Air conditioning fundamentals Flashcards
most people feel most comfortable when surrounded by air temperatures of
21 - 27 C
why are cabs difficult to heat
because of the larger surface area of windows and poor insulation
what is the most desirable cab humidity level
40 to 45 %
the purpose of the heater/ air conditioning unit is to
provide an air exchange , control humidity , heat and cool the cab and allow fresh filtered air to enter the cab
heat energy always moves from
a hotter area to a colder area or from a high heat energy to a lower one
how dose the air conditioning system remove hot air from a cabs interior
by moving the heat from inside the cab to the evaporator core ( the cooling element ) and transferring unwanted heat outside the cab
what are the three heat movement methods
conduction , convection , radiation
what is conduction
heat dissipation by transferring heat energy from one particle to another within and object
what is convection
is heat transfer by movement of warm gas or liquids from one place to another
what is radiation
is heat movement by electromagnetic rays or moving particles
what are the two methods to measure heat
heat intensity and heat quality
how is heat intensity measured
by measuring the intensity of molecular motion of a substance
how is heat quality measured
by measuring how much heat energy a substance contains
what are the three states of matter
solid liquid vapour
what are the two important changes of state that happen in a air conditioning system
vaporization and condensation
the temperature at which a substance changes state depends on
the pressure surrounding the substance
the higher the pressure surrounding the substance
the higher the temperature at which the substance changes state
the lower the pressure that surrounds a substance
the lower the temperature at which a substance will change state
what is the normal refrigerant used in truck air conditioning systems
R-134a refrigerant
what is superheat
when all the liquid refrigerant has gone through a state of change into a vapour and continues to absorb heat energy and will continue to absorb heat with no change in pressure
what are the two applications for calculating superheat in an air conditioning system
to determine how well the expansion devise is working and to determine how efficiently the evaporator is working
where will most manufacturers run superheat temperatures
between 8 - 12 F