methods for the calculation of physical effects1 009 kho tài liệu bách khoa

2 Methods for the calculation of physical effects PUBLICATIEREEKS GEVAARLIJKE STOFFEN Publicatiereeks Gevaarlijke Stoffen Methods for the calculation of Physical Effects Due to releases of hazardous materials (liquids and gases) Methods for the calculation of physical effects – due to releases of hazardous materials (liquids and gases) – ‘Yellow Book’ CPR 14E Editors: C.J.H van den Bosch, R.A.P.M Weterings This report was prepared under the supervision of the Committee for the Prevention of Disasters and is published with the approval of The Director-General for Social Affairs and Employment The Director-General for Environmental Protection The Director-General for Public Order and Security The Director-General for Transport The Hague, 1996 The Director-General for Social Affairs and Employment Committee for the Prevention of Disasters Third edition First print 1997 Third edition Second revised print 2005 I TNO Research performed by TNO - The Netherlands Organization of Applied Scientific Research List of authors Chapter General introduction Ir C.J.H van den Bosch Dr R.A.P.M Weterings Chapter Outflow and Spray release Ir C.J.H van den Bosch Ir N.J Duijm Chapter Pool evaporation Ir C.J.H van den Bosch Chapter Vapour cloud dispersion Dr E.A Bakkum Ir N.J Duijm Chapter Vapour cloud explosion Ir W.P.M Mercx Ir A.C van den Berg Chapter Heat flux from fires dIr W.F.J.M Engelhard Chapter Ruptures of vessels Mrs Ir J.C.A.M van Doormaal Ir R.M.M van Wees Chapter Interfacing of models Ir C.J.H van den Bosch Annex Physical properties of chemicals Ir C.J.H van den Bosch II Contents Preamble Preface Revision history General introduction Outflow and Spray release Pool evaporation Vapour cloud dispersion Vapour cloud explosion Heat flux from fires Rupture of vessels Interfacing of models Annex Physical properties of chemicals III Preamble When the first edition of this ‘Yellow Book’ was issued, it contained calculation methods to be performed on pocket calculators Although the second edition in 1988 presumed that personal computers would be available to perform the required calculations, only part of the report was updated Today more powerful computers are generally available, thus enabling the use of more complex and more accurate computing models This third edition is a complete revision by TNO Institute of Environmental Sciences, Energy Research and Process Innovation It is based on the use of these powerful PC’s and includes the application of proven computing models Special attention is paid to provide adequate directions for performing calculations and for the coupling of models and calculation results The revision of the ‘Yellow Book’ was supervised by a committee in which participated: Dr E.F Blokker, chairman Mr.Ir K Posthuma, secretary Dr B.J.M Ale Drs R Dauwe Ir E.A van Kleef Mrs Ir M.M Kruiskamp Dr R.O.M van Loo Ing A.J Muyselaar Ing H.G Roodbol Drs.Ing A.F.M van der Staak Ing A.W Peters Ir M Vis van Heemst Dienst Centraal Milieubeheer Rijnmond Ministerie van Sociale Zaken en Werkgelegenheid Rijksinstituut voor Volksgezondheid en Milieu DOW Benelux N.V Ministerie van Binnenlandse Zaken Dienst Centraal Milieubeheer Rijnmond Ministerie van Volkshuisvesting, Ruimtelijke Ordening en Milieubeheer Ministerie van Volkshuisvesting, Ruimtelijke Ordening en Milieubeheer Rijkswaterstaat Ministerie van Sociale Zaken en Werkgelegenheid Ministerie van Verkeer en Waterstaat AKZO Nobel Engineering B.V With the issue of this third edition of the ‘Yellow Book’ the Committee for the Prevention of Disasters by Hazardous Materials expects to promote the general use of standardised calculation methods of physical effects of the release of dangerous materials (liquids and gases) The Hague, 1996 THE COMMITEE FOR THE PREVENTION OF DISASTERS BY HAZARDOUS MATERIALS, Drs H.C.M Middelplaats, chairman IV Preface to the PGS edition of the Yellow Book Starting from June 1st 2004, the Advisory Council on Dangerous Substances (Adviesraad Gevaarlijke Stoffen - AGS) was installed by the Cabinet At the same time the Committee for the Prevention of