Generally as much as we have studied phase separation mainly deals with two components separating into separate phases.However I do not understand why there would be something that will act opposite to the concentration gradient that we all have been studying since childhood days.Why should one act opposite to the other?If possible please explain the phenomenon mathematically and with the help of graphs.
The reason for the phase separation is the non-convexity of the free energy. Consider for instance the free energy of an elastic bar
\psi(\varepsilon)=\frac{1}{2}\mu \varepsilon^2(\varepsilon-1)^2
where \varepsilon =u^\prime is the strain. If you plot this function, you will see that it has two minima achieved at zero and 1 and one maximum in between, so the energy is non-convex. As we know, the bar will be in stable equilibrium if its energy is minimal. For some boundary condition the uniform deformation with constant strain cannot give the minimum to the energy, and in this case the phase separation occurs. For the details please consult
Book Introduction to micromechanics
(Chapter 1 and exercise 1.3)
The second edition of this book will appear soon.
When gasoline becomes saturated, a layer of ethanol and water, known as phase separation, can form in the tank. Since the density of this layer is less than water, typical water floats may not detect its presence.
The increased use of blended fuels creates a potential for a condition known as phase separation. Phase separation occurs when water is present. It can happen in almost any situation where gas is stored. In your car’s fuel tank, large above or underground fuel storage tanks, or boat tanks, even the gas can that you stored in your garage. Many times you may not be aware that phase separation has happened. However, using fuel that has experienced phase separation can cause considerable damage to engines and other systems.
Ethanol bonds with water easier than it does fuel. Fuel blends containing ethanol are highly susceptible to phase separation. When fuel containing even the smallest amount of ethanol comes in to contact with water, regardless of liquid form or humidity, the ethanol absorbs some or all the water. When the liquid reaches the saturation point, the water and ethanol will phase separate. Therefore, creating two, and sometimes three, distinct new layers. It appears as an upper layer of gasoline with a cloudy layer of ethanol and water below it, and in many cases, the third layer of water at the bottom of it.
1. Separation onto phases will lower the average Gibbs energy and thus the equilibrium state is phase separated
2. Phase separation occurs at different rates depending upon the temperature
3. Vapour pressure of the components
4. Concentration gradients.
- Badges
- Science topic
- Similar topics
- Engineering
- Chemical Engineering