Ch. 1 Fire Dynamics Flashcards
Ch. 1 pg. 13
The rate at which a fuel releases energy over time depends on many variables including: (4)
Chemical composition
Arrangement
Density of the fuel
Availability of oxygen for combustion
Ch. 1
The rate at which heat transfers is related to the _____________ of the bodies and the _____________ of the materials involved.
Temperature differential
Thermal conductivity
Note: The greater the temperature differences between the bodies, the greater the transfer rate.
Ch. 1 Conduction
Conduction is the transfer of heat through and between solids. Conduction occurs when a material is heated as a result of direct contact with a heat source. Heat transfer due to conduction is dependent upon three factors:
- Area being heated
- Temperature differences between the heat source and the material being heated
- Thermal conductivity of the heated material.
Ch. 1
The British Thermal Unit is the amount of heat required to raise the temperature of ________ of water by _______ Fahrenheit.
1 lbs.
1 degree
Ch. 1. Convection
Convection is the transfer of thermal energy by the circulation of movement of a fluid (liquid or gas).
Heat transfer due to convection is dependent upon three factors.
- Area being heated
- Temperature difference between the hot fluid or gas and the material being heated.
- Turbulence and velocity of moving gases
Ch. 1. Fuel pg 30
Fuel is the oxidized or burned material or substance in the combustion process. Most fuels are organic, containing carbon and other elements. Organic fuels can be divided into hydro-carbon based fuels, such as: (4)
- gasoline
- fuel oil
- Plastics
- Cellulose-based materials (wood and paper)
Ch. 1 fire dynamics: Solids
The _______ and ______ of a solid fuel relative to the source of heat also affects the way the fuel burns.
proximity
orientation
Ch. 1. fire dynamics; Oxygen
Oxygen in the air is the primary _______ agent in most fires.
oxidizing
the energy release in fire is directly proportional to the amount of oxygen available for combustion.
Ch. 1 Fire dynamics: Thermal Layering
________ is defined as the space between the air intake and the exhaust outlet.
Flow Path
Changes in ventilation and flow path can significantly alter thermal layering.
Ch. 1. fire dynamics: Flow Path
A flow path’s effectiveness to transport ambient air to the seat of the fire is based on the following: (4)
> size of ventilation opening
Length of the path traveled
Number of obstructions
Elevation differences between the base of the fire and the opening.
Ch. 1 fire dynamics: Unplanned ventilation
The source of new oxygen does not have to __________ from outside the building. When floors fail above basement fires, the interior air in the structure becomes a new oxygen source.
originate
Ch. 1 fire dynamics: Modern vs legacy
In single-family residential structures, the square footage of houses increased __________ between _____ and _____.
150%
1973
2008
Ch.1 Fire Dynamics
Fires can take various forms, but ____ fires, involve a chemical reaction between some type of ___ and ____, most commonly air.
All
Fuel and Oxidizer
______ are not combustible but will support or enhance combustion
Oxidizers
Ch. 1 pg.10
The study of matter and energy and includes chemistry and physics.
Physical Science
______ Can undergo many types of physical and chemical change
Matter
Occurs when a substance remains chemically the same but changes in size,shape and appearance
water freezing and liquid boiling are examples
Physical Change
When a substance changes from 1 type of matter into another.
Example: 2 or more substances combining to form compounds
Chemical Reaction
Chemical reaction involving the combination of an oxidizer
Oxidation
Occurs when a a force is applied to an object over a distance or when a substance undergoes a chemical,biological or physical change, this describes what?
Work
Amount of energy that and object can release at some point
potential energy.
Energy a moving object possesses
kinetic energy
Fuels have a certain amount of potential energy before they are ignited based on their____.
Chemical Composition
Rate at which a fuel releases energy over time depends on: (4)
- chemical composition
- Arrangement
- Density of fuel
- Availability of oxygen for combustion
Types of energy(7)
chemical thermal mechanical electrical light nuclear sound
In terms of ___ the potential chemical energy of a fuel converts into heat and light during combustion
Fire behavior
Energy is measured in?
Joules
In the customary system, the unit of measurement for heat is the….
British Thermal Unit (BTU)
1 pound water increased 1 degree fahrenheit
Reactions that emit energy as they occur
Exothermic Reactions
Fire is an exothermic reaction that releases energy in the form of __ and ___
Heat and Sometimes Light
Reactions that absorb energy
Endothermic Reaction
Example: water going from a liquid to a gas.
Fire Triangle Components (3)
Fuel
Oxygen
Heat
Fire Tetrahedron Components (4)
Fuel
Oxygen
Heat
Self sustaining chemical reaction
The fire tetrahedron model includes the Chemical Chain Reaction to explain ____ or _____ phase combustion
Flaming or Gas
An _____ chemical chain reaction must also be present for a fire to occur.
Uninhibited
Fuels must be in a ___ state to burn
Gaseous
When heat is transferred to a liquid or a solid the ___ increases and the substance converts to a gaseous state, also called ______
Temperature
Off-gassing
Temperature is the measurement of heat.
In ____, Off-gassing is a chemical change known as pyrolysis
Solids
Pyrolysis is off gassing of solids
Vaporization is off gassing of liquids