In this article, I'm going discuss about Steam Condenser in briefly. At the end of this article, you will learn How a Steam Condenser works, Definition and Types of a steam condenser, and more. So let's get started.
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 or Needs of a Steam Condenser:
The functions or the needs of the condenser in a steam power plant are the following:
As I mentioned above a steam condenser is used to maintain the low back pressure of the exhaust end of the turbine to increases the efficiency and decrease the specific steam consumption of a plant.
It is used for converting the low-pressure steam to the liquid for 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 which is continuously circulating from condenser to 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 two types of device 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, by the help of condensate extraction pump it is again re-circulate 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 flow of condensate can be stabilized.
This is the basic phenomena on how a steam condenser works, in the next section we will see the classification of the steam condenser, and how each type of condenser works in details.
Classifications of Steam Condenser:
The condenser can be broadly classified into two types:
Direct Contact type Condenser
Direct Contact type Condenser:
In direct contact type condenser the steam (Condensate) and the cooling water mixes and come together as a single stream.
It's generally available in the market as 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 condenser is three types:
As it is one type of direct contact type condenser that's why here condensate and the cooling water is mix together and comes out. Here as the steam comes with the cooling water that's why recirculating of 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 can be categorized into 4 more types:
Parallel flow jet condenser
Counterflow or Low-level jet condenser
Barometric or High-level jet 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 same, both of this comes from the top of the condenser and comes out after mixing from the bottom of the condenser.
Counter flow or Low-level Jet Condenser:
It is just the opposite of 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 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 tailpipe.
In this type of condenser, there is no condensate extraction pump is there, the flow is completely done by 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 same as 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 increase the pressure at the exhaust of the condenser which helps to extract the condensate out of the condenser.
Now let's talk about the other type of condenser that is Surface Condenser.
Surface condensers are generally used in the power plant. 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 flowing 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 condense water from the condenser.
There are two types of water pass, one is single-pass where water is flowing in the 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 Single-Pass and Two-Pass condenser 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 is categorized into four types:
Downflow surface condenser
Central flow condenser
Down flow Surface Condenser:
In downflow surface condenser exhaust steam from the prime over enters from the top of the condenser and flows downwards due to the gravitational force and the effect of air-extraction pump.
When the steam flows downwards it's in touch with several cooling tubes and lose the heat and get condensed. Later on the condense water extract from the bottom surface of the condenser by the help of Condensate Extraction Pump.
Central Flow Condenser:
In this type of condenser, steam enters from the top of the condenser. The suction end of the air extraction pump is fitted at the centre of the condenser or tube.
Due to this design, steam is forcefully passed radially which ensure better heat transfer as the contact area of tubes and steam is now more. After heat exchange, the condensate stored at the bottom of the condenser and by the help of condenser removal pump it is extracted.
In this type of condenser, the condensate is also heated by the help of exhaust steam which comes into the condenser, and then the condensate is feed to the steam generator. It dramatically improves the efficiency of the steam generation plant.
Here the exhaust steam comes from the turbine enters into 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 vapourised. As the heat is now taken from the steam so it is now converted into water and collected outside of the condenser.
Applications of Steam Condenser:
The applications of Steam Condenser are listed below:
Condenser like 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:
As there are two types of condenser available one is direct contact condenser, and the other one is the surface condenser, so it obvious that their advantages will be different as well.
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 surface condenser, it dramatically improves the vacuum efficiency.
As in surface condenser, there is no mixing occurs, so we can get the pure condensate which can be reused in the boiler.
Quantity of the cooling water needed for heat exchange purpose is relatively low.
Disadvantages of Steam Condenser:
Steam Condenser also have some disadvantages, they are listed below according to the types:
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 condenser 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.
So there you have it: A Overview of Steam Condenser.
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