In winter air-conditioning practice, the supply air must be both warmed and given additional moisture to achieve indoor comfort. What is the name of the combined process used to increase air temperature and raise its humidity simultaneously?

Introduction / Context:
Winter air-conditioning aims to condition outdoor cold and relatively dry air so that indoor spaces feel comfortable. The two key tasks are to raise the air temperature and to increase its moisture content so occupants do not feel dryness and static electricity. This question checks the foundational psychrometric concept and the correct naming of the process used in HVAC engineering.

Given Data / Assumptions:

• The outdoor air is cold and has low absolute humidity in winter.
• Comfort targets usually require temperatures around 20–24°C and relative humidity about 30–50% depending on standards.
• The process is performed by heating coils and humidifiers within an air-handling unit.

Concept / Approach:
On a psychrometric chart, heating at constant humidity ratio moves horizontally to the right (temperature increases, moisture constant). Humidification at nearly constant dry-bulb temperature moves the state point upward (humidity ratio increases). In winter systems, both are applied: first heat to a comfortable temperature, then inject moisture (steam or water spray/atomization) to achieve the target humidity. The combined name in HVAC terminology is “heating and humidification.”

Step-by-Step Solution:

Verification / Alternative check:
A standard winter air-handling schematic shows an outdoor air damper, preheat coil (if needed), main heating coil, and a humidifier section. The psychrometric path is a rightward move due to heating followed by an upward or slightly slanted move due to humidification. This matches the named process exactly.

Why Other Options Are Wrong:

• Cooling and dehumidification: A summer process, opposite of winter needs.
• Humidification only: Would not correct low temperature discomfort.
• Dehumidification only: Reduces moisture and is used for muggy summer air.
• Adiabatic saturation only: A theoretical process; real winter systems add heat and moisture with equipment.

Common Pitfalls:
Assuming raising humidity alone will improve comfort when air is still too cold; or confusing summer and winter processes on the psychrometric chart.

Final Answer:
Heating and humidification