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To Improve the Methods Using to Distinguish Congested Area in Process Plants by CFD

Rahimi, Farshad | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43156 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Rashtchian, Davoud
  7. Abstract:
  8. Among probable hazards in chemical industries: vapor cloud explosion (VCE) is one of the worst and most destructive ones. More than half of the major process inci¬dents, according to the statistics, are VCEs. VCE causes the most serious consequences; therefore, it attracts many attentions to itself. Accordingly, plenty of researches have been done for the purpose of protection against VCE effects. All efforts in this field can be categorized in two different main activities; firstly, prescribing safety distances between groups of hazardous equipment and vulnerable areas, secondly, using facilities which reinforce vulnerable areas against explosion blasts. Regardless to which category is under con¬sideration; both of them need VCE modeling.
    Many empirical-based models have been proposed up to now. It has been revealed that all of them have one common disad¬vantage. There is no clear procedure for identifying congested enough areas to launch strong VCEs. The other basically dif¬ferent approach in explosion modeling is CFD-based modeling. In this approach all unclear aspects of other models can be computed through explosion parameters such as over pressure, flame speed and etc.
    One of the parameter which is important in identifying congested enough areas and their separating distance from nearby areas is flame speed. After VCE occurrence, its front head starts moving outward explosion center from ignition point. Flame front movement and acceleration continuous until congestion is present. When flame goes out of congested area, its’ speed decay promptly and reaches zero at far distances.
    Many explosion feature can affect flame speed and its’ decay rate but the important ones are explosive material and congested area specifications. In the present study, the effects of these investigated through explosion modeling with CFD tools. After modeling it revealed that congestion parameters like, volume blockage or area blockage not only affect flame maximum velocity but also its‘ decay rate and also material can affect both of them
  9. Keywords:
  10. Flame Speed ; Computational Fluid Dynamics (CFD) ; Vapor Cloud Explosion ; Congested Area

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