Surface Condenser: Definition, Working Principle, Construction, Types, Applications, Advantages, and Disadvantages [Notes with PDF]

In this article, you will be going to learn about Surface Condenser, so let’s get started!

What is a Surface Condenser?

A surface condenser is a device used in thermal power plants which converts steam into water without any physical contact between steam and coolant. The surface condenser is one of the most important devices used in thermal power plants. If a surface condenser is not used in a thermal power plant, a large amount of water will be needed in order to run the plant. 

Construction of a Surface Condenser:

A cylindrical type surface condenser consists of a large cylindrical vessel. Water tubes are fitted horizontally inside the cylinder, and there is a continuous flow of water inside the tubes. The direction of flow of water in the upper half of the tubes is opposite to that of the lower half of the tubes.

There are water inlets and water outlets. There are two water storage tanks located at two horizontal ends of the cylindrical vessel. A baffle is provided for separation. Steam enters the cylinder from the exhaust steam inlet. There is a valve at the bottom of the condenser from where condensate can be extracted. Two perforated tubes are perpendicular to the water carrying tubes.

Single Pass Surface Condenser
Diagram of a Surface Condenser, Learn Mechanical

Principle and Working of Surface Condenser:

Basic working principle of a surface condenser is transfer of heat from a higher temperature body to a lower temperature body. In a surface condenser steam (high temperature body) liberates its heat to the cooling water tubes ( low temperature body). The process of heat transfer the hot steam gets converted to water. 

The steam enters from the exhaust Steam inlet and comes in contact with the water carrying tubes. The water in the tubes has a circulating flow.  As soon as the exhaust steam comes in contact with the water-cooled tubes, the process of heat transfer begins. The heat from the steam is removed and converted into a liquid which Is known as condensate. This condensate is then removed from the cylindrical vessel through a valve located at the bottom of the cylinder.

Types of Surface Condenser:

There are 4 basic types of surface condensers,

  1. Downflow surface condenser
  2. Central flow surface condenser
  3. Evaporative surface condenser
  4. Regenerative surface condenser

#1 Down-Flow Surface Condenser:

In a downflow surface condenser, the hot steam enters from the top of the condenser. The flow of steam in the ‘downflow surface condenser’ is in the y (-ve) direction that is in a downward direction with respect to the whole system. The flow of steam is downwards because of gravity and vacuum created by the air pump.

The water tubes are present in between, where the flow of water is perpendicular to the direction of the flow of steam, that is in z(-ve) and z(+ve) directions simultaneously. A baffle is present in the condenser, which does not allow the steam to reach the air filters. As soon as the exhaust steam comes in contact with the water-cooled tubes, the process of heat transfer takes place as a result of which steam loses its heat to the cooling water tubes and condensate gets deposited at the bottom. This condensate is then extracted through a valve.

Down Flow condenser
Diagram of Down-flow surface condenser, Learn Mechanical

#2 Central Flow Surface Condenser:

A central flow surface condenser is an advanced and improved version of a downflow surface condenser. The only difference is that in the central flow surface condenser the air pump is situated at the center of the system, unlike the downflow surface condenser. The exhaust steam enters from the top due to gravity.

The direction of the exhaust steam is changed and forced towards the center of the system with the help of an air pump. This is the reason why this system is named a central flow surface condenser. The direction of flow of steam and cooling water is perpendicular to the surface of the tube. Heat transfer between water and steam takes place when steam and cooling tubes come in contact with each other, hence there is a formation of condensate.

Central Flow condenser
Diagram of Central-flow surface condenser, Learn Mechanical

#3 Evaporative Surface Condenser:

This type of condenser is known as an Evaporative condenser because the cooling water gets evaporated in such types of condensers. In Evaporative condensers, the hot steam flows inside the tubes and cooling water is sprayed on it. The cooling water from the cooling tank reaches the header with the help of a pump.

The header sprays water over the tubes carrying hot steam. As soon as the water comes in contact with the hot tubes it evaporates and steam inside the tubes gets converted to liquid. Fins are attached to the tubes in order to increase the surface area and decrease the time for cooling.

Evaporative condenser
Diagram of Evaporative condenser, Learn Mechanical

#4 Regenerative Surface Condenser:

A regenerative surface condenser is suitable for high-temperature plants. The type of condensate used here is known as regenerative condensate. The temperature of condensate is increased by passing it through exhaust steam.

Due to high-temperature condensate can be reused.

The efficiency of the condenser is increased.

Applications of Surface Condensers:

Surface condensers are used in different sectors, those are:

  • Thermal power stations:

In thermal power stations, water is heated more than its boiling point in order to generate steam which in turn is used to rotate the turbine. After passing through the turbine the steam is fed into a surface condenser where it is converted into water and then reused. 

  • Caustic recovery plants:

In a caustic recovery plant, weak soda lye is converted to strong caustic soda by treating it. This treatment involves the emission of heat in the form of steam. This is where a surface condenser is used to convert the steam into condensate (weak lye) which is to be reused. 

  • Treatment of contaminants:

Contaminated water is a general problem for any industry these days. Surface Condenser alone cannot fulfil the requirement hence Ejectors using surface condensers are used for treatment.

Advantages of Surface Condenser:

The advantages of surface condenser are:            

  • Quality of cooling water:

Any quality of cooling water can be used in surface condensers because there is no direct contact of cooling water and exhaust steam. 

  • Suitable for high capacity plants:

Due to its large size and better efficiency than jet condensers, surface condensers can be used for heavy industrial purposes. 

  • Pure condensation:

Pure condensation is possible in the case of a surface condenser as there is no mixing of exhaust steam and cooling water, so the quality of condensate obtained is pure. This condensate can also be used as boiler feedwater. 

  • High vacuum:

The vacuum created by the air pump is high in the case of surface condensers. This helps in removing uncondensed air and lowers the pressure inside the condenser. This low pressure in turn increases the thermal efficiency of surface condensers.

  • Air pump power:

The power required to drive the air pump in a surface condenser is much less than the power required to drive a pump in a jet condenser. 

Disadvantages of Surface Condenser:

There are a couple of drawbacks of using a surface condenser, those are:

  • Complex design:

Design of a surface condenser is quite complex. There are several mechanical parts working at the same time. It is difficult to understand the complex design of a surface condenser. 

  • Handling: 

Handling of a surface condenser is not easy; it requires skilled labors. Due to the complex engineering involved, the handling should be done with care to avoid any human injuries. 

  • Large size of the condenser:

A surface condenser is used for heavy industrial purposes hence the size of condensers are quite large. Therefore the whole setup of surface condenses requires a large area.

  • Cost of surface condenser:

Due to its large size the cost of surface condensers are high. It requires more power hence the cost of running also becomes more.

  • Quantity of water required:

As the size of equipment is large and it is used for heavy industrial purposes. The amount of water required to efficiently run a condenser is also high.


This is all about Surface Condenser, I hope you found this article helpful. Do let me know if you have any doubts or queries on this topic by leaving comments below.

More Resources:

Media Credits:

  • All the images are made by Saubhik Roy-Design Team LM.
  • Feature Image is modified by the author.


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Anup Kumar Dey

A Mechanical Engineer with 19 years of working experience in various renowned MNCs.

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