Heat exchangers are devices used to transfer heat between fluids. They transfer heat from outgoing vapors and liquids to incoming fluids to reduce fuel consumption. Common applications include heating, cooling, power generation, and industrial processes. The main types are double pipe, shell and tube, plate, plate and shell, and spiral heat exchangers. Double pipe exchangers have one pipe inside another but low efficiency. Shell and tube exchangers use bundles of tubes in a shell and are robust for high pressures. Plate exchangers use parallel plates for compactness while spiral exchangers use coiled tubes. Selection depends on parameters like pressure, temperature, and space.

1. Heat Exchangers
Dr. Leji Latheef
Assistant Professor in Chemistry
Al-Ameen College, Edathala

2. Heat Exchangers
• Device used to transfer heat between one or more fluids.
• In a two way tube hot stream will flow inside the tube and cold stream also
flow outside the tube. A series of these types of tubes are arranged inside
the exchangers.
• Used to transfer heat from outgoing vapours, liquids and streams to
incoming boil thereby reducing the fuel consumption in the furnace.
• used in space heating, refrigeration, air conditioning, power stations, chemical
plants, petrochemical plants, petroleum refineries and sewage treatment.

3. Types of heat exchangers
Double pipe heat exchangers
Shell and tube heat exchanger
Plate Heat exchangers
Plate and shell heat exchanger
Spiral Heat exchangers

4. Double pipe heat exchangers
• Simplest types of heat exchangers used in industries.
• The double pipe heat exchanger is one heat exchanger pipe
inside another larger pipe for either counter flow or parallel
flow pattern.
• one fluid flows inside a pipe and the other fluid flows between
that pipe and another pipe that surrounds the first.
• concentric tube construction.
• Flow in a double-pipe heat exchanger can be co-current or
counter-current.
• Hot process fluid flowing through the inner pipe transfers its
heat to cooling water flowing in the outer pipe.

5. Double pipe heat exchangers
Merits
• The simplest exchangers used in industries.
• cheap for both design and maintenance, making
them a good choice for small industries.
Demerits
• Low efficiency and large high space occupation.
Hence not commonly used in large scales.

6. Shell and tube heat exchanger
 Shell and tube heat exchangers consists of a shell with a bundle of tubes inside
it.
 One fluid runs through the tubes, and another fluid flows over the tubes
(through the shell) to transfer heat between the two fluids.
 Heat is transferred from one fluid to the other through the tube walls, either
from tube side to shell side or vice versa.
 The fluids can be either liquids or gases on either the shell or the tube side.
 The ends of each tube are connected to plenums (sometimes called water
boxes) through holes in tube sheets.
 The tubes may be straight or bent in the shape of a U, called U-tubes.

7. Shell and tube heat exchanger
USES
 used for high-pressure applications (with pressures greater than 30 bar
and temperatures greater than 260 °C).
 This is because the shell and tube heat exchangers are robust (strong) due
to their shape.
 This type of heat exchangers are commonly used in refineries.

8. Plate Heat exchangers
• Series of parallel metal plates that are placed one above the other to
transfer heat between two fluids.
• Composed of many thin, slightly separated plates that have very large
surface areas and small fluid flow passages for heat transfer.
• Materials used for the plates are stainless steel, titanium and aluminium
• The space between two adjacent plates forms the channel in which the
fluid flows.
• Inlet and outlet holes at the corners of the plates allow hot and cold
fluids through alternating channels in the exchanger so that a plate is
always in contact on one side with the hot fluid and the other with the
cold.

9. Plate Heat exchangers
• Plate heat exchangers also differ in the types of plates that are used, and in the
configurations of those plates.
• When compared to shell and tube exchangers, the stacked-plate arrangement typically
has lower volume and cost.
• plate exchangers typically serve low to medium pressure fluids, compared to medium
and high pressures of shell and tube.

10. Plate and shell heat exchanger
• Combines plate heat exchanger with shell and tube heat exchanger technologies.
• contains a fully welded circular plate pack made by pressing and cutting round plates and
welding them together is inserted into the shell which distributes the stress and eliminates
the need for gaskets.
• Plate and shell technology offers high heat transfer, high pressure and high operating
temperature.
• In particular, it does completely without gaskets, which provides security against leakage
at high pressures and temperatures.
• It’s compact and light in weight,
• Since it has no gaskets, it can withstand higher pressure and temperatures than plate heat
exchangers.

11. Plate and shell heat exchanger
USES
•Power Industry
•Air Treatment
•Petrochemical Industry
•Refrigeration
•Evaporators & Condensers

12. Spiral Heat exchangers
• This is a coiled tube configuration exchangers.
• The term refers to a pair of flat surfaces that are
coiled to form the two channels in a counter-flow
arrangement.
• Each of the two channels has one long curved path.
• A pair of fluid ports are connected tangentially to the
outer arms of the spiral, and axial ports are common

13. Spiral Heat exchangers (SHE)
• Compact design reduces space requirements.
• Maximum heat transfer
• Curving passage creates high turbulence;
• Natural scrubbing action eliminates deposits;
A compact SHE may be used to have a smaller
footprint (requires minimal space for installation and
servicing) and thus lower all-around capital costs,
• oversized SHE may be used to have
less pressure drop, less pumping energy,
higher thermal efficiency, and lower energy costs.