What is a condenser in a power plant? How does it work?

Summary

A turbine works between two terminal points [1] upstream steam pressure and[2] downstream stream condenser pressure to deliver energy for mechanical work. The pressure in the condenser is set by the cooling tower's cold water temperature. The cold water temperature of the cooling tower must be less than the saturated temperature of vapor at the condenser. pressure.. This is the limiting point of condenser pressure.

Here is a typical enthalpy balance across a cooling tower

(T hot - T cold) water =( H out - H in) air, H is the enthalpy of air.for a cooling tower operating at L/G =1T cold water < saturated temperature of steam at condenser pressure

A condenser in a power plant is a device that converts steam, after it has passed through the turbine, back into water. Its main function is to extract maximum enthalpy or total energy H = U + W. U is internal energy and W is work energy which increases the efficiency of the power plant. The enthalpy (H) is the total energy, which is?the sum of the internal energy of the system plus the product of the pressure of the gas in the system times the volume of the system as explained above. By reducing the pressure below atmospheric pressure, the condenser helps to retain the maximum amount of heat energy in the steam, allowing for better superheating. Overall, the condenser plays an important crucial role in the power plant cycle by maximizing the enthalpy extraction from the steam and ensuring effective energy utilization.

Details

How pressure is set in a condenser?

The condenser pressure is set to maximize enthalpy extraction and obtain the maximum superheat from the steam. The lower the condenser pressure, the more heat can be extracted from the steam, resulting in higher turbine efficiency. By reducing the condenser pressure, the steam expands further in the turbine, maximizing the enthalpy drop and increasing the work output. This improves the overall efficiency of the power plant. Additionally, a lower condenser pressure allows for more superheating of the steam, which increases the thermal output of the steam turbine. Conders are run under vacuum. The pressure is set in the condenser until the steam reaches saturation pressure and all superheat has been extracted to maximize enthalpy to turbine for maximum work.

Cooling tower

It is an important part of a power plant. Regarding heat transfer to the cooling tower, it is a separate calculation from the enthalpy balance across the cooling tower. The primary purpose of the cooling tower is to remove the heat absorbed from the condenser by the coolant (typically water). This is achieved through evaporation.

How does a condenser work?

Limiting pressure of the condenser

A turbine works between two terminal points [1] upstream steam pressure and[2] downstream stream condenser pressure to deliver energy for mechanical work. The pressure in the condenser is set by the cooling tower's cold water temperature. The cold water temperature of the cooling tower must be less than the saturated temperature of vapor at the condenser pressure.. This is the limiting point of condenser pressure.

Here is a typical enthalpy balance across the cooling tower

(T hot - T cold) water =( H out - H in) air, H is the enthalpy of air for a cooling tower operating at L/G =1

T cold water < saturated temperature of steam at condenser pressure

The condenser works at constant pressure

Why? ?

The answer is quite simple. You can extract enthalpy only at constant pressure.

Details

Enthalpy is a thermodynamic property that combines the internal energy of a system with the work done on or by the system. When the steam condenses in the condenser, it releases heat to the cooling medium, resulting in a decrease in enthalpy. This heat transfer process is essential for maximizing energy extraction from the steam. By maintaining a constant pressure, the condenser allows for the efficient extraction of enthalpy from the steam. The constant pressure Cp condition enables the steam to transfer both its internal energy and work, that is total energy, H = U + W, resulting in a higher overall energy extraction. This is because at constant pressure, the steam can continue to deposit its enthalpy even after its internal energy is completely utilized. In contrast, operating at constant volume Cv would limit the heat transfer process to only the steam's internal energy, potentially reducing the overall energy extraction efficiency.

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