From an energy saving viewpoint, full melting of phase change material in thermal storage systems should be achieved. Constrained ice melting with natural convection inside a horizontal H-shaped capsule with adiabatic curved sidewalls is not completed because energy input from hot surfaces overheats the liquid phase on top while stable thermal stratification on bottom persists. Although 90°inclination of capsule engenders full melting of pure ice, the melting process is still sluggish due to low thermal conductivity of ice/water. Hence, heat transfer enhancement techniques using mono Cu, hybrid Ag/MgO nanoparticles, and 310 stainless steel fins are incorporated into system. Existing enthalpy-based lattice Boltzmann method with double distribution function model in single-phase framework is implemented. Insertion of Ag-MgO hybrid nanoparticles within horizontal H-shaped enclosure does not eradicate persistent thermal stratification. Full melting time inside 90°inclined capsule is diminished 13.6 and 24.5%, respectively, when the volume fraction of hybrid nanoparticles is increased from 0.0 to 0.01 and 0.02. While mono Cu nanoparticles give a better thermal performance in contrast to Ag-MgO hybrid nanoparticles, their price is double. Lower volume fraction (0.01) of mono Cu nanoparticles is prescribed since storage capacity is less decreased. Compared to pure PCM melting, partial internal fins mounted on bottom hot surface diminish full melting time 28.0%. However, magnitude of maximum velocity in molten PCM demonstrates that existence of fins considerably limits growth of natural convection flow.
