In this article, we shall cover the definition, functions, working principle, types, applications, advantages, and disadvantages of Steam Condensers. We have provided a PDF For the same.
What is a Steam Condenser?
A steam condenser is a closed vessel heat exchanger that is used to convert low-pressure steam to water. The pressure inside a steam condenser is kept below the atmospheric pressure to increase efficiency. It is generally used for lowering the backpressure of the exhaust of the turbine end.
The Functions of a Steam Condenser
The functions of the condenser in a steam power plant are the following:
- The steam condenser is used to maintain the low back pressure of the exhaust end of the turbine to increase efficiency and decrease the specific steam consumption of a plant.
- It is used for converting low-pressure steam to liquid i.e. water and we can feed this water again into the boiler without doing any further treatment.
- It also increases the heat transfer rate by eliminating other non-condensable gases from the exhaust steam.
Basic Working Principle of Steam Condenser
Inside a steam condenser, there is a flow of cooling water that is continuously circulating from the condenser to the cooling tower and cooling tower to the condenser. So when exhaust low-pressure steam comes from the turbine and passes through the condenser, it (steam) gets condensed to water, as the steam loses the heat, the extracted heat from the steam is carried out via the circulating cooling water.
There are two types of devices fitted on the condenser, one is the condensate extraction pump, and the other one is the air extraction pump. So when the steam condensed into water, with the help of a condensate extraction pump it is again re-circulated to the steam generator. And via air-extraction pump, the vacuum inside the condenser is created so that cooling water can circulate easily and also the flow of condensate can be stabilized.
Classifications of Steam Condenser
The condenser can be broadly classified into two types which are as follows
- Direct Contact type Condenser
- Surface Condenser
Surface condensers are generally used in power plants. This type of condenser is also called shell and tube type condenser. Here there is no contact between exhaust steam and cooling water. So the extracted condensate can be reused in the boiler without any water treatment.
Within the condenser space, there are several horizontal tubes, inside which cooling water is flowing. At the above portion of the condenser, the exhaust steam enters and flows downwards, when the steam in contact with the tubes inside which cooling water is flowing, the steam gets condensed, here the heat transfer is done by conduction and/or convection. A condensate extraction pump is fitted at the bottom which helps to extract the condensed water from the condenser.
There are two types of water pass, one is a single pass where water is flowing in one direction and the other one is a double pass or two passes where water circulated within the condenser tube in both directions. The details figure of the Single-Pass and Two-Pass condensers are shown in the figure.
Also in this type of condenser, there is a tube sheet is fitted at each end of the condenser where the water tubes are rolled to avoid leakage. Surface Condenser are further categorized into four types
- Downflow surface condenser
- Central flow condenser
- Regenerative condenser
- Evaporative condenser
Down flow Surface Condenser
In the downflow surface condenser exhaust steam from the prime mover enters from the top of the condenser and flows downwards due to the gravitational force and the effect of the air-extraction pump.
When the steam flows downwards it’s in touch with several cooling tubes and loses the heat and gets condensed. Later on, the condensed water is extracted from the bottom surface of the condenser with the help of a Condensate Extraction Pump.
Central Flow Condenser
In central flow condenser, steam enters from the top of the condenser. The suction end of the air extraction pump is fitted at the center of the condenser or tube.
Due to this design, steam is forcefully passed radially which ensures better heat transfer as the contact area of tubes and steam is now more. After heat exchange, the condensate is stored at the bottom of the condenser, and with the help of a condenser removal pump, it is extracted.
In a Regenerative condenser, the condensate is also heated with the help of exhaust steam which comes into the condenser, and then the condensate is fed to the steam generator. It dramatically improves the efficiency of the steam generation plant.
In the evaporative condenser the exhaust steam comes from the turbine and enters the condenser within a tube. At the above section of the condenser, there are a couple of nozzles fitted from which cooling water is sprayed.
