Numerical investigation of natural circulation loop with supercritical CO2 on the thermal control system of micro spacecrafts

Aiming at the heat dissipation problem under the strict constraints of mass, volume, and power consumption in micro spacecrafts, the feasibility of applying a natural circulation loop (NCL) to the thermal control system is performed for the CubeSats (Cube satellites) of orbiting operations or the micro-rovers of extraterrestrial explorations. A 3-dimensional NCL model under variable gravity conditions corresponding the environment of aerospace is established, and the supercritical CO2 as the coolant. The heat transfer and thermal performance of NCL under gravity range of 10-6 g to 10 g are analyzed numerically, including the Earth orbit, the surface of the Moon and the Mars etc. The calculation results present that the gravity has a great influence on the flow circulation characteristics and thermal performance of the NCL. The applicability of employing NCL on the thermal control system of micro spacecrafts is validated with the gravity no less than 0.05 g. It is worth noting that, by designing the range of temperature from inlet to outlet of the heated tube covering the large specific heat region, the superior thermal performance can be obtained on account of the strong heat-carrying capacity of supercritical fluid, even under the low gravity with a small mass flow rate. Finally, a flow correlation is proposed considering the effect of gravity, flow regime, buoyancy force, and geometric factors, which is suitable on the NCL in the thermal control system of micro spacecrafts, and the R2 is 99.77%.