Question

The psychrometric process in which air is cooled and humidified but no heat is supplied or rejected is called ________.

• A. Cooling and humidification
• B. Mixing of air streams
• C. Dehumidification
• D. Cooling with adiabatic humidification

Hint:

Think of air passing over a water spray with no outside heat added or removed.

Answer 1

The Correct Option is D

Step 1: Read the conditions:
The air is cooled and humidified. No heat is supplied or rejected from outside. So the process is adiabatic, which means no heat enters or leaves the system.

Step 2: Understand how it works:
When air passes through a water spray or a wet pad, water evaporates. The latent heat needed for evaporation comes from the air itself. So the dry bulb temperature falls and the moisture content rises. Total heat of the air stays nearly constant. This is evaporative cooling.

Step 3: Check the options:
Option (D), cooling with adiabatic humidification, matches this process.
Option (A), cooling and humidification, is a general name that does not say that no heat is exchanged. A plain cooling and humidifying process may use a cold coil or spray that takes heat out.
Option (B), mixing of air streams, joins two air streams and does not add water.
Option (C), dehumidification, removes moisture, so it is the opposite.

Final Answer:
The process is cooling with adiabatic humidification. This is option (D).