What happens to cycle efficiency if the cooling water system flow rate increases?

What happens to cycle efficiency if the cooling water system flow rate increases?

• A. Increases the heat transfer coefficient which lowers condenser temperature and pressure, therefore increasing efficiency
• B. Increases condenser pressure
• C. No change
• D. Decreases efficiency

Answer: (A)

When the cooling water flow rate is increased, the condenser can remove heat more effectively. This raises the condenser’s heat transfer coefficient, allowing the exhaust steam to condense at a lower temperature. A lower condenser temperature means a lower condenser pressure, since the saturation pressure decreases with temperature. With a smaller condenser pressure, the steam expands more in the turbine, producing more turbine work while the pump work doesn’t change much. Since the heat input to the cycle is essentially the same, the net work rises, so the cycle efficiency increases. In short, boosting cooling water flow improves heat removal in the condenser, lowers its operating pressure, and this larger expansion in the turbine leads to higher overall efficiency.

When the cooling water flow rate is increased, the condenser can remove heat more effectively. This raises the condenser’s heat transfer coefficient, allowing the exhaust steam to condense at a lower temperature. A lower condenser temperature means a lower condenser pressure, since the saturation pressure decreases with temperature.

With a smaller condenser pressure, the steam expands more in the turbine, producing more turbine work while the pump work doesn’t change much. Since the heat input to the cycle is essentially the same, the net work rises, so the cycle efficiency increases.

In short, boosting cooling water flow improves heat removal in the condenser, lowers its operating pressure, and this larger expansion in the turbine leads to higher overall efficiency.