Thermal performance and entropy generation in a heated concave chamber filled with NEPCM-water nanofluids

Abstract

A study is conducted using the finite element technique to examine the fluid flow, heat transfer and entropy production in a chamber due to natural convective flow of NEPCM (Nano-Encapsulated Phase Change Material) water nanofluid. NEPCM particles possess a core-shell architecture, wherein the phase change material (PCM) constitutes the core. The chamber has a heated curved (concave type) boundary in bottom, cooled lateral boundaries, and an adiabatic curved (concave type) boundary at top. The lateral boundaries are maintained at an isothermal temperature of T = T_c, whilst the bottom curved boundary is non-isothermally heated to $T=T_c+\left(T_h-T_c\right)\sin \left(\pi \frac{x}{L}\right)$. A detailed analysis of entropy production and heat transfer along with the heat capacity ratio, isotherms, and streamlines is conducted and presented for different significant relevant parameters in the form of suitable graphs and tables. The results of this study revealed that the average Nusselt number values rise while employing NEPCM water as the working fluid compared to the base fluid water. The radius of curvature substantially affects both the average Nusselt number and average entropy production. The maximum percentage rise in average Nusselt number occurs when Stefan number (Ste) is 0.2 and radius of curvature (Rb) is 0.5, about 17.74 %. The most substantial reduction in average entropy production occurs at Ste = 0.2 for Rb = 1, reaching around 27.73 %.