by m. m.s. ahmed, e. e. khalil , m. m.a.hassan and h. o...

NUMERICAL INVESTIGATION OF SMOKE MANAGEMENT & CONTROL IN ATRIUM”

By

M. M.S. Ahmed, E. E. Khalil , M. M.A.Hassan and

H. O. Haridy

Cairo University, Cairo-Egypt

Presented by Prof.Dr.Essam E Khalil , ASHRAE Fellow, Director at Large

International Conference ENERGY in BUILDINGS 2017 - CYPRUS

Thursday May 4, 2017 - Limassol, Cyprus

OUTLINE

1. Introduction.

2. Literature review.

3. Objective.

4. Governing equations.

5. FDS Validation.

6. Grid sensitivity analysis.

7. Results.

8. Conclusions.

9. Recommendation for future works

2

Atrium :

An opening connecting two or more stories other than enclosed stairways which is closed at the top and not defined as mall

3 Dubai's Burj Al Arab, atrium

Wednesday, May 10, 2017

Hazard of atrium fires

Fire in atrium generates :

• Smoke at high temp.

• Smoke reduces visibility needed for escaping.

• Toxic gases endangers people life.

4

Hazard of atrium fires. Tenability criteria in building fires,Society of Fire Safety


Exposure to heat

Exposures to temperatures above 250°F (121°C) can result in skin pain and burns, and exposures to temperatures below this temperature can result in heat stroke (hyperthermia).

5

Heat tolerance for humans, with low air movement. SFPE Handbook


Exposure to toxic gases

In building fires, the most common asphyxiant is carbon monoxide (CO) and, to a lesser extent, hydrogen cyanide (HCN) which is more toxic.

6

Tolerance to CO and HCN. SFPE Handbook


Visibility

Criteria for visibility have been suggested ranging from 13 to 46 ft (4 to 14 m) (Jin 2008).

7

Walking speed versus visibility. SFPE Hand book


Smoke layer

The accumulated thickness of smoke below a physical or thermal barrier.

8

Smoke layer Klote, ASHRAE Journal, June 2012 .


Smoke management system

Smoke filling

9

The smoke management system must maintain the base of the smoke layer above the design height. Lougheed, Considerations in the Design of Smoke Management Systems for Atrium


Smoke exhaust

10

The smoke management system must maintain the base of the smoke layer above the design height. Lougheed, Considerations in the Design of Smoke Management Systems for Atrium

Plug-holing

11

Plugholing phenomenon Lougheed, Considerations in the Design of Smoke Management Systems for Atriums .

Plug-holing is a phenomenon where air below the smoke layer is pulled through the smoke layer into the smoke exhaust.


• Doheim,et al [16] ,used FDS to study the effect of atrium shape on natural smoke ventilation, Three fire simulations were performed for three atria with the same area (225 m2),the same height (18m) ,the same volume and different configurations.

Schematic diagrams for the atrium configurations [16].

• It was concluded that the rectangular configuration contributes better to smoke

ventilation design than square and triangular configurations by maintaining a clear height for longer time

• the triangular prism configuration is the most critical shape among the three configurations regarding smoke ventilation by having the highest soot mass fraction concentration and the highest temperature

12

2.LITERATURE REVIEW


Effect of fire location

13

Cases to study effect of fire location

Qin et al (2008) used FDS to study the effect of gravity venting on smoke layer height and plume temperature, Also study the effect of fire source location on smoke layer height

Atrium geometry

It was concluded that : • Descent of the smoke layer is faster in the case of fire at the center of the atrium.

• Highest plume temperature when fire source is located at the center of the atrium and

the lowest temperature when fire source at the corner of the atrium. Wednesday, May 10, 2017

14

El Banhawy (2007) used CFD to investigate smoke extraction with rooftop exhaust fans and side wall exhaust fans.

Atrium model

• It was concluded that side wall exhaust fans near the roof had proved to be more efficient than rooftop exhaust fans in terms of extracting smoke without plug-holing.


