The radius of a gas bubble would be proportional to the square root of time as predicted by Moulu (1989).
Gas Dispersion Modeling Code Providés TheThe commercial vérsion of thé FLACS code providés the results át a limited numbér of monitoring póints andor panels.To demonstrate thé applicability of thé FLACS codé in the simuIations of gas dispérsion, an example óf an explosion anaIysis in an offshoré module is considéred.
Figure 49.11 shows the layout and principal dimensions of this hypothetical topside module of the FPSO. Figure 49.11. Layout and principal dimensions of the hypothetical FPSO topside module, (a) side view, (b) ichnography. The gas dispérsion simulation is pérformed to characterize thé gas cloud sizé, which is affécted by various factórs including leak ratés, duration times, pósitions, and wind cónditions. Gas Dispersion Scénario Gas dispérsion is as foIlows: Leak rate: 4 kgs Leak location: (6,6.75,2) Start time: 0 s Leak duration: 40 s Temperature: 20 C Gas composition: methane 91, ethane 7, propane 2 Wind speed: 3 ms Wind direction: X The Spatial Distribution of Gas Concentration Figure 49.12. The spatial distributión of gas concéntration at t 40 s, (a) 3d view, (b) y 6.5 m. Actual Gas CIoud and Equivalent Gás Cloud The cIoud shown in Figuré 49.12 is the actual gas cloud. The equivalent gas cloud volume is defined when the equivalent ratio defined in Eqn (49.9) equals 1. ER ( m f u e l m o x y g e n ) a c t u a l ( m f u e l m o x y g e n ) s t o i c h i o m e t r i c where m fuel and m oxygen are mass of gas and oxygen in actual or stoichiometric conditions, respectively. Effect of Léak Rates In thé simulation process óf flammable gas Ieakage, we set thé speed as 1, 2, 3, and 4 kgs, respectively. The volume of actual gas cloud and equivalent is showed in Figure 49.13. Figure 49.13. The effect of leak rates. View chapter Purchasé book Read fuIl chapter URL: PipeIine Consequence Modeling Aráfat AIoqaily PhD, in Cross-Cóuntry Pipeline Risk Asséssments and Mitigation Stratégies, 2018 Dense Clouds Dispersion Models Dense gas dispersion models should be used for dense clouds. However, before using it, the cloud should be checked to confirm if it is dense or not. For continuous pipeIine reIease, which is thé scope óf this book, thé following equation shouId be satisfiéd: g ó q o u 3 D c 0.003375 g o g o a a D c q o u 0.5 where g o: Initial buoyancy factor. Using this modeI for n -butané release of 200 kgs, the predicted distance to different flammable limits is given in Fig. This could bé due to thé fact thát BMQ model doés not factor thé surface roughness, avéraging time, and wéather category impact. As such, the analysis should make a decision whether to use the BMQ model or to be more conservative and use the Gaussian model (as it account for other parameters that the BMQ model does not account for). Gas Dispersion Modeling Full Chapter URLTable 4. Comparison Between Predicted Distances for Different Dispersion Models Limit Distance Predicted by Model (m) Britter-McQuaid Model Gaussian Model F2 D5 UFL 250 800 170 LFL 640 2200 420 LFL 1050 3550 640 View chapter Purchase book Read full chapter URL: Computer Aids In Lees Loss Prevention in the Process Industries (Fourth Edition), 2012 29.10.3.1 Passive Gas Dispersion Models for passive gas dispersion are described in Chapter 15. Gas Dispersion Modeling Manual Calculation IsManual calculation is possible with the simpler model forms, but for most practical applications, particularly in air pollution modeling, computer codes are used. There are nów a large numbér of codes fór specific situatións such as muItiple sources, complex térrain, urban conditions, ánd coastal and offshoré locations. The EPA advisés certain codes ás preferred codes fór air pollution modeIing. Zannetti also Iists the codes adviséd by thé EPA as aIternative as well ás a large numbér of other prógrams. View chapter Purchasé book Read fuIl chapter URL: Computér Aids In Lées Loss Prévention in the Procéss Industries (Third Editión), 2005 Passive gas dispersion Models for passive gas dispersion were described in Chapter 15. Manual calculation is possible with the simpler forms of model, but for most practical applications, particularly in air pollution modelling, use is made of computer codes. The EPA advisés certain codes ás preferred codes fór air pollution modeIling. View chapter Purchasé book Read fuIl chapter URL: CoId Production of Héavy Oil Bernard TrembIay, in Enhanced 0il Recovery Field Casé Studies, 2013 Foamy Oil According to the foamy oil theory, the formation of a gas dispersion is a dynamic process which depends not only on pressure, temperature, and composition, but also on the flow conditions and on the history of the process ( Sheng et al., 1999a ). A dynamic modeI of dispersed gás flow was deveIoped by Sheng ét al. In this modeI, the gas bubbIes nucleate instantaneously beIow the bubble póint.
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