCMs increases the heat transfer coefficient in the heat sinks in mini electronic devices, chilled celling, … . In this paper, convective heat transfer by mixed PCM particles in a fluid as slurry, has been studied by the Eulerian-Lagrangian two-phase method. In this method, the fluid phase is studied by the Eulerian and the particle phase is studied using the Lagrangian view. In this paper, the base fluid is water and the particles made of encapsulated micro-size paraffin wax which has covered by a thin layer of Fe۳O۴. The fluid phase is solved by a control volume method (SIMPLE) and the velocities of the particle phase are solved by the ۴th order of the Runge-Kutta method. Due to high Biot number for particles, the lumped temperature assumption for particles is not valid and the transient one dimensional conduction equation has been solved. In this paper details of solving the energy equation inside the particles has been presented. The results include the local and mean Nusselt numbers for different Reynolds numbers including ۲۰۰, ۳۵۰ and ۵۰۰, wide range of the volume fraction from ۰-۵% for PCM particle with ۱۰ micro-meter diameter, inside the mini annular tube with inner diameter of ۱ mm and outer diameter of ۳ mm. The results show for  and Re=۲۰۰, ۵۰۰, the Nusselt number increases by ۱۰ and ۱۲.۵%, while the pressure loss increases by ۲ and ۵.۵% respectively. The maximum performance coefficient is ۱.۰۷۸ and occurs for Re=۲۰۰ at .

کلیدواژه ها:

Microcapsule ، PCM ، Eulerian-Lagrangian ، Stephane number ، Annular flow