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Psychrometrics and Humidity Control Flashcards

7 cards from real 313D practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. What does the term 'psychrometrics' refer to in HVAC?

    Answer: The study of thermodynamic properties of moist air

    Psychrometrics is the engineering science that studies the thermodynamic properties of moist air — mixtures of dry air and water vapor.

  2. What is the dew point temperature?

    Answer: The temperature to which air must be cooled for water vapor to begin condensing

    Dew point is the temperature at which air becomes saturated and water vapor condenses into liquid, assuming constant pressure and moisture content.

  3. On a psychrometric chart, wet-bulb temperature lines run in which direction?

    Answer: Diagonally downward from the saturation curve toward the lower right

    Wet-bulb temperature lines slope diagonally downward from upper left to lower right on a psychrometric chart and nearly coincide with lines of constant enthalpy.

  4. What is relative humidity (RH)?

    Answer: The ratio of actual moisture content to the maximum moisture air can hold at that temperature

    Relative humidity is the ratio of actual water vapor pressure to saturation water vapor pressure at the same temperature, expressed as a percentage.

  5. What is the key difference between sensible heat and latent heat in air conditioning?

    Answer: Sensible heat causes a measurable temperature change; latent heat involves phase change without temperature change

    Sensible heat changes the temperature of air (measurable with a thermometer), while latent heat is absorbed or released during phase changes like evaporation or condensation.

  6. What does enthalpy measure in an HVAC psychrometric context?

    Answer: The total heat content of moist air, combining both sensible and latent heat

    Enthalpy represents the total heat content of moist air, expressed in BTU per pound of dry air, and includes both sensible (temperature) and latent (moisture) components.

  7. What indoor relative humidity range does ASHRAE recommend for occupant comfort in residential buildings?

    Answer: 30–60%

    ASHRAE recommends maintaining indoor RH between 30% and 60% to ensure occupant comfort and prevent mold growth or dry-air discomfort.

Psychrometrics and Humidity Control Flashcards — 313D Study Cards with Answers