INVESTIGATION OF FOULING MECHANISMS TO GUIDE THE DESIGN OF DIESEL ENGINE EXHAUST DRIVEN ABSORPTION HEAT PUMPS A Thesis Presented to The Academic Faculty by Victor C. Aiello In Partial Fulfillment of the Requirements for the Degree Master of Science in the School of Mechanical Engineering Georgia Institute of Technology December 2016 COPYRIGHT © 2016 BY VICTOR AIELLO INVESTIGATION OF FOULING MECHANISMS TO GUIDE THE DESIGN OF DIESEL ENGINE EXHAUST DRIVEN ABSORPTION HEAT PUMPS Approved by: Dr. Srinivas Garimella, Advisor School of Mechanical Engineering Georgia Institute of Technology Dr. William J. Wepfer School of Mechanical Engineering Georgia Institute of Technology Dr. Peter Loutzenhiser School of Mechanical Engineering Georgia Institute of Technology Date Approved: November 21, 2016 ACKNOWLEDGEMENTS I would first like to thank my advisor, Dr. Srinivas Garimella, for providing the opportunity to work on an intriguing and challenging research project. I am grateful for being given a balance of direction and autonomy that has allowed for an invaluable learning experience. I would also like to thank the members of the Sustainable Thermal Systems Lab for their unique willingness to provide technical guidance and support. I would particularly like to thank Marcel Staedter for his mentorship and Girish Kini for his incredible dedication to this research project. It has been an honor to work with and learn from such an inspiring and hard working group of people. Lastly, I would like to thank my family, for this accomplishment would not have been possible without their unwavering support. iii TABLE OF CONTENTS ACKNOWLEDGEMENTS iii LIST OF TABLES vii LIST OF FIGURES x LIST OF SYMBOLS AND ABBREVIATIONS xvii SUMMARY xx CHAPTER 1. Introduction 1 1.1 Absorption Heat Pump 2 1.2 Waste-heat Recovery Applications 5 1.3 Scope of Work 7 1.4 Organization of Thesis 9 CHAPTER 2. Literature Review 11 2.1 Engine Exhaust Waste-Heat Recovery Systems 11 2.2 Diesel Generator Emissions 17 2.2.1 In-use Diesel Generators 17 2.2.2 Effect of Fuel Type 18 2.3 Fundamental Fouling Investigations 21 2.3.1 Deposition Mechanisms 21 2.3.2 Deposit Removal Mechanisms 33 2.3.3 Deposit Properties 40 2.4 Component Level Fouling Investigations 41 2.5 Summary 45 CHAPTER 3. Experimental Facility 48 3.1 Cycle Model of Waste-Heat Driven Absorption Heat Pump 48 3.2 Fin-Tray Desorber 50 3.3 Model of Experimental Facility 54 3.3.1 Tube-in-Tube Heat Exchanger Model 57 3.3.2 Pressure Drop Model 68 3.3.3 Heater and Chiller Sizing 70 3.4 Experimental Facility Design and Control 75 3.4.1 Equipment and Instrumentation 75 3.4.2 Data Acquisition and Controls 81 3.5 Experimental Methodology and Procedure 84 3.5.1 Experimental Methodology 84 3.5.2 Experimental Procedure 87 3.6 Fouling Layer Analysis 90 3.6.1 Imaging Procedure 90 3.6.2 Image Processing 91 iv CHAPTER 4. Single-Tube Experiments 96 4.1 Data Reduction 96 4.1.1 Exhaust Heat Transfer Rate 97 4.1.2 Coolant Heat Transfer Rate 104 4.1.3 Heat Transfer Rate Comparison 109 4.1.4 Fouling Thermal Resistance 111 4.1.5 Pressure Drop 115 4.1.6 Predicted Deposition 118 4.2 Experimental Results 119 4.2.1 Exhaust Nusselt Number 119 4.2.2 Validation of Experimental Results 123 4.2.3 Steady State Experiments 132 4.2.4 Transient Experiments 146 4.3 Comparison with Literature 154 CHAPTER 5. Desorber Design and Experiments 157 5.1 Desorber Modeling 157 5.2 Desorber Design Selection 165 5.3 Experimental Set-up 177 5.4 Data Analysis 179 5.4.1 Heat Transfer Rates 179 5.4.2 Fouling Resistance 181 5.4.3 Pressure Drop 188 5.5 Experimental Results 189 5.6 Comparison of Results 195 5.6.1 Single-Tube Experiments 195 5.6.2 Desorber Modeling 199 CHAPTER 6. Conclusions and Recommendations 202 6.1 Conclusions 202 6.2 Recommendations 207 6.2.1 Fundamental Fouling Relationships 207 6.2.2 System Level Implementation 208 6.2.3 Exhaust-Side Tube Enhancement 209 6.2.4 Exhaust Emission Treatment 210 APPENDIX A. Test Facilicty Pressure Drop Modeling 212 APPENDIX B. Thermocouple Radiation Correction 223 APPENDIX C. Predicted Deposition 228 APPENDIX D. Test Facility Model Sample Calculations 234 APPENDIX E. Single-Tube Experiments Sample Calculations 244 APPENDIX F. Desorber Model Sample Calculations 257 v APPENDIX G. Desorber Experiments Sample Calculations 262 References 267 vi LIST OF TABLES Table 2.1: Diesel engine waste-heat recovery system investigations ............................... 14 Table 2.2: Exhaust gas coupled heat exchangers for waste-heat recovery ....................... 16 Table 2.3: Investigations of diesel engine emissions ........................................................ 20 Table 2.4: Experimental fouling deposition investigations .............................................. 