3. INTRODUCTION:
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In intercoolers, boilers, heaters and condensers inside
power plants as well as other engineering processes,
heat exchangers are utilized for controlling heat
energy. Heat exchangers are devices that regulate
efficient heat transfer from one fluid to another.
4. What is the heat exchanger?
A heat exchanger is a device that facilitates the process of
heat exchange between two fluids that are at different
temperatures. Heat exchangers are used in many engineering
applications, such as refrigeration, heating and air-
conditioning systems, power plants, chemical processing
systems and food processing systems.
5. Classification of heat exchangers by flow configuration:
There are four basic flow configurations:
1- Counter current flow:
Illustrates an idealized counterflow exchanger in which the two fluids flow parallel to each other but in opposite
directions. This type of flow arrangement allows the largest change in temperature of both fluids and is therefore most
efficient (where efficiency is the amount of actual heat transferred compared with the theoretical maximum amount of
heat that can be transferred).
6. 2 - Co-current flow:
Cocurrent flow heat exchangers, the streams flow parallel to each other and in the same
direction as shown in below, This is less efficient than countercurrent flow but does
provide more uniform wall temperatures.
7. 3- Crossflow:
Crossflow heat exchangers are intermediate in efficiency between
countercurrent flow and parallel flow exchangers. In these units, the
streams flow at right angles to each other.
8. 4- Hybrids such as Cross Counterflow and Multi Pass Flow:
In industrial heat exchangers, hybrids of the above flow types are
often found. Examples of these are combined crossflow/counterflow
heat exchangers and multi pass flow heat exchangers.
9. Classification of Heat Exchangers by design Configuration:
The most common types of heat exchangers:
1- Double-pipe heat exchanger:
When one fluid flows through
the smaller pipe, the other flows
through the annular gap between
the two pipes. These flows may
be parallel or counter-flows in a
double pipe heat exchanger.
10.
11. 2. Shell-and-tube heat exchanger:
Consists of a number of tubes mounted inside a cylindrical shell. Two fluids can exchange heat,
one fluid flows over the outside of the tubes while the second fluid flows through the tubes. The
fluids can be single or two phase and can flow in a parallel or a cross/counter flow arrangement.
12.
13. 3. Plate Heat Exchanger:
Consist of fins or spacers sandwiched
between parallel plates. The fins can be
arranged so as to allow any combination of
crossflow or parallel flow between adjacent
plates. It is also possible to pass up to 12 fluid
streams through a single exchanger by careful
arrangement of headers. They are normally
made of aluminum or stainless steel and
brazed together. Their main use is in gas
liquefaction due to their ability to operate
with close temperature approaches.
14.
15. 4. Condensers and Boilers Heat
exchangers:
Condensers and Boilers Heat
exchangers using a two-phase heat
transfer system are condensers, boilers
and evaporators. Condensers are
instruments that take and cool hot gas
or vapor to the point of condensation
and transform the gas into a liquid
form. The point at which liquid
transforms to gas is called vaporization
and vice versa is called condensation.
Surface condenser is the most common
type of condenser where it includes a
water supply device