Disasters (Commissie voor de Preventie van Rampen- CPR) was abolished CPR issued several publications, the so-called CPR-guidelines (CPR-richtlijnen), that are often used in environmental permits, based on the Environmental Protection Law, and in the fields of of labour safety, transport safety and fire safety The CPR-guidelines have been transformed into the Publication Series on Dangerous Substances (Publicatiereeks Gevaarlijke Stoffen – PGS) The aim of these publications is generally the same as that of the CPR-guidelines All CPR-guidelines have been reviewed, taking into account the following questions: Is there still a reason for existence for the guideline or can the guideline be abolished; Can the guideline be reintroduced without changes or does it need to be updated The first print (1997) of the 3rd edition Yellow Book contained typographical errors that occurred during the conversion of the Yellow Book documents from one word processing system to another Most of these conversion errors occurred especially with formulas, leading to erroneous and non-reproducible results when calculation examples and formulas were recalculated This PGS edition (2005) is a second print that has been thoroughly checked for errors Every chapter starts with a condensed summary of changes to give the user an idea about what was changed and where it was changed Despite all effort, it might be possible that errors still persist If this is the case, or if you have any other remarks about the Yellow Book, please send a mail to: info@infomil.nl Hard copies of this PGS-2 edition can be obtained from Frank van het Veld, TNO Department of Industrial & External Safety: YellowBook@tno.nl, or fax +31 55 549 3390 Also on behalf of my colleagues at the Ministries of Transport, Social Affairs and of the Interior, The State Secretary of Housing Spatial Planning and the Environment (VROM) Drs P.L.B.A van Geel november 2005 V CPR 14E Revision history of the ‘Yellow Book’ Revision history Date Release Comments 19 April 2005 3rd edition 2nd print, version Please refer to the modification paragrahs of all chapters 25 July 2005 3rd edition 2nd print, version The appendix of chapter was missing and has now been included Table 6.A.2 and Figure 6.A.11 were not corresponding and has been corrected Chapter General introduction C.J.H van den Bosch, R.A.P.M Weterings 1.1 Table of contents of chapter 1.1 1.2 1.3 1.4 1.5 1.2 Introduction to chapter 1.3 Educational objectives and target groups 1.4 Contents of the Revised Yellow Book 1.5 1.3.1 General remarks 1.5 1.3.2 Remarks on the individual chapters 1.6 User instructions 1.8 References 1.9 CPR 14E Chapter of the ‘Yellow Book’ 75 70 Distance cross-wind (y) [m] 65 60 55 50 45 40 35 30 25 20 15 10 -5 -10 -15 -20 -25 -30 -35 -40 -45 -50 -55 -60 -65 -70 -75 40 60 80 100 120 140 Distance down-wind (x) [m] 160 180 200 220 Figure 4.26 Isocontour of 15 g/m3 due to a vertical jet release of chlorine 4.6.5.4 Short-duration or instantaneous pool release The example to illustrate this source type is an instantaneous release of propane, possibly by a BLEVE accident The release forms a cloud of pure propane gas at ambient conditions The input data for the SLAB computer model are summarised in Table 4.23, with the exception of the physical properties of propane, which are already given in Table 4.21 4.127 Table 4.22 SLAB input for an instantaneous release Definition of source term: Definition of numerical step: Temperature of the source material [K]: Mass flow rate of the source [kg/s]: Area of the source [m2]: Duration of the release, for a finite-duration source [s]: Source mass, for an instantaneous release [kg]: Height of the source [m]: Concentration averaging-time [s]: Maximum down-wind distance in the calculation [m]: First height where the concentration is calculated [m]: Second height where the concentration is calculated (is used only when ZP(1) > 0) [m]: Third height where the concentration is calculated (is used only when ZP(1:2) > 0) [m]: Fourth height where the concentration is calculated (is used only when ZP(1:3) > 0) [m]: Surface roughness height [m]: Measurement height of