CRST CRST Refrigerants & Thermodynamics

Question 1

What is the boiling point of R-134a at atmospheric pressure (14.7 psia)?

Accepted Answer

-15.07°F (-26.15°C)

Answer

R-134a has a boiling point of approximately -15.07°F at atmospheric pressure, making it suitable for medium-temperature refrigeration applications.

Question 2

Which refrigerant is classified as an A1 safety group per ASHRAE 34?

Accepted Answer

R-134a

Answer

R-134a is classified A1 — 'A' indicating lower toxicity and '1' indicating no flame propagation, making it a non-toxic, non-flammable refrigerant.

Question 3

What thermodynamic process occurs in the evaporator of a vapor-compression refrigeration cycle?

Accepted Answer

Refrigerant absorbs heat from the load and vaporizes at constant pressure

Answer

In the evaporator, liquid refrigerant absorbs latent heat from the refrigerated space and changes phase to vapor at a constant low pressure.

Question 4

What does the term 'subcooling' refer to in a refrigeration system?

Accepted Answer

Cooling liquid refrigerant below its condensing temperature at a given pressure

Answer

Subcooling is the number of degrees the liquid refrigerant is cooled below its saturation (condensing) temperature at the same pressure, ensuring all refrigerant is fully liquid entering the expansion device.

Question 5

What does the Global Warming Potential (GWP) of a refrigerant measure?

Accepted Answer

Its heat-trapping potential relative to CO2 over 100 years

Answer

GWP measures a refrigerant's ability to trap heat in the atmosphere relative to carbon dioxide (CO2 = 1) over a 100-year period.

(CRST) Certified Refrigeration Service Technician Practice Test

(CRST) Certified Refrigeration Service Technician Practice Test

CRST CRST Refrigerants & Thermodynamics