Smoke Layer Height Calculations In An Atrium

INTERNATIONAL MASTER OF SCIENCE IN FIRE SAFETY ENGINEERING

FIRE DYNAMICS ADVANCED ASSINGMENT 3

JESSE HUNTER

2012

Part 1 In this assignment I will calculate an appropriate size of theheat and smoke vents in the atrium of building EC1. The atrium building EC1 is located at Lund University School of Economics and Management. In case of fire the results of fire will be quite differentas compared to small student room. The heat and smoke vents in building EC1 are placed at the highest point in the atrium. They consist of vertical windows which are opened by an electrical motor whenfire is detected.

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Dimensions of the atrium The atrium has the following dimensions: Length: 19m Width: 19m Height: 13.5m Opening: 2.5m x 2.5m Windows: 1.5m x 19m

Fig 1. Scheme of theatrium, building EC1 The vent area is the area of the windows in the top of the atrium: = 19 × 1.5 × 4 = 114 Inlet opening area: = 2.5 × 2.5 = 6.25

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Assumptions Two assumptions have to be done inorder to determine if the vent area is enough to avoid that the smoke layer affect people who are evacuating. The first assumption is that the smoke layer is not going to descend more than the height ofthe openings: = 13.5 − 1.5 = 12

The second assumption is the size of the fire; in this case the fire is going to be: =5 Calculations The following calculations, is to demonstrate if the actualvent area is enough for the atrium. The mass flow from the plume: = For, = 0.21

Eq. 4.21 from Enclosure Fire Dynamics

= 82.177

= 293 , ρ = 1.2 kg m

Pressure difference: ∆P = ∆P =
( )

Eq.8.64 from Enclosure Fire Dynamics

82.177 = 147 Pa 2 × 1.2(0.7 × 6.25)

Effective heat conduction coefficient for concrete, in 10 minutes: ℎ=

Eq. 8.61 from Enclosure Fire Dynamics

ℎ = 0.033Area of smoke in contact with concrete:
,

= 19

× 19

= 361

Effective heat conduction coefficient for glass, thickness 1,5cm: h = h = =
. .

Eq. 6.16 from Enclosure Fire Dynamics =...