ambient parameters [m]: Ambient wind speed [m/s]: Temperature of ambient air [K]: Relative humidity of ambient air [%]: Stability class: 4.128 instantaneous release largest step size 288.15 400 IDSPL = 14.600 3600 500 QTIS = 14.600 HS = 9.61 TAV = 3600 XFFM = 10.000 ZP(1) = 0 ZP(2) = 0 ZP(3) = 0 ZP(4) = 0.03 (grass) 10 288.15 (Pasquill class F) Z0 = 0.03 ZA = 10 UA = TA = 288.15 RH = 0.7 STAB = NCALC = TS = 230.9 QS = AS = 652.8 TSD = CPR 14E Chapter of the ‘Yellow Book’ 160 Distance cross-wind (y) [m] 140 120 100 80 60 40 20 -20 -40 -60 -80 -100 -120 -140 -160 150 200 250 300 350 400 450 Distance down-wind (x) [m] 500 550 600 Figure 4.27 Isocontour of 9.3 g/m3 at 240 s after a release of propane At 240 s after release the isocontour of 9.3 g/m3 (molar fraction 0.5%) has been calculated with SLAB at a height of m, and the results are plotted in Figure 4.27 The largest extent to the 0.5% contour is 913 m at 410 s after release This distance is also estimated with the model of Britter and McQuaid The nomogram 4.14 for 1/3 instantaneous releases should be read with the parameter ( g o 'V o /u a ) = 6.36 along the horizontal axis, which gives a value for x/Vo1/3 of 10 for the 0.05% contour on the horizontal axis, i.e x = 184 m, which is in reasonable agreement with the result from SLAB, although one should bear in mind that the Britter and McQuaid model leads to the same result irrespective of the atmospheric stability 4.129 4.7 Discussion 4.7.1 Introduction to Section 4.7 This section provides additional information on limitations of selected models, alternative solutions, and gaps of knowledge at present 4.7.2 Changes in atmospheric conditions Both the Gaussian plume model as the selected dense gas dispersion model describe dispersion for stationary atmospheric conditions The models are not able to describe phenomena during changes in the boundary layer meteorology, such as passage of fronts, diurnal variation of wind speed and wind direction near coasts, etc As the meteorological conditions change continuously, the total travel time for which the models are valid needs to be maximised to about hours The maximum travel distance is thus about 104 ua m For larger distances use needs to be made of dedicated long range dispersion models 4.7.3 Still air Gaussian plume models are normally excluded for use in still air By minimising σv in formula (4.49) the range of applicability is extended compared to conventional Gaussian plume models This minimum value of σv is probably small, thus conservative from a point of view of maximum concentration For continuous releases during very low wind speed for which ua < σv, accumulation of plume material at the source will appear (upwind dispersion by wind fluctuations becomes of the same order of magnitude as down-wind convection by wind speed), and the source need to be treated as a series of instantaneous releases where σx is calculated (also in the surface layer) by formula (4.61d), and the argument ua t in the function Fz (ua t, z) is replaced by x for surface layer releases 4.7.4 Accuracy of the Gaussian plume model In Figure 4.6 regions of atmospheric conditions are indicated The use of the Gaussian plume model is well assessed for the ‘near neutral upper layer’ As discussed in Section 4.3.2, vertical dispersion in the surface layer, although not strictly Gaussian, is also well understood Dispersion in the ‘mixed layer’ and ‘free convection layer’ is proven to be not Gaussian in nature For the ‘local scaling layer’, ‘z-less scaling layer’, and ‘intermittency layer’ no alternative for Gaussian plume modelling has been suggested so far The Gaussian plume model will at best have an accuracy of a factor of for the near neutral upper layer [Olesen et al., 1992] 4.130 CPR 14E Chapter of the ‘Yellow Book’ 4.7.5 Dispersion over obstacles Neither the Gaussian plume model, jet and plume models, nor the dense gas models as presented in the previous sections allow predictions to be made which take into account the effects of obstacles It is not allowed to introduce obstacle effects by increasing the roughness length for the calculation: in effect, the height of