Natural convection in a cubical cavity filled with a fluid showing temperature-dependent viscosity

Abstract

We present a numerical and experimental study of laminar natural convection flow in a fluid filled cubical cavity. The fluid is a dielectric oil used for cooling distribution and power transformers. As most liquids, this oil exhibits temperature-dependent viscosity. The cubical cavity of interest has an imposed temperature difference between two opposite vertical walls while the other walls are insulated. The cavity dimensions are 0.1 m × 0.1 m × 0.1 m. Four characteristic Rayleigh numbers ranging from 1.7 × 10⁸ to 6.3 × 10⁸ were analyzed. The numerical study was carried out by applying the Finite Element Method to solve the 3D Navier?Stokes and heat equations using the in-house developed Par-GPFEP code. The influence of temperature-dependent viscosity on the total transferred heat and on the flow pattern, have been evaluated. Although there are several studies regarding the flow in a square cavity in this configuration, there is limited information in the literature on the 3D flow in cubical cavities with variable properties of the working fluid. We could not find in the open literature experimental measurements that we could use to validate our numerical results. For this reason an experimental setup was developed. The velocity field was visualized and measured by Particle Image Velocimetry (PIV). The temperature profiles in the vertical mid-axis at mid-plane of the cavity were measured and compared with the numerical results. We found reasonable agreement between numerical simulations and experimental measurements.