An open feedwater heater allows for the mixing of steam and feedwater at what type of pressure?

An open feedwater heater operates by allowing steam to mix with feedwater at atmospheric pressure. In this setup, the steam is introduced directly into the feedwater, causing the temperature of the feedwater to rise through the heat exchange process. This mixing occurs without the vessel being pressurized, meaning that it can efficiently transfer heat to the feedwater while maintaining conditions that prevent the risk of over-pressurizing the system.

Operating at atmospheric pressure also simplifies the design and safety of the feedwater heater, as it eliminates the need for pressure-rated components that would be required in both low and high-pressure systems. The steam used can condense inside the heater, providing thermal energy to the feedwater while venting any non-condensed gases to the atmosphere.

Other pressure conditions like low, medium, and high do not apply to an open feedwater heater. Low pressure would suggest that the system is still somewhat pressurized, and high pressure would imply that the system must manage an elevated risk of failure due to pressure containment. Therefore, it’s important to recognize that the open feedwater heater's operation at atmospheric pressure is a critical aspect of its function and design in steam systems.