ABSTRACT Title: ANALYSIS OF HOLD TIMES FOR GASEOUS FIRE SUPPRESSION AGENTS IN TOTAL FLOODING APPLICATIONS Sean O’Rourke, Master of Science, 2005 Advisor: Frederick W. Mowrer, Associate Professor, Department of Fire Protection Engineering Many of the clean agents currently used in total flooding fire suppression applications have vapor densities greater than ambient air. The denser agent-air mixture creates hydrostatic pressure differences causing flow of the mixture out of the enclosure as well as flow of ambient air in through leakage paths inherent in building construction. Hold time refers to the amount of time it takes for the concentration of the agent-air mixture to drop below a specified concentration at a designated height within the protected enclosure. In this study an experimental test enclosure was used to evaluate an analytical model of agent-air mixture leakage and to investigate the effects of different leakage areas on agent hold times. The analytical model, known as the descending interface model, demonstrated favorable agreement with experimental measurements for heights greater than one-half the height of the enclosure for the agent used in this investigation. ANALYSIS OF HOLD TIMES FOR GASEOUS FIRE SUPPRESSION AGENTS IN TOTAL FLOODING APPLICATIONS By Sean Thomas O’Rourke Thesis submitted to the Faculty of the Graduate School of the University of Maryland, College Park in partial fulfillment of the requirements for the degree of Master of Science 2005 Advisory Committee: Professor Frederick W. Mowrer, Chair Professor James Milke Professor Peter Sunderland © Copyright by Sean Thomas O’Rourke 2005 Acknowledgments This project was supported by 3M’s Performance Materials Division. I would like to thank Paul Rivers of 3M for his support and technical guidance while working on this project. Additionally I would like to thank Dr. Frederick Mowrer, my advisor, for his assistance, guidance and time while completing this work. I would also like to thank the other members of my thesis committee, Dr James Milke, and Dr Peter Sunderland, for their support of this project. Finally, I would like to thank the faculty and staff, as well as my fellow graduate students, in Fire Protection Engineering for their help with this work and my time here at the University of Maryland. ii Table of Contents Acknowledgments .......................................................................................... ii Table of Contents...........................................................................................iii List of Figures................................................................................................ iv List of Tables .................................................................................................. v Chapter 1: Introduction................................................................................... 1 1.1 Background............................................................................................................... 1 1.2 Description of Total Flooding Application............................................................... 3 1.3 Project Objectives ..................................................................................................... 5 Chapter 2: Theoretical Considerations ........................................................... 6 2.1 Literature Review...................................................................................................... 6 2.2 Hydrostatic Pressure Profile within an Enclosure .................................................... 8 2.3 Leakage Area and Flowrate ...................................................................................... 9 2.4 Flow Models ........................................................................................................... 10 2.4.1 Descending Interface Model............................................................................ 11 2.4.2 Continuous Mixing Model............................................................................... 13 2.4.3 Wide Interface.................................................................................................. 14 2.5 Other Considerations .............................................................................................. 16 2.6 Agent-Air Density................................................................................................... 16 2.7 Leakage Area .......................................................................................................... 19 Chapter 3: Experimental ............................................................................... 21 Chapter 3: Experimental ............................................................................... 