1. Enclosure Fire Dynamics
Chapter 1: Introduction
Chapter 2: Qualitative description of enclosure fires
Chapter 3: Energy release rates, Design fires
Chapter 4: Plumes and flames
Chapter 5: Pressure and vent flows
Chapter 6: Gas temperatures
(Chapter 7: Heat transfer)
Chapter 8: Smoke filling
(Chapter 9: Products of combustion)
Chapter 10: Computer modeling
Each course unit represents breaking down the problem into individual pieces

2. Overview General on smoke control in buildings
Examples of applications
Derivation of conservation equations
Smoke filling in small room with small opening: Zukoski method
Smoke filling in large room with large opening: Steady-state method
Natural ventilation
Mechanical ventilation
Pressurization of lower layer
EFD simply provides a bunch of equations.
This lecture will go into detail at the beginning on what we are trying to do with smoke filling.
It’s fine to calculate smoke filling, but you also need to know how to do something about it.

3. How do people die in fires? MGM Grand Hotel
Many fire deaths
far away from fire

4. Reasons for smoke control
Life safety – maintain the escape path as long as possible
Firefighter safety – improve visibility
Firefighter operations – reduce time to put out fire
Property protection – reduce smoke damage
Property protection – reduce temperature and external radiation to fuel packages
Continuity of operations = Open for business sooner

5. Smoke management – preventing smoke spread
Smoke control
Use of mechanical fans for pressurization
Smoke and heat venting
Natural (link operated vents)
Mechanical

6. Locations for smoke control
Atria
Warehouses (rack storage)
High rise buildings (stairwells)
Shopping malls
Performance based designs
Increase travel distance
Substitute for rated construction (smoke barriers)
Elevators for egress

7. Example: Atria Atrium – singular (one) Atria – plural (many)
Opening through floors

8. Example: Atrium

9. Example: Preventing smoke spread

10. Example: Smoke management-pressure
Compartmentation with pressurization
We can calculate required pressure difference

11. Example: Single injection point
Fail with door open near injection point
Limit to 8 stories (Klote and Milke)

12. Example: Multiple injection points
More injection points limits local loss of pressure
Determining the design number of open doors can be difficult
Is it better to remove smoke high or low in the stairway?

13. Example: Smoke control by air flow
Airflow without barriers can control smoke if the air velocity is sufficient
Not usually a recommended method (expensive)
Airflow can enhance burning rate

14. Example: Mechanical exhaust from a large volume space

15. Example: Balcony spill plume
In many cases, the mass flow rate is larger than from an axi-symmetric plume

16. Example: Roof vents

17. Example: Natural smoke venting
Reduced flow due to obstructions, wind and sprinklers
Makeup (replacement) air required

18. Example: Venting of fire gases

19. Activation of smoke control system
Smoke detector
Thermal detector
Smoke density detector
Specified optical density/obscuration
Beam detectors
Avoid manual activation, but provide manual activation for fire department

20. Overview General on smoke control in buildings
Examples of applications
Derivation of conservation equations
Smoke filling in small room with small opening: Zukoski method
Smoke filling in large room with large opening: Steady-state method
Natural ventilation
Mechanical ventilation
Pressurization of lower layer
EFD simply provides a bunch of equations.
This lecture will go into detail at the beginning on what we are trying to do with smoke filling.
It’s fine to calculate smoke filling, but you also need to know how to do something about it.

21. Conservation equations
Conservation of mass (C of M)
Conservation of energy (C of E)
Conservation of momentum
Conservation of species
(O2, CO2, H2O, soot, fuel)

22. Compartment Fire Environment

23. Finite Control Volume

24. Infinitesimal Control Volume
All four give the same result, but just in a different form

25. Control volume could be one of two layers
Hand calculations
Two-zone computer models

26. Or the control volume could be one small piece of the overall enclosure
Computational Fluid Dynamics
or CFD models

27. Control surface Surface defining a control volume
Mass, energy etc. pass through the control surface

28. Overview General on smoke control in buildings
Examples of applications
Derivation of conservation equations
Smoke filling in small room with small opening: Zukoski method
Smoke filling in large room with large opening: Steady-state method
Natural ventilation
Mechanical ventilation
Pressurization of lower layer
EFD simply provides a bunch of equations.
This lecture will go into detail at the beginning on what we are trying to do with smoke filling.
It’s fine to calculate smoke filling, but you also need to know how to do something about it.

29. Smoke filling in a room with a small opening (vent)
Conservation of mass
CV is lower layer
Plume is ignored or could be included in upper layer
Mass leaves CV through plume and vent (positive)

30. Smoke filling in a room with a small opening (vent)
Remember the Zukoski plume equation
Use the energy equation to find
Substitute and into C of M equation

31. Smoke filling in a room with a small opening (vent)
A numerical/graphical solution is possible
Generalize results by using dimensionless numbers

32. Non-dimensional smoke filling equation
Dimensionless height:
Dimensionless HRR:
Dimensionless time:
Dimensionless form of smoke filling equation

33. Result of numerical solution by Zukoski (ceiling and floor leaks)

34. Limitations of Zukoski model
Small room and small opening
Zukoski plume equation
Valid for weak sources
No heat loss
No pressure change with time
Uniform pressure throughout room
Expect approximate results only

35. Overview General on smoke control in buildings
Examples of applications
Derivation of conservation equations
Smoke filling in small room with small opening: Zukoski method
Smoke filling in large room with large opening: Steady-state method
Natural ventilation
Mechanical ventilation
Pressurization of lower layer
EFD simply provides a bunch of equations.
This lecture will go into detail at the beginning on what we are trying to do with smoke filling.
It’s fine to calculate smoke filling, but you also need to know how to do something about it.

36. Steady state smoke control
Spaces are typically large (tall)
Openings are large, so there is little (no) pressure buildup inside enclosure
Flow rates through vents are a function of hydrostatic pressure differences
Pressure difference varies over height of opening
Two direction vent flow
More directions possible with smoke filling in second compartment
C of M and C of E equations coupled
Must solve at the same time

37. Steady state smoke control
Now do something to stop the upper layer from descending (moving)
Rate of smoke venting (exhaust) equals rate of smoke production (entrainment in plume)
Steady state
Conditions no longer changing with time
Method of Tanaka and Yamana

38. Steady state smoke control
Mass conservation for upper layer
Conservation of energy for upper layer
Heat loss to walls now important

39. Steady state smoke control
We already solved this energy equation in Chapter 6
But now we know z’, so we know the area of the wall being heated, Aw
Semi-infinite solid with Tg=Ts

40. Look at three cases for removing smoke
Natural ventilation
Mechanical ventilation
Pressurization of lower layer

41. Steady state smoke control natural ventilation from upper layer
Mass and energy equations are coupled
Should solve both at same time
Pressure difference at top of layer moves smoke
Thicker layer = greater mass flow
Look at solution by trial and error

42. Steady state smoke control natural ventilation from upper layer
Trial and error solution
Guess a layer height
Solve mass and energy balances
Correct layer height guess and density
Resolve mass and energy balance

43. Steady state smoke control mechanical ventilation from upper layer
A fan is now placed at the top of the compartment to remove smoke
Generally know the fan exhaust rate [m3/s]

44. Steady state smoke control mechanical ventilation from upper layer

45. Steady state smoke control pressurization of lower layer
A few cautions about pressurization of the lower layer by mechanical ventilation

46. Full scale test results

47. Some final cautions
There is not universal agreement by fire researchers on these equations
Some, but not much, full scale testing
Fire model results versus correlations
Sometimes easier to just use a fire model
Some models have been validated (tested) under smoke control conditions

48. Any questions?