When the cooling water is coming into the contact with the tube inside which steam is following then some portion of the cooling water is absorbed heat and vaporized. As the heat is now taken from the steam so it is now converted into water and collected outside of the condenser.
Direct Contact type Condenser
In a direct contact type condenser the steam (Condensate) and the cooling water mix and come together as a single stream. It’s generally available in the market at a low cost, and the design of this type of condenser is pretty much simple. However, where the mixture of cooling water and condensate is not permissible we can’t use this type of condenser.
Direct contact type condensers are further classified into three sub-types
- Jet Condenser
- Barometric Condenser
- Spray Condenser
As it is one type of direct contact type condenser that’s why here condensate and the cooling water is mixed and comes out. Here as the steam comes with the cooling water that’s why recirculating the cooling water to the boiler is not possible until it passes through a water treatment plant. However, the condensing capability of the jet condenser is very much higher than the other.
The jet condenser are further classified into four sub-types
- Parallel flow jet condenser
- Counterflow or Low-level jet condenser
- Barometric or High-level jet condenser
- Ejector Condenser
Parallel Flow Jet Condenser
In a parallel flow jet condenser, the direction of flow of the steam and the direction of flow of the cooling water is the same, both of these come from the top of the condenser and come out after mixing from the bottom of the condenser.
Counter flow or Low-level Jet Condenser
It is just the opposite of a parallel flow jet condenser, here cooling water comes from the top of the condenser, and exhaust steam enters to the condenser from the bottom side section of the condenser. So the direction of the cooling water is downwards, and the direction of exhaust steam is upward. That’s why this type of condenser is called a Counterflow condenser.
Barometric or High-level Jet Condenser
In the barometric condenser, the condenser shell is fitted above the hot well at a height of 10.36 m. To achieve this the discharge section of this type of condenser is fitted with a long vertical pipe, or it is also called a tailpipe.
In this type of condenser, there is no condensate extraction pump is there, the flow is completely done with the help of gravitational force. However, a cooling water injection pump is there to deliver the cooling water from the top of the condenser. The other working of this type of condenser is the same as the Counterflow condenser.
An ejector condenser has a no-return valve through which exhaust steam enters to the condenser. It also has several convergent nozzles which help to decrease the pressure of the inner section of the condenser, hence due to low pressure, the exhaust steam draws into the condenser through the no-return valve, and mixes with the cooling water and condensate.
In the end, there is again a divergent nozzle where the kinetic energy is again converted to the pressure energy, and an increase in the pressure at the exhaust of the condenser helps to extract the condensate out of the condenser.
Applications of Steam Condenser
The applications of Steam Condenser are as follows
- The condenser like the surface condenser is used in the thermal power plant to condensate the exhaust steam from the turbine.
- Steam condensers are used in many food processing industries as well.
Advantages of Steam Condenser
Steam Condenser has some advantages depending on its types which are as follows
Advantages of Direct Contact Condenser
- The jet condenser is simple in design.
- Built-in cost is very much less.
Advantages of Surface Condenser
- In the case of a surface condenser, it dramatically improves vacuum efficiency.
- As in a surface condenser, there is no mixing occurs, so we can get the pure condensate which can be reused in the boiler.
- The quantity of cooling water needed for heat exchange purposes is relatively low.
Disadvantages of Steam Condenser
Steam Condenser has some disadvantages depending on its types which are as follows
Disadvantages of Direct Contact Condenser
- As cooling water and condensate come out in one stream, so here it is not possible to reuse the condensate without water treatment.
- Vacuum efficiency is low in direct contact condensers like the jet condenser.
Disadvantages of Surface Condenser
- Design is complicated so the initial cost is more.
- The maintenance cost of this type of condenser is relatively higher.
- The size of this type of condenser s large so needs more floor space.
A steam condenser converts steam into water and is crucial in many industrial applications. It conserves energy, prevents equipment damage, and is used in power generation, refrigeration, and air conditioning. There are different types with varying pros and cons, including corrosion and leaks. Choosing the right condenser requires careful consideration of system needs and requirements.