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MATHEMATICAL MODELLING OF TWO-PHASE RELEASE PHENOMENA IN HAZARD ANALYSIS

Objective

TO PROVIDE MATHEMATICAL MODELS SUITABLE FOR DETERMINING THE SOURCE TERM FOR SUBSEQUENT DISPERSION CALCULATIONS NEEDED IN THE RISK-ASSESSMENT OF MAJOR CHEMICAL PLANT.


THIS STUDY FORMS PART OF A COLLABORATIVE PROPOSAL EMBRACING THEORETICAL AND EXPERIMENTAL WORK ON TWO-PHASE FLOWS WITHIN PRESSURE VESSELS AND PIPEWORK, FLASHING RELEASE AND FORMATION OF TWO-PHASE JETS OR CLOUDS AND ALSO THE POSSIBLE SUBSEQUENT IGNITION AND COMBUSION OR EXPLOSION. THE OVERALL PROJECT IS OUTLINED IN A SEPARATE TECHNICAL ANNEX.
THE WORK AT SRD IN THIS PROPOSAL IS CLOSELY LINKED TO THE PROPOSALS OF HSE. THE WORK ALL CONCERNS MATHEMATICAL MODELS OF PRESSURISED RELEASES OF THE INTEGRAL KIND, THAT ITS WHICH CALCULATE PROPERTIES OF A CLOUD AVERAGED OVER ITS VOLUME OR PROPERTIES OF A JET AVERAGED OVER ITS CROSS-SECTION. ONLY ORDINARY DIFFERENTIAL EQUATIONS NEED TO BE SOLVED, BUT APPROXIMATE RELATIONS HAVE TO BE DETERMINED, BY DIMENSIONAL ANALYSIS OR BY EMPIRICAL CORRELATION OF DATA. AN ALTERNATIVE MATHEMATICAL APPROACH IS TO SOLVE IN MUCH GREATER DETAIL PARTIAL DIFFERENTIAL EQUATIONS DESCRIBING DISTRIBUTIONS OF THE FLOW PROPERTIES IN SPACE AND TIME. WHILE THE SECOND METHOD IS MORE FUNDAMENTAL AND OFFERS THE PROSPECT OF MORE ACCURATE RESULTS, IT IS ALSO VASTLY MORE EXPENSIVE IN COMPUTER TIME AND THEREFORE IMPRACTICAL FOR DIRECT USE IN RISK ASSESSMENT. IN THE PRESENT COLLABORATIVE PROPOSAL, PART OF THE WORK OF CEA INVOLVES DEVELOPMENT OF SUCH A MODEL. IT IS ANTICIPATED THAT INSIGHTS AND QUANTITATIVE CORRELATIONS DERIVED FROM THAT WORK MAY BE AN IMPORTANT SUPPLEMENT TO THE EXPERIMENTAL DATA IN PROMOTING DEVELOPMENT AND VALIDATION OF INTEGRAL MODELS AS PROPOSED HERE.
THREE KINDS OF RELEASE OF PRESSURISED LIQUEFIED GAS WILL BE STUDIED. THESE ARE (A) THE STEADY-STATE CONTINUOUS RELEASE GIVING A TWO-PHASE, (B) THE TOTAL CATASTROPHE RELEASE GIVING AN EXPANDING SPHERICALLY SYMMETRIC TWO-PHASE CLOUD AND (C) THE DIRECTED SEMI-CATASTROPHIC RELEASE IN WHICH RELEASE IS VIRTUALLY INSTANTANEOUS, AS FOR THE CATASTROPHIC RELEASE, BUT THE FLUID IS INITIALLY DIRECTED ALONG A SINGLE AXIS. THE DIRECTED SEMI-CATASTROPHIC RELEASE MIGHT RESULT FROM REMOVAL OF ONE END OF A CYLINDRICAL VESSEL. THE STEADY-STATE AND CATASTROPHIC RELEASES HAVE ALREADY BEEN STUDIED AT SRD. MODELS HAVE BEEN DEVELOPED BUT EXISTING DATA HAS PROVED INADEQUATE TO TEST THEIR FUNDAMENTAL HYPOTHESE AND DETERMINE THE ACCURACY OF THEIR PREDICTIONS. THE THIRD KIND OF RELEASE HAS NOT YET BEEN STUDIED IN THE CONTEXT OF MAJOR-HAZARD RISK ASSESSMENT AND SO DEVELOPMENT OF A MODEL IS INCLUDED IN THIS PROPOSAL.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

AEA Technology plc
Address
Culcheth Laboratory Wighsaw Lane
WA3 4NE Warrington
United Kingdom