Top-rated ScreenCasts

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10.06 - Relating VLE to Distillation Click here. 100 1

Distillation is the primary choice for separations in the petrochemical industry. Because the majority of chemical processing involves separations/purifications, that makes distillation the biggest economic driver in all of chemical production. Therefore, it is very important for chemical engineers to understand how distillation works (21min, uakron.edu) and how VLE plays the major role. This video is a bit long, but it puts into context how phase diagrams and thermodynamic properties relate to very important practical applications. You may find it helpful to reinforce the conceptual video with some sample calculations.(12min) At the end of the video, you should be able to answer the following:

Consider the acetone+ethanol system. Use SCVP (Eqn 2.47) to answer the following.

  1. Sketch a Txy diagram for acetone+ethanol at 1 bar with accurate Tsat's. Label completely.
  2. Which component pertaining to #1 would have enhanced concentration in the distillate?
  3. Accurately sketch the yx diagram pertaining to #1
  4. Use Raoult's Law to estimate αLH pertaining to #1.
  5. Use your sketch from 3 to estimate Nmin  to go from x1=0.1 to 0.9.
  6. Use the Fenske equation to estimate Nmin  with splits of 0.9 and 0.1.
02.01 Expansion/Contraction Work Click here. 100 2

Vocabulary in Sections 2.1-2.3: Forms of "Work." (uakron.edu, 11 min) Making cookies is hard work. In discussing work, we develop several shorthand terms to refer to specific common situations: expansion-contraction work, shaft work, flow work, stirring work, "lost" work. These terms comprise the headings of sections 2.1-2.3, but it is convenient to discuss them all at once. The important thing to remember is that work is really just force times distance, pure and simple. The shorthand terms are not intended to complicate the discussion, but to expedite the analysis of the energy balance. Developing some familiarity with the terms related to common daily experiences may help you to assimilate this new vocabulary. Sample calculations (13min) illustrate a remarkable difference when one is faced with gas compression vs. liquid pump work. 

Comprehension Questions:
1. How is "expansion-contraction" work related to force times distance?
2. What is the expression for "flow" work? Explain how it relates to force times distance for fluid flowing in a pipe.
3. What expression can we use for calculating "shaft" work, as in a pump or turbine? What is the technique of calculus to which it is related?

07.11 - The molecular basis of equations of state: analytical theories Click here. 100 1

Nature of Molecular Parking Lots - RDFs(20min, uakron.edu) Molecules occupy space and they move around until they find their equilibrium pressure at a given density and temperature. Cars in a parking lot behave in a similar fashion except the parking lot is in 2D vs. 3D. Despite this exception, we can understand a lot about molecular distributions by thinking about how repulsive and attractive forces affect car parking. For example, one important consideration is that you should not expect to see two cars parked in the same space at the same time! That's entirely analogous for molecular parking. Simple ideas like this lead to an intuitive understanding of the number of molecules distributed at each distance around a central molecule. From there, it is straightforward to multiply the energy at a given distance (ie. u(r) ) by the number of molecules at that distance (aka. g(r) ), and integrate to obtain the total energy. A similar integral over intermolecular forces leads to the pressure. And, voila! we have a new conceptual route to developing engineering equations of state.
Comprehension questions:
1. Sketch u(r)/epsilon and g(r) vs. r/sigma for square well spheres at a very low density. Use a solid line for g(r) and a dashed line for u(r)/epsilon.
2. Sketch u(r)/epsilon and g(r) vs. r/sigma for hard spheres at a high density. Use a solid line for g(r) and a dashed line for u(r)/epsilon.
3. Sketch u(r)/epsilon and g(r) vs. r/sigma for square well spheres at a high density. Use a solid line for g(r) and a dashed line for u(r)/epsilon.

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. 

07.11 - The molecular basis of equations of state: analytical theories Click here. 100 1

Nature of Molecular Energy - Example Calculation(8min, uakron.edu) Given an estimate for the radial distribution function (RDF) integrate to obtain an estimate of the internal energy. The result provides an alternative to the attractive term of the vdW EOS.

10.08 - Concepts for Generalized Phase Equilibria Click here. 100 1

Concepts for General Phase Equilibria (12:33) (msu.edu)

The calculus used in Chapter 6 needs to be generalized to add composition dependence. Also, we introduce partial molar properties and composition derivatives that are not partial molar properties. We introduce chemical potential These concepts are used to show that the chemical potentials and component fugacities are used as criteria for phase equilibria.

14.10 Solid-liquid Equilibria Click here. 100 2

Solid-liquid Equilibria using Excel (7:38min, msu)

The strategy for solving SLE is discussed and an example generating a couple points from Figure 14.12 of the text are performed. Most of the concepts are not unique to UNIFAC or Excel. This screeencast shows how to use the solver tool to find solubility at at given temperature.

01.6 Summary Click here. 100 1

The objectives for Chapter 1 were:

1. Explain the definitions and relations between temperature, molecular kinetic energy,
molecular potential energy and macroscopic internal energy, including the role of intermolecular potential energy and how it is modeled. Explain why the ideal gas internal energy
depends only on temperature.
2. Explain the molecular origin of pressure.
3. Apply the vocabulary of thermodynamics with words such as the following: work, quality,
interpolation, sink/reservoir, absolute temperature, open/closed system, intensive/extensive
property, subcooled, saturated, superheated.
4. Explain the advantages and limitations of the ideal gas model.
5. Sketch and interpret paths on a P-Vdiagram.
6. Perform steam table computations like quality determination, double interpolation.

To these, we could add expressing and explaining the first and second laws. Make a quick list of these expressions and explanations in your own words, including cartoons or illustrations as you see fit,  starting with the first and second laws.

17.07 - Temperature Dependence of Ka Click here. 100 2

Example 17.4 and 17.5 solved using Kcalc.xlsx (6:01) (msu.edu)

The full form of the temperature dependence of Ka is implemented in Kcalc.xlsx and Kcalc.m. This screecast covers the use of Kcalc.xlsx for Example 17.4 and Example 17.5 of the textbook.

Comprehension Questions:

1. CO and H2 are fed in a 2:1 ratio to a reactor at 500K and 20 bars with a catalyst that favors only CH3OH as its product. Calculate ΔGRº and ΔHRº.
2. CO and H2 are fed in a 1:1 ratio to a reactor at 500K and 20 bars with a catalyst that favors only CH3OH as its product. Calculate ΔGRº and ΔHRº.
3. CO and H2 are fed in a 1:1 ratio to a reactor at 600K and 20 bars with a catalyst that favors only CH3OH as its product. Calculate ΔGRº and ΔHRº.
4. CO and H2 are fed in a 1:1 ratio to a reactor at 500K and 20 bars with a catalyst that favors only CH3OH as its product. Calculate ΔGTº and ΔHTº. Check your answer for ΔGTº using the value given for Ka in Example 17.1.
5. CO and H2 are fed in a 1:1 ratio to a reactor at 600K and 10 bars with a catalyst that favors only CH3OH as its product. Calculate Ka, ΔGTº and ΔHTº.
6. CH3OH is fed to a reactor at 200ºC and 1 bar with a catalyst that produces CO and H2. Calculate Ka, ΔGTº and ΔHTº for this reaction and compare to the literature values given in Example 17.6 of Section 17.10.
7. CH3OH is fed to a reactor at 300ºC and 1 bar with a catalyst that produces CO and H2. Calculate Ka for this reaction and compare to the value given in Example 17.6 of Section 17.10. Give two reasons why the two estimates are not identical.




10.02 - Vapor-Liquid Equilibrium (VLE) Calculations Click here. 100 2

VLE Routines - General Strategies (4:49) (msu.edu)

Deciding which routine to use is more challenging than it appears. Also understanding the strategy used to solve the problems is extremely helpful in being able to develop the equations to solve instead of trying to memorize them.

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