What is the expected outcome of using an isothermal humidifier?

• A. The air temperature remains nearly constant while steam is injected.
• B. The air temperature increases as steam is injected.
• C. The humidity increases without changing temperature.
• D. The system requires additional cooling to maintain temperature.

Answer: (A)

Isothermal humidification adds moisture to the air without changing the dry-bulb (air) temperature. This type of humidifier introduces steam at about the same temperature as the airstream, so the latent heat released when the water vapor condenses does not produce a noticeable rise in air temperature. The result is that the air temperature stays essentially constant while humidity increases as steam is added. This is why the defining outcome is maintaining a nearly constant temperature even as moisture levels rise. Optionen that imply heating or the need for extra cooling don’t reflect the isothermal behavior.