What does the term "saturation line" refer to in a psychrometric chart?

The term "saturation line" on a psychrometric chart specifically refers to the line that indicates the maximum moisture content that air can hold at a given temperature. As air temperature increases, the capacity of the air to hold moisture also increases, meaning the saturation line shifts upward. This line represents the conditions under which water vapor in the air is in equilibrium with liquid water; any point on this line corresponds to a relative humidity of 100%.

Understanding the saturation line is crucial for analyzing the properties of moist air and for applications such as HVAC design and environmental engineering, where moisture management is vital. Points below the saturation line indicate that the air contains less moisture than it is capable of holding (sub-saturated air), while points above the line denote supersaturated conditions. This knowledge is essential when dealing with processes involving evaporation and condensation in various chemical engineering applications.