Cubes of sugar, 1 cm on a side, are placed in water at 25ºC. Estimate the time before the lumps have dissolved; that is, when the sugar concentration at the lump is 10% by weight. Assume that the diffusivity of sugar into water is 6.9 x 10^-10m^2/s, the convective mass transfer coefficient is 6.4 x 10^-6m^2/s, and the self-diffusivity of sugar is 1 x 10^-5m^2/s. The density of sugar may be taken as 1500 kg/m^3.
What will be an ideal response?
This is a transient mass transfer problem and can be modelled as a lumped mass
capacity problem if the mas transfer Biot number is less than about 0.1. The Biot
number is
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