🔍 Key Concepts

• Direct-contact (DC) heater operation – how steam and feedwater interact inside the heater • Condensation vs. evaporation – which process actually uses up the incoming steam in the DC heater • What happens when a steam control valve is already wide open (no more throttling possible)

💭 Think About

• Inside a DC heater, when steam enters and mixes with the incoming water, what physical process makes the steam disappear and transfer its heat? • If the control valve is already wide open, what variable inside the heater can still change the amount of steam that actually flows in and is used? • Think about whether the water level, spring pressure, or steam’s phase change is the main factor that determines how much steam is drawn from the auxiliary exhaust line under steady, normal operation.

✅ Before You Answer

• Distinguish clearly between condensation of steam and evaporation of water in a DC heater • Ask: with the valve wide open, which listed factor would directly affect how much steam is actually used up inside the heater, rather than just sitting there? • Confirm which choice is most closely tied to the heat transfer and phase-change process occurring when steam meets cooler feedwater in a DC heater