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Numerical Investigation of the Effect of Influential Geometrical Parameters on the Plugholing Phenomenon in Smoke Extraction

Zebardasti Nik, Ali | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55930 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Afshin, Hossein
  7. Abstract:
  8. Correct and timely extraction of smoke is very important in fire incidents. Statistics show that more than seventy percent of fire casualties are caused by breathing toxic gases. One of the destructive factors in the operation of the smoke exhaust system is the plugholing phenomenon. In this phenomenon, due to the improper design of the ventilation system, the exhaust vent extracts air instead of smoke. The plugholing phenomenon causes the accumulation of smoke in the structure, therefore it is essential to know this phenomenon to prevent it. In this research, the plugholing phenomenon in the smoke extraction process has been investigated by the numerical simulation method. To investigate this phenomenon, we have studied the influence of effective parameters, including vent geometry and arrangement, structure geometry, and heat release rate. The results of this research showed that increasing the ratio, width and distance of the vent to the nearest adjacent wall, as much as the length of the vent, delays the occurrence of the plugholing. It was also found that increasing the ratio of the distance between two vents and the width of the structure to the length of the vent also reduces the probability of this phenomenon. At the end of this research, a correlation has been presented to predict the plugholing phenomenon, which shows the relation between the effective parameters at the threshold of this phenomenon. Another result of this research is providing an optimal value for the ratio of parameters in order to make the ventilation system work better. Actually, the results of the simulations showed that in order to avoid the negative effect of the wall, the ratio of the distance of the vent from the wall to its length should be more than 0.75. It was also said that in places with several vents, the ratio of the distance between the vents to each other to their length should be greater than 0.75 for the case where the vents are relatively equidistant from the fire, and if the vents are in a row, this ratio should be greater than be 7.0
  9. Keywords:
  10. Numerical Simulation ; Fire ; Heat Release Rate ; Vent Arrangement ; Vent Geometry ; Plugholing ; Internal Geometry Structure

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