Natural convective flow and heat transfer of Nano-Encapsulated Phase Change Materials (NEPCMs) in a cavity

Free convective flow and heat transfer of a suspension of Nano Encapsulated Phase Change Materials (NEPCMs) in an enclosure is studied. NEPCM particles are core-shell structured with Phase Change Material (PCM) as the core. The enclosure is a square cavity with top and bottom insulated walls and differentially-heated isothermal vertical walls. The NEPCM particles circulate under natural convection inside the cavity. The PCM cores undergo phase change from solid to liquid and absorb some of the surrounding's heat in the form of latent heat in the hot region, and release the absorbed heat in the cold region by solidification. The governing equations representing the conservation of mass, flow, and heat of NEPCM suspension are introduced in the form of partial differential equations. The governing equations are transformed into non-dimensional form and solved by the finite element method. A grid check and validation test are performed to ensure the accuracy of the results. The outcomes show that the fusion temperature of NEPCM particles is the key factor affecting the heat transfer enhancement of NEPCMs in the natural convection flow. The enhancement of heat transfer is highly dependent on the non-dimensional fusion temperature, theta(f), and very good performance can be achieved in the range of 1/4 < theta(f) < 3/4. Comparing to the base fluid, a relative enhancement of about 10% can be achieved by using NEPCMs at a non-dimensional fusion temperature of 1/4. (C) 2019 Elsevier Ltd. All rights reserved.