the cloud should always exceed (except for very near to the source) the roughness length by an order of magnitude As discussed in Section 4.2.7, effects of obstacles should be taken into account if the smaller value of height or width of the obstacle(s) is larger than the local cloud height Obstacle effects can be treated in a few ways For passive dispersion some simple models exist for dispersion in the wake of single buildings for which the ratio of widthto-height does not exceed about [Duijm and Webber, 1993] These models assume a uniform distribution of concentration in the wake of a building However, differences of a factor 10 are often observed Some progress is being made in developing simple models for (dense) gas dispersion over simple obstacle arrays, such as fences perpendicular to the wind, uniformly distributed blocks, and ‘street-canyon’ like situation [Duijm and Webber, 1993; VDI, 1990] For situations for which no such specific ‘simple’ model exists, one needs to use either physical modelling by means of atmospheric boundary-layer wind or water tunnels, or computational fluid dynamic codes (CFD) For passive dispersion in near neutral conditions, for which plume rise or plume descent is not relevant, wind tunnel simulations are as yet unsurpassed for costs and accuracy For buoyant or dense releases, additional scaling parameters need to be used in wind tunnels which lead to compromises between viscous effects and density effects These effects need to be assessed carefully for each case CFD-modelling as yet needs approximations with respect to the representation of turbulence Here again these approximations should be assessed carefully for each case, the situations with stable stratification (either atmospheric or from the dense gas cloud) being the most critical 4.7.6 Concentration fluctuations The selected models account for different averaging-times and ‘instantaneous’ lateral plume widths These plume widths need to be considered as so-called ensemble-averaged width and these calculations not exclude fluctuations of plume width and concentrations to occur The last decade much attention has been paid to develop general models that describe concentration fluctuations (or at least statistics of concentration fluctuations) in passive and dense gas clouds and plumes As yet no generalised model for concentration fluctuations is available There is evidence that quantities of instantaneous dense and passive releases, such as dose and maximum concentration, are log-normally distributed over the ensemble of realisations For continuous releases less definite conclusions with respect to distribution functions can be given, partly because here intermittency masks part of the observations 4.131 4.7.7 Removal processes In Sections 4.2.8 and 4.2.9 some attention is paid to chemical reactions and deposition, respectively The selected models not account for these processes For slow chemical reactions and wet deposition, one may write a first order decrease of material in the plume: d q (x) = – C q (x) dx (kg/(m⋅s))◊ (4.175) where q (x) is the source strength to be used in the (Gaussian) plume model at distance x, and C some constant, depending on the chemical reaction or the washout rate For dry deposition at the ground one may calculate the total flux by integration of (4.5) over the plume width and decrease q (x) in the plume model by this loss of material (source depletion model) However, dry deposition will affect the concentration near the ground, thus changing the vertical distribution of material A model to describe this phenomenon was developed by Rao [1981] Although not strictly correct, it provides sufficiently accurate predictions for practical values of deposition velocities and wind speeds [Bakkum, 1993] 4.132 CPR 14E Chapter of the ‘Yellow Book’ 4.8 Literature Bakkum, E.A (1993), Een numeriek algoritme voor de berekening van droge depositie en uitwassing van emissies in de atmosfeer (in Dutch), TNO-IMET report 93-211 Beals G.A., (1971) Guide to local diffusion of air pollutants, tech report 214 Weather Services USAF, NTIS, AD 726984 Beljaars, A.C.M., A.A.M Holtslag (1990), A