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CFD 11 Month > IFSTA CH 4 Fire Dynamics > Flashcards

IFSTA CH 4 Fire Dynamics Flashcards

(105 cards)

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1
Q

physical change

A

substance remains chemically the same but changes in size, shape or appearance (ex. freezing/boiling)

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2
Q

Chemical reaction

A

occurs when a substance changes from on type of matter into another

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3
Q

oxidation

A

chemical reaction involving the combination of an oxidizer with other materials

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4
Q

timeline of oxidation

A
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5
Q

potential energy

A

the amount of energy that an object can release at some point in the future

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6
Q

kinetic energy

A

energy that a moving object possesses

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7
Q

exothermic reaction

A

reactions that emit energy as they occur

ex. Fire, releases energy in the form of heat and sometimes light

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8
Q

endothermic reaction

A

reactions that absorb energy as they occur

ex. converting water to steam

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9
Q

fire triangle

A
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10
Q

Fire Tetrahedron

A
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11
Q

eliminate any of the elements in the fire triangle

A

the fire will be extinguished

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12
Q

ignition

A

fuels must be in a gaseous state in order to burn

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13
Q

pyrolysis

A

occurs when a solid fuel is converted into a gaseous fuel

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14
Q

vaporization

A

is the conversion of a liquid to a vapour by heat energy

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15
Q

piloted ignition

A

most common form of ignition

occurs when a mixture of fuel and oxygen encounter an external heat source with sufficient heat or thermal energy to start the combustion reaction

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16
Q

autoignition

A

occurs without any external flame or spark to ignite the fuel gases or vapours

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17
Q

autoignition temperature (AIT)

A

minimum temp at which a fuel in the air must be heated in order to start self-sustained combustion

always higher then its piloted ignition temperature

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18
Q

two modes of combustion

A

flaming and non-flaming

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19
Q

non-flaming combustion

A

occurs more slowly and at a lower temperature, producing a smoldering glow in the materials surface (fire triangle)

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20
Q

flaming combustion

A

commonly referred to as fire

produces a visible flame above the materials surface

occurs when a gaseous fuel mixes with oxygen in the correct ratio and heats to ignition temperature (fire tetrahedron)

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21
Q

products of combustion

A

often described as heat and smoke

materials produced and released during burning

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22
Q

incomplete combustion

A

smoke is a product of incomplete combustion

combustion is incomplete when any of the fuel is left after combustion has occurred

has the potential to burn

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23
Q

carbon monoxide

A

toxic and flammable product of the incomplete combustion of organic materials

colorless and odorless gas

acts as a chemical asphyxiant (frequent cause of death in civilians)

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24
Q

hydrogen Cyanide (HCN)

A

toxic flammable substance produced int he combustion of materials containing nitrogen

is a significant byproduct of the combustion of polyurethane foam used in many household furnishing

