This document discusses heat exchangers and their classification. It defines a heat exchanger as a device that transfers thermal energy between two or more fluids without mixing them. Heat exchangers are classified based on fluid flow arrangement (parallel, counter, cross flow) and heat transfer method (tubular, plate). Common examples include shell-and-tube exchangers, radiators, and cooling towers. Counter flow configuration is most efficient as it produces the largest temperature changes in each fluid. Tubular heat exchangers use concentric tubes or a shell and tube design for fluid separation. Plate heat exchangers come as flat or spiral plate types.

1. 1
HEAT TRANSFER
Mr. E. D. Ahire M.S. PHARM
Assistant Professor,
Divine Collage of Pharmacy

2. Introduction
 A heat exchanger are the devices built for efficient heat
transfer from one medium to another. The media may be
separated by a solid wall, so that they never mix or they may
be in direct contact
 They are widely used in Petroleum refineries, Chemical
plants, Natural gas processing refrigeration, Power plants,
Air conditioning and space heating systems
 An equipment that permits efficient transfer of heat from a
hot fluid to a cold fluid without any contact or with direct
contact of fluids
 Such an equipment iscalled as “Heat Exchangers”

3. In Technically term we can say……
A heat exchanger is a device that is used to transfer thermal
energy (enthalpy) between two or more fluids or between a
solid surface and a fluid, in thermal contact
Introduction

4. Applications
 Typical applications involve heating or cooling of a fluid
stream of concern and evaporation or condensation of
single- or multi component fluid streams
 In other applications, the objective may be to recover or reject
heat, or sterilize, pasteurize, fractionate, distill, concentrate,
crystallize, or control a process fluid
 Common examples of heat exchangers are shell-and tube
exchangers, automobile radiators, condensers, evaporators,
air preheaters, and coolingtowers

5. Classification of heat exchangers
 Heat exchangers are classified on the type of fluid flow
arrangement and on method of heat transfer
 Types on the basis of fluid flow
1) Parallel flow Heat Exchanger
2) Counter flow Heat Exchanger
3) Cross flow Heat Exchanger

6. Parallel flow Heat Exchanger
1) Parallel flow
• In a parallel flow (also referred to as cocurrent or cocurrent
parallel stream) exchanger, the fluid streams enter together at