What is a primary benefit of a feed-water heater?

A primary benefit of a feed-water heater is that it can decrease thermoshock damage to the boiler. This type of heater preheats the water before it enters the boiler, which helps to reduce the temperature difference between the incoming water and the boiler's operating temperature. By mitigating this temperature difference, the likelihood of rapid thermal expansion or contraction within the boiler components is greatly reduced. This balancing of temperatures can lead to enhanced longevity and reliability of the equipment, preventing cracking and other forms of stress-related damage that can occur from sudden temperature changes, also known as thermoshock.

The other options highlight issues that are not aligned with the benefits of feed-water heaters. Increased maintenance costs tend to be a potential downside, not a benefit, as they require regular upkeep related to their operation. Air accumulation in the boiler can lead to inefficiencies and presentation of hazards, which is contrary to the purpose of using a feed-water heater. Lastly, while complexity in systems may sometimes be seen as a disadvantage, a feed-water heater serves to improve system efficiency rather than adding unnecessary complexity.