Interdiffusivities and mass transfer coefficients of NaF gas

To clarify the vaporization phenomena of sodium fluoride (NaF), the interdiffusivities of NaF in N(2), Ar, and He were measured by thermogravimetric analysis from 1300 to 1770 K. At 1540 K, the interdiffusivity of NaF in N(2) (2.46 cm(2)/s) was slightly larger than that in Ar (2.40 cm(2)/s), while the interdiffusivity of NaF in He (6.00 cm(2)/s) was significantly larger than those in the N(2) and Ar systems. The Chapman-Enskog equation was used to calculate the interdiffusivities of NaF in N,, Ar, and He. Calculated results were in good agreement with observations for nitrogen and argon; however, calculated results for the NaF-He system were significantly higher than those observed. Overall experimental mass transfer coefficients were described by a Ranz-Marshall type correlation based upon the Nusselt number (Nu), the Reynolds number (Re), and the Schmidt number (Sc): Nu = 7.0 + 0.28 (Re)(4)(Sc)(2) in which the viscosities in the NaF-N(2), Ar, or He system were calculated from the Lennard-Jones parameters developed in this study.