39 Questions
What is the main purpose of a steam condenser in a steam engine or turbine?
To maintain a very low back pressure on the exhaust side
What happens to the thermal efficiency of a condensing unit compared to a non-condensing unit?
Thermal efficiency increases
Which organ is responsible for removing the condensed steam, air, and uncondensed water vapor and gases from the condenser in a steam condensing plant?
Wet air pump
What is the function of the hot well in a steam condensing plant?
To discharge condensate and provide boiler feed water
How does a steam condenser impact the available heat energy for converting into mechanical work?
Increases the available heat energy
Which element of a steam condensing plant helps convert the condensed steam into boiler feed water?
Hot well
What is the primary function of a turbine nozzle?
To convert a portion of steam energy into kinetic energy
In what type of turbine does the nozzle direct high-velocity steam against blades?
Impulse turbine
What is the purpose of the throat in a convergent-divergent nozzle?
To allow for changes due to steam expansion
Why does a convergent-divergent nozzle produce steam at higher velocities compared to a convergent nozzle?
Due to higher expansion ratio
What leads to the reduction in final velocity of steam in a nozzle?
Shock losses at the nozzle exit
Why does friction between the nozzle surface and steam affect nozzle efficiency?
Causes frictional heat increase and absorption by steam
What is the main difference between a jet condenser and a surface condenser?
In a jet condenser, the steam and water come in direct contact, while in a surface condenser they do not.
Which type of condenser is preferred when the cooling water can be easily made suitable for the boiler feed?
Jet condenser
What is the purpose of the baffle plate in a low-level parallel-flow jet condenser?
To ensure proper mixing of steam and cooling water
Which type of jet condenser obviates the need for an extraction pump due to its height above the hot well?
High level jet condenser (Counter-flow)
How does an ejector condenser function to draw in exhaust steam and associated air?
By increasing steam velocity through cones to decrease pressure
What distinguishes counter-flow type jet condensers from parallel-flow type?
In counter-flow type, steam and cooling water enter from opposite directions.
Why is a surface condenser commonly used?
To return the condensate back to the boiler.
What happens to the kinetic energy in an ejector condenser's diverging cone?
It converts into pressure energy higher than atmospheric pressure.
In what direction does cooling water flow in a single-pass surface condenser?
In one direction through all tubes.
Which type of surface condenser has a provision for its own injection pump?
High level surface condenser.
What is the formula to calculate corrected vacuum in mm of Hg?
(760 - Absolute pressure in mm of Hg)
How is vacuum efficiency defined?
The ratio of the actual vacuum to the maximum obtainable vacuum
What does condenser efficiency measure?
The ratio of the temperature corresponding to the vacuum and inlet temperature of cooling water
How are cooling towers classified based on the material used?
(a) Timber, (b) Concrete, (c) Steel duct type
What is a disadvantage of natural draught cooling towers?
Performance variation with seasonal changes in air temperature
In a cooling tower, what is cooled due to evaporation?
The bulk of water
What is the main function of a steam nozzle?
To convert heat energy of steam to kinetic energy
What is the formula for calculating vacuum efficiency?
(Actual vacuum / Maximum obtainable vacuum)
'Condenser efficiency' can be defined as _____.
(Rise in temperature of cooling water) / (Temp.corresponding to the absolute pressure in the condenser - Inlet temp. of cooling water)
'Cooling Towers' are used in power plants primarily for _____.
"Cooling hot water from condenser to be reused for steam condensation"
What type of condenser has the air suction at the top, with steam rising up and then flowing back down near the outer surface of the condenser?
Inverted flow type
Which type of condenser is applied to condensers adopting a regenerative method of heating of the condensate?
Regenerative type
What is the main advantage of a surface condenser mentioned in the text?
High vacuum can be obtained
What is a key disadvantage of surface condensers according to the text?
High maintenance cost
Which type of condenser requires proper cleaning of cooling water to avoid accumulation of dust inside the tubes?
Evaporative type
In which type of condenser is there no direct contact between cooling water and steam, allowing even poor quality cooling water to be used?
Inverted flow type
What does a vacuum in case of a condenser mean?
Pressure below atmospheric pressure
Study Notes
Classification of Condensers
- Jet Condensers:
- Exhaust steam and water come in direct contact
- Temperature of condensate is the same as cooling water leaving the condenser
- Types: parallel-flow, counter-flow, and ejector types
- Surface Condensers:
- Exhaust steam and water do not come in direct contact
- Steam passes over outer surface of tubes through which cooling water is maintained
- Types: single-pass, double-pass, down flow, central flow, inverted flow, regenerative, and evaporative types
Low Level Jet Condensers
- Parallel-flow type:
- Exhaust steam and cooling water enter from the top and flow downwards
- Baffle plate ensures proper mixing of steam and cooling water
- Extraction pump discharges condensate to the hot well
- Counter-flow type:
- Steam moves upwards and comes in contact with water, which gets condensed
- Condensate and water mixture is sent to the hot well by an extraction pump
- Air is removed by an air suction pump
High Level Jet Condensers
- Counter-flow type:
- Shell is placed at a height of about 10 meters above the hot well
- No extraction pump is required, but an injection pump is needed if water is not under pressure
Ejector Condensers
- Exhaust steam and cooling water mix in hollow truncated cones
- Cold water flows down through the cones, increasing its velocity and decreasing its pressure
- Exhaust steam and air are drawn through the cones and finally lead to a diverging cone
- Condensate is discharged into the hot well
Nozzles
- Types: convergent, convergent-divergent
- Convergent-divergent nozzles produce steam at higher velocities due to higher expansion ratio
- Nozzle efficiency is affected by frictional losses, including friction between nozzle surface and steam, internal friction of steam, and shock losses
Steam Condensing Plant
- Organs: condenser, supply of cooling water, wet air pump, hot well, and vacuum gauge
- Functions: maintains low back pressure, supplies pure and hot feed water to the boiler, and increases thermal efficiency
Vacuum Efficiency
- Defined as the ratio of actual vacuum to maximum obtainable vacuum
- Maximum obtainable vacuum is obtained when there is only steam and no air in the condenser
Condenser Efficiency
- Defined as the ratio of the difference between outlet and inlet temperatures of cooling water to the difference between temperature corresponding to the vacuum in the condenser and inlet temperature of cooling water
Cooling Towers
- Types: natural draught, mechanical draught (forced draught and induced draught)
- Factors affecting cooling: temperature of air, humidity, temperature of hot water, size and height of tower, velocity of air, accessibility of air, degree of uniformity in descending water, and arrangement of plates
Surface Condensers
- Advantages: slightly better vacuum, no need to treat condensate chemically, high vacuum, condensate can be reused, low pumping power, and less chances of losing vacuum
- Disadvantages: high initial cost, large floor area, high maintenance cost, more head is necessary, and proper cleaning of cooling water is necessary
Learn about the purpose and benefits of a steam condenser, including how it helps maintain low back pressure on the exhaust side of a steam engine or turbine, leading to increased thermal efficiency. Discover the importance of steam condensers in converting heat energy into mechanical work.
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