What phenomenon describes an increase in boiler water level due to a sudden increase in load?

The phenomenon that describes an increase in boiler water level due to a sudden increase in load is known as "swell." When the load on a boiler increases suddenly, the immediate effect can cause an increase in steam production. This rapid increase in steam generation results in a temporary rise in the water level within the boiler. This occurs because the liquid water in the boiler cannot immediately accommodate the increased demand for steam, leading to a displacement of water as steam bubbles form and rise to the surface.

Swell is particularly important in high-pressure or high-capacity boilers, where understanding the dynamics of water level changes can prevent flooding or carryover of water into steam lines. Identifying swell helps operators take corrective actions to maintain safe and efficient operation.

In contrast, the other terms relate to different hydraulic or phase change phenomena. Shrinkage refers to a decrease in water volume due to lower pressure conditions leading to less steam generation. Condensation involves the change of steam back into water, usually occurring when heat is removed. Evaporation represents the conversion of liquid into vapor, but it does not describe the effect on water level under increased load conditions specifically.