15

Stair Model for a single floor – Isometric View

Complete stairwell model

Khalil (2009) used CFD to investigate the effect of leakage area from doors on stairwell pressurization.


Pressure Difference Contours for Cases A,B,C,D at v=2.52 m/s.

16

(B) (A) (C) (D)

Model leakage area = 0.029 m2

Case A : Increase of leakage area by 12.7 %. Case B : Increase of leakage area by 25 %. Case C : decrease of leakage area by 12 %. Case d : decrease of leakage area by 25 %.

It was concluded that :

• For the same volume flow rate in, the pressurization of the stairwell is less than the theoretical pressurization value.

• Increasing the flow rate by 20% covers the friction losses.

• CFD predictions shows that for leakage area increase of 10%, the system is capable of pressurization, for a leakage increase of 20%, the system capable of maintaining positive pressure but without the acceptable minimum difference.

17 Wednesday, May 10, 2017

3.OBJECTIVE OF PRESENT WORK

• Explore The use of FDS Simulation as a Design Tool of smoke management system.

• Simulating fire and smoke management system in a real atrium in Dar Al Handasah building ,Smart village, Egypt.

• Investigate the effect of make up air inlets configuration on smoke layer and tenability conditions.

• Investigate the effect of increasing spacing between fans on plug-holing phenomenon.


4.GOVERNING EQUATIONS

19 FDS Technical reference guide , NIST.


5.VALIDATION

20 Schematic diagram of the PolyU /USTC atrium[20].

Full-scale experimental tests are difficult to be carried out. So the validation for FDS is carried out using experiments done by Chow and cui [20] on PolyU / USTC atrium.


21

Out View of the PolyU / USTC Atrium


FDS Simulation

22

Fire area (m2)

Measured HRR (KW)

Simulation grid size

Number of cells

Experiment 1 0.28 248 0.12 x 0.13 x 0.13 3240000

Experiment 2 0.785 393 0.15 x 0.15 x 0.15 2172000

Experiment 3 4 1560 0.16 x 0.16 x 0.16 1740480

Validation cases


Experiment 1

23

90; 22

165; 17

250; 12

330; 7

465; 2 0

5

10

15

20

25

30

35

40

45

0 100 200 300 400 500

Smo

ke la

yer

he

igh

t (m

)

Time (sec)

FDS

EXPERIMENTAL

Εκθετική (FDS)

Absolute average error = 14 %


45; 22

75; 17

120; 12

195; 7

300; 2

0

5

10

15

20

25

30

35

0 50 100 150 200 250 300

Smo

ke la

yer

he

igh

t (m

)

Time (sec)

FDS

EXPERIMENTAL

Εκθετική (FDS)

Experiment 2



Experiment 3

25

0

5

10

15

20

25

30

35

40

0 50 100 150 200

Σειρά1

Σειρά2

Εκθετική (Σειρά1)



Present study Real atrium in Dar Al Handasah in smart village

26

Out view of Dar Al Handasah building Wednesday, May 10, 2017

27

Inside view of the atrium Wednesday, May 10, 2017

Model description

28

Plan view of atrium Atrium isometric


6.GRID SENSITIVITY ANALYSIS

29

Ambient temperature

(K)

Fire heat release rate

(MW)

Fire ramp up time (Sec)

Ventilation

297 5 330 All doors & windows are

closed leaving air gap of 0.2 m for make up air

Cell size Number of cells

Case 1 0.4 x 0.4 x 0.4 m 240000

Case 2 0.3 x 0.3 x 0.3 m

600000

Case 3 0.2 x 0.2 x 0.2 m

1085000

Boundary conditions


Smoke layer height at 1

30

0

5

10

15

20

25

30

0 100 200 300 400 500 600

Smo

ke la

yer

he

igh

t (m

)

Time (Sec)

240000 Cell

600000 Cell

1085000 Cell



31

0

5

10

15

20

25

30

0 100 200 300 400 500 600

Smo

ke la

yer

he

igh

t (m

)

