Heat and Mass Transfer

Running head: HEAT AND MASS TRANSFER 1
Heat and Mass Transfer
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HEAT AND MASS TRANSFER 2
Heat and Mass Transfer
The study of the dissolution of particles assumes that matter is made up of tiny particles
or molecules that are always in a continuous random motion (Rai et al., 2016).
The rate of dissolution of a solute in a solvent increase with an increase in temperature.
Heating the solvent increases the average kinetic heat transfer of its molecules dislodging more
particles from the surface of the solute. For instance, sugar crystals dissolve faster in water at
high temperatures. Furthermore, temperature affects the amount of solute that dissolves in a
solvent. More sugar particles dissolve in water at high temperatures until the solution becomes
saturated (Chen, 2013).
Stirring also increases the rate of dissolution. In the static case, where the sugar is settled
at the bottom of the glass, the dominant mechanism of mass transfer is described using molecular
diffusion described by Fick's law. J=−D ∂ C
∂ x . Stirring introduces convective mass transfer in
the sugar solution thus increasing its rate of dissolution. The coefficient of mass transfer of sugar
particles between two sections of water is given by
N A =k c ( C A 1−C A 2 )=kl ( CA 1 −CA 2 ) =k x (x A 1−x A 2 )
The N Ain the equation is the molar flux of the sugar crystals while k is the coefficient of
mass transfer. Stirring does not affect the amount of sugar dissolving in water (Welty, et al.,
2013).
The size the of sugar particles also affect its rate of dissolution in water. Larger sugar
particles give a slow rate of dissolution due to a slow convective mass transfer. Increasing the