1. Three-Section Structure Explained

Drain Cooler Section (DCS)

• Position: Located at the outlet side of the heater.

• Function: Cools down the condensate (drain) further by transferring heat to the feedwater. The drain is cooled close to the saturation temperature of the next lower-pressure heater.

• Benefit: Achieves stepwise utilization of steam energy and avoids thermal energy loss.

Condensing Section (CS)

• Position: The main body of the high pressure heater.

• Function: The extraction steam from the turbine condenses in this section, releasing a large amount of heat to the high-pressure feedwater flowing inside the tubes.

• Importance: This is the core working zone of the heater and determines its heat transfer efficiency.

Subcooling Section (SS)

• Position: Near the drain outlet.

• Function: Further cools the condensate below the saturation temperature to prevent steam carryover.

• Benefit: Improves system stability, reduces the risk of water hammer, and ensures safer operation.

2. Advantages of the Three-Section Design

1. Higher Heat Utilization

   • The three-section design ensures that steam energy at different temperature levels is fully absorbed.

2. Improved Operational Safety

   • The subcooling section prevents steam-water mixture carryover and protects downstream equipment.

3. Better Economic Performance

   • By recovering more heat from the drains, the system minimizes heat loss and reduces operational costs.

4. Extended Service Life

   • Dividing the heat transfer process into sections reduces thermal stress and improves equipment durability.

3. Typical Applications

Tubular high pressure heaters with three-section structure are commonly used in:

• Large-scale coal-fired power plants

• Combined cycle power plants (gas-steam systems)

• Nuclear power plant feedwater heating systems

4. Conclusion

The three-section structure — Drain Cooler Section, Condensing Section, and Subcooling Section — is the key design feature of tubular high pressure heaters. It enables maximum recovery of steam energy, improves feedwater temperature, and ensures safe, reliable, and economical operation of power generation units.

With the growing demand for energy efficiency and environmental protection, the three-section tubular high pressure heater will continue to play a vital role in modern power plants.