Humidification process insight: During humidification of air, how does the specific humidity (humidity ratio) change?

Introduction / Context:
Humidification is common in comfort conditioning, textile mills, and process industries. The key variable is specific humidity (also called humidity ratio), defined as kilograms of water vapour per kilogram of dry air.

Given Data / Assumptions:

• Moisture is added to air (e.g., steam or evaporation).
• Pressure is near atmospheric and constant for chart use.
• No dehumidifying surfaces present.

Concept / Approach:
Adding moisture increases the mass of water vapour per unit mass of dry air. Hence, the humidity ratio must rise. Depending on the method (evaporative vs steam injection), dry-bulb temperature may fall or rise, but the specific humidity will increase.

Step-by-Step Solution:

Verification / Alternative check:
On a psychrometric chart, humidification moves the state point to the right (higher w), either up-left (evaporative cooling) or up-right (steam injection) depending on sensible heat exchange.

Why Other Options Are Wrong:
“Remains constant” and “decreases” contradict the definition of humidification; zero or negative values are nonphysical under the stated process.

Common Pitfalls:
Confusing relative humidity (a percentage) with humidity ratio; RH can decrease during steam injection if temperature rises rapidly, even though w increases.

Final Answer:
Increases