Investigating Heat and Mass Transfer in the Dissolution of Particles

This report delves into the principles of heat and mass transfer concerning the dissolution of particles, emphasizing the role of temperature, stirring, and particle size in influencing dissolution rates. It explains that the dissolution rate of a solute in a solvent increases with temperature due to the enhanced kinetic energy of solvent molecules, and stirring accelerates dissolution by introducing convective mass transfer, as opposed to the slower molecular diffusion described by Fick's law. The report also highlights that the size of sugar particles affects the dissolution rate, with larger particles dissolving more slowly due to reduced convective mass transfer, while increased surface area accelerates dissolution. The document references key literature to support its explanations of diffusion, advection, and convection in 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 =kc ( CA 1−C A 2 )=kl ( C A 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

HEAT AND MASS TRANSFER 3
surface area increases the rate of dissolution of sugar in water because a larger number of
molecules are available for convective mass transfer (Rai et al., 2016).
Mass transfer can either be caused by diffusion (due to concentration gradient), advection
(due to movement of the fluid) or convection (a net transport from the effect of diffusion and
advection) (Welty, 2013).
Diagrammatic illustration of the rate of dissolution

HEAT AND MASS TRANSFER 4
References
Chen, G. (2013). Probing Nanoscale Heat Transfer Phenomena. Annual Review of Heat
Transfer. http://dx.doi.org/10.1615/annualrevheattransfer.2013005911
Welty, J. R., Rorrer, G. R. and Foster, D. G. (2013). Fundamentals of Momentum, Heat, and
Mass Transfer. 6th ed. New York: Wiley.
Rai, D., Kitamura, A., Rosso, K., Sasaki, T., & Kobayashi, T. (2016). Issues concerning the
determination of solubility products of sparingly soluble crystalline solids
http://dx.doi.org/10.1515/ract-2015-2540