Mass Transfer
When a system contains two or more components whose concentration vary from point to point, there is a natural tendency for mass to be transferred, minimizing any concentration difference within the system. Mass Transfer in a system is governed by Fick's First Law: 'Diffusion flux from higher concentration to lower concentration is proportional to the gradient of the concentration of the substance and the diffusivity of the substance in the medium.' Mass transfer can take place due to different driving forces. Some of them are:
- Mass can be transferred by the action of a pressure gradient(pressure diffusion)
- Forced diffusion occurs because of the action of some external force
- Diffusion is caused by temperature gradients (thermal diffusion)
This can be compared to Fourier's Law for conduction of heat:
where D is the diffusivity constant.
Read more about this topic: Transport Phenomena
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