If the feedwater temperature to a boiler is increased without changing the firing rate, what happens to the steam flow?

Increasing the feedwater temperature to a boiler while keeping the firing rate constant enhances the efficiency of the heat exchange process within the boiler. When the feedwater enters the boiler at a higher temperature, less energy is required to raise the water to its boiling point and convert it into steam. As a result, more steam can be produced because a portion of the energy from the combustion process is used more effectively.

When the feedwater temperature is raised, it effectively means that the initial condition of the water is closer to the condition needed for it to become steam. Thus, for the same amount of heat input (given by the firing rate), a greater amount of steam can be generated, leading to an overall increase in steam flow. This phenomenon illustrates the principles of thermodynamics and efficiency in boiler operation, directly linking the temperature of the feedwater to the boiler's steam output potential.