Thermodynamics Flashcards
7 cards from real HVAC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Thermodynamics flashcards as text
What term describes the heat absorbed by a refrigerant as it changes from liquid to vapor at constant temperature?
Answer: Latent heat of vaporization
Latent heat of vaporization is the energy absorbed during the phase change from liquid to vapor without a temperature change.
Which thermodynamic process occurs when a gas expands without any heat transfer to or from the surroundings?
Answer: Adiabatic
An adiabatic process involves no heat exchange with surroundings, so temperature changes are driven entirely by work.
In a standard vapor-compression refrigeration cycle, where does the refrigerant absorb heat from the conditioned space?
Answer: Evaporator
The evaporator coil absorbs heat from the indoor air, causing the refrigerant to evaporate and cool the space.
What is the Coefficient of Performance (COP) of a refrigeration system if it removes 12,000 BTU/hr using 2,000 BTU/hr of work input?
Answer: 6.0
COP = heat removed / work input = 12,000 / 2,000 = 6.0.
Which law of thermodynamics states that heat will not spontaneously flow from a cold body to a hot body?
Answer: Second Law
The Second Law of Thermodynamics establishes the natural direction of heat flow and the concept of entropy.
Subcooling in a refrigeration system refers to cooling the refrigerant below its:
Answer: Condensing temperature
Subcooling occurs when liquid refrigerant is cooled below the saturation (condensing) temperature, increasing system efficiency.
What happens to the boiling point of a refrigerant when pressure is increased?
Answer: It increases
Higher pressure raises the saturation temperature (boiling point) of a refrigerant, a fundamental pressure-temperature relationship.