Theoretical investigation of natural convection heat transfer in inclined and fully divided CO_2 enclosures on Mars

摘要

This work presented extensive numerical studies on fluid flow and heat transfer in inclined and fully divided CO2 enclosures with partitions on Mars. An atmospheric pressure of 1000 Pa, a gravitational acceleration of 3.62 m/s(2), and a Prandtl number of 0.77 were considered in the computation. The hot and cold walls were maintained at uniform temperatures of T-h = 240 K and T-c = 200 K, while the others were assumed as adiabatic, and the boundary condition of partitions was assumed as coupled. The velocity fields, temperature contours, and heat flux through CO2 enclosures were presented for a Rayleigh number of 7270, an aspect ratio of 7.14, tilt angles from 0 degrees to 90 degrees, and partition numbers of 0, 1, 2, and 3. It was observed that three flow regimes formed successively when the tilt angle increased, namely the Rayleigh-Benard convection, transition convection, and single-cell convection. The transition regime was the most unstable regime. The values of two critical tilt angles between the three flow regimes were also obtained. With increasing angle, the heat flux slightly decreased in the first regime, significantly decreased in the second regime, and initially increased and then slightly decreased in the third regime. The opposite effect of partitions on the first and the third regimes was explained by the field synergy principle. The partition advanced the formation of the single-cell convection to a lower angle and also alleviated the fluctuation in the heat flux for various tilt angles, which contributes to the future thermal design of Mars rovers operating on rugged Mars surface. (C) 2018 Elsevier Ltd. All rights reserved.