Abstract: No-vent filling technology utilizes the characteristic relationship between the saturation pressure and the temperature of a vapor-liquid two-phase working fluid in an evaporation and condensation system, achieving a fluid filling/refilling technology with neither moving components nor vent requirement for pressure reduction. In order to equivalently verify the feasibility and designed efficiency of the recycling and refilling method in microgravity on the ground, the level of fluid bottle for refilling or recovery is adjustable, with respect to the system to be refilled or recovered, to offset the influence of gravity as much as possible. Recovery and refilling tests for working fluids of R134a, fully degassed FC-72, and insufficiently degassed FC-72 are conducted on ground. The data of pressure and temperature of the loop system are used to analyze the internal transport during the working fluid replacement process. The pressure change rate (less than 0.1kPa/s) is verified to be a qualified criterion to end the filling or recovery. The results show that both fluids working under medium pressure and low pressure can achieve recovery rates and filling rates of over 95%, meeting the design requirements. Considering that the phenomenon of vapor-lock in ground pipelines disappears under microgravity, resulting in a smaller temperature difference required to drive the working fluid, and making it easier to replace the working fluid, it can be considered feasible to use no-vent filling technology for on-orbit working fluid replacement，and that the level of working fluid bottle is not continuously adjustable leads to inefficient offset of the gravity influence, which in turn constitutes the main measurement error of the filling rates or recovery rates. Depending on the application requirements, this method can also be improved and applied to the replacement or refilling of working fluids with larger capacities.

Key words: charging and recovery, FC-72, no-vent, efficiency, ground test