What is the feedwater temperature given in the boiler example?

What is the feedwater temperature given in the boiler example?

• A. 212°F
• B. 235°F
• C. 240°F
• D. 225°F

Answer: (D)

Feedwater temperature is the temperature of the water as it enters the boiler, after condensate has returned and any feedwater heating has occurred. This temperature matters because it sets how much heat must be added to bring the water up to steam, influencing the boiler’s energy balance and efficiency.

In the boiler example, the feedwater is specified as 225°F. That value reflects the water after it has been preheated by the plant’s condensate return paths and any feedwater heaters or economizers. It sits above the pure condensate temperature but below the boiler’s steam saturation point, representing a realistic preheated state rather than cold feedwater. This lets you calculate the required heat input by comparing the enthalpy of water at 225°F with the enthalpy of the produced steam at the boiler’s operating pressure.

Other temperatures like 212°F correspond to atmospheric boiling and aren’t representative of feedwater in a pressurized boiler system; higher values such as 235°F or 240°F could be plausible in different setups, but the example uses 225°F, which is why that choice is correct.