# Top-rated ScreenCasts

Text Section | Link to original post | Rating (out of 100) | Number of votes | Copy of rated post |
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17.12 Energy Balances for Reactions | Click here. | 20 | 1 |
Equilibrium constants and adiabatic reactor calculations with Excel (uakron.edu, 6 min) We previously discussed adiabatic reactor calculations in Section 3.6 with application to the dimethyl ether process. At that time, we accepted the expression for equilibrium constant as given. In Chapter 17, we must recognize how to compute the equilibrium constant for ourselves. This presentation illustrates the calculations for Example 17.9. These kinds of calculations often occur in the context of an overall process, rather than in isolation. Therefore, the presentation shows how to apply Eqn 3.5b with pathway 2.6c to characterize the enthalpies of process streams and solve for the extent of reaction and adiabatic outlet temperature simultaneously. Comprehension Questions: 1. Suppose the reactor inlet feed was: kmol/hr of 110 N2, 300 H2, 15NH3 and 16 CH4. Solve for the adiabatic reactor temperature and extent of reaction in that case. |

08.07 - Implementation of Departure Functions | Click here. | 20 | 5 |
Helmholtz Example - Modified vdW EOS (uakron.edu, 13min) A aρ/RT). Note that the limits of integration matter for this EOS. The audio is inferior for this live video, but it responds to typical questions and confusion from students in the audience. Some students might find it helpful to hear the kinds of questions that students ask. The responses slow the derivation down so that no steps are skipped and key steps are reiterated multiple times. Just turn the volume up!
Comprehension questions: 1. Which part of this EOS is non-zero at the zero density limit of integration? 2. Is there a sign error on one of the terms in this video? Check the derivation independently. 3. Derive the Helmholtz departure given Z = 1 + 4bρ/(1-bρ)2 - (9.5a)/{1ρ/RT-[1-4a/bRTb4ρ+2]}.
(bρ)4. Derive the Helmholtz departure given Z = 1 + 4bρ/(1-2bρ) - (9.5a){1+4ρ/RT[1-2aρ/bRT2]}/{1(bρ)-[1-4a/bRTb4ρ+2]})/{1(bρ)-[1-4a/bRTb4ρ+2]}(bρ) |

08.07 - Implementation of Departure Functions | Click here. | 20 | 1 |
Helmholtz Example - Scott+TPT EOS. (uakron.edu) A a)/{1ρ/RT-[1-4a/bRTb4ρ+2]}.(bρ) |

04.03 The Macroscopic View of Entropy | Click here. | 20 | 1 |
Once we establish equations relating macroscopic properties to entropy changes, it becomes straightforward to compute entropy changes for all sorts of situations. To begin, we can compute entropy changes of ideal gases (learncheme, 3 min). Entropy change calculations may also take a more subtle form in evaluating reversibility (learncheme, 3min). Comprehension Questions: 1. Nitrogen at 298K and 2 bars is adiabatically compressed to 375K and 5 bars in a continuous process. (a) Compute the entropy change. (b) Is this process reversible, irreversible, or impossible? |

08.07 - Implementation of Departure Functions | Click here. | 20 | 1 |
Internal Energy Departure - PR EOS starting from Helmholtz Departure (uakron.edu,9min) This Comprehension Questions: Starting from the Helmholtz Departure function and referring to the above results... 1. Derive the internal energy departure function for the "modified vdW" EOS. |

09.06 - Fugacity Criteria for Phase Equilibria | Click here. | 20 | 1 |
When liquid is added to an evacuated tank of fixed volume, equilibrium is established between the vapor and liquid. (3min,learncheme.com) The fugacity criterion characterizes this equilibrium as occurring when the escaping tendency from each phase is equal. |

11.05 - Modified Raoult's Law and Excess Gibbs Energy | Click here. | 20 | 2 |
Extending the M1 derivation of the activity coefficient to multicomponent mixtures (uakron.edu, 14min) is straightforward but requires careful attention to the meaning of the subscripts and notation. It is a good warmup for derivations of more sophisticated activity models. This presentation begins with a brief review of the M1 model and its relation to the Gibbs excess function, then systematically explains the notation as it extends from the binary case to multiple components. Comprehension Questions |

03.6 - Energy Balance for Reacting Systems | Click here. | 20 | 1 |
In case you need a little extra help on energy balances after iterating mass balances, this video walks you through the process. (8min, uakron.edu) for the same process flow diagram related to dimethyl ether synthesis. Comprehension Questions: 1. Choose any process flow diagram from your material and energy balances (MEB) textbook that has a recycle stream. Solve the problem using this technique and compare to the answer you obtained in MEB class. Estimate stream enthalpies for every stream and compute the overall energy balance of all product streams to all feed streams. Does the process require net heat addition or removal? |

11.01 Modified Raoult's Law and Excess Gibbs Energy | Click here. | 20 | 1 |
Modified Raoult's Law and Excess Gibbs Energy (6:27) (msu.edu) What are 'postive deviations' and 'negative deviations'? What are the 'rules of the game' for working with deviations from Raoult's law? This screencast show the three main stages of modeling deviations from Raoult's law: 1) obtaining the activity coefficient from experiment; 2) fitting the activity coefficient to an excess Gibbs energy model; 3) using the fitted model to perform bubble, dew, flash calculations. These three stages are often jumbled up when first learning about activity coefficients, so explicit explanation of the strategy may be helpful. |

05.2 - The Rankine cycle | Click here. | 20 | 1 |
Rankine Example Using Steam.xls (uakron.edu, 15min) High pressure steam (254C,4.2MPa, Saturated vapor) is being considered for application in a Rankine cycle dropping the pressure to 0.1MPa; compute the Rankine efficiency. This demonstration applies the Steam.xls spreadsheet to get as many properties as possible. Comprehension Questions: 1. Why does the proposed process turn out to be impractical? 2. What would you need to change in the process to make it work? Assume the high and low temperature limits are the same. Be quantitative. 3. What would be the thermal efficiency of your modified process? |