Smoke Toxicity, Linings and Enclosure Fires

| June 26, 2015

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Assignment 3 – Smoke toxicity, linings and enclosure fires

 

Scenario 1. A 25 kg cube of expanded polyurethane foam (200kg/m3) sitting on the floor catches fire on the top surface (ignited by an errant welder) and burns to completion with flaming combustion in a warehouse. The warehouse dimensions are 70m x 30m x 10m.

 

Average concentrations of gases released and the O2 content during the first 9 minutes of the fire were measured in an experimental simulation and are given below in Table 1.

 

Table 1.

Time

(min)

1 2 3 4 5 6 7 8 9
CO (ppm) 0 0.62 1.86 3.72 9.92 14.88 24.80 37.20 62.00
HCN

(ppm)

0 0.007 0.022 0.045 0.119 0.179 0.298 0.446 0.744
CO2

(%)

0 0.0013 0.0039 0.0078 0.0208 0.0311 0.0519 0.0778 0.1297
O2

(%)

21 21.00 20.99 20.98 20.96 20.94 20.90 20.84 20.74

 

 

TASKS:

  1. Calculate and graph the Heat Release Rate (HRR) over time based on the data of gases measured above and an assumed Effective Heat of Combustion. This is Curve 1. (Hints: Assume that all the CO produced from the fire remains in the building. As discussed in the lecture the link between HRR, mass loss and toxic species production.). What is the total MJ released during the 9 minutes?

 

  1. Situation 2. If the material was located on a wall as a lining 25mm thick and ignited at the bottom. Qualitatively estimate the HRR and draw in an approximate HRR curve. This is Curve 2. Compare the curve 1 and 2, discuss. (Word limit 150)

 

  1. Situation 3. Recalculate the HRR Curve 1 if the material was timber instead of polyurethane and the CO levels in Table 1 occur. (hint: would the mass of timber burnt be the same) This is Curve 3. Compare the curve 1 and 3 and discuss. What products are now likely to occur that were not generated by the polyurethane? How would the visibility change? (Word limit 150)

 

  1. Situation 4. Assume the combustion of the block of is in limited oxygen supply conditions, how does this change the burning and toxic products and the numbers in the Table, discuss. (Word limit 150)

 

  1. If the polyurethane is used as wall lining with a metal face in a Class 7 building, which test is required to be undertaken according to the NCC BCA Vol 1 (Clause C1.10)? Briefly describe the  method (150 words max) and discuss any limitations of the test method (Word limit 150)

 

  1. You are asked by a client to use the zone model CFAST to predict the values of the test in Table 1 for Scenario 1. Can you do it? Briefly discuss the inputs required and limitations of the model. The client asks if CFAST is a two layer zone model. What is your response (Word limit 200)

 

  1. You are then asked by a client to use the zone model CFAST to predict the gas species CO, CO2, and O2 for Scenario 2.  Can you do it? Discuss the inputs required and limitations of the model. (Word limit 150)

 

  1. You are asked by a client to use the CFD model FDS to predict the values in Table 1 for Scenario 2. Can you do it? Discuss the inputs required and limitations of the model. (Word limit 150)

 

METHODOLOGY:

 

 

  1. It is recommended but not compulsory that the students generate spread sheets using the information in the table.

 

  1. Discuss the approach you’ve adopted, explain your assumptions and reference input data values. Show calculations which were not based on the spread sheets. Discuss your results.

 

  1. If you use spread sheets capture screen images of your spread sheets with all the input and output values and units clearly identified and attach them to your returned assignment submission.

 

  1. Should you require any further information for your calculations please email webb@csiro.au. Please note inquiries should only relate to any missing input information needed for calculations.

 

 

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Numerical simulation of fluid-structure- interaction using Arbitrary-Lagrangian-Eulerian
Smoke Toxicity, Linings and Enclosure Fires

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Category: Engineering

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