Intro To A/C Flashcards
Refrigeration is the process of______ the air in a defined space
adding moisture to
cleaning
increasing the movement of
lowering the temperature of
lowering the temperature of
The temperature of a material decreases if the material _______ and nothing else happens that would have the opposite effect.
condenses
contacts a cooler material
contacts a warmer material
freezes
contacts a cooler material
The two kinds of air conditioning are
comfort and process
commercial and industrial
heat transfer and change of state
temperature and humidity
comfort and process
One of the physical states of matter is
atom
element
gas
molecule
Gas
You can cause matter to change its physical state by
adding or removing heat
allowing it to age
chemically altering it
separating its atoms
adding or removing heat
Thermal energy that is directly related to the temperature of a material is called _____ heat
• change of state
• latent
• potential
• sensible
sensible
A temperature of 45° is about the same as ______°C.
7
13
25
58
7
Heat can be transferred from one place to another by the process of
• change of state
• conduction
• diffusion
insulation
Conduction
The latent heat of vaporization of a substance is the amount of heat the substance absorbs as it
condenses
evaporates
freezes
melts
evaporates
A refrigeration system has been turned off for several days. It contains both liquid refrigerant and vapor. Suddenly a line containing the refrigerant breaks. What happens inside the system?
• Nothing, because it is turned off
• The liquid refrigerant boils
• The pressure increases
• The refrigerant gets warmer
The liquid refrigerant boils
From the compressor, refrigerant flows to the
condenser
evaporator
metering device
reservoir
condenser
The graph below is the pressure temperature chart for a refrigerant. Point ______ represents a condition of superheating
1
2
3
4
1
Compared to a dry-expansion evaporator, a flooded evaporator of the same size
contains no refrigerant vapor
is more efficient
leaks refrigerant
requires no metering device
is more efficient
The purpose of a cooling medium is to
absorb excess refrigerant vapor
condense the water vapor in moist air
remove heat from compressed refrigerant vapor
superheat refrigerant vapor
remove heat from compressed refrigerant vapor
An automatic expansion valve is a metering device that maintains a constant pressure in the
compressor
condenser
evaporator
surge drum
evaporator
The properties of air that are important in psychrometrics include
enthalpy
odor
oxygen content
velocity
enthalpy
In a sling psychrometer, the wet-bulb temperature is usually lower than the dry-bulb. If the difference is very small, you know that the air is quite
cool
dry
humid
warm
humid
Air that is saturated is air that is at the
desired temperature
dewpoint temperature
lowest possible relative humidity
optimum oxygen content
dewpoint temperature
Relative humidity changes if the_____ changes, but the specific humidity does not.
barometric pressure
dewpoint temperature
dry-bulb temperature
weight of dry air
dry-bulb temperature
To calculate the enthalpy of a sample of air, you must include
latent heat of the air
latent heat of the water vapor
relative humidity of the air
specific humidity of the air
latent heat of the water vapor
In order to remove the moisture that enters a refrigeration system during repair, you must evacuate the system by using a_____ to make all the moisture vaporize.
charging hose
manometer
torch
vacuum pump
vacuum pump
One useful method of detecting leaks in a refrigeration system involves using a(n) _____ leak detector.
chromatographic
electronic
high frequency
infrared
electronic
Relative humidity can be measured directly with a(n)
dewpoint thermometer
hydrometer
hygrometer
psychrometeric chart
hygrometer
Which of the following is a correct match between an electrical value and the instrument used to measure it?
• Current; ohmmeter
• Current; wattmeter
• Power; ammeter
• Resistance; ohmmeter
Resistance; ohmmeter
