Short Answer:

A condenser is a device used in steam power plants to convert exhaust steam from the turbine into water by removing its latent heat. It works by cooling the steam using cold water or air, turning it back into condensate (water), which is then reused in the boiler.

In simple words, a condenser helps maintain low pressure at the turbine exhaust and improves the overall efficiency of the power plant. It also conserves water by recycling it back to the boiler, making the system more economical and efficient for continuous operation.

Detailed Explanation :

Condenser

A condenser is an essential component of a steam power plant that performs the function of condensing or converting the exhaust steam from the turbine into water. This process is achieved by removing the latent heat of vaporization of the steam through a cooling medium, usually cold water or air. The condensed steam, known as condensate, is then reused in the boiler to produce fresh steam, completing the Rankine cycle.

The main purpose of a condenser is to maintain a low pressure at the exhaust of the turbine so that the steam can expand more and do maximum work. By converting steam into water at low pressure, the condenser not only increases the efficiency of the turbine but also minimizes wastage of steam and saves energy.

Working Principle

The working of a condenser is based on the principle of heat transfer — where the heat from the exhaust steam is absorbed by a cooling medium (such as water or air). When the steam comes in contact with the cooling surface, it loses heat and gets converted into water.

In a steam power plant, exhaust steam from the turbine enters the condenser at low pressure. The cooling water flowing through the tubes or over the surface absorbs the heat from the steam. The steam thus condenses into water and is collected in a condensate extraction pump, which sends it back to the boiler for reuse.

The process of condensation helps in:

Reducing back pressure on the turbine, which increases efficiency.
Saving water by reusing the condensed steam.
Reducing the energy requirement of the boiler.

Functions of Condenser

To condense exhaust steam from the turbine into water.
To maintain low back pressure on the turbine exhaust.
To improve the thermal efficiency of the power plant.
To recover and reuse condensate in the boiler feed system.
To minimize steam wastage and operational cost.

Types of Condensers

Condensers are mainly divided into two categories based on the type of cooling medium and the method of condensation.

Surface Condenser

In a surface condenser, exhaust steam and cooling water do not come into direct contact. The cooling water flows inside a set of tubes, while the steam flows over the outside surface of these tubes. The heat from the steam is transferred to the cooling water through the tube walls, condensing the steam into water.

Features:

Used in large power plants.
Condensate is pure and can be reused in the boiler.
Operates under vacuum conditions.

Advantages:

Reuses condensate, saving water.
Suitable for high-capacity steam turbines.
High efficiency due to maintained vacuum.

Disadvantages:

High initial cost.
Requires regular maintenance and cleaning of tubes.

Jet Condenser

In a jet condenser, the exhaust steam and cooling water come into direct contact and mix together. The steam transfers its heat to the cooling water and gets condensed. The mixture of condensate and cooling water is then discharged, usually not reused for boilers.

Features:

Simple design and low cost.
Compact in size and easy to install.
Used in small or medium power plants.

Advantages:

Simple construction.
Low maintenance cost.

Disadvantages:

Condensate cannot be reused directly.
Less efficient compared to surface condensers.

Main Components of a Condenser

Condenser Shell: The outer body that contains the steam and cooling arrangement.
Tubes: Carry cooling water in surface condensers for heat exchange.
Inlet and Outlet Nozzles: For steam entry and exit of cooling water.
Condensate Extraction Pump: Removes condensed water from the condenser.
Air Pump: Removes non-condensable gases to maintain a vacuum.
Cooling Water Circulation Pump: Circulates cooling water through tubes or nozzles.

Importance of Vacuum in Condenser

A vacuum is maintained in the condenser to ensure that the steam expands completely in the turbine. The vacuum reduces the back pressure on the turbine blades, allowing more work to be done by the steam before condensation.

If air or gases leak into the condenser, the vacuum is reduced, lowering efficiency. Hence, an air extraction pump is used to continuously remove these non-condensable gases and maintain the required vacuum level.

Advantages of Using a Condenser

Improved Efficiency: Low back pressure increases the expansion of steam and improves turbine efficiency.
Water Conservation: Condensate is reused, saving a large amount of water.
Reduced Fuel Consumption: The boiler requires less heat to convert condensate back into steam.
Better Performance: Maintains steady operation and increases plant reliability.
Environmental Benefits: Reduces steam and heat wastage into the atmosphere.

Applications of Condenser

Used in thermal power plants to improve turbine efficiency.
Found in refrigeration and air-conditioning systems to condense refrigerants.
Used in marine engines for steam recovery and reuse.
Employed in chemical and process industries where vapor condensation is required.

Conclusion

In conclusion, a condenser is a vital component of a steam power plant that condenses exhaust steam into water by removing its heat. It helps maintain low back pressure in the turbine, increases efficiency, and conserves water by reusing the condensate. Condensers can be of two main types—surface condenser and jet condenser—depending on whether steam mixes with cooling water or not. A properly designed and maintained condenser ensures economical operation, energy savings, and improved performance of the entire power generation system.