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|13.04 - UNIQUAC||Click here.||100||3||
Group contributions are used widely in property prediction. The volumes and surface areas have been determined by x-ray data and high-temperature collision data. The UNIQUAC and UNIFAC activity coefficient methods use these quantities to calculation volume fractions and surface area fractions. The assignment of functional groups for a molecule must be done carefully to assure agreement with the groups used by the model developers.
1. Estimate R and Q for 1,4 dihydroxy benzene.
2. Estimate R and Q for n-propyl alcohol and compare them to the values for IPA.
3. Estimate R and Q for methyl-npropyl ketone.
|10.08 - Concepts for Generalized Phase Equilibria||Click here.||100||1||
When expressing the derivative of the total Gibbs energy by chain rule, there is one particular partial derivative that relates to each component in the mixture: the "chemical potential." By adapting the derivation from Chapter 9 of the equilibrium constraint for pure fluids, we can show that the equilibrium constraint for mixtures is that the chemical potential of each component in each phase must be equal. That is fine mathematically but it is not very intuitive. By translating the chemical potential into a rigorous definition of fugacity of a component in a mixture, we recognize that an equivalent equilibrium constraint is that the fugacity of each component in each phase must be equal. (8min, Live, uakron.edu) This offers the intuitive perspective of, say, molecules from the liquid escaping to the vapor and molecules from the vapor escaping to the liquid; when the "escaping tendencies" are equal, the phases experience no net change and we call that equilibrium.
|11.02 - Calculations with Activity Coefficients||Click here.||96||5||
Dew Temperature (7:57) (msu.edu)
The culmination of the activity coefficient method is application of the fitted activity coefficients to extrapolate from limited experiments in a Stage III calculation. The recommended order of study is 1) Bubble Pressure; 2) Bubble Temperature; 3) Dew Pressure; 4) Dew Temperature. Note that an entire Txy diagram can be generated with bubble temperature calculations; no dew calculations are required. However, many applications require dew calculations, so they cannot be avoided. The dew calculations are more complicated than bubble calculations, because the liquid activity coefficients are not known until the unknown liquid mole fractions are found. This screencast describes the procedure and how to implement the method in Matlab or Excel.
|10.01 - Introduction to Phase Diagrams||Click here.||96||5||
Introduction to Phase Behavior (9:37) (msu.edu)
1. Referring to the Txy diagram on slide 3, estimate T, nature (ie. L,V, V+L, L+L), composition(s), and amount of the phase(s) for points: a, b. d, g.
|07.06 Solving The Cubic EOS for Z||Click here.||95||4||
1. Peng-Robinson PVT Properties - Excel (3:30) (msu.edu)
Introduction to PVT calculations using the Peng-Robinson workbook Preos.xlsx. Includes hints on changing the fluid and determining stable roots.
1. At 180K, what value of pressure gives you the minimum value for Z of methane? Hint: don't call solver.
2. At 30 bar, what value of pressure gives Z=0.95 for methane?
3. Compute the molar volume(s) (cm3/mol) for argon at 100K for each of the following?
|07.09 -The Molecular Basis of Equations of State: Concepts and Notation||Click here.||93.3333||3||
Nature of Molecular Interactions - Macro To Nano(8min). (uakron.edu) Instead of matching the critical point, we can use experimental data for density vs. temperature from NIST as a means of characterizing the attractive energy and repulsive volume. A plot of compressibility factor vs. reciprocal temperature exhibits fairly linear behavior in the liquid region. Matching the slope and intercept of this line characterizes two parameters. This characterization may be even more useful than using the critical point if you are more interested in liquid densities than the critical point. In a similar manner, you could derive an EOS based on square-well (SW) simulations and use the SW EOS to match the NIST data(11min), as shown in this sample calculation of the ε and σ values for the SW potential. In this lesson, we learn how to characterize the forces between individual atoms, which may seem quite unreal or impractical when you first encounter it. On the other hand, "nanotechnology" is a scientific discipline that explores how the manipulation of nanostructure is now quite real with very significant practical implications. "The world's smallest movie" shows dancing molecules, (IBM, 2min) demonstrating the reality of molecular manipulation, and the accompanying text explains some of the practical implications. Along similar lines, researchers at LLNL and CalTech have developed 3D printers that can display "voxels" (the 3D analog of pixels) of ~1nm3. That's around 10-100 atoms per voxel. Since 2013-14, chemical/materials engineers have been building nanostructures (TEDX, 13min) in the same way that civil engineers build infrastructure.
|14.10 Solid-liquid Equilibria||Click here.||93.3333||3||
SLE using Excel with the M1 model (7min, uakron.edu)
Similar to LLE in Excel, the iteration feature can be used to quickly solve for SLE at multiple temperatures.
|04.09 Turbine calculations||Click here.||90||2||
General procedure to solve for steam turbine efficiency. (LearnChemE.com, 5min) This video outlines the procedure without actually solving any specific problem. It shows how inefficiency affects the T-S diagram and how to compute the actual temperature at the turbine outlet.
|14.09 - Numerical procedures for binary, ternary LLE||Click here.||90||2||
LLE Calculations: UNIFAC from Actcoeff.xlsx Calculation of LLE. (5 min) (LearnChemE.com)
|09.08 - Calculation of Fugacity (Liquids)||Click here.||90||2||
Liquid fugacity relative to vapor fugacity. (LearnChemE, 5 min) This screencast shows a sample derivation and sample calculation for the vapor equation of state given by: Z = 1-0.01P, solve for: (a) the vapor fugacity at 500K and 30 bar (b) the liquid fugacity in equilibrium with the same vapor at 500K and 30bar (c) the liquid fugacity at 500K and 60 bar. Data: VL = 25 cm3/mol.
1. How much did raising the pressure to 60 bar change the liquid fugacity (bars) (+/- 1%)?