software library for the calculation of surface fluxes over land and sea, Environmental software, 5, pp 60-68 Bianconi, R., M Tamponi (1993), A mathematical model of diffusion from a steady source of short-duration in a finite mixing layer, Atmospheric Environment 27A, pp 781-792, Blackmore D.R et al (1982), Heavy gas dispersion models, Journal of Hazardous Materials (1982) 107 Briggs, G.A (1969), Plume rise, U.S Atomic Energy Commission Report TID-25075 Britter, R.E and McQuaid, J (1988), Workshop on the dispersion of dense gases, HSE Contract Research Report No 17 A.J Byrne, S.J Jones, S.C Rutherford, G.A Tickle, D.M Webber (1992), Description of ambient atmospheric conditions for the computer code DRIFT, SRD/HSE R553, SRD, Culcheth, U.K Chatwin P.C (1968), The dispersion of a puff of passive contaminant in the constant stress region, Quart J R Met Soc., 94, pp 350-360 Chen, C.J and Rodi, W (1980), Vertical turbulent buoyant jets, Pergamon Press, Oxford Colenbrander, G.W (1980), A mathematical model for the transient behaviour of dense vapour clouds, 3rd Int Symp on Loss Prevention and Safety Promotion in the Process Industry (Basle) 4.133 Commissie TNO voor het onderzoek ten dienste van het Milieubeheer (1976) Modellen voor de berekening van de Verspreiding van Luchtverontreiniging, Staatsuitgeverij 1976 Cox, R.A., and Carpenter, R.J (1979), Further developments of a dense vapour cloud dispersion model for hazard analysis, Proceedings of the symposium on heavy gas dispersion, Frankfurt Davidson, G.A (1989), Simultaneous trajectory and dilution predictions from a simple integral plume model, Atmospheric Environment 23, 341 Deaves, D.M (1992), Dense gas dispersion modelling, Journal of loss prevention in the process industry (1992) 219 Drivas P.J and Shair F.H (1974), Dispersion of an instantaneous crosswind line source of tracer released from an Urban highway, Atm Env 8, pp 475-485 Duijm, N.J., Webber, D.M (1993 or 1994), Dispersion in the presence of buildings, Problem Clouds - II, April 15/16, 1993, Amsterdam, The Netherlands and accepted for publication in J of Los Prevention in the Process Industries, 1993 or 1994 Eidsvik, K.J (1980), A model for heavy gas dispersion in the atmosphere, Atmospheric Environment 14, 769 Erbrink, J.J (1991), A practical model for the calculation of σy and σz for use in an on-line Gaussian dispersion model for tall stacks, based on wind fluctuations, Atm Env., 25A, 2, pp 277-283 Ermak, D.L et al (1982), A comparison of dense gas dispersion model simulations with Burro series LNG spill test results, Journal of Hazardous Materials (1982) 129 Ermak, D.L., Rodean, H.C., Lange, R and Chan, S.T (1988), A survey of denser-than-air atmospheric dispersion models, LLNL Report under contract W-7405-ENG-48 Ermak, D.L (1990), User’s manual for SLAB: an atmospheric dispersion model for denser-than-air releases, Lawrence Livermore National Laboratory, California 94550 4.134 CPR 14E Chapter of the ‘Yellow Book’ Fryer, L.S and Kaiser, G.D (1979), DENZ, a computer program for the calculation of the dispersion of dense toxic or explosive gases in the atmosphere, Report UKAEA SRD R/52 Golder, D (1972), Relations among stability parameters in the surface layer, Boundary-Layer Met., 3, pp 47-58 Gryning, S.E., A.A.M Holtslag, J.S Irwin, B Sivertsen (1987), Applied Dispersion modelling based on meteorological scaling parameters, Atmospheric Environment 21/1, pp 79-89 Guinnup, D (1992), Non-buoyant Puff and Plume Dispersion Modelling Issues, Plant/Operations Progress 11/1, pp 12-15 Hanna S.R., Briggs G.A en Hosker Jr R.P (1982), Handbook of Atmospheric Diffusion, DOE/TIC-11223 (DE 82002045), 1982 Hanna, S.R and Drivas, P.J (1987), Guidelines for the use of vapor cloud dispersion models, CCPS American Institute of Chemical Engineers New York Hanna, S.R., Strimaitis, D.G., and Chang, J.C (1991), Evaluation of commonly-used hazardous gas dispersion models, Final Report under contract FO8635-89-C-0136, Sigma Research Corporation, Concord Hanna, S.R (1990), Lateral Dispersion in Light Wind Stable Conditions, Proceedings of the EURASAP Meeting and GNFAO/CNR Workshop on Atmospheric