CHAPTER 11 Heat Exchangers

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CHAPTER 11Heat Exchangers
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Heat Exchanger Types

• Heat exchangers are the devices used for heat
  exchange between two fluids that are at different
  temperatures and separated by a solid wall.
• Heat exchangers are classified according to flow
  arrangement and type of construction.
• Concentric-Tube (Double-Pipe) Heat Exchangers

• Simplest configuration.
• Hot and cold fluids move in the same direction
  in parallel-flow arrangement.
• Hot and cold fluids move in the opposite
  direction in counterflow arrangement.
• Superior performance associated with counter
  flow.

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• Cross-flow Heat Exchangers
• For cross-flow over the tubes, fluid motion, and
  hence mixing, in the transverse direction (y) is
  prevented for the finned tubes, but occurs for
  the unfinned condition.
• Heat exchanger performance is influenced by
  mixing.

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• Shell-and-Tube Heat Exchangers
• Baffles are used to increase the convection
  coefficient of the shell-side fluid by inducing
  turbulent mixing and by establishing a cross
  flow.

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• Shell-and-Tube Heat Exchangers
• The number of tube and shell passes may be
  varied, e.g.

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Compact Heat Exchangers

• Have dense arrays of finned tubes or plates and
  widely used to achieve large heat rates per unit
  volume, particularly when at least one of the
  fluids is a gas.
• Characterized by large heat transfer surface
  areas per unit volume, small flow passages, and
  laminar flow.

• Fin-tube (flat tubes, continuous plate fins)
• Fin-tube (circular tubes, continuous plate fins)
• Fin-tube (circular tubes, circular fins)
• Plate-fin (single pass)
• (e) Plate-fin (multipass)