Free convection in two composite enclosures filled with water and nano encapsulated phase change particles

Abstract

Phase change heat transfer in two composite enclosures were studied numerically in the current study. Both enclosures consist of porous and fluid layers, with the all layers filled with the water-nano encapsulated phase change materials (NEPCPs). The first enclosure is surrounded by a porous layer having different sizes and permeabilities, while the second enclosure is center-inserted by a porous layer. As the porous layer thickness approaches zero, both enclosures transition into clear-fluid enclosure. The NEPCPs are fabricated using a polyurethane shell encapsulating an n-nonadecane core. The n-nonadecane undergoes a phase transition, enabling it to store or release a substantial amount of latent heat. To solve the governing equations, a Galerkin finite element method is employed. Our present model’s results are compared to those of earlier published studies. The governing parameters under consideration are: the volume ratio scale of porous medium, 0≤θS≤π/2, the NEPCPs volume fraction, 0.0≤ϕ≤0.05, the fusion temperature, 0.1≤TF≤0.5, the thermal conductivity ratio, 0.5≤ke≤10 and the Darcy number, 10−5≤Da≤10−2. The findings show that heat transfer performance of the both enclosures are complex functions of the NEPCPs concentration, fusion temperature and two-layer configuration. An increase in values of Nu¯I up to 66% is obtained when the concentration is adjusted from 1% to 5%. Similarly, an increase in values of Nu¯II up to 36% is obtained as the concentration is adjusted from 1% to 5%.