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Double pipe heat exchanger • Two sets of concentric pipes, two connecting tees, and a

return head and a return bend.• A device whose purpose is the transfer of thermal

energy between two fluids.

• Heat Exchanger-HX

• Common applications: Boilers, Coolers, Condensers, Evaporators.

• Common design consists of tow fluids separated by a conducting medium.

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Classification

Heat transfer mechanism Degree of surface compactness Heat transfer type Flow arrangement Number of passes Construction

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Classification Direct contact type: Cooling towers, Spray towers Indirect contact type

Cooling tower Spray tower

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Classification Single Pass arrangement Multiple pass arrangement

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Classification The choice of a particular flow arrangement depends

upon the required heat exchanger effectiveness, fluid flow paths, allowable thermal stresses, temperature levels and other design criteria.

Heat exchangers may be classified according to their flow arrangement. • Parallel-flow • Counter-flow • Cross-flow• Divided-flow• Split-flow

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Classification

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Classification The heat exchangers classify based on geometry of

construction are,• Plate Heat Exchangers• Extended surface Heat Exchangers• Tubular Heat Exchangers

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Classification Plate Heat Exchanger

• Limited to below 25 bar and 2500C

• Plate heat exchangers have three main types : gasketed ,spiral and lamella heat exchangers.

• The most common of the plate-type heat exchangers is the gasketed plate heat exchanger

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Classification

Plate type heat exchanger

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Classification

Spiral heat exchanger

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Classification

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Classification Plate Heat Exchanger

Aadvantages

• Plate heat exchangers yield heat transfer rates three to five times greater than other types of heat exchangers.

• The design of the plate heat exchanger allows to add or remove plates to optimize performance, or to allow for cleaning, service, or maintenance.

• Plate exchangers offer the highest efficiency mechanism for heat transfer available in industry.

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Classification Plate Heat Exchanger

Disadvantages

• Plate exchangers are limited when high pressures, high temperatures, or aggressive fluids are present.

• Because of this problem these type of heat exchangers have only been used in small, low pressure applications such as on oil coolers for engines.

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Classification Extended surface heat exchangers

• Plate fin heat exchanger

• Tube fin heat exchanger

Tube fin exchanger Plate fin exchanger

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Classification

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Classification

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Classification Tubular heat exchanger

• Material and design development

• Widely used

• No limit to range of temperatures and pressures

• Two types

1. Double pipe heat exchanger

2. Shell and tube heat exchanger

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Classification Double pipe heat exchangerThey consist of one pipe concentrically located inside a second larger pipe.

Double pipe exchanger

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Classification Phase change heat exchangers

• Condensers(water cooled, air cooled)• Reboilers• Evaporators

Air cooled condenser

Forced draft

Induced draft

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Classification Phase change heat exchangers

Water cooled condenser

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Classification Area density: Ratio of heat transfer area to the volume

of heat exchanger Compact Heat exchanger

• Area density greater than 700 m2/m3 or 213 ft2/ft3 or hydraulic diameter ≤ ¼ inch for gas stream.

• Area density greater than 400 m2/m3 or 122 ft2/ft3 for liquid stream).

Non-compact Heat exchanger

• Area density less than 700 m2/m3 for gas stream.

• Area density less than 400 m2/m3 for liquid stream.

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Classification

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