ChEg 355 Transport Phenomena Lecture 2 8/24/00

1. ChEg 355 Transport PhenomenaLecture 28/24/00 Mark J. McCready Professor and Department Chair Chemical Engineering B.Ch.E. University of Delaware, 1979 Ph.D. University of Illinois, 1984 mjm@nd.edu 219-631-7146 mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

2. Review from last time mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

3. Favorite quotes • Sufficiently advanced technology is indistinguishable from magic • An engineer can always befuddle a financial person with technology, but a financial person can never overwhelm an engineer with numbers mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

4. ChEg 355 homepage • http://www.nd.edu/~mjm/cheg355.html mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

5. Favorite quotes • The more you know, the better engineer you will be! • I knew then as I can confirm now, nothing would ever be as hard to understand as transport phenomena and the Navier-Stokes equations. I was never again intimidated by quantitative problems and I appreciated the need to formulate simpler problems that gave useful results. mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

6. Favorite quotes The history of modern science has shown repeatedly that a quantitative description of nature can often be achieved most successfully by first idealizing natural phenomena, i.e. by setting up a simplified model, either physical or mathematical, which crudely describes the essential behavior while neglecting details. (In fact, one of the outstanding characteristics of great contributors to modern science has been their ability to distinguish between what is essential from what is incidental) ........" mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

7. Who said them • A top design engineer from DuPont • A CEO of a steel company • One of the most influential chemical engineering professors of all time • A top research/technology engineer from Shell • An ND Cheg Alum who is a VP for General Mills mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

8. Previous Conclusions • The niche in fluid mechanics for chemical engineers is understanding the effects of small scale phenomena that cause large scale outcomes including systems with reaction and mass transfer • This course possesses great depth and should be useful to your educational development even if you do not use it day to for a living mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

9. Dimensional analysis • Outline • A few general cogitations • Motivation • Dealing with complex problems that do not allow solution of governing equation • Can learn some physics the easy way • Sometimes just the easiest thing to do • How to do it • Pick variables, form into dimensionless groups mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

10. Some cogitations • Chemical Engineering at Notre Dame • From an external report: 1998: • “The undergraduate program in chemical engineering is excellent. The faculty regard undergraduates as an essential part of the overall program… • Chemical Engineering is perhaps the most demanding major in any university because of the number and difficulty of courses in a typical program. … • This is one of the ‘elite’ chemical engineering programs with a carefully selected student population equivalent in quality to those of the best private schools in the country. The faculty recognize this challenge and meet it. • The chemical engineering program is tough, at least as difficult as those in the schools represented by the Panel (Princeton, Delaware, Minnesota, Penn, Caltech)… mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

11. Course Goals • http://www.nd.edu/~mjm/cheg355goals.html mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

12. DimensionlessConfucius Proverb • He who knows not and knows he knows not is a child, teach him, Cr~1 • He who knows not and knows not he knows not is a fool, shun him, Cr<<1 • He who knows and knows not he knows is asleep, awaken him, Cr>>1 • He who knows and knows he knows is wise, follow him Cr~1 mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

13. Flow past a sphereWhat is the drag? mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

14. Typical Problem • For a CSTR, how to make it “S”? • How fast to stir? • What size stirrer? mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

15. Solve pipe flow • http://www.nd.edu/~mjm/dimensional.analysis.nb • We will get some more physical arguments, look at some (fake) data, then see how to do dimensional analysis using Mathematica mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

16. Pipe flow data mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

17. Notes for chalk lecture • I hope you took notes as these are illegible! mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

18. Chalk notes • http://www.nd.edu/~mjm/cheg355_lect2_notes.pdf mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept

19. Conclusions • Dimensional analysis is often a good starting point for correlating data and making a model • If done correctly, the dimensionless groups have important physical significance as ratios of competing effects • Number of groups comes from Buckingham Pi, G =P-D • Procedure is straightforward, please try a couple. mjm@nd.eduhttp://www.nd.edu/~mjmhttp://www.nd.edu/~chegdept