Top-rated ScreenCasts

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07.06 Solving The Cubic EOS for Z Click here. 100 2

6. Solving for density (uakron.edu, 9min) An alternative to solving directly for Z is to solve for density then compute Z=P/(ρRT). This requires iterative solution and it is not very expedient for repetitive calculations, but it requires no rearrangement of the EOS and it is easy to visualize. This sample calculation is illustrated here for the vdW EOS, solving for the density of propane as: (a) liquid 25C,11bars (b) liquid 62C,35bars (c) vapor at 80C and 30bars.

Comprehension Questions:

1. Solve for the liquid density (mol/cm3) of n-pentane at 62C and 2.5 bars using the vdW EOS.
2. Solve for the Z-factor of liquid n-pentane at 62C and 2.5 bars using the vdW EOS.
3. What's the value of the Z-factor at 80C and 30 bars according to this presentation?

08.08 - Reference States Click here. 100 1

Peng-Robinson Properties - Excel (6:56) (msu.edu)

Provides an overview of using the Peng-Robinson spreadsheet Preos.xlsx for calculation of H, U, S and use of solver.

Comprehension Questions:

1. For liquid propane at 298K and 1 MPa, and a reference state of 298K and 1bar propane vapor, what is the ideal gas contribution to "H-HR" (J/mol)?
2. For liquid propane at 298K and 1 MPa, and a reference state of 298K and 1bar propane vapor, what is the ideal gas departure contribution: "H-Hig" (J/mol)?
3. For liquid propane at 298K and 1 MPa, and a reference state of 298K and 1bar propane vapor, what is the tabulated value of "H" (J/mol)?
4. Explain the similarity and difference between the numerical values of "H" and "H-Hig".
5. Ethane at 350K and 5 bars is expanded through an adiabatic, reversible turbine to 1 bar. What is the temperature (K) at the turbine outlet?

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.




08.02 - The Internal Energy Departure Function Click here. 100 1

Departure Function Derivation Principles (8:03) (msu.edu)
This screencast covers sections 8.2 - 8.8. Concepts of using the equation of state to evaluate departure functions. The screencasts also discusses the choice of density integrals or pressure integrals. The use of a reference state is discussed.

05.2 - The Rankine cycle Click here. 100 1

Thermal Efficiency with a 1-Stage Rankine Cycle. (uakron.edu, 12min) Steam from a boiler enters a turbine at 350C and 1.2MPa and exits at 0.01MPa and saturated vapor; compute the thermal efficiency (ηθ) of the Rankine cycle based on this turbine. (Note that this is something quite different from the turbine's "expander" efficiency, ηE.) This kind of calculation is one of the elementary skills that should come out of any thermodynamics course. Try to pause the video often and work out the answer on your own whenever you think you can. You will learn much more about the kinds of mistakes you might make if you take your best shot, then use the video to check yourself. Then practice some more by picking out other boiler and condenser conditions and turbine efficiencies. FYI: the conditions of this problem should look familiar because they are the same as the turbine efficiency example in Chapter 4. That should make it easy for you to take your best shot.

Comprehension Questions:

1. The entropy balance is cited in this video, but never comes into play. Why not?

2. Steam from a boiler enters a turbine at 400C and 2.5 MPa and exits a 100% efficient turbine at 0.025MPa; compute the Rankine efficiency. Comment on the practicality of this process. (Hint: review Chapter 4 if you need help with turbine efficiency.)

17.07 - Temperature Dependence of Ka Click here. 100 2

You can customize Kcalc.xlsx (uakron.edu, 17min) to facilitate whatever calculations you may need to perform. This presentation shows how to implement VLOOKUP to automatically load the relevant Hf, Gf, and Cp values. It also shows how to automatically use the Cp/R value when a,b,c,d values for Cp are not available. Finally, it shows how a fairly general table of inlet flows, temperatures, and pressures can be used to set up the equilibrium conversion calculation. The initial set up is demonstrated for the dimethyl ether process, then revised to initiate solution of Example 17.9 for ammonia synthesis.

Comprehension Questions:

1. The video shows how the shortcut Van't Hof equation can be written as lnKa=A+B/T. What are the values of A and B for the dimethyl ether process when a reference temperature of 633K is used?
2. The video shows how the shortcut Van't Hof equation can be written as lnKa=A+B/T. What are the values of A and B for the ammonia synthesis process when a reference temperature of 600K is used?

08.08 - Reference States Click here. 100 1

This sample calculation shows how to compute the liquefaction in the Linde process for methane as the operating fluid. (uakron, 8min) The Linde process is a slight variation on the OVC cycle wherein the liquefied fraction exiting the throttle is captured as product and removed from the process. There is also heat integration in the sense that the cold vapor is used to precool the feed to the throttle.

FYI: Since natural gas is mostly methane, this process could be easily adapted to the production of liquefied natural gas (LNG) or liquified petroleum gas (LPG, mostly propane). Liquefied gases may seem impractical when you first encounter them, but they are more efficient for transport because they are so much more dense than the gases. Keeping them as liquids is basically a reflection of the effectiveness of the insulation. If any gas leaks from the relief valve (~1.1 bar), then liquid must evaporate to fill the space. The requisite heat of vaporization in that case cools the remaining below the boiling temperature. No heat = no vaporization.

