Thermal analysis of nanofluid saturated in a semicircular hot enclosure cooled by a rotating half‐immersed active circular cylinder subject to a convective condition

Abstract

AbstractIn this study, the natural and mixed convections were numerically investigated using semicircular enclosures heated by an isotherm‐heat flux along a semicircular enclosure wall. The concentric conductive rotating cylinder was designed with a semicircular enclosure. The lower half‐cylindrical wall was immersed in nanofluid (Cu–water) that filled the enclosure, whereas the upper half‐cylindrical wall was subjected to ambient convection. The horizontal walls were thermally insulated. The Galerkin finite element process was used for the dimensionless governing equations of velocity and temperature and then modeled by COMSOL 5.5. The parameters were represented in the following ranges: radial aspect ratios, 0.4 ≤ r/R ≤ 0.8; thermal conductivity ratio, 1 ≤ Kr ≤ 10; angular rotational velocity, 0 ≤ Ω ≤ 1000; ambient convection heat transfer coefficient, 5 ≤ ≤ 20; and nanofluid concentration, 0 ≤ φ ≤ 0.05. The Prandtl number (Pr) and Rayleigh number (Ra) were taken as constants at Pr = 6.2 and Ra = 105. Results showed that the convection influence was prominent when the angular rotational velocity was increased, whereas the influence was minimal when the aspect ratio was increased. An inverse relation was found between heating and cooling thermal penetration depths with respect to angular rotational velocity for the thermal conductivity ratio and all aspect ratios. Our numerical work was compared with past research for validation. Findings indicate a strong agreement between the findings of the current research and those in the past studies.