Heat Ex Changers Types

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Heat Exchangers

Heat exchangers are used to transfer heat from one stream to

another. They are used to heat streams and to cool streams.The streams can be heated or cooled by other process streams,or they can be heated by steam and cooled by cooling water.

Design Constraints

1. Cost wish to have an exchanger that costs the least.

2. Efficiency wish to have an exchanger that operates mostefficiently, with minimum loss of energy in the transfer, andminimum drop in pressure of the fluids.

3. Space wish to have an exchanger that is small.

4. Materials want an exchanger built from materials that arecompatible with the process streams and dont cost a lot.

5. Maintenance want an exchanger that can be easily cleaned.

6. Ease of construction.

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Heat Exchangers

Typical questions that chemical engineers might have about

heat exchangers:

1. What size heat exchanger do I need in a new process?

2. What type of heat exchanger do I need in a new process?

3. What are the heat transfer coefficients on the tube side andon the shell side?

4. Is an existing heat exchanger operating properly?

5. How much fouling can the exchanger withstand before theperformance is degraded? How do I know if this has

occurred with an operating heat exchanger?

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Heat Exchangers

The driving force for the operation of a heat exchanger is thetemperature difference between the fluids. The higher thetemperature difference, the smaller the heat exchanger.However, the temperature difference is limited by boilingpoints of the liquids, scaling, materials of construction, etc.

The proper design of a heat exchanger is a trade-off of priceand performance.

Heat Exchangers: Chapter 15 in McCabe et al., 6th edition.

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Heat Exchangers - Types

Heat exchangers come in many different types:

1. Co-current.

2. Counter-current

3. Double pipe

4. Spiral

5. Finned

6. Compact

7. Shell and tube (most common in chemical processindustries)

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Heat Exchangers - Types

Co- and Counter- current: The exchanger is constructed of

concentric tubes. One fluid occupies the outer pipe, the other theinner.

Co-current: fluids flow in same direction

Counter-current: fluids flow in opposite direction

Co-current Counter-current

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Heat Exchangers - Types

Double-Pipe: A heat exchanger built from concentric tubes.

These are simple to construct, but may require a lot of physicalspace to achieve the desired heat transfer area. Can be used forgases and liquids.

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Heat Exchangers - Types

Double-Pipe Heat Exchanger

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Heat Exchangers - Types

Double-Pipe Heat Exchanger

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Heat Exchangers - Types

Spiral: Constructed from sheets of metal wound in a circular

fashion. The fluids flow in adjacent chambers between the sheetsof metal.

This design is based

on the ease offabrication.

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Heat Exchangers - Types

Spiral Heat Exchanger

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Heat Exchangers - Types

Finned: contain fins on one heat exchange surface to increase the

heat exchange surface.

Heat registers is a home hot waterheating system is an example of thistype.

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Heat Exchangers - Types

Compact heat exchangers: constructed from round or squarechannels. Car radiator is an example of this type.

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Heat Exchangers - Types

Shell and Tube: Most common in chemical process industries. This

type provides a large heat transfer surface in a small space, canoperate at high pressures, are easy to clean and can be made of awide variety of materials.

1-1 Counter Current Exchanger (1-shell, 1 tube pass)

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Heat Exchangers - Types

Shell and Tube Heat Exchanger

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Heat Exchangers - Types

1-2 Heat Exchanger: 1 shell pass, 2 tube passes.

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Heat Exchangers - Types

2-4 Heat Exchanger: 2 shell passes, 4 tube passes.

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Heat Exchangers - Temperatures

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Heat Exchangers - Types

Shell and Tube Heat Exchanger

1 shell pass

2 tube passes

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Heat Exchangers - Types

End detail in heat exchanger

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Heat Exchangers - Types