Experimental and Numerical Studies on the Performance of Polyethylene Graphene Based Composite Phase Change Materials for Thermal Energy Storage

Abstract

Thermal energy storage domain is filled with composite phase change materials (CPCMs) for thermal performance analysis. The assessment is carried out for different nano additive materials such as copper and Al2O3 with square and rectangular geometric models. The interface morphology is used to understand the flow structure, and two-dimensional energy transport. The flow patterns are depending on the orientation (deep and shallow) of flow domain and initial sub-cooling. The orientation also has significant effect on formation of natural convection currents, heat transfer rate, and melting time. Effects of deep domain orientation (45 ̊, 90 ̊, 135 ̊ and 180 ̊) with different wall heating (base, left, top) conditions are analyzed numerically during melting and solidification processes. As the orientation changes, the heat transfer rate gets influenced significantly and convection currents amplifies. Next, to study the effect of geometry on melting and solidification characteristics, three different geometrical models of square, pentagon and hexagon are considered. Among the three models, hexagon model shown optimum results for both the heating and cooling processes with uniform and smooth variation in liquid fraction and temperature. To achieve the competence in thermophysical properties nanoparticle are blended to base materials (polyethylene). In the present work, linear low-density polyethylene (LLDPE) is blended with functionalized graphene with different concentrations (1, 3 and 5%) and CPCMs are named as CPCM-1, CPCM-2 and CPCM-3 for 1, 3 and 5% respectively. Polyethylene-based composites with optimal concentration (3%) can be utilized for thermal energy storage applications. Higher nanoparticle concentration (5%) emulsifies the molecules and generates micelles between themselves. The present work also attempts to address the energy issues by converting recycled plastics into thermal storage materials (TSM). Unfavorable thermophysical properties of plastic make it impractical, but these inadequacies can be amended by blending with additives of superior thermophysical properties such as functionalized graphene (f-Gr) and carbonbased nanoparticles. The experimental results shown energy level enrichment with nanoadditive concentration. Among the TSM, CPCM-2 shows relatively better storage capability due to incorporation of optimum concentration of enhancing material. The solidification process takes place through convection and radiation mode of heat transfer. An energy storage estimation is also performed through characterization, numerical and experimental studies. Thermal energy storage model implementation determines the better utilization of thermal energy for a greener environment.