Define absolute humidity precisely Absolute humidity is defined as the mass of water vapour contained in a unit volume of the air–vapour mixture. Is the statement “mass of water vapour present in 1 m³ of dry air” correct?

Introduction / Context:
Psychrometric terminology distinguishes between absolute humidity, specific humidity (humidity ratio), and relative humidity. Precision matters in calculations of loads and coil selection.

Given Data / Assumptions:

• Absolute humidity (sometimes called absolute moisture content) is mass of water vapour per unit volume of the moist air mixture.
• Specific humidity (humidity ratio) is mass of water vapour per unit mass of dry air.

Concept / Approach:
The phrase “per 1 m³ of dry air” belongs to humidity ratio, not absolute humidity. Absolute humidity uses the actual volume occupied by the moist mixture (air plus vapour) at its state point.

Step-by-Step Solution:

Verification / Alternative check:
Psychrometric chart axes and standard formulas separate volumetric measures (absolute humidity) from mass ratios (specific humidity); textbooks consistently define them this way.

Why Other Options Are Wrong:
Adding conditions like saturation or standard pressure does not change the fundamental definition; the denominator remains the moist mixture volume for absolute humidity.

Common Pitfalls:
Using terms “absolute” and “specific” interchangeably; this can lead to significant sizing errors because volume and mass bases differ.

Final Answer:

Disagree