What Is Water And Where Does It Come From Flashcards
(44 cards)
Two ways water extinguishes fire..
Cooling / absorbing heat (primary)
Smothering
Specific heat def.
A measure of the heat-absorbing capacity of a substance
BTU
British thermal unit
Amount of heat required to raise the temp of one pound of water 1 degree F
(Starting at 60 degrees)
Latent heat of vaporization def
Heat absorbed by a substance when it changes from a liquid to a vapor
Additional amount of energy required to convert liquid to steam
970 BTUs
Exposed surface area relevance
The speed that water absorbs heat increase in proportion to water surface exposed to heat
Water to steam expansion ratio
1:1,700
Specific gravity def
Density of a liquid in relation to water
Les than 1 float on water
Greater than 1 sink in water
Most flammable liquids are less than 1
1st principle of pressure
Fluid pressure is perpendicular. To any force on which it acts.
Second principle of fluid pressure.
Fluid pressure at rest is the same in all directions
Or there is no pressure in all directions
Used in hydrostatic testing.
Third principle or fluid pressure
Confined pressure is transmitted equally in all directions
Fourth principle of fluid pressure
Pressure of fluid in an open vessel is proportioned to its depth.
Fifth principle of fluid pressure
Fluid pressure in a open vessel is proportionate to is density
Sixth principle of fluid pressure
Pressure at the bottom of a vessel is independent of the shape of that vessel.
Head pressure def
Height of the water supply above the Discharge orifice.
Static pressure def
Stores potential energy available to force water though pipes hoses and nozzles
Normal operating pressure
Pressure found in a water distribution system during normal consumption demands.
Residual pressure def
Part of the pressure that is left after friction loss is taken into account.
Flow pressure
Forward velocity at the discharge opening
Elevation vs. altitude.
Fire terms
Elevation - measures from the center line of the pump or the bottom of a static water source
Altitude - above or below sea level
Friction loss due to old hose vs. new
Up to %50 greater
1st Principle of friction loss
Varies directly with length of hose
2nd principle of friction loss
Friction loss varies with the squares of the increase in velocity.
If increased from 200 - 400. 2 squared
Or 200 - 600. 3 squared
Third principle of friction loss
FL varies inverse to the 5th power with increasing hose diameter.
2.5 to the fifth over 3 to the fifth.