Time (Sec)

240000 Cell

600000 Cell

1085000 Cell



32

0

5

10

15

20

25

30

0 100 200 300 400 500 600

Smo

ke la

yer

he

igh

t (m

)

Time (Sec)

240000 Cell

600000 Cell

1085000 Cell



33

0

5

10

15

20

25

30

0 100 200 300 400 500 600

Smo

ke la

yer

he

igh

t (m

)

Time (Sec)

240000 Cell

600000 Cell

1085000 Cell


Visibility variation at height of 22.25 m using different grid size

34

0

5

10

15

20

25

30

35

0 100 200 300 400 500 600

Vis

ibili

ty (

m)

Time (Sec)

240000 Cell

600000 Cell

1085000 Cell


Temperature variation at height of 22.25 m using different grid size

35

0

20

40

60

80

100

120

0 100 200 300 400 500 600

Tem

pe

ratu

re (

oC

)

Time (Sec)

240000 Cell

600000 Cell

1085000 Cell


CO Concentration variation at height of 22.25 m using different grid size

36

0

5

10

15

20

25

0 100 200 300 400 500 600

CO

Vo

lum

e f

ract

ion

(p

pm

)

Time (Sec)

240000 Cell

600000 Cell

1085000 Cell

• there is no significant difference between case 2 and case3. Based on the grid sensitivity analysis case 2 is chosen for present study to save time.

Study cases Name Condition

Case 1 No mechanical exhaust

Case 2

Ventilation with 5 rooftop exhaust fans (each 30 m3/s), Make up air through three opening doors (each

26.1 m2 ) and three operable windows (each 9 m2

Lowest surface of operable windows at height of 11.7 m.

Case 3 Ventilation with 5 rooftop exhaust fans (each 30 m3/s), Make up air through three opening doors (each

26.1 m2 )

Case 4


26.1 m2) and three operable windows (each 9 m2

,Lowest surface of operable windows at height of 18.7 m.

Case 5 Same as case 4 with changing exhaust fan location.

Case 6


26.1 m2) ,three operable windows (each 9 m2

Lowest surface of operable windows at height of 11.7 m and opposed doors opening at each floor

Case 7 Same as case 4 with increasing the spacing between fans.

Case 8 Simulation case for atrium evacuation,500 persons.

37

Name Condition

Case 1 No mechanical exhaust

Case 2


26.1 m2 ) and three operable windows (each 9 m2

Lowest surface of operable windows at height of 11.7 m.

Case 3 Ventilation with 5 rooftop exhaust fans (each 30 m3/s), Make up air through three opening doors (each

26.1 m2 )

Case 4


26.1 m2) and three operable windows (each 9 m2

,Lowest surface of operable windows at height of 18.7 m.

Case 5 Same as case 4 with changing exhaust fan location.

Case 6


26.1 m2) ,three operable windows (each 9 m2

Lowest surface of operable windows at height of 11.7 m and opposed doors opening at each floor

Case 7 Same as case 4 with increasing the spacing between fans.

Case 8 Simulation case for atrium evacuation,500 persons.

Study cases

38

Case 1

39

Pressure distribution


Case 2


Case 3


Case 4


Case 5


Case 6


Atrium evacuation


7.RESULTS Effect of Exhaust fan

0

5

10

15

20

25

30

0 100 200 300 400 500 600

Smo

ke la

yer

he

igh

t (m

)

Time (Sec)

CASE 1

CASE 2

47

Smoke layer height at point 2

0

10

20

30

40

50

60

70

80

0 100 200 300 400 500 600

Tem

pe

ratu

re (

oC

) Time (sec)

Case 1

Case 2

Temperature at point A

Comparison between case 1 & case2 Case 1 : no vent Case 2 : 5 fans located at the roof with total exhaust flow rate 150 m3/sec


0

5

10

15

20

25

30

35

0 100 200 300 400 500 600

Vis

ibili

ty (

m)

Time (sec)

Case 1

Case 2

0

2

4

6

8

10

12

0 100 200 300 400 500 600

CO

Vo

lum

e f

ract

ion

(p

pm

)

Time (sec)

Case 1

Case 2

Carbon monoxide volume fraction at point A Visibility at point A

From the previous figures, it can be noted the effect of using exhaust fans on • Smoke layer is kept at a higher level. • Lower temperature at human level. • Increase visibility. • Reduce carbon monoxide concentration at human level.