21 3.1 Test Apparatus Description..................................................................................... 21 3.2 Experimental Methodology .................................................................................... 25 Chapter 4 Results and Discussion................................................................. 27 4.1 Agent Discharge...................................................................................................... 27 4.2 Concentration Profiles ............................................................................................ 28 4.3 Enclosure Pressure.................................................................................................. 34 4.4 Dimensionless Comparison .................................................................................... 37 Chapter 5: Summary and Conclusions ......................................................... 41 References..................................................................................................... 61 Appendix A: Raw Data and Supplemental Graphs ...................................... 43 Appendix B: Pressure Transducer Calibration Curves................................. 59 iii List of Figures Figure 1 Schematic of Total Flooding Clean Agent Application ....................................... 4 Figure 2 Hydrostatic Pressure Profile Schematic ............................................................... 9 Figure 3 Effect of density ratio on velocity ratio.............................................................. 18 Figure 4 Effect of Area Ratio DiNenno and Forssell Analysis ........................................ 19 Figure 5 Effect of Area Ratio Dimensionless Analysis.................................................... 20 Figure 6 Schematic of Test Apparatus, elevation view .................................................... 22 Figure 7 Schematic of Agent delivery system .................................................................. 23 Figure 8 Photograph of (a) Test Apparatus and (b) Agent Delivery System.................... 23 Figure 9 Agent Discharge Nozzle..................................................................................... 24 Figure 10 Inline Pressure Profiles..................................................................................... 27 Figure 11 Temperatures within the enclosure................................................................... 28 2 Figure 12 Time-Concentration profile, Ao=Ai=0.00038 m , Co=4.7%............................ 30 2 Figure 13 Time-Concentration profile, Ao=Ai=0.000253 m , Co=4.7%.......................... 31 2 Figure 14 Time-Concentration profile, Ao=Ai=0.000127 m , Co=4.7%.......................... 32 2 2 Figure 15 Time-Concentration profile, Ao=0.000127 m Ai=0.00038 m , Co=4.8% ...... 33 2 2 Figure 16 Time-Concentration profile, Ao=0.00038 m Ai=0.000127 m , Co=4.9% ...... 34 2 Figure 17 Initial Transient Hydrostatic Pressure Profile Ao=Ai=0.00038 m , Co=4.7%. 35 2 Figure 18 Hydrostatic Pressure Differences Ao=Ai=0.00038 m , Co=4.7%.................... 36 2 Figure 19 Hydrostatic Pressure Differences Ao=Ai=0.000127 m , Co=4.7%.................. 37 Figure 20 Dimensionless Descending Interface, Experimental data C=80%(Co)............ 38 Figure 21 Dimensionless Descending Interface Experimental data @ C=50%(Co)........ 40 2 Figure A 1:Experiment 072805_Test 2 Pressure Profiles Ao=Ai=0.00038 m ................. 46 2 Figure A 2: Experiment 072805_Test 2 Concentration Profiles Ao=Ai=0.00038 m ...... 46 2 Figure A 3: Experiment 080105_Test1 Pressure Profiles Ao=Ai=0.00038 m ................. 47 2 Figure A 4 Experiment 080105_Test1 Concentration Profiles Ao=Ai=0.00038 m ........ 47 2 Figure A 5 Experiment 080305_Test1 Pressure Profiles Ao=Ai=0.00038 m .................. 48 2 Figure A 6 Experiment 080305_Test1 Concentration Profiles Ao=Ai=0.00038 m ......... 48 2 Figure A 7 Experiment 080305_Test2 Pressure Profiles Ao=Ai=0.000253 m ................ 49 2 Figure A 8 Experiment 080305_Test1 Concentration Profiles Ao=Ai=0.000253 m ....... 49 2 Figure A 9 Experiment 080305_Test6 Pressure Profiles Ao=Ai=0.000235 m ................ 50 2 Figure A 10 Experiment 080305_Test1 Concentration Profiles Ao=Ai=0.000235 m ..... 50 2 Figure A 11 Experiment 080305_Test3 Pressure Profiles Ao=Ai=0.000127 m .............. 51 2 Figure A 12 Experiment 080305_Test3 Concentration Profiles Ao=Ai=0.000127 m ..... 51 2 Figure A 13 Experiment 080305_Test5 Pressure Profiles Ao=Ai=0.000127 m .............. 52 2 Figure A 14 Experiment 080305_Test5 Concentration Profiles Ao=Ai=0.00038 m ....... 52 2 Figure A 15 Experiment 080505_Test1 Pressure Profiles Ao=Ai=0.000127 m .............. 53 2 Figure A 16 Experiment 080505_Test1 Concentration Profiles Ao=Ai=0.000127 m ..... 53 2 Figure A 17