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Condensers &

Cooling Towers

byMr. S. R. Khandagale

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CondenserIt is a device which condenses working fluid with the help of cooling media (another circulating fluid)

• IF cooling media is air Air cooled condenser mostly used in refrigeration or mobile equipment

• IF cooling media is water water cooled condenser mostly used in stationary plants

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Steam condenserIt is condenser which is used to condense steamSteam condensers are mostly water cooled i.e. in steam condenser working fluid steam cooling media water• Functions 1. Maintain condensing pressure below atmospheric for improving efficiency2. to supply hot(?) and pure water to cycle again

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Elements in condensing plant

• (

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ClassificationDepending upon contact of working fluid and cooling media

A. Jet condenser Direct Contact B. Surface Condenser Indirect contact

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Jet Condenser

a. Low level jet condenser Cooling water required to lift up to 5.5 m i. Counter flow Cooling media & steam flow in opposite direction ii. Parallel Flow Cooling media & steam flow in same direction

b. High level jet condenser Cooling water required to lift above 10.33 mc. Ejector jet condenser

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1. Low level Counter flow jet steam condenser

Condensate extraction pump Required

Cooling water pump Not required

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2. High level counter flow jet condenser

Cooling water pump required Condensate extraction pump not required

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Ejector Condenser

1. Non return valve

2. Convergent Nozzle: It reduces pressure of cooling water

3. Convergent divergent nozzleIt increases pressure on mix of cooling water and steam upto atmospheric

This system is simple, reliable and cheap

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B. Surface Condenser

1. Shell and tube surface condenser a. Single Pass b. Double Pass

2. Central flow surface condenser3. Down flow surface condenser4. Inverted flow surface condenser

5. Evaporative condenser

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Shell and tube Surface Condenser

Cooling water flows through tubes

Steam flows through shell

As cooling water passes 2 times it is double pass condenser

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Down Flow Surface Condenser

Steam extraction pump at down

Baffles guides the steam flow .

Also called cross flow heat exchanger as steam & water fow right angles to each other

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CENTRAL FLOW SURFACE CONDENSER

Air extraction pump is located at the center of the condenser tubes.

Provides the better contact of steam

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EVAPORATIVE CONDENSER (Cooling water evaporates)

Cooling water evaporates

Steam through pipes Cooling water sprinkles through nozzles

Fins are provided to a)Act as obstruction to flow of water drops

b) increase heat transfer surface area

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JET CONDENSER SURFACE CONDENSER

Direct contact Indirect contact

Condensation due to mixing Condensation due to heat transfer by conduction and convection

Maintenance cost is low Maintenance cost is high.

Less Vacuum created More Vacuum created

Small floor space required Large floor space required

Condensate can not be directly used as feed water

Condensate can be directly used as feed water

Less power for pumping More power for pumping

Less quantity of cooling water required Large quantity of cooling water required

Suitable for low capacity plants Suitable for large capacity plants

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Cooling Tower• Cooling towers are commonly used to remove

excess heat that is generated & represent a relatively inexpensive and dependable means of

removing low-grade heat from cooling water

Working fluid cooling water Cooling media air

Some of cooling water evaporates leading to cooling effect

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Cooling tower types

• Natural draft Air circulation due to density differences

• Mechanical or forced or induced draft Air circulation due to fans

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Natural Draft Cooling Towers. Flow is due to sprays or a differential in air density

air velocities for the vertical spray tower are relatively low

normally used when operating temperatures are not critical to the system.

staged pumping systems are normally recommended to reduce energy use in periods of reduced load and ambient conditions.

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Mechanical / forced /induced draft cooling towers

Air Circulation is due to fans

Increased air flow improves evaporation rate

centrifugal fan Incoming airaxial air Outgoing air

Higher capacity

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Factors governing operation of Cooling tower

• The dry-bulb and wet-bulb temperatures of the air

• The temperature of warm water

• The area of contact between air and hot water

• The contact time between the air and the water

• The air pressure drop

• The desired temperature of the cooled water