Air-conditioning processes — definition nuance for dehumidification Assess the statement: “The process of removing moisture from the air, without change in its dry-bulb temperature, is called dehumidification.” Choose the best option.

Introduction / Context:Dehumidification is the removal of water vapor from moist air. In practice, dehumidification can occur with temperature changes (cooling and reheating) or, in special arrangements, at nearly constant dry-bulb temperature using desiccants. The statement emphasizes a constant dry-bulb scenario.

Given Data / Assumptions:

• Focus on the definition of the process, not a single method.
• Dry-bulb temperature may be held approximately constant via heat exchange while moisture is removed.

Concept / Approach:Dehumidification is defined by a decrease in humidity ratio (specific humidity). Many methods exist: cooling below dew point (then reheating), or passing air over hygroscopic desiccants that absorb moisture. Chemical dehumidification can be arranged so that sensible heat is removed/added to keep dry-bulb nearly constant, satisfying the described condition.

Step-by-Step Solution:Identify dehumidification criterion: reduction in w (humidity ratio).Recognize that “without change in dry-bulb temperature” describes a particular implementation (isothermal dehumidification), commonly achievable with desiccant systems and appropriate heat balancing.Therefore, the statement remains correct, albeit describing a specific case of dehumidification.

Verification / Alternative check:Psychrometric charts include “isothermal dehumidification” lines showing movement leftward (lower w) at constant T_db, confirming the definition is acceptable.

Why Other Options Are Wrong:(b) Incorrect because dehumidification does not require T_db to change; it may or may not change. (c) and (d) restrict the statement to a single method; multiple methods can, with appropriate heat exchange, maintain nearly constant T_db. (e) “Above the saturation line” is nonsensical wording in this context.

Common Pitfalls:Assuming all practical dehumidification must cool air; desiccant systems can remove moisture with minimal change in dry-bulb temperature when heat of sorption is managed.

Final Answer:Correct