An automatic non-return valve is typically used with which of the following?

An automatic non-return valve is typically used with a boiler to prevent the backflow of water or steam. In a boiler system, these valves are essential for maintaining the desired direction of flow, ensuring that water flows into the boiler and that steam or heated water does not flow back into the feedwater system. This is particularly important in maintaining pressure and safety within the boiler system, as backflow could lead to potential hazards or operational issues.

While heat exchangers and compressors may also utilize various types of valves for flow control, the specific function and application of an automatic non-return valve are critical for boiler operations. This valve ensures that once water or steam enters the boiler, it cannot flow back, thus protecting the integrity and efficiency of the boiler system. In cooling towers, while valves are used, the function does not specifically pertain to preventing backflow in the same critical manner as in boilers.