CRST Refrigerants & Thermodynamics Flashcards

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

Answer: -15.07°F (-26.15°C)

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

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

Answer: R-134a

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

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

Answer: Refrigerant absorbs heat from the load and vaporizes at constant pressure

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

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

Answer: Cooling liquid refrigerant below its condensing temperature at a given pressure

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.

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

Answer: Its heat-trapping potential relative to CO2 over 100 years

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

Which refrigerant has an Ozone Depletion Potential (ODP) of zero and is commonly used in new commercial refrigeration systems in the US?

Answer: R-404A

R-404A has an ODP of zero (no chlorine atoms) and became widely adopted for commercial refrigeration as a replacement for ozone-depleting R-502 and R-22.