Dispersion in Low Wind speeds and Foggy Conditions, Torino, Sept 5-7, 1989, ed D Anfossi & A Longhetto, Il Nuova Cimento della società italiana di fisica vol 13 C, num 6, pp 889-894 Hanna, S.R and Chang, J.C (1992), Evaluation of commonly-used hazardous gas dispersion models, Addition of the HGSYSTEM model, Final Report A232-300, Sigma Research Corporation, Concord Havens, J (1989), DEnse GAs DISpersion version 2.1 Havens, J and Spicer, T (1990), TECJET: An atmospheric dispersion model, Risk Analysis 10 (1990) 459 4.135 Havens, J (1992), Review of dense gas dispersion field experiments, Journal of loss prevention in the process industry (1992) 28 Holtslag, A.A.M (1984), Estimates of diabatic wind speed profiles from near-surface weather observations, Boundary-Layer Meteorology 29, pp 225-250 Holtslag, A.A.M., and F.T.M Nieuwstadt (1986), Scaling the atmospheric boundary layer, Boundary-Layer Meteorology 36, pp 201-209 Holtslag, A.A.M (1987), Surface fluxes and boundary layer scaling - model and applications, KNMI WR-no 87-2, De Bilt Holtslag, A.A.M., and H.A.R de Bruin (1987), Applied modelling of the night-time surface energy balance over land, submitted to J of Climate and Applied Meteor Hoot, T.G., Meroney, R.N and Peterka, J.A (1973), Wind tunnel tests of negatively buoyant plumes, NTIS Report PB-231-590 Hsu, S.A (1992), An overwater stability criterion for the offshore and coastal dispersion model (research note), Boundary-Layer Met., 60, pp 397-402 Jagger, S.F (1983), Development of CRUNCH: a dispersion model for continuous releases of denser-than-air vapour into the atmosphere, Report UKAEA SRD R 229 Jones, S.J., Mercer, A., Tickle, G.A., Webber, D.M and Wren, T (1991), Initial verification and validation of DRIFT, Report SRD/HSE/R580 Kaiser, G.D and Walker, B.C (1978), Releases of anhydrous ammonia from pressurised containers and the importance of denser than air mixtures, Atmospheric Environment 12, 2289 KNMI (1974), Luchtverontreiniging en Weer, Staatsuitgeverij, The Hague KNMI (1979), Luchtverontreiniging en weer, 2e druk, Staatsuitgeverij, ’s Gravenhage 4.136 CPR 14E Chapter of the ‘Yellow Book’ Li, X., Leijdens, H and Ooms, G (1986), An experimental verification of a theoretical model for the dispersion of a stack plume heavier than air, Atmospheric Environment 20 McFarlane, K., Prothero, A., Puttock, J.S., Roberts, P.T and Witlox, H.W.M (1990), Development and validation of atmospheric dispersion models for ideal gases and hydrogen fluoride, Technical Reference Manual Shell Reseach Report TNER.90.015 Mercer, A et al (1993), Comparison of heavy gas dispersion models for instantaneous releases, to be published in Journal of Hazardous Materials (1993) Olesen, H.R., T Mikkelsen, eds (1992), Proceedings of the workshop Objectives for Next Generation of Practical Short-Range Atmospheric Dispersion Models, NERI, Roskilde, Denmark Ooms, G (1972), A new method for the calculation of the plume path of gases emitted by a stack, Atmospheric Environment 6, 899 Ooms, G and Duijm, N.J (1984), Dispersion of a stack plume heavier than air, IUTAM Symposium, Springer Verlag Panofsky, H.A., and J.A Dutton (1984), Atmospheric Turbulence, John Wiley & Sons, New York Pasquill F and Smith F.B., (1983) Atmospheric Diffusion, Ellis Horwood Ltd., Chichester Pasquill, F and F.B Smith (1983), Atmospheric Diffusion, 3rd ed., Ellis Horwood, Chichester Peterson, R.L (1978), Plume rise and dispersion for varying ambient turbulence, thermal stratification and stack exit conditions, PhD Thesis, Colorado State University Press, W.H et al (1986), Numerical Recipes – The Art of Scientific Computing, Cambridge University Press, Cambridge Puttock, J.S et al (1991), Dispersion models and hydrogen fluoride predictions, Journal of loss prevention in the process industry (1991) 16 4.137 Rao, K.S (1981), Analytical solutions of a gradient-transfer model for plume deposition and sedimentation, NOAA technical memorandum ERL-ARL-109, NTIS, U.S Dept of Commerce PB 82-215153 Radian Corporation (1988), Description of the Radian complex hazardous air release model Saffman P.G (1962), The effect of wind shear on horizontal