Abstract
In order to support the future thermal control and energy conservation design for the Mars rover, numerical studies on natural convection in CO2 enclosures on Mars’ surface were conducted for both horizontal and vertical enclosures. The parameters are as follows: the atmospheric pressure was 1000 Pa, the gravitational acceleration was 3.62 m/s2, and the Prandtl number was 0.77. The heat flux, temperature, and velocity fields of the CO2 enclosures were obtained with the aspect ratio ranging from 5.56 to 200 and the Grashof number ranging from 430 to 2.6 × 104. It was found that natural convection formed more easily in the horizontal enclosures than that in the vertical enclosures when the enclosures had same thickness. With the increasing thickness of the enclosures, Rayleigh–Bénard convections formed in the horizontal enclosures, while only single-cell convections formed in the vertical enclosures. The heat flux through the horizontal enclosures was greater than that through the vertical enclosures with the same thickness when natural convection formed. The maximum difference between them reached 35.26%, which was illustrated by the field synergy principle. A hysteresis phenomenon of the natural convection dominating the heat transfer was found in the vertical enclosure on Mars’ surface. New values for the critical Grashof number and correlations for the average Nusselt number for both the horizontal and vertical CO2 enclosures on Mars’ surface were also developed.
Highlights
In order to support exploration on Mars, Mars rovers are sent to Mars’ surface to work long hours
This paper focuses on the numerical study of the fluid flow and heat transfer characteristics inside CO2 enclosures on Mars’ surface, paying attention to whether the different orientation of the enclosure could affect the heat transfer characteristics inside the enclosure
A reasonable explanation for this phenomenon is that the heat transfer mode turned to natural convection dominant from pure heat conduction dominant when the enclosure thickness increased to a critical thickness
Summary
In order to support exploration on Mars, Mars rovers are sent to Mars’ surface to work long hours. The main work described in this paper is as follows: (1) conducting the numerical simulation of the fluid flow and heat transfer inside the CO2 enclosures to obtain the relationship between the heat transfer characteristics and the thickness of the vertical and horizontal enclosures; (2) analyzing the velocity and temperature distribution in order to explain further the fluid flow and heat transfer characteristics inside the enclosure; (3) interpreting the different formation of the fluid flow between the horizontal and vertical enclosures and demonstrating the hysteresis phenomenon of the natural convection dominating the heat transfer in the vertical enclosure on Mars’ surface; (4) applying the field synergy principle (FSP) to illustrate the different heat flux between the horizontal and vertical enclosures; (5) acquiring the critical Grashof number and developing the correlations of the average. Nusselt number in the horizontal and vertical CO2 enclosures on Mars
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