Author: admin
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Introduction
The extent to which the components of an alloy are miscible depends on the interaction between the atoms: In these solid solutions, different types of atoms or molecules exist in the same crystal lattice. A good example of a solid solution is the Cu-Ni system, for which the phase diagram is shown below Phase diagram…
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Resistances
We can use concepts of mass transfer resistance to make the analysis of mass transfer with combined mechanisms much easier. Definition of resistance A resistance is the driving potential (or driving force) divided by the transfer rate: resistance=driving potentialtransfer rate We are probably familiar with Ohm’s law, in which the driving potential is the voltage and the…
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Combined diffusion and convection
What do we do in cases like this hypothetical mass transfer device? Given the concentrations of species A at points 1 and 2 (��1, ��2), how do we compute the rate of mass transfer between them? We need to consider convective and diffusive mass transfer in multiple media. Concentration profiles The concentration profile owing purely to…
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Mass Convection
As we saw earlier, mass transfer refers to mass in transit due to a species concentration gradient in a mixture, and mass convection is one of the mechanisms for this transit. Mass transfer by convection involves the transport of material between a boundary surface (such as solid or liquid surface) and a moving fluid or…
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The diffusion coefficient
One of the big unknowns in Fick’s equation above is the diffusion coefficient, ���. The diffusion coefficient (or diffusivity) is a proportionality constant between the molar flux due to molecular diffusion and the gradient in the concentration of the species (or the driving force for diffusion). On a theoretical basis, the diffusion coefficient is proportional to…
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Diffusion
Describing diffusion quantitatively Exercise: Diffusion Suppose we have molecule � diffusing in a domain between boundary 1 and boundary 2, where ��,1 and ��,2 are held fixed. What happens to �� between boundary 1 and boundary 2 and what is the rate of diffusional mass transfer (moles/time) across some area �? Note that � represents an area � by � into the figure. Here is a particle simulation. Fick’s law of diffusion…
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Concentration profiles
A concentration profile is a sketch that indicates the magnitude of the concentration as a function of position. This sketch is often superimposed on a process to indicate where these changes occur. This is analogous to a velocity profile for fluid flow. Exercise: Concentration profile Based on the molecular distribution below, draw the concentration profile of species � as…
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Mass transfer: What is it?
Mass transfer Mass transfer is mass in transit due to a species concentration gradient in a mixture. By concentration gradient, we mean a spatial difference in the abundance of the chemical species. Modes of mass transfer diffusion convection Example: The story of engineering the contact lens The cornea of the eye needs oxygen from the air Mindful of…
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Frequently Asked Questions
What is a rectifier? A rectifier is an electronic device that converts an alternating current into a direct current by using one or more P-N junction diodes. Q2 What are the types of rectifiers? The following are the types of rectifiers: Q3 What is a half-wave rectifier? The type of rectifier that converts only the…
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What Are Some Applications of Rectifiers?
Some common applications of rectifiers are: Stay tuned to BYJU’S and fall in love with learning! Subscribe BYJU’S app for more such information and science and math concepts.