THERMODYNAMIC STUDIES ON ALTERNATE BINARY WORKING FLUID COMBINATIONS AND CONFIGURATIONS FOR A COMBINED POWER AND COOLING CYCLE By SANJAY VIJAYARAGHAVAN A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2003 ACKNOWLEDGMENTS The work presented in this dissertation was completed with the encouragement and support of many wonderful people. Working with Dr. Yogi Goswami has been a tremendous experience. He expects his students to be self-starters, who work independently on their projects. I appreciate his patience and mentorship in areas within and beyond the realm of research and graduate school. Dr. Sherif Sherif was a terrific source of discussion, advice, encouragement and hard to find AES proceedings. Dr. James Klausner, Dr. David Hahn, and Dr. Ulrich Kurzweg agreed to be on my committee and took the time to read and critique my work, for which I am grateful. Dr. Hahn was also on my master’s committee and supervised me during my assignment as a TA for two terms. Dr. Bill Lear has to be thanked for advice on jet pumps and Dr. Skip Ingley for his interest in the cycle. Dr. Leon Lasdon from the University of Texas sent me the FORTRAN version of the GRG code and answered my questions very promptly. Although my particular project did not require much of his marvelous skills, the senior engineering technician at the Solar Park, Chuck Garretson, was very supportive. Watching him and working with him have taught me many things. He is a wonderful resource for any student at the lab. Barbara Graham over the years and now recently Vitrell McNair at the solar office have cheerfully helped me in many ways in the course of my stay here. Mrs. Becky Hoover will have to be thanked for her help and constant reminders to finish up. ii My fellow students at the solar lab have been stimulating company. Some of them particularly have to be acknowledged. Gunnar Tamm, Chris Martin and Nitin Goel took interest in my work and provided constructive feedback. Gunnar has also been at the lab almost as long as I have, and he has been fun to work with. Former students such as Viktoria and Andrew Martin, and Adrienne Cooper have stayed in touch and encouraged me. I would like to particularly thank my family for putting up with my being so far away from home, and for their love, support and eternal optimism. This section is not complete without mentioning friends, old and new, too many to name individually, who have been great pals and confidants over the years. iii TABLE OF CONTENTS Page ACKNOWLEDGMENTS...................................................................................................ii LIST OF TABLES ...........................................................................................................viii LIST OF FIGURES............................................................................................................ ix NOMENCLATURE.........................................................................................................xiii ABSTRACT..................................................................................................................... xvi CHAPTER 1 BACKGROUND ......................................................................................................... 1 Introduction.................................................................................................................. 1 Background .................................................................................................................. 2 Rankine Cycle....................................................................................................... 3 Power Cycles for Low Temperature Heat Sources............................................... 5 Organic Rankine cycles (ORC) ..................................................................... 5 Supercritical cycles........................................................................................ 6 Maloney and Robertson cycle ....................................................................... 8 Kalina cycle ................................................................................................... 9 Other ammonia based cycles ....................................................................... 13 Use of Mixtures as Working Fluids in Thermodynamic Cycles ........................ 14 The Combined Power and Cooling Cycle .......................................................... 16 Introduction ................................................................................................. 16 A summary of past research on the cycle .................................................... 18 Specific motivation for work in this dissertation......................................... 21 2 EFFICIENCY DEFINITIONS FOR THE COMBINED CYCLE............................. 24 Conventional Efficiency Definitions ......................................................................... 24 First Law Efficiency ........................................................................................... 25 Exergy Efficiency ............................................................................................... 25 Second Law Efficiency....................................................................................... 26 The Choice of Efficiency Definition .................................................................. 28 Efficiency Expressions for the Combined Cycle ....................................................... 28 First Law Efficiency ........................................................................................... 28 Exergy Efficiency ............................................................................................... 30 iv Second Law Efficiency....................................................................................... 30 Lorenz cycle ................................................................................................ 30 Cascaded cycle analogy............................................................................... 32 Validity of Expressions....................................................................................... 35 Case 1: Comparing this Cycle to Other Combined Cooling and Power Generation Options ................................................................................ 36 Case 2: Comparing a Combined Cycle to a Power Cycle ........................... 36 Some Examples of Application to the Combined Cycle............................................ 37 Conclusions................................................................................................................ 41 3 CYCLE SIMULATION AND OPTIMIZATION ..................................................... 42 Optimization Method Background............................................................................. 42 Search Termination............................................................................................. 46 Sensitivity Analysis ............................................................................................ 46 Application Notes ............................................................................................... 47 Cycle Modeling.......................................................................................................... 48 State Point Calculation........................................................................................ 49 State point 1................................................................................................. 49 Point 2.......................................................................................................... 51 Points 5 and 11 ............................................................................................ 52 Points 6 and 7 .............................................................................................. 53 Point 8.......................................................................................................... 53 Point 9.......................................................................................................... 54 Point 10........................................................................................................ 54 Points 12 and 3 ............................................................................................ 55 Point 13........................................................................................................ 56 Point 14........................................................................................................ 56 Point 15........................................................................................................ 57 Point 4.......................................................................................................... 57 Variable Limits ................................................................................................... 57 Constraint Equations........................................................................................... 59 Model Limitations............................................................................................... 61 4 OPTIMIZATION OF BASIC CYCLE CONFIGURATION USING AMMONIA- WATER MIXTURE AS THE WORKING FLUID .................................................. 62 Simulated Conditions................................................................................................. 63 Optimization results ..................................................................................................