1. 1 When Things Go Wrong William Josephson – A.U. Chem. Eng. Jaya Krishnagopalan – T.U. Chem. Eng. Dave Mills – A.U. Chem. Eng. 2007 AIChE Annual Meeting Salt Lake City, Utah

2. 2 Outline & … 4 Experiments Conduction Reynolds Number Friction factor Viscosity For Each Experiment What should occur What did occur Why it happened What was learned

3. 3 …Motivation

4. 4 Conduction Heat Transfer  Objectives To investigate Fourier’s Law for the linear conduction of heat along a simple brass bar To determine the average thermal conductivity of brass in the temperature range studied To observe the effect of temperature on the thermal conductivity of brass in the range studied

5. 5 Conduction Heat Transfer Apparatus

6. 6 Conduction Heat Transfer

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10. 10 Conduction Heat Transfer  Told students of problem  Let them devise workaround  Most students made use of knowledge of sample material – calculated 3 conductivities – eliminated bad thermocouple

11. 11 Reynolds Number  Objectives Compute Reynolds number Observe and quantify transitional flow

12. 12 Reynolds Number Apparatus

13. 13 Reynolds Number - “Ideal” Results ReObservations 500Parallel streamlines – laminar flow 1000Laminar 1500Laminar 2000Laminar 2500Parallel & interacting streamlines – transient flow 3000Interacting streamlines - turbulent flow 3500Turbulent 4000Turbulent 4500Turbulent 5000Turbulent

14. 14 Reynolds Number The Problem Mixing of streamlines at Re = 700 Occurred for all groups

15. 15 Reynolds Number Expected Reported Results ReObservations 500Parallel streamlines – laminar flow 600Laminar 650Parallel & interacting streamlines – transient flow 700Turbulent flow 800Turbulent 1000Turbulent 2000Turbulent 3000Turbulent 4000Turbulent 5000Turbulent

16. 16 Reynolds Number Actual Reported Results ReObservations 500Parallel streamlines – laminar flow 600Laminar 650Parallel & interacting streamlines – laminar flow 700Interacting streamlines - laminar flow 800Interacting streamlines - laminar flow 1000Interacting streamlines - laminar flow 2000Interacting streamlines - laminar flow 3000Interacting streamlines - transient flow 4000Interacting streamlines - turbulent flow 5000Turbulent

17. 17 Reynolds Number Cause of the Problem (physical) Nozzle at end of dye introduction pipe

18. 18 Reynolds Number Cause of the Problem (“mental”) Poor wording in handout: “If the Reynolds number is less than 2100, the flow is considered laminar. If the Reynolds number is greater than 4000, the flow is considered turbulent.”

19. 19 Piping  Objectives To determine relationship between friction factor and Reynolds Number & roughness Friction losses in fittings (globe valve, elbows) Orifice meter

20. 20 Piping Apparatus Pipe A Pipe C Pipe D Pipe E Pipe B Direction of Flow

21. 21 Piping What we want them to do

22. 22 Piping What we get (sometimes) Important! – This is not the “problem”

23. 23 Piping What we get (other times) Important! – This is the “problem”

24. 24 Piping  The Problem – friction factors for SS Pipe below those of PVC  Consideration of the Problem Recheck the numbers A Lie in the handout?? (e.g., wrong info re pipe size) Deeper Thoughts – is this an issue w/ the SS pipe or the PVC pipes? Or both?

25. 25 Viscosity  Objectives To investigate rheology of several liquids  Confirm Newtonian fluids  Determine if shear-thickening, shear-thinning or something else  Temperature effect on a Newtonian fluid

26. 26 Viscosity

27. 27 Viscosity Apparatus

28. 28 Viscosity – Ketchup Results

29. 29 Viscosity – Corn Starch Results

30. 30 Corn Starch Viscosity  The Problem – data indicates shear thinning  Consideration of the Problem Recheck the numbers Try different concentrations Is corn starch really shear thickening?

31. 31 Corn Starch Viscosity  Is it really shear thickening??

32. 32 Corn Starch Viscosity Consideration of the Problem (cont.) Observe operation of viscometer esp. spindle interactions w/ fluid – closely read literature The Answer (& the solution)

33. 33 Viscosity Corn Starch Results w/ Vane

34. 34 What Went Wrong & What Happened  Conductivity Bad Sensor, students were told a priori Students derived workaround  Reynolds Number Physical Setup Students re-examined their thinking (as did the instructor!)  Piping Arguably, nothing went wrong Students have to think  Viscosity Improper equipment Students had to think & observe

35. 35 A Sincere Thank You To the students in CENG 320 Unit Operations Laboratory I – T.U. & CHEN 3820 Chemical Engineering Laboratory I – A.U.