spread from an instantaneous ground source, Quart J R Met Soc., 88, pp 382 Seinfeld, J.H (1986), Atmospheric Chemistry and Physis of Air Pollution, John Wiley & Sons, New York Slade D.H (1968), Meteorology and Atomic Energy, U.S Atomic Energy Commission Singer, I.A., Smith, M.E (1953), J Meteorol., 10, 2, pp 92-114 Stern, A.C., R.W Boubel, D.B Turner, D.L Fox (1984), Fundamentals of Air Pollution, 2nd ed., Academic Press, London Stull, R.B (1988), An Introduction to Boundary Layer Meteorology, Atmospheric Sciences Library, Kluwer Academic Publishers, Dordrecht Tyldesley J.B and Wallington C.E (1965), The effect of wind shear and vertical diffusion on horizontal dispersion, Quart J R Met Soc., 91, pp 158-174 (1965) Ulden, A.P van, and A.A.M Holtslag (1985), Estimation of Atmospheric Boundary Layer Parameters for Diffusion Applications, Journal of Climate and Applied Meteorology, 24, pp 1196-1207 Ulden, A.P van (1991), A surface-layer similarity model for the dispersion of a skewed passive puff near the ground, Atmospheric Environment 26A/4, pp 681-692 VDI Richtlinie 3783 Blatt (1990), Ausbreitung von storfallbedingten Freisetzungen schwerer Gase - Sicherheitsanalyse, Beuth Verlag GmbH, Berlin 4.138 CPR 14E Chapter of the ‘Yellow Book’ Webber, D.M et al (1992), A model of a dispersing dense gas cloud, and the computer implementation DRIFT, UKAEA Report SRD/HSE R586-587 Werkgroep Verspreiding Luchtverontreiniging (1984), Parameters in the long-term model of air pollution Dispersion - New recommendations, TNO-SCMO, P.O Box 186, 600 AD Delft, The Netherlands Wheatley, C.J and Webber, D.M (1984), Aspects of the dispersion of denser-than-air vapours relevant to gas cloud explosions, Final Report SR/007/80/UK/H UK Atomic Energy Authority Witlox, H.W.M et al (1990), HGSYSTEM user/technical manuals, References to chapter 4, Vapour Cloud Dispersion Zeman, O (1982), The dynamics and modelling of heavier-than-air cold gas releases, Atmospheric Environment 16, 741 4.139 CPR 14E Chapter of the ‘Yellow Book’ Appendix 4.1 A method for estimating the solar elevation A4.1 The Julian day number The Julian day number, Jn, can be defined as the number of days elapsed since the first of January For a date of the form DD-MM-YYYY, YYYY is first examined to see if it is a leap year The following table is used for the calculation MM X 10 11 12 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 031 059 090 120 151 181 212 243 273 304 334 365 Jn = DD + XMM-1 (a1.1) in non-leap years, and up to February in all years, and Jn = DD + XMM-1 + (a1.2) in leap years after February A4.2 The solar elevation In this section, all arguments of goniometrical functions are in radians From Jn the solar longitude (SL) can be evaluated by, SL = 4.871 + 0.0175 Jn + 0.033 sin(0.0175 Jn) (rad) (a1.3) where SL is in radians The solar declination (SD) follows from SD = arc sin(0.398 sin(SL)) (rad) (a1.4) These three quantities are used to compute the smallest angle through which the earth must turn to bring the meridian of the given location directly under the sun π α = ψ w ⋅ + 0.043 sin ( ⋅ SL ) – 0.033 sin ( 0.0175J n ) + π ⋅ ( t u /12 – ) 180 (a1.5) appendix 4.1-1 where ψw is the western longitude (˚W) of the location and tu is the universal time in hours the solar elevation, χ, is given in radians by:   π π χ = arc sin  sin ( SD ) ⋅ sin  ϕ  + cos ( SD ) ⋅ cos  ϕ  ⋅ cos ( α )   180  180   (a1.6) where ϕ is the latitude of the location (˚N) This scheme provides an estimate for χ with an accuracy of within 0.05 rad appendix 4.1-2 ... available for assessing the physical effects of accidental releases of hazardous materials For this purpose the handbook Methods for the calculation of physical effects of the release of dangerous... Gevaarlijke Stoffen Methods for the calculation of Physical Effects Due to releases of hazardous materials (liquids and gases) Methods for the calculation of physical effects – due to releases of hazardous... With the issue of this third edition of the ‘Yellow Book’ the Committee for the Prevention of Disasters by Hazardous Materials expects to promote the general use of standardised calculation methods