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Impeller Power Draw Across the Full Reynolds Number

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Impeller Power Draw Across the Full Reynolds Number IMPELLER POWER DRAW ACROSS THE FULL REYNOLDS NUMBER SPECTRUM Thesis Submitted to The School of Engineering of the UNIVERSITY OF DAYTON In Partial Fulfillment of the Requirements for The Degree of Master of Science in Chemical Engineering By Zheng Ma Dayton, OH August, 2014 IMPELLER POWER DRAW ACROSS THE FULL REYNOLDS NUMBER SPECTRUM Name: Ma, Zheng APPROVED BY: ______________________ ________________________ Kevin J. Myers, D.Sc., P.E. Eric E. Janz, P.E. Advisory Committee Chairman Research Advisor Research Advisor & Professor Chemineer Research & Chemical & Materials Engineering Development Manager NOV-Process & Flow Technologies ________________________ Robert J. Wilkens, Ph.D., P.E. Committee Member & Professor Chemical & Materials Engineering _______________________ ___________________________ John G. Weber, Ph.D. Eddy M. Rojas, Ph.D., M.A., P.E. Associate Dean Dean, School of Engineering School of Engineering ii ABSTRACT IMPELLER POWER DRAW ACROSS THE FULL REYNOLDS NUMBER SPECTRUM Name: Ma, Zheng University of Dayton Research Advisors: Dr. Kevin J. Myers Eric E. Janz The objective of this work is to gain information that could be used to design full scale mixing systems, and also could develop a design guide that can provide a reliable prediction of the power draw of different types of impellers. To achieve this goal, the power number behavior，including three operation regimes, the limits of the operation regimes, and the effect of baffling on power number，was compared across the full Reynolds number spectrum for Newtonian fluids in a laboratory-scale agitator. Six industrially significant impellers were tested, including three radial flow impellers: D-6, CD-6, and S-4, and also three axial flow impellers: P-4, SC-3, and HE-3. Results in laminar regime indicate that baffling has no effect on power number in this operation regime. There is an inversely proportional relationship between power number and Reynolds number. The upper limit for this operation regime should be lower than 10, the limit commonly noted in the literature. The product of power number and iii Reynolds number in this particular regime is approximately proportional to the number of blades for these six impellers; however, other shape factors that were not included in this study also contribute to it. In turbulent operation, baffling has a significant effect on power number: the power number for most impellers remains relatively constant in the baffled configuration while that for unbaffled configuration decreases with increasing Reynolds number. The impeller blade number is not the dominant factor that affects power number in this regime. Two hydrofoil impellers, SC-3 and HE-3, exhibit much lower power numbers when compared with the other impellers. Additionally, the impellers with higher power numbers in baffled tank tend to have lower ratios between unbaffled power number and average baffled power number when comparing at same Reynolds number. No difference between two configurations, baffled and unbaffled, exists at low Reynolds number end of transitional regime, and the difference starts at intermediate Reynolds number and increases with an increase of Reynolds number. In the baffled configuration, four out of six impellers exhibit a minimum power number. In the unbaffled configuration, power numbers drop with increasing Reynolds number throughout the entire transitional regime for all impellers. The ratio of unbaffled to turbulent average power number for the six impellers retains a consistent order through the entire Reynolds number range with two high efficiency impellers having the highest ratio, then pitched blade impeller, and three radial flow impellers having the lowest ratios. iv ACKNOWLEDGEMENTS I would like to thank Dr. Kevin Myers for all the help he has given throughout the past three years. Without his encouragement and guidance I would have never made it this far. Dr. Myers gave me a great opportunity to pick up chemical engineering from basics three years ago. He accepted me to work on this research so I can complete the degree with a written thesis and get prepared for future study. I will be thankful to him for his support and benefactions forever. I also want to thank Eric Janz who offered me this opportunity to be part of the team and gave me the access to carry out this experiment in the Chemineer laboratory. I want to express my thankfulness to Prof. Robert Wilkens for being my committee member and providing constructive feedback on my thesis. I would also like to thank Erin Duff, Robert Strong, and Michael Adams for their support on both the laboratory measurements and my daily life. I want to acknowledge everyone else who has offered support: my family for their continuous love; my boyfriend, Zhengchao, as he has tried his best to take care of me and been supportive all the way through; Jin, my best friend here in UD, for all the suggestions and her willingness to share my joys and sorrows; Jie and his wife, Jing, who encouraged me when I had a tough time. I would have failed my study here in UD without those people. v TABLE OF CONTENTS ABSTRACT ................................................................................................................... iii ACKNOWLEDGEMENTS ............................................................................................ v LIST OF FIGURES ...................................................................................................... vii LIST OF TABLES ......................................................................................................... ix NOMENCLATURE ...................................................................................................... xi CHAPTER 1 INTRODUCTION .................................................................................... 1 1.1 Background ............................................................................................... 1 1.2 Power Number and Reynolds Number...................................................... 2 1.3 Rheology ................................................................................................... 4 1.4 System Geometry ...................................................................................... 5 1.5 Objective ................................................................................................... 6 CHAPTER 2 EXPERIMENTAL SETUP AND PROCEDURE .................................... 7 2.1 Experimental Setup ................................................................................... 7 2.2 Viscosity Measurement ............................................................................. 9 2.3 Procedure ................................................................................................. 10 CHAPTER 3 RESULTS AND DISCUSSION ............................................................. 12 CHAPTER 4 CONCLUSIONS AND RECOMMENDATIONS ................................. 42 BIBLIOGRAPHY ......................................................................................................... 46 APPENDIX: RAW AND REDUCED EXPERIMENTAL DATA .............................. 47 vi LIST OF FIGURES Figure 1-1: Haake viscometer data for corn syrup at different temperatures (μ [=] Pa s) .. 5 Figure 2-1: Experimental apparatus .................................................................................... 8 Figure 2-2: Readout of torque and speed from agitator ...................................................... 9 Figure 2-3: Assembled agitator shaft and impeller ............................................................. 9 Figure 3-1: D-6 low Reynolds number data ..................................................................... 13 Figure 3-2: CD-6 low Reynolds number data ................................................................... 13 Figure 3-3: S-4 low Reynolds number data ...................................................................... 14 Figure 3-4: P-4 low Reynolds number data ...................................................................... 14 Figure 3-5: SC-3 low Reynolds number data ................................................................... 15 Figure 3-6: HE-3 low Reynolds number data ................................................................... 15 Figure 3-7: Comparison of baffled low Reynolds number data ....................................... 18 Figure 3-8: D-6 high Reynolds number data .................................................................... 19 Figure 3-9: CD-6 high Reynolds number data .................................................................. 19 Figure 3-10: S-4 high Reynolds number data ................................................................... 20 Figure 3-11: P-4 high Reynolds number data ................................................................... 20 Figure 3-12: SC-3 high Reynolds number data ................................................................ 21 Figure 3-13: HE-3 high Reynolds number data ................................................................ 21 Figure 3-14: Comparison of baffled high Reynolds number data .................................... 25 Figure 3-15: Comparison of unbaffled high Reynolds number data ................................ 26 vii Figure 3-16: D-6 transitional Reynolds number data ....................................................... 27 Figure 3-17: CD-6 transitional Reynolds number data ..................................................... 27 Figure 3-18: S-4 transitional Reynolds number data .......................................................
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