SUBLIMATION OF NAPHTHALENE SPHERES IN A NATURAL CONVECTION ENVIRONMENT

Solid naphthalene of 99.9% purity was melted and cast into spheres using two-piece silicone molds. When cured, the spheres were removed from the molds and hung from a calibrated digital scale where data of mass loss over time were collected to obtain the sublimation rate in a natural convection environment. Data were collected until the sphere\u27s diameter had been reduced by approximately 1% so any discrepancy in shape seen after long periods of time would not influence the results. Data were used to find the mass transfer coefficient which was a characteristic of both the geometry and sublimating material. Several dimensionless mass transfer parameters were calculated, including the Sherwood, Rayleigh, Grashof, and Schmidt numbers. The Schmidt number was found to have a constant value of 2.47, and the product of this number and the Grashof number resulted in a range of values for the Rayleigh number of 1.11 x 103 to 7.76 x 103. The range of Sherwood numbers calculated were 8.83 to 17.8. An empirical equation was developed from the analysis of solid naphthalene spheres of diameter 30 mm, 40 mm, 50 mm, and 58 mm. This equation relates the Sherwood number to the Rayleigh number from a linear curve fit of the data that takes the form and correlates the data well with an R2 value of 0.997