30 Table 2.5: Modeling investigations of fouling deposition ................................................ 33 Table 2.6: Investigations of deposit removal mechanisms ............................................... 39 Table 2.7: Investigations on fouling deposit layer properties ........................................... 44 Table 2.8: Component level fouling investigations .......................................................... 44 Table 3.1: Component heat duties and UAs ( Forinash (2015)) ....................................... 49 Table 3.2: Nusselt number for laminar flow in an annulus with one surface insulated and the other at constant temperature (Bergman et al., 2011) ................................................. 62 Table 3.3: Range of modeling results ............................................................................... 69 Table 3.4: Equipment and instrumentation specifications ................................................ 76 Table 3.5: Specifications of generator, load bank, and exhaust flow control valve ......... 80 Table 3.6: Generator emissions comparison ..................................................................... 80 vii Table 3.7: Summary of controllers and PI gains............................................................... 84 Table 3.8: Steady state test matrix .................................................................................... 86 Table 3.9: Transient test matrix ........................................................................................ 87 Table 4.1: Calibration of wedgemeter for flow coefficient ............................................ 100 Table 4.2: Influence coefficients for fully developed laminar flow through an annulus with uniform heat flux maintained at both sides (Bergman et al., 2011) ...................... 109 Table 4.3: Relative uncertainty of each measured variable in the calculation of exhaust heat transfer rate .............................................................................................................. 110 Table 4.4: Relative uncertainty of each measured variable in the calculation of coolant heat transfer rate .............................................................................................................. 110 Table 4.5: Comparison of uncertainty analysis for fouling resistance calculation ......... 115 Table 4.6: Modified correlation coefficients for exhaust Nusselt number correlation fit ......................................................................................................................................... 122 Table 4.7: Comparison of fouling layer properties for the continuous and duty cycle tests ......................................................................................................................................... 153 Table 4.8: Comparison of the deposit mass gain of this study to that reported in the literature .......................................................................................................................... 156 Table 4.9: Comparison of the deposit thickness and thermal conductivity of this study to that reported in the literature ........................................................................................... 156 viii Table 5.1: Desorber model inputs from heat pump cycle model .................................... 157 Table 5.2: Desorber designs evaluated in parametric study ........................................... 168 Table 5.3: Comparison of the physical characteristics of the simulation desorber designs ......................................................................................................................................... 175 Table 5.4: Equipment and instrumentation in desorber experimental facility ................ 178 Table 5.5: Summary of conditions in desorber fouling experiment ............................... 190 ix LIST OF FIGURES Figure 1.1: Schematic of simple absorption heat pump ...................................................... 3 Figure 2.1: Literature survey of experimental investigations into fouling deposition mechanisms ....................................................................................................................... 28 Figure 2.2: Exhaust velocity and coolant temperature thresholds for deposit layer removal ........................................................................................................................................... 38 Figure 2.3: Comparison of experimental conditions of this study to the literature .......... 46 Figure 3.1: Cycle model predictions of desorber inlet and outlet solution temperature at various ambient temperatures ........................................................................................... 50 Figure 3.2: Desorber column with labeled inlets