Define the 'blowdown percentage' for boiler operations.

The blowdown percentage refers specifically to the proportion of water that is intentionally removed from a boiler to control the levels of Total Dissolved Solids (TDS). In boiler operations, as water is heated, impurities and dissolved solids accumulate, which can lead to issues such as scaling or foaming, reducing the efficiency and safety of the boiler system. To mitigate these problems, a certain volume of water, often containing a higher concentration of these dissolved solids, is periodically removed from the system. This process is known as blowdown.

By maintaining an appropriate blowdown percentage, operators can ensure that the concentration of TDS remains within acceptable limits, thereby optimizing boiler performance and extending equipment lifespan. This practice is essential for maintaining water quality and operational efficiency in steam boilers.

The other options do not accurately reflect the concept of blowdown percentage. The release of steam during operation does not account for the control of dissolved solids, and energy loss during heating pertains to thermal efficiency rather than water management. Moreover, the amount of water returned to the boiler system relates to makeup water rather than blowdown practices.