48

Effect of make up air velocity

49


0

5

10

15

20

25

30

0 100 200 300 400 500 600

Smo

ke la

yer

he

igh

t (m

)

Time (Sec)

v = 1 m/s

V = 1.7 m/s

10

15

20

25

30

35

0 200 400 600

Vis

ibili

ty (

m)

Time (Sec)

V = 1 m/s

V = 1.7 m/s

Visibility at point A

From the above figures, it can be noted that the effect of increasing make up air velocity by reducing make up air inlet area make the smoke layer descend to a lower level and reduce visibility at human level.

Effect of make up air inlet height

0

5

10

15

20

25

30

0 100 200 300 400 500 600

Smo

ke la

yer

he

igh

t (m

)

Time (Sec)

Case 2

Case 4

50


The above figure shows the effect of increasing the level at which make up air enters the atrium. Case 2 : lowest surface of operable windows at 11.7 m Case 4 : lowest surface of operable windows at 18.7 m

-10

0

10

20

30

40

50

60

0 100 200 300 400 500 600

Flo

w r

ate

(m

3 /se

c)

Time (Sec)

Door 2

Window 2

51

-10

0

10

20

30

40

50

60

0 100 200 300 400 500 600

Flo

w r

ate

(m

3 /se

c)

Time (Sec)

Door 2

Window 2

Flow through openings -Case 4 Flow through openings -Case 2

From the above figures ,it is noted that :increasing make up air inlet height increase air flow rate through the door which increase make up air velocity and reduce the flow rate entering from the window due to neutral pressure plan may descend below the window

Effect of opposed opening doors

15

17

19

21

23

25

27

29

31

33

0 100 200 300 400 500 600

Vis

ibili

ty (

m)

Time (Sec)

Case 2

Case 6

52

0

5

10

15

20

25

30

0 100 200 300 400 500 600

Smo

ke la

yer

he

igh

t (m

)

Time (Sec)

Case 2

Case 6

Smoke layer height at point 3 Visibility at point A

From the above figures ,it is noted that smoke layer height slightly increase and visibility distance increase at human level. From simulation ,it can be noted that air enters from communicating space in to atrium at lower level ,However at the last floor smoke flow from atrium to the communicating space.

Plug-holing

53

Spacing between fans = 5 m Spacing between fans = 6.3 m


distance between fans 2.8 d

Visibility contours at X = 8.5 m after 407 sec

54

distance between fans 3.5 d



55

distance between fans 2.8 d distance between fans 3.5 d



56

distance between fans 2.8 d distance between fans 3.5 d


8.CONCLUSIONS

• FDS is a powerful tool that can simulate smoke spread this was clear when comparing validation model with experimental data.

• The present research has highlighted the importance of smoke management in atrium during fires within the atrium

• increasing make up air velocity has adverse effect on smoke layer

height and tenability conditions at human level.

• increasing make up air inlet height 25 % of atrium height increase the smoke layer depth 20 % of atrium height.

• Increasing distance between exhaust fans reduce plug-holing phenomenon and enhance tenability conditions at human level.


9.RECOMMENDATIONS FOR

FUTURE WORK

• Considering relatively large fires of higher heat release rate (up to 25 MW).

• Study the effect of pressurizing stairwell related to the atrium to prevent smoke spread to stairs.

• Study the effect of mechanical make-up air supply on smoke layer and tenability conditions.

• Study the effect of sprinkler on fire heat release rate.


THANK YOU

Wednesday, May 10, 2017 59

by m. m.s. ahmed, e. e. khalil , m. m.a.hassan and h. o...

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