Gravity-driven two-phase fluid loop

Disclosed is a gravity-driven two-phase fluid loop, consisting of an evaporator (1), a vapour pipeline (2), a condenser (3), a liquid storage device (4), a liquid pipeline (6) and a control valve (5), wherein the gravity formed by the altitude difference between the liquid storage device (4) and the evaporator (1) is used as a driving force; an isotopic nuclear heat source is used as a heat source; the heat is transferred by way of the gas-liquid transformation of a gas-liquid two-phase working medium filled into the loop; and the condenser (3) is arranged to be V-shaped, such that the liquid working medium in the liquid storage device (4) can be prevented from flowing back into the condenser (3) due to the lunar surface inclination.