Acoustic precondensation phenomena in freons

Measurements of the acoustic resonance properties of three freons have been made using the lowest mode of a rectangular chamber at room temperature, and pressures from 1 atm to near the freon‐saturated vapor pressure. A large increase in the acoustic admittance of the walls is observed as the chamber pressure approaches the vapor pressure. The current experimental results are found to be in qualitative agreement with previous experimental studies of precondensation phenomena in propane and nitrogen. The observed admittance increase, which may be more than ten times the admittance caused by viscous and thermal‐conductive wall effects, is found to depend on the molecular weight of the freon as predicted by a theoretical model of the acoustic admittance of a precondensed thin liquid film that forms on the chamber walls.