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Heat Exchangers

Heat Exchangers

• Heat exchangers are one of the most common pieces of equipment found in all plants.

• Heat Exchangers are components that allow the transfer of heat from one fluid (liquid or gas) to another fluid.

• In a heat exchanger there is no direct contact between the two fluids. The heat is transferred from the hot fluid to the metal isolating the two fluids and then to the cooler fluid.

Types of Heat Exchangers

Double-Pipe Exchanger

Double Pipe

Simplest type has one tube inside another - inner tube may have longitudinal fins on the outside

However, most have a number of tubes in the outer tube - can have very many tubes thus becoming a shell-and-tube

Shell-and-Tube Heat Exchanger

Shell-and-Tube Heat Exchangers are the most important type of HE.

It is used in almost every type of industry. This type of heat exchanger consists of a set of

tubes in a container called a shell. The fluid flowing inside the tubes is called the

tube side fluid and the fluid flowing on the outside of the tubes is the shell side fluid.

Main Components of Shell-and-Tube Heat Exchangers

Some common heat-exchanger terms

Tube side: Inside the tubes. Shell side: Outside the tubes, between the

tubes and the shell. Tube sheet A thick plate provided with holes

(one per tube) in which the tubes are fixed. Tube bundle Consists of tubes, tube sheet and

baffle plates Shell A cylinder of plate in which the tube bundle

is placed

TEMA Heat Exchangers

Shell and Tube Heat Exchangers Construction

Fixed Tube-sheet type U-tube type Floating Head type

Front head type A-type B-type

B

Channel and removable cover Bonnet (integral cover)

A

Shell type

E-type F shell

E F

One-pass shell Two-pass shell

Longitudinal baffle

More shell types G and H shells normally only used for horizontal thermosyphon

reboilers J and X shells if allowable pressure drop can not be achieved in

an E shell

J

HG

X

Split flow Double split flow

Divided flow Cross flow

Longitudinalbaffles

Low-finned Tubes

Flat end to go into tube sheet and intermediate flat portions for baffle locations

Available in variety of metals including stainless steel, titanium and inconels

Plate and frame

Plates hung vertically and clamped in a press or frame.

Gaskets direct the streams between alternate plates and prevent external leakage

Plates made of stainless steel or higher quality material

Plates corrugated to give points of support and increase heat transfer

Plate Heat Exchanger

Chevron Washboard

Plate types

Corrugations on plateimprove heat transfergive rigidity

Many points ofcontact and atortuous flow path

General view of plate exchanger

“Plate exchanger” normally refers to a gasketed plate- and-frame exchanger

Flow Arrangement within a PHE

Alternate plates (often same plate types inverted)

Gasketsarranged foreach stream toflow betweenalternate plates

Air-Cooled or Fin-Fan Exchanger

Air-cooled exchanger

Air blown across finned tubes (forced draught type)

Can suck air across (induced draught)

Finned tubes

ACHE bundle

Spiral Heat Exchanger

Spiral Heat Exchangers Spiral heat exchangers can be used in most applications in the

chemical process industry In many difficult applications where fouling and plugging are

problems, a standard shell and tube design may not be effective

While a spiral heat exchanger often has a higher initial cost, it may provide a lower life cycle cost due to lower fouling rates and ease of maintenance

A spiral heat exchanger is composed of two long, flat plates wrapped around a mandrel or center tube, creating two concentric spiral channels

In a spiral heat exchanger, the hot fluid flows into the center of the unit and spirals outward toward the outer plates while at the same time, the cold fluid enters the periphery and spiral inward, exiting at the center