In: Mechanical Engineering
Naphthalene is commonly used as a repellent against
moths to protect clothing during storage. Consider a 1 cm diameter
spherical naphthalene ball hanging in a closet at 25 oC. The
density and vapour pressure of naphthalene at 25 oC are 1100 kg/m3
and 11 Pa, respectively and mass diffusivity of naphthalene in air
at 25 oC is 0.61 x 10-5 m2/s.
a. consider the variation of diameter with time,
determine how long it will take for the naphthalene to sublimate
completely.
b. If instead of being stored in a closet, the
naphthalene is exposed to dry air flowing at a velocity of 2 m/s.
Both the naphthalene and the air were kept at 25 oC. It is observed
that 12 g of naphthalene has sublimated in 15 min. Determine the
mass transfer coefficient and the flux for mass transfer from
naphthalene.