is 35x more toxic than CO

HCN prevents the body from using oxygen at the cellular level

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25
carbon dioxide
is a product of complete combustion of organic materials it displaces existing oxygen which creates an oxygen deficient atmosphere
26
pressure
is the force per unit of area applied perpendicular to a surface gases always move from areas of higher pressure to areas of lower pressure
27
health effects of CO
28
health effects of HCN
29
Heat
is the thermal kinetic energy needed to release the potential chemical energy in a fuel
30
temperature
is the measure of heat
31
heat (HRR) - candle example
one candle burns at the same temperature as ten candles however the heat release rate of the ten candles is 10x greater than on candle at the same temperature
32
HRR and PPE
the temperature tells you it is safe to go in but the heat transfer rate - not the temperature - tells you how long you can stay in
33
chemical energy
most common source of heat in combustion reactions
34
self-heating
a form of oxidation is a chemical reaction that increases the temperature of a material without the addition of external heat
35
spontaneous ignition
ignition without the addition of external heat
36
electrical energy can occur in several ways, including
resistance heating overcurrent or overload arcing sparking
37
resistance heating - electrical
electric current flowing through a conductor produces heat
38
overcurrent or overload - electrical
when the current flowing through a conductor exceeds its designed limits
39
arcing
high-temp electric discharge across a gap or through a medium
40
sparking - electrical
when an electric arc occurs, glowing particles can form and splatter away from the arcing point
41
temperature - Celsius/Fahrenheit conversion
42
mechanical energy
friction and compression generate mechanical energy movement of two surfaces against each other compressed gas
43
heat transfers from
warmer objects to cooler objects
44
Heat transfers in 3 ways
conduction convection radiation
45
conduction
transfer of heat through and between solids a material is heated as a result of direct contact with a heat source
46
Convection
transfer of thermal energy by the circulation or movement of a fluid
47
convection - vertical movement
due to the buoyancy of smoke and fire gases
48
convection - lateral movement
usually the result of pressure differences between
49
radiation
transmission of energy as electromagnetic waves travels in a straight line at the speed of light (ex. sun) common cause of exposure fires
50
fuel
is the oxidized or burned material or substance in the combustion process fuel in a combustion reaction is known as the reducing agent
51
gases
for flaming combustion to occur, fuels must be in a gaseous state
52
HRR in watts
53
vapor density
describes the density of gases in relation to air air has a vapor density of 1
54
gases of a vapor density less than one will
rise
55
gases of a vapor density greater than 1 will
sink
56
liquids
have mass and volume but no definite shape
57
specific gravity
ratio of the mass of a given volume of a liquid compared to the mass of an equal volume of water at the same temperature water is assigned a specific gravity of 1
58
specific gravity of less than 1 will
float
59
specific gravity of greater than 1 will
sink
60
flash point
is the minimum temperature at which a liquid gives off sufficient vapors to ignite but not sustain combustion in the presence of a piloted ignition source
61
fire point
the temperature at which a piloted ignition of sufficient vapors will begin a sustained combustion reaction
62
solubility
describes the extent to which a substance will mix with water
63
miscible
materials that are miscible in water will mic in any proportion
64
polar solvents
flammable liquids that have an attraction to water will mix readily with water
65
solids
have a definite size and shape
66
surface-to-mass ratio
ratio of the surface area of the fuel to the mass of the fuel as the ratio increases, the particles ability to ignite increases
67
oxygen
primary oxidizing agent in most fires normally air consist of about 21% oxygen
68
flammable (explosive) range
range between the upper flammable limit and lower flammable limit in which a substance can ignite
69
lower explosive (flammable) limit
minimum concentration of fuel vapor and air that supports combustion to lean to burn
70
upper explosive (flammable) limit
concentration above which combustion cannot take place too rich to burn
71
chemical flame inhibition
occurs when an extinguishing agent, interferes with this chemical reaction, forms a stable product and terminates the combustion reaction
72
fuel limited
when sufficient oxygen is available for flaming combustion incipient stage = fuel limited
73
ventilation-limited
have access to all the fuel need to maintain combustion the fire does not have access to enough oxygen to continue to burn
74
stages of fire development
incipient stage growth stage fully developed stage decay stage
75
three key factors that control how the fire develops
fuel properties ventilation available heat conservation
76
flammable (explosive) range photo
77
surface-to-mass ratio photo
78
incipient stage
starts with ignition (where the fire begins) fuel-limited fire portable extinguishers or small hose line can extinguish
79
ceiling jet
hot gases in the plum rise until they encounter the ceiling, then begin to spread horizontally
80
growth stage
a visual indicator that a fire is leaving the incipient stage is flame height when flame reach 2.5 feet high, radiant heat begins to transfer more than convection can become vent-limited or fuel limited
81
fuel package location and entrainment of air
82
Thermal layering
the tendency of gases to form into layers according to temperature, gas density and pressure
83
neutral plane
interference between the hot gas layers and cooler layer of air net pressure is zero where the layers meet
84
rapid fire development
refers to the rapid transition from the growth stage or early decay stage to a ventilation-limited fully developed stage
85
flashover
rapid transition from the growth stage to the fully developed stage the combustible materials and fuel gases in the compartment ignite almost simultaneously changes from a two-layer condition to a single (untenable)
86
rollover
significant indicator of flash over condition where unburned fire gases that have accumulated at the top of the compartment ignite and flames propagate through the hot gas layer or across the ceiling
87
four common elements of flashover
transition in fire development rapidity compartment pyrolysis of all exposed fuel surfaces
88
fully developed stage
occurs when the heat release rate of the fire has reached its peak because of a lack of either fuel or oxygen
89
backdraft
an increase in ventilation such as opening door or window can result in an explosively rapid combustion of the flammable gases occurs in a space containing a high concentration of heated flammable gases that lack sufficient oxygen for flaming combustion
90
fuel-limited conditions
the available fuel limits the peak heat in a fuel-limited, fully developed fire ex. campfire
91
ventilation-limited conditions
lacks the oxygen available to grow
92
decay stage
runs out of available fuel or oxygen
93
flow path
composed of two regions - ambient air flow in - hot exhaust flow out unidirectional due to pressure differences
94
smoke explosion
occurs when a mixture of unburned fuel gases and oxygen comes in contact with an ignition source
95
effects of firefighting operations
temperature reduction fuel removal oxygen exclusion chemical flame inhibition
96
temperature reduction
using foam or water to cool
97
fuel removal
typically a tactic in wildland, liquid and gas fires
98
oxygen exclusion
flow path control door control/tactical ventilation
99
chemical flame inhibition
using extinguishing agents other than water and foam to interrupt the combustion reaction and stop flame production ex dry chemicals
100
fuel load
total quantity of combustible content of a building, space or fire area
101
compartments
any open space with no complete fire barrier dividing is considered a compartment compartmentation - layout of the various open spaces in a structure
102
pulsing smoke
backdraft
103
rollover
flashover
104
flashover indicators
increase temperature rollover lowering of hot gas layer (neutral plane)
105

CFD 11 Month (32 decks)

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