THERMODYNAMIC PROPERTIES OF WOOD Flashcards
- a branch of physics that studies how energy changes in a system
THERMODYNAMICS
- heat is a form of energy that corresponds to mechanical work (that is, exerting a force on an object over a distance)
THERMODYNAMICS
- deals with the transfer of energy from one place to another and from one form to another
THERMODYNAMICS
- The key concept is that heat is a form of energy corresponding to a definite amount of mechanical work
THERMODYNAMICS
- the branch of mechanics concerned with the motion of bodies under the action of forces
DYNAMICS
Fire Tetrahedron: Fire can’t exist without the four elements:
- heat
- oxygen
- chemical reaction
- fuel
3 WAYS BY WHICH HEAT CAN BE TRANSFERRED:
- conduction
- convection
- radiation
- heat transfer from molecules to molecules
CONDUCTION
- heat transfer by the movement of heated particles as in air currents
Convection
- energy in the form of heat or light rays is sent out from atoms and molecules as they undertake internal change
Radiation
4 ESSENTIAL THERMAL PROPERTIES OF WOOD
- Thermal Conductivity
- Heat Capacity
- Thermal Diffusivity
- Coefficient of Thermal Expansion
- usually represented by k
THERMAL CONDUCTIVITY
- measure of the rate at which heat flows through a specified material
THERMAL CONDUCTIVITY
- Expressed as the amount of heat that flows per unit time through a unit area subjected to unit temperature difference
THERMAL CONDUCTIVITY
- Units used to measure the heat flow or heat transfer are watts per square meter kelvin or W/(m2/k), and sometimes in equivalent units of watts per square meter degree Celsius or W/(m2/°C).
THERMAL CONDUCTIVITY
- amount of energy needed to raise the temperature of a specific material (in this case, a wood sample) by 1 degree Celsius (or Kelvin or Fahrenheit).
HEAT CAPACITY OF WOOD
factors that affect heat capacity of wood are ________ and ___________ but are basically not affected by its density or species
temperature; moisture content
- Measure of how fast a wood can absorb heat from its nearby environment
THERMAL DIFFUSIVITY OF WOOD
- It is also defined as the ratio of thermal conductivity to the product of density and heat capacity
THERMAL DIFFUSIVITY OF WOOD
- Measures the dimensional changes in wood as affected by changes in temperature.
COEFFICIENT OF THERMAL EXPANSION IN WOOD
The oven dry thermal expansion coefficients of a sample wood are positive in _________ (radial, tangential and longitudinal)
all sections
wood _______ or _____ on heating and _______ on cooling.
swells or expands; contracts
wood has _____heat capacity than steel
high
steel has _____ heat transfer than wood
faster
wood has ____ thermal diffusivity
lower
BTU means
British Thermal Unit
- a three dimensional representation of requirements for fire to occur (fuel, heat and oxygen)
Fire Triangle
- fuel to release vapor
heat
- to sustain combustion
Oxygen
- a subsequent exothermic chain reaction in the material
chemical reaction
- combustible material
fuel
