Steam Condenser Function: How it Works in Condensing Steam Locomotives

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Questions and Answers

What is the main purpose of a steam condenser?

To increase back pressure on the exhaust side of the piston

To condense steam and absorb heat released by it (correct)

To decrease thermal efficiency of the engine

To reduce the available heat energy for converting into mechanical work

Why does a condensing unit have higher thermal efficiency compared to a non-condensing unit?

Because it allows the steam to expand to a greater extent (correct)

Because it can only be used with high-pressure steam engines

Because it uses more water for cooling purposes

Because it has a higher back pressure

Which organ of a Steam Condensing Plant is responsible for removing the condensed steam, air, and uncondensed water vapour and gases from the condenser?

Hot well

Wet air pump (correct)

Condenser

Supply of cooling water

What is the function of the hot well in a Steam Condensing Plant?

To collect and discharge the condensate and provide boiler feed water Signup and view all the answers

Which component of a Steam Condensing Plant is responsible for removing heat released by steam?

Condenser Signup and view all the answers

How does a condensing unit benefit the available heat energy for converting into mechanical work?

By allowing the steam to expand to a greater extent Signup and view all the answers

What is the function of a turbine nozzle in an impulse turbine?

Converts kinetic energy into shaft work Signup and view all the answers

What is the purpose of the throat in a convergent-divergent nozzle?

To allow steam expansion without changing velocity Signup and view all the answers

Why does a convergent-divergent nozzle produce steam at higher velocities than a convergent nozzle?

Because of higher expansion ratio Signup and view all the answers

What effect does internal friction of steam have on nozzle efficiency?

Increases the enthalpy drop Signup and view all the answers

Which factor contributes to frictional losses in a convergent-divergent nozzle?

Conversion of kinetic energy into heat Signup and view all the answers

What is the adiabatic assumption about the flow of steam through a nozzle?

Neither heat is supplied nor rejected during expansion Signup and view all the answers

What type of surface condenser has the air suction at the top and the steam enters at the bottom?

Inverted flow type Signup and view all the answers

Which type of surface condenser allows the exhaust steam to flow in a direction right angle to the direction of flow of water?

Down flow type Signup and view all the answers

What is the underlying principle of an evaporative condenser?

Evaporating water under partial pressure Signup and view all the answers

What is a key advantage of using a surface condenser?

Condensate can be reused for boiler feed water Signup and view all the answers

Which factor contributes to reducing the pressure drop of steam in a central flow type condenser?

Large passages for steam flow Signup and view all the answers

What distinguishes a regenerative type condenser from other types?

Applies a regenerative method of heating the condensate Signup and view all the answers

Why is it important to clean the cooling water used in surface condensers?

To avoid dust accumulation in tubes Signup and view all the answers

What is the purpose of a non-return valve provided at the exhaust steam inlet?

To prevent failure of cooling water supply to condenser. Signup and view all the answers

What is the formula to calculate the corrected vacuum in mm of Hg?

760 - (Actual barometric height - Actual vacuum) Signup and view all the answers

What is the formula for vacuum efficiency?

Actual vacuum/Maximum obtainable vacuum Signup and view all the answers

What does condenser efficiency measure?

The difference between inlet and outlet temperatures of cooling water Signup and view all the answers

What is the purpose of a cooling tower in power plants?

To cool the hot water from the condenser for reuse Signup and view all the answers

Which factor does NOT affect the cooling of water in a cooling tower?

Temperature of hot water Signup and view all the answers

What distinguishes natural draught cooling towers from mechanical draught cooling towers?

Usage of fans for air circulation Signup and view all the answers

What are some advantages of concrete hyperbolic cooling towers over mechanical towers?

Lower initial cost Signup and view all the answers

What is the main function of a steam nozzle?

To drive steam turbines with high-velocity steam jet Signup and view all the answers

Which classification is NOT used for cooling towers based on material composition?

Mechanical draught Signup and view all the answers

In a natural draught cooling tower, how is heat removed from falling water?

By direct contact with rising air and evaporation Signup and view all the answers

What is the difference between a jet condenser and a surface condenser?

In a jet condenser, the exhaust steam and water come into direct contact, while in a surface condenser they do not. Signup and view all the answers

What is the purpose of a baffle plate in a low level jet condenser?

To ensure proper mixing of steam and cooling water Signup and view all the answers

Which type of jet condenser does not require an extraction pump?

High level counter-flow Signup and view all the answers

What is the purpose of the perforated trays in a low-level counter-flow jet condenser?

