In psychrometric terms, the humidity ratio (also called specific humidity or moisture content) is defined as the mass of water vapor present per kilogram of dry air. Is this definition correct?

Introduction / Context:
Psychrometrics uses the humidity ratio to quantify moisture in air-conditioning calculations. It is critical for coil sizing, dehumidification strategies, and calculating latent loads in HVAC systems.

Given Data / Assumptions:

• Standard psychrometric definitions at typical barometric pressures.
• Humidity ratio often denoted by w.

Concept / Approach:
The humidity ratio is defined as w = m_vapor / m_dry_air. Because the basis is per kilogram of dry air, w remains well-defined across a wide range of conditions and is independent of relative humidity’s percentage expression. This contrasts with specific volume or enthalpy, which depend on the total moist-air mixture properties.

Step-by-Step Solution:

Verification / Alternative check:
On the psychrometric chart, moving vertically changes w; calculations of dew point and mixing lines rely on this definition.

Why Other Options Are Wrong:

• (b) Incorrect; the given definition is standard.
• (c) and (d) add unnecessary conditions; the definition holds broadly.
• (e) Per kilogram of moist air would be mass fraction of vapor, not the standard humidity ratio.

Common Pitfalls:
Confusing mass fraction (per moist air) with humidity ratio (per dry air) or mixing absolute humidity with relative humidity.

Final Answer:
True