Refrigeration Fundamentals & Thermodynamics Flashcards

What is the primary purpose of the refrigeration cycle in an HVAC system?

Answer: To transfer heat from a low-temperature region to a high-temperature region

The refrigeration cycle transfers heat from a cool space to a warmer environment by using a refrigerant that absorbs and releases heat as it changes phase.

In the vapour-compression refrigeration cycle, at which component does the refrigerant absorb heat from the space being cooled?

Answer: Evaporator

The evaporator is where the low-pressure liquid refrigerant boils and absorbs latent heat from the surrounding space, providing the cooling effect.

What is the unit of heat energy used in Canadian HVAC calculations?

Answer: Joule (J) or kilojoule (kJ)

Canada uses SI (metric) units, so heat energy is measured in joules (J) or kilojoules (kJ) in accordance with Canadian standards.

What does 'latent heat' refer to in refrigeration?

Answer: Heat absorbed or released during a phase change without a temperature change

Latent heat is the energy absorbed or released when a substance changes phase (e.g., liquid to vapour) at a constant temperature, which is the principle behind refrigerant phase changes in the cycle.

What is superheat in a refrigeration system?

Answer: The temperature of refrigerant above its boiling point in the vapour state

Superheat is the number of degrees the refrigerant vapour is above its saturation (boiling) temperature at a given pressure, measured at the evaporator outlet or compressor suction.

What is subcooling in a refrigeration system?

Answer: The number of degrees the liquid refrigerant is cooled below its condensing temperature

Subcooling refers to cooling the liquid refrigerant below its saturation temperature at the condenser outlet, which prevents flash gas in the liquid line and improves system efficiency.