A2L -Low Global Warming Potential
(LGWP) 4B9 Ch1 Test Questions
Answered Correctly.
First fundamental principle of refrigeration: - Answer A substance must absorb or reject
latent heat in order to change state.
Refrigerants - Answer Liquids that boil below the freezing point of water.
- continuously draws heat away from a body of water
Second fundamental principle of refrigeration: - Answer The pressure exerted on the surface
of a boiling liquid affects the temperature at which the liquid boils.
Saturation temperature - Answer the temperature corresponding to a particular saturation
pressure.
- heat will cause a change in state but not a change in temperature
Saturation pressure - Answer the pressure applied to the boiling liquid surface when
saturation temperature is reached.
- directly related to saturation temp
Third fundamental principle of refrigeration: - Answer For every saturation pressure, there is
one corresponding saturation temp.
Lithium Bromide (LiBr) - Answer A salt with a high affinity for water, used to develop low
pressure in the evaporator of an absorption refrigeration system.
American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) - Answer
Identifies all refrigerants with the capital letter R followed by a number.
(water = R718, to work as a refrigerant, water must be boiled in a deep vacuum)
Ammonia (R-717) - Answer At atmos pressure, boils at -33.3C
Fourth fundamental principle of refrigeration: - Answer One of the physical properties of
every pure liquid is a characteristic set of saturation pressures and temps.
Refrigerated space - Answer The location being cooled by a refrigeration system.
, Refrigerated medium - Answer The substance being cooled by a refrigerant.
Evaporator - Answer The part of a refrigeration system in which liquid refrigerant changes
state to produce a cooling effect.
A simple refrigerator is impractical for freezing food because: - Answer a. the temp of the
refrigerated space (-29C) is good for freezing food but not preserving fresh produce.
b. there is no means of controlling the temp of the refrigerated space because the refrigerant
can only boil at atmospheric pressure.
c. the refrigerant vapour vents directly to the atmos.
Backpressure Regulator - Answer An automatic valve or control device used to maintain a set
pressure, and therefore a set temp, in an evaporator.
- installed at the evaporator outlet, by adjusting the valve, refrigerant vapour flow can be
adjusted. (this changes sat. pressure and sat. temp.
Liquid receiver - Answer A pressure vessel installed in the high side of a refrigerating system
for storage of liquid refrigerant.
Metering Device - Answer Any one of several devices used to control the flow of liquid
refrigerant into an evaporator.
What must be installed between the liquid receiver and the evaporator? - Answer A
metering device.
- if too much refrigerant enters the evaporator, the vapour and unboiled liquid will leave the
evaporator and cause damage to the compressor.
- if there is not enough refrigerant, the evaporator will starve and run dry.
Compressor - Answer A mechanical device for increasing the pressure of a gas.
Cooling medium - Answer A substance to which a heat exchanger rejects heat
What tasks does the compressor serve? - Answer 1. keeps the refrigerant vapour higher then
the temp of the cooling media.
2. the pressure of the refrigerant vapour must be raised to a point where the condensed liquid
refrigerant will remain a liquid.
3. draws refrigerant vapour at a low pressure and discharges it at a high pressure.
(LGWP) 4B9 Ch1 Test Questions
Answered Correctly.
First fundamental principle of refrigeration: - Answer A substance must absorb or reject
latent heat in order to change state.
Refrigerants - Answer Liquids that boil below the freezing point of water.
- continuously draws heat away from a body of water
Second fundamental principle of refrigeration: - Answer The pressure exerted on the surface
of a boiling liquid affects the temperature at which the liquid boils.
Saturation temperature - Answer the temperature corresponding to a particular saturation
pressure.
- heat will cause a change in state but not a change in temperature
Saturation pressure - Answer the pressure applied to the boiling liquid surface when
saturation temperature is reached.
- directly related to saturation temp
Third fundamental principle of refrigeration: - Answer For every saturation pressure, there is
one corresponding saturation temp.
Lithium Bromide (LiBr) - Answer A salt with a high affinity for water, used to develop low
pressure in the evaporator of an absorption refrigeration system.
American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) - Answer
Identifies all refrigerants with the capital letter R followed by a number.
(water = R718, to work as a refrigerant, water must be boiled in a deep vacuum)
Ammonia (R-717) - Answer At atmos pressure, boils at -33.3C
Fourth fundamental principle of refrigeration: - Answer One of the physical properties of
every pure liquid is a characteristic set of saturation pressures and temps.
Refrigerated space - Answer The location being cooled by a refrigeration system.
, Refrigerated medium - Answer The substance being cooled by a refrigerant.
Evaporator - Answer The part of a refrigeration system in which liquid refrigerant changes
state to produce a cooling effect.
A simple refrigerator is impractical for freezing food because: - Answer a. the temp of the
refrigerated space (-29C) is good for freezing food but not preserving fresh produce.
b. there is no means of controlling the temp of the refrigerated space because the refrigerant
can only boil at atmospheric pressure.
c. the refrigerant vapour vents directly to the atmos.
Backpressure Regulator - Answer An automatic valve or control device used to maintain a set
pressure, and therefore a set temp, in an evaporator.
- installed at the evaporator outlet, by adjusting the valve, refrigerant vapour flow can be
adjusted. (this changes sat. pressure and sat. temp.
Liquid receiver - Answer A pressure vessel installed in the high side of a refrigerating system
for storage of liquid refrigerant.
Metering Device - Answer Any one of several devices used to control the flow of liquid
refrigerant into an evaporator.
What must be installed between the liquid receiver and the evaporator? - Answer A
metering device.
- if too much refrigerant enters the evaporator, the vapour and unboiled liquid will leave the
evaporator and cause damage to the compressor.
- if there is not enough refrigerant, the evaporator will starve and run dry.
Compressor - Answer A mechanical device for increasing the pressure of a gas.
Cooling medium - Answer A substance to which a heat exchanger rejects heat
What tasks does the compressor serve? - Answer 1. keeps the refrigerant vapour higher then
the temp of the cooling media.
2. the pressure of the refrigerant vapour must be raised to a point where the condensed liquid
refrigerant will remain a liquid.
3. draws refrigerant vapour at a low pressure and discharges it at a high pressure.
