What does "superheat" refer to in steam systems?

Superheat refers specifically to steam that has been heated above its saturation temperature, which is the temperature at which water boils and turns into steam for a given pressure. When steam is superheated, it is no longer in equilibrium with water—meaning it has additional energy beyond what is required just to convert water from liquid to vapor. This increase in temperature results in a greater thermal energy that allows the steam to do more work, particularly in turbines and engines.

In practical applications, superheating increases the efficiency of steam systems because superheated steam has a higher energy content, which translates to more effective energy transfer when it interacts with turbines. Additionally, it can help to prevent the formation of water droplets that could lead to erosion in turbine blades, as well as improve the overall thermodynamic performance of the steam cycle.

In contrast, steam at its saturation temperature is simply steam in thermal equilibrium with water, while liquid water heated to boiling point describes water that is about to become steam. Steam that has cooled after usage would generally be at a lower energy state and is not considered superheated. Through understanding these distinctions, it is clear why the definition focusing on steam heated above its saturation temperature is critical in steam system operations.