In a thermal power plant a cooling tower cools

Question

Examoogle · Accepted Answer

Water from condenser

Explanation: In a thermal power plant, the cooling tower is used to cool the circulating water that has absorbed heat from the steam inside the condenser. By rejecting this heat to the atmosphere, the water is cooled down so it can be recirculated back to the condenser to continue the condensation cycle.

Working Principle: The condenser uses cooling water to condense exhaust steam into liquid. This process heats the water. This warm water is pumped to the cooling tower where it is sprayed into an airflow. Through evaporative cooling and sensible heat transfer, the water temperature drops, and the cooled water is collected in the basin to be reused.

Key Formulas: $Q = \dot{m} C_p \Delta T$ — Heat transfer equation representing the thermal energy rejected by the water; $\eta = 1 - \frac{T_{low}}{T_{high}}$ — Carnot efficiency limitation driving the need for effective heat rejection

Key Points: Cooling towers minimize the consumption of make-up water by recycling the cooling medium.; The process involves latent heat transfer via evaporation and sensible heat transfer to the ambient air.; Efficient condensation in the condenser maintains high vacuum, which is critical for turbine efficiency.

Advantages: Reduces the thermal pollution of natural water bodies.; Highly water-efficient in closed-loop configurations.

Disadvantages: Significant evaporative water loss to the atmosphere.; Requires maintenance to prevent scaling and biological growth.

Applications: Thermal Power Plants; Nuclear Power Stations; Industrial HVAC systems

Additional Info: Option A is incorrect because steam from the boiler is the working fluid that enters the turbine, not the cooling system.. Option B is incorrect because steam from the turbine enters the condenser to be condensed, not the cooling tower.. The condenser serves as the heat exchanger between the steam cycle and the cooling water loop.

Answer: D is correct — The cooling tower cools the circulating water that was heated while condensing steam in the condenser.

Exam Tip: Always distinguish between the 'working fluid' (steam/water in the Rankine cycle) and the 'cooling medium' (the water loop interacting with the atmosphere via the cooling tower).

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