What distinguishes a closed feed-water heater from an open one?

A closed feed-water heater is characterized by separate compartments for feed-water and steam, which is what distinguishes it from an open feed-water heater. In a closed feed-water heater, the feed-water and steam do not mix directly; instead, the steam heats the feed-water through a heat exchanger. This design allows for more efficient heat transfer, as the steam can condense and transfer its heat to the feed-water without contaminating it.

The separation of the two fluids also helps maintain the purity of the feed-water, as there's no risk of the steam carrying over any impurities or dissolved gases into the water supply. This is particularly significant in minimizing oxidation and maintaining the overall health of the feed-water system.

In contrast, an open feed-water heater allows for direct contact between the steam and the feed-water, which can lead to mixing and the potential for impurities. This fundamental difference in design and function highlights why the identification of separate compartments is essential in understanding the operation of closed versus open feed-water heaters.