Free convection from a localized heated cylinder with nano encapsulated phase change material and water in a square enclosure

The present study looks on free convection caused by a temperature variation between a cold enclosure and a hot cylinder. The upper cylinder surface has a localized heated, which is otherwise adiabatic. The enclosure’s empty area is filled with hybrid nanofluids. This new type of fluid consists of nano-encapsulated phase-change material (NEPCM) suspended in the water (H2O) as the host fluid. The NEPCM has a polyurethane as a shell with an n-nonadecane as a core within. The n-nonadecane stores heat on charging state and releases the heat on discharging state. During charging and discharging, the latent heat was extracted and it can circulate the heat inside the enclosure. The governing parameters considered are the heater portion, 0.25≤S≤0.75, the Stefan number, 0.2≤Ste≤0.7, the fusion temperature, 0.1≤Θf≤0.5, the heating intensity, 104≤Ra≤106, and the NEPCM concentration, 0≤ϕ≤0.05. The findings demonstrate that by suspending 1% of hybrid particles, the heat transfer rate may be increased over 10%. •Free convection of polyurethane–nonadecane and H2O is addressed.•A finite heated segment is located on the top cylinder surface which is otherwise adiabatic.•The fusion temperature and heating portion are an essential parameter in the heat transfer.•A 1% increase in the concentration of hybrid nanoparticles enhanced the Nusselt by 10%.