CRST CRST Refrigerants & Thermodynamics 2

Question 1

What is 'superheat' in a refrigeration system?

Accepted Answer

The temperature of suction vapor above the saturation temperature at suction pressure

Answer

Superheat is the number of degrees that suction vapor exceeds the saturation temperature at the measured suction pressure, ensuring only dry vapor enters the compressor.

Question 2

Per EPA Section 608, what is the maximum allowable leak rate for refrigeration equipment with a charge of 50 lbs or more used in commercial processes before repair is required?

Accepted Answer

30% per year

Answer

EPA Section 608 requires owners of commercial refrigeration equipment with charges of 50 lbs or more to repair leaks when the annual leak rate exceeds 30%.

Question 3

When recharging a system with an HFC blend refrigerant (such as R-410A), how must the refrigerant be added from the cylinder?

Accepted Answer

As a liquid (cylinder inverted or using a liquid valve)

Answer

HFC blends like R-410A must be charged as liquid to maintain the correct blend ratio, as vapor-charging can cause fractionation and alter the refrigerant composition.

Question 4

What happens to the pressure-temperature relationship of a refrigerant mixture that 'glides'?

Accepted Answer

The temperature changes during phase change at constant pressure

Answer

Zeotropic refrigerant blends exhibit temperature glide, meaning the evaporation or condensation temperature shifts (slides) across a range during phase change at constant pressure.

Question 5

What is the primary purpose of a refrigerant receiver in a commercial refrigeration system?

Accepted Answer

Store liquid refrigerant to accommodate system demand changes and ensure liquid feed to the expansion device

Answer

A liquid receiver stores excess refrigerant charge, provides a stable liquid supply to the expansion device, and accommodates load variations without flooding or starving the system.

(CRST) Certified Refrigeration Service Technician Practice Test

(CRST) Certified Refrigeration Service Technician Practice Test

CRST CRST Refrigerants & Thermodynamics 2