To break up water into jets Signup and view all the answers

What is another name for a high-level counter-flow jet condenser?

Barometric condenser Signup and view all the answers

What is the function of an air suction pump in a low level jet condenser?

To remove air from the system Signup and view all the answers

Where does the cold water flow in an ejector condenser?

Cold water flows downward through hollow cones. Signup and view all the answers

What happens to the pressure energy of condensed steam, cooling water, and air in an ejector condenser?

It decreases to atmospheric pressure. Signup and view all the answers

Study Notes

Vacuum Measurement and Correction

Vacuum is measured in mm of Hg using a vacuum gauge
Corrected vacuum in mm of Hg = (760 - Absolute pressure in mm of Hg) = 760 - (Actual barometric height - Actual vacuum)

Vacuum Efficiency

Defined as the ratio of actual vacuum to maximum obtainable vacuum
Maximum obtainable vacuum is when only steam is present in the condenser, with no air
Vacuum efficiency = Actual vacuum / Maximum obtainable vacuum = Actual vacuum / (Barometer pressure - Absolute pressure of steam)

Condenser Efficiency

Defined as the ratio of the difference between outlet and inlet temperatures of cooling water to the difference between the temperature corresponding to the vacuum in the condenser and inlet temperature of cooling water
Condenser efficiency = Rise in temperature of cooling water / (Temp. corresponding to vacuum in the condenser - Inlet temp. of cooling water)

Cooling Towers

Used to cool hot water from the condenser so it can be reused
Water is made to trickle down in contact with air, causing some water to evaporate and cool the remaining water
Factors affecting cooling of water in a cooling tower:
- Temperature of air
- Humidity of air
- Temperature of hot water
- Size and height of tower
- Velocity of air entering tower
- Accessibility of air to all parts of tower
- Degree of uniformity in descending water
- Arrangement of plates in tower

Classification of Cooling Towers

Natural draught cooling towers
Mechanical draught cooling towers
- Forced draught cooling towers
- Induced draught cooling towers

Natural Draught Cooling Tower

Hot water is pumped to troughs and nozzles, then sprayed into a pond, where air enters and takes up heat
Advantages:
- Low operating and maintenance cost
- Trouble-free operation
- Less ground area required
- Can be built to withstand high winds
Disadvantages:
- High initial cost
- Performance varies with seasonal changes in air temperature and humidity

Steam Condenser

A device that condenses steam and absorbs heat released by steam
Serves two purposes:
1. Maintains a very low back pressure on the exhaust side of the piston or turbine
2. Supplies pure and hot feed water to the boiler

Organs of a Steam Condensing Plant

Condenser
Supply of cooling water
Wet air pump (to remove condensed steam, air, and uncondensed water vapor and gases)
Hot well (where condensate is collected and used as feed water for the boiler)

Steam Nozzle

A passage of varying cross-section that converts heat energy of steam into kinetic energy
Major function: to produce a steam jet with high velocity to drive steam turbines
Two types:
- Convergent nozzle
- Convergent-divergent nozzle

Steam Flow through Nozzles

Assumed to be adiabatic flow since no heat is added or rejected during expansion
Work done is equal to adiabatic heat drop, which is equal to Rankine area

Nozzle Efficiency

Defined as the ratio of actual velocity of steam to ideal velocity
Reduced due to frictional losses between the nozzle surface and steam, and internal friction of steam itself
Derivation of nozzle efficiency is shown in diagrams

Surface Condensers

Classified into:
- Down flow type
- Central flow type
- Inverted flow type
- Regenerative type
- Evaporative type
Advantages:
- Slightly better vacuum can be obtained
- No need to treat the condensate chemically
- High vacuum (about 73.5 cm Hg) can be obtained
- Condensate can be reused as boiler feed water
- Low pumping power required
- Less chance of losing vacuum
Disadvantages:
- High initial cost
- Requires large floor area
- High maintenance cost
- More head is necessary to obtain sufficient head on hot well pump
- Proper cleaning of cooling water is necessary

Classification of Condensers

Jet Condenser
- Parallel-flow type
- Counter-flow type
- Ejector type
Surface Condenser
- Single-pass type
- Double-pass type

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Description

Explore the functions and benefits of a steam condenser, including its role in maintaining low back pressure on the exhaust side of a steam engine or turbine. Learn how a condensing unit can increase available heat energy for converting into mechanical work and improve thermal efficiency.

Steam Condenser Functions and Benefits

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