Source Term Models for Superheated Releases of Hazardous Materials Thesis submitted for the Degree of Doctor of Philosophy of the University of Wales Cardiff by Vincent Martin Cleary BEng (Hons) September 2008 UMI Number: U585126 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. Dissertation Publishing UMI U585126 Published by ProQuest LLC 2013. Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 Chapter 1 Introduction Abstract Source terms models for superheated releases of hazardous liquefied chemicals such as LPG have been developed, governing both upstream and downstream conditions. Water was utilised as the model fluid, not least for reasons of safety, but also for its ability to be stored at conditions that ensure it is superheated on release to atmosphere. Several studies have found that at low superheat jet break-up is analogous to mechanical break-up under sub-cooled conditions. Hence, a non-dimensionalised SMD correlation for sub-cooled liquid jets in the atomisation regime has been developed, based on data measured using a Phase Doppler Anemometry (PDA) system, for a broad range of initial conditions. Droplet SMD has been found to correlate with the nozzle aspect ratio and two non- dimensionalised groups i.e. the liquid Reynolds number and Weber number. An adaptation of the Rossin-Rammler distribution has been proposed for jets undergoing mechanical break-up. Through a high-speed photographic study (lOOOfps), three distinctive break-up regimes of superheated jets have been identified. Mechanical break-up has been confirmed to dominate jet disintegration at low superheat. Criteria for transition between regimes have been established based on the liquid Jakob number and Weber number. Using a PDA system, droplet SMD data has been produced for fully flashing jets at two sets of initial conditions and three axial downstream locations, with radial measurements performed at each position. Droplet SMD has been found to increase with nozzle diameter. An adaptation of the Rossin-Rammler distribution has been proposed for fully flashing jets. The proposed correlation for sub-cooled break-up, the PDA data for superheated releases and the established transition criteria have been compiled to produce a complete SMD model governing transition from mechanical break-up to full flashing. The model has been validated against three previous studies of flashing jets. An additional high speed photographic study (up to 50,000fps) of the upstream flow structure of superheated jets has been performed using Perspex nozzles. The downstream break-up regime has been found to depend on both the upstream bubble growth rate and concentration. Chapter 1 Introduction Declaration This work has not previously been accepted in substance for any degree and is not concurrently submitted in candidature for any degree. Signed.......0 . TrA?.. \....................... (candidate) Date. ^ ^^ ^ Statement 1 This thesis is being submitted in partial fulfilment of the requirements of the degree of PhD. Signed ..................................... (candidate) . Date........................................... Statement 2_________________________________________ This thesis is the result of my own independent investigation, except where otherwise stated. Other sources are acknowledged by explicit references. Signed ............................ (candidate) Date ...... \9..f.!P./. Statement 3 I hereby give consent for my thesis, if accepted, to be available for photocopying and inter- library loan, and for the title and summary to be made available to outside organisations. Signed.. ......nU ^ , AI r......y^ .............. (candidate) Date... .\ P. J .A P. Chapter 1 Introduction “They say that every dog has his day and today is woof day. That might sound crazy but I want to go and bark! ” Ian Holloway May 2004 Chapter 1 Introduction Acknowledgements___________________________________ Firstly, I must express my gratitude to Professor Phil Bowen, for presenting me with the opportunity to undertake this study and for all his help and support. My thanks also go to Henk Witlox and Mike Harper at DNV for the financial support that I was generously afforded and for their considerable input throughout this study. My thanks also go to the technicians in the workshop for their invaluable assistance with the practical aspects of this study. Particular thanks must go to Paul Malpas, Alan Griffiths and Malcolm Seaboume without whose encyclopaedic knowledge of all things mechanical, none of this would have been possible. Thanks also to Andrew Crayford and Peter Kay for all their help in this regard. Thanks to all the members of the South Wales Celtic Supporters Club, especially Gerry, Dex and the clan, Ray, Craig, Tim and Andy. Cedwch y ffydd! Thanks to all my friends, especially Sull, Mark, Michael, Nick, Gall, Damo, Shearer, Mark O’D, the boy Lockett, Ray, Alan, Rhys, Chris, Robin, Christophe, and Alex. It’s been emotional! Very special thanks go to my family, especially my sisters Rosemary and Colette. They blazed the trail, I simply followed. My most heartfelt thanks go to my mum who has made me the man I am today. This is for you. My final thoughts are for my dad. If I stood on this book, I’d nearly be as tall as him. - iv - Chapter 1 Introduction Table of Contents Abstract ...........................................................................................................................i Declaration .................................................................................................................... ii Acknowledgements.....................................................................................................iv List of Figures and Tables........................................................................................... ix Nomenclature.............................................................................................................xiv Chapter 1 Introduction................................................................................................ 1 1.1 Motivation..................................................................................................................... 2 1.2 Physical Phenomenology.........................................................................................4 1.2.1 Thermodynamic Boundary Conditions ..................................................................................4 1.2.2 Analogies with Other Two-Phase Industrial Processes .......................................................6 1.3 Overview of Current Understanding.........................................................................6 1.4 Thesis Aim and Objectives.........................................................................................7 Chapter 2 Literature Review........................................................................................9 2.1 Introduction................................................................................................................ 10 2.2 Primary Input Parameters........................................................................................10 2.3 Jet Break-Up............................................................................................................... 11 2.3.1 Mechanical Break-Up...........................................................................................................12 2.3.2 Low Superheat .................................................................................................................... 18 2.3.3 ‘External’ Flashing Atomisation ........................................................................................... 20 2.3.4 ‘Internal’ Flashing .................................................................................................................21 2.3.5 Rainout ..................................................................................................................................33 2.4 Previous Large-Scale Studies................................................................................. 35 2.4.1 CCPS Experiments and RELEASE Model ..........................................................................36 2.4.2 EEC Programme: STEP ......................................................................................................37 2.4.3 HSL Experiments ................................................................................................................38 2.4.4 Von Karman Institute Experiments ....................................................................................39 2.5 Measurement Techniques....................................................................................... 40 2.5.1 Sample Collection ................................................................................................................40 2.5.2 Laser-based Diffraction ........................................................................................................41 - v - Chapter 1 Introduction 2.5.3 Phase Doppler Anemometry ...............................................................................................42