One-dimensional model of evaporation and condensation in the presence of a noncondensable gas with applications to cryogenic fluid storage

摘要

This paper considers the one-dimensional flow of vapor between two liquid surfaces due to evaporation and condensation taking into account diffusion through a noncondensable gas and nonequilibrium inter-facial kinetics. An explicit relationship is developed for the mass flux J as a function of the characteristic mole ratio of noncondensable gas X, and several simplifications are made to arrive at an effective heat transfer coefficient. A characteristic mole ratio X_c is also identified that demarcates the transition to a kinetically-limited regime when X«X_c from a diffusively-limited regime when X » X_c. Numerical results obtained over a wide range of parameters show that even with a small amount of noncondensable gas, the interfacial temperature drop can be quite significant primarily because of diffusional resistance, an observation that has important practical implications, especially in the field of cryogenic fluid storage.