What is the primary consequence of maintaining a higher vacuum in the condenser on turbine operation?

What is the primary consequence of maintaining a higher vacuum in the condenser on turbine operation?

• A. Increases boiler pressure
• B. Increases turbine work output
• C. Decreases condenser duty
• D. Increases fuel consumption

Answer: (B)

Lowering the exhaust pressure in the condenser (creating a deeper vacuum) reduces the back pressure on the turbine. This means the steam inside the turbine can expand further from boiler pressure down to a lower condenser pressure, yielding a larger expansion amount and thus more work per unit of steam. In other words, the turbine delivers more mechanical energy for the same mass flow of steam, which is the primary consequence of a higher condenser vacuum and a more efficient cycle. The boiler pressure is set by the boiler itself, not by the condenser, so deeper vacuum does not raise boiler pressure. The condenser must still reject heat to maintain that vacuum, and in practice the heat rejection requirement doesn’t decrease simply because the vacuum is deeper. Regarding fuel use, the improved turbine work and overall efficiency tend to reduce fuel consumption for the same power output, rather than increase it. The key point focused on turbine operation is that deeper vacuum increases the work the turbine can extract.

Lowering the exhaust pressure in the condenser (creating a deeper vacuum) reduces the back pressure on the turbine. This means the steam inside the turbine can expand further from boiler pressure down to a lower condenser pressure, yielding a larger expansion amount and thus more work per unit of steam. In other words, the turbine delivers more mechanical energy for the same mass flow of steam, which is the primary consequence of a higher condenser vacuum and a more efficient cycle.

The boiler pressure is set by the boiler itself, not by the condenser, so deeper vacuum does not raise boiler pressure. The condenser must still reject heat to maintain that vacuum, and in practice the heat rejection requirement doesn’t decrease simply because the vacuum is deeper. Regarding fuel use, the improved turbine work and overall efficiency tend to reduce fuel consumption for the same power output, rather than increase it. The key point focused on turbine operation is that deeper vacuum increases the work the turbine can extract.