17.06 Determining the Spontaneity of Reactions Click here. 100 1

Which way will a reaction go? (3:40) (msu.edu)

When both reactants and products are present in a reactng mixture, the direction the reaction will proceed is not necessarily indicated by the sign of ΔGo or Ka. Rather, it is determined by ΔG. This screencasts provides guidance for understanding this concept.

Comprehension Questions: (Hint: review Example 17.1 before answering.)

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. When the conversion of H2 is 32%, will the reaction go forwards towards product or back to reactants?
2. 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. When the conversion of CO is 52%, will the reaction go forwards towards product or back to reactants?
3. 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. When the conversion of H2 is 42%, will the reaction go forwards towards product or back to reactants?
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. When the conversion of H2 is 42%, will the reaction go forwards towards product or back to reactants?

17.05 - Effect of Pressure, Inerts, Feed Ratios Click here. 100 1

How to push, pull, persuade a reaction (3:32) (msu.edu)

Pressure can be used to influence conversion for reactions where gas phase species are present. Feed ratios, inerts, or simultaneous reactions can also be used.

Comprehension Questions:

1. The principle by which a change in temperature, pressure, or concentration leads to a counteracting change in equilibrium is known as:_____.
2. For the reaction: CO + 2H2 = CH3OH, an increase in pressure will cause the products to: ___ (decrease, increase, or be unaffected). Explain.
2. For the reaction: CH4 + H2O = CO + 3H2, an increase in pressure will cause the products to: ___ (decrease, increase, or be unaffected). Explain. (FYI: this reaction, known as "steam reforming" is an important step in making chemicals from natural gas.)
3. For the reaction: CO + 2H2 = CH3OH, adding an inert component will cause the products to: ___ (decrease, increase, or be unaffected). Explain.
4. We discuss temperature effects in detail later, but for now you should be able to make predictions based on ____ principle (cf. #1 above). An exothermic reaction gives off heat. Therefore, adding heat to an exothermic reaction (ie. raising the temperature) will cause the products to: ___ (decrease, increase, or be unaffected). Explain.
5. For the reaction: H2O + CO = H2 + CO2, an increase in pressure will cause the products to: ___ (decrease, increase, or be unaffected). Explain. (As a first approximation, you may neglect deviations from ideal gas behavior, but then discuss the effect these deviations would have if you did take them into account. Which component's fugacity would be most affected by these deviations and how do these deviations change with pressure?)
6. For the reaction: coal + H2O = CO + H2, an increase in pressure will cause the products to: ___ (decrease, increase, or be unaffected). Explain. (Hint: carbon in the form of coal is solid and does not exist in the vapor phase. cf. section 17.14. It might be helpful to think of the reverse reaction, known as coking, where the solid carbon precipitates from the gas. This is a very simple example of simultaneous reaction and phase equilibrium.)
7. For the reaction: CO + 2H2 = CH3OH, adding an inert liquid to the reactor through which all products are removed will cause the products to: ___ (decrease, increase, or be unaffected). Explain. (Hint: this is a bit more sophisticated example of simultaneous reaction and phase equilibrium. How will the inert liquid alter the concentrations in the vapor? Remember that the fugacities are proportional to the gaseous partial pressures.)


11.09 - Fitting Activity Coefficients to Multiple Data Click here. 100 1

Fitting Pxy data using Excel (9:00) (msu.edu)

An illustration of using Excel for fitting Pxy data of the IPA+water system using the M2 model and some suggestions for working with the GammaFit.xls file, showing that the sum of squared deviations is 14 mmHg^2. Dividing by the number of points (18 including x1=0 and x1=1), and taking the square root gives a root mean square deviation (rmsd) of 0.89 mmHg. Noting that the pressure ranges from roughly 30-60 mmHg, this corresponds to roughly 2%rmsd. This effectively corresponds to sample validation of the M2 model for the IPA+water system since the deviation of 2% is quite small. We could argue that a model is valid as long as the rmsd is less than 10%, but you need to report the %rmsd and show the plot in order to be clear. For example, if the plot shows that there is systematic deviation from the experimental data, then a better model probably exists and should be sought. If there is no systematic deviation and the data are simply very scattered, then the model is probably as good as can be expected.

Comprehension Questions:

1. If experimental data for vapor pressures are included for a particular data set, should you use the values from the data set or the values calculated from Antoine's equation?
2. What is the objective function applied by the GammaFit spreadsheet?
3. Apply the procedure illustrated here optimize the M2 model for the ethanol+benzene data given in HW 10.2. What values do you obtain for A12 and A21 in that case? What is the value of the rmsd that you obtain?
4. Explain how you would modify this spreadsheet to apply to the M1 model.
5. Explain how you would modify this spreadsheet to apply to data obtained at constant pressure instead of constant temperature.

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