In HVAC chemical dehumidification (using hygroscopic absorbers or adsorbers), which of the following changes correctly describe the air-state outcomes as moisture is removed?

Introduction / Context:
Chemical dehumidification removes moisture from air by exposing it to hygroscopic materials (desiccants) such as silica gel, lithium chloride, or solid desiccant wheels. Unlike cooling-based dehumidification, this process is exothermic and usually warms the air while reducing its moisture content.

Given Data / Assumptions:

• Process is a chemical (desiccant) dehumidification step, not cooling coil dehumidification.
• Air loses moisture to the desiccant; heat of adsorption/absorption raises air temperature.
• Psychrometric properties of interest: dry-bulb temperature, wet-bulb temperature, and dew point temperature.

Concept / Approach:
When moisture is removed at nearly constant enthalpy input from adsorption heat, the humidity ratio decreases. Dry-bulb temperature typically increases because the exothermic process adds sensible heat to the air stream. Lower moisture content shifts both dew point and wet-bulb temperatures downward, since both are functions of moisture content at a given pressure.

Step-by-Step Solution:

Verification / Alternative check:
Plot the initial and final states on a psychrometric chart: the final state shows lower humidity ratio, a lower dew point, a lower wet-bulb, and a higher dry-bulb temperature as commonly observed with desiccant wheels (before any post-cooling stage).

Why Other Options Are Wrong:

• (a), (b), (c) each capture only one aspect; chemical dehumidification causes all three listed changes.
• (e) Incorrect because wet-bulb also changes due to altered moisture content, and dry-bulb typically rises.

Common Pitfalls:
Confusing chemical dehumidification with cooling coil dehumidification (cooling and dehumidifying), where dry-bulb temperature generally decreases. Also, assuming wet-bulb stays constant is a misconception from evaporative processes, not chemical drying.

Final Answer:
All of these