Smoke extraction system.

 

 

 

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Assignment Details – Answer ALL Questions
This is a sprinklered 5-storey shopping mall with smoke extraction system. The entire
mall has been split into 3 fire compartments (i.e. Arcade 1, Atrium & Arcade 2) by
automatic fire shutters as shown below. The layout of the mall is shown in the sketch
below. The ceiling-to-floor height is assumed to be 4m.
Figure 1 Typical Floor Plan of the shopping mall
Figure 2 Section at the centre of the shopping mall
x
y
Not to scale
x
y
Not to scale
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The fire breaks out at the centre of the atrium as described below and indicated in
Figure 3.
Fire
Scenario
Location Growth
Rate
Maximum Heat
Release Rate
Dimension of fire
bed
1 Centre of
Atrium at
G/F
Medium 1.0MW 2mx2m
2 Centre of
Atrium at
G/F
Ultra-Fast 1.5MW 3mx3m
Figure 3 Fire scenarios to be studied
Each student needs to complete the following tasks:
1. CFAST is a zone model that divide the compartment into two control volumes,
a relatively hot upper layer and a relatively cool lower layer, please derive the
system of ordinary differential equation for the compartment pressure. Each
student shall use CFAST to simulate the impact of fires and smoke in the
building environment for 10 minutes duration. The smoke layer height, smoke
temperature and gases concentration of the fire compartments shall also be
reported. (30 Marks)
2. Each student shall also use the Fire Dynamics Simulator (FDS) to predict the
following for 10 minutes duration: (40 Marks)
 Temperature distribution;
 CO concentration;
 Soot visibility distribution;
 Radiation heat flux along the egress route.
3. Please propose the smoke extraction system with recommended flowrate to
extent the ASET of the shopping mall. (30 Marks)
x
y
Not to scale
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Remarks
Each student shall:
 state the assumptions,
 state boundary conditions,
 state approaches;
 reporting the simulation results and related screenshots captured in
Smokeview for each fire scenario;
 maximum 30 pages and printed on both sides.
Marking Criteria for Assignment
The submitted assignment will be marked according to the following criteria:
Questions Marking
Allocation
Marking Criteria
Q1 30 Demonstrate both understanding and application of
CFAST and evaluative skills on the fire and smoke
development for the designed fire scenario.
Q2 40 Demonstrate the use of FDS with fire engineering
knowledge and relevant material. Assumption shall be
made with appropriate supporting materials like
guidebook, journal paper and etc.
Q3 30 Application of fire safety measures like the smoke
extraction system for fire safety level enhancement with
FDS results.
Total 100

 

 

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