🔍 Key Concepts

• heat transfer in heat exchangers (conduction and convection) • temperature difference (ΔT) as the driving force for heat transfer • Basic heat transfer relation: Q = U · A · ΔT

💭 Think About

• Which of the listed factors actually provides the "driving force" that pushes heat from the steam side to the feedwater side? • Among the choices, which one appears directly (or most directly) in the standard heat transfer equation for a heater? • Ask yourself: if I change each variable slightly, which change would cause the largest and most immediate change in the rate of heat transfer under otherwise normal conditions?

✅ Before You Answer

• Focus on the factor that directly changes the driving temperature difference between hot and cold fluids. • Remember that pH and density usually affect corrosion, scaling, or flow characteristics more than the instantaneous rate of heat transfer in normal operation. • Consider whether pump speed primarily affects pressure/flow, or whether it is truly the main control on the rate of heat transfer in a properly designed feedwater heater.