What are the three types of feed-water regulator systems?

The three types of feed-water regulator systems primarily include on-off, modulating, and metering types. Each type serves a different function in managing the flow of feed water within a system.

The on-off regulator operates based on preset conditions, triggering a complete opening or closing of the feed water flow. This type is typically simpler and is used in systems where precise control is not as critical.

Modulating regulators provide more precise control by allowing for gradual adjustments to flow rates. This type maintains optimal conditions within the system, making it suitable for applications where maintaining specific temperatures or pressures is essential.

Metering regulators focus on delivering a measured quantity of water to the system, ensuring consistent and accurate flow rates according to the system’s demands. This is particularly beneficial in processes where precise water supply is vital for efficiency and effectiveness.

The other options presented do not accurately represent the standard types of feed-water regulator systems. Terms like "mixing" and "thermodynamic" do not specifically describe the primary regulation methods used in feed-water management. Thus, the combination of on-off, modulating, and metering aligns with the widely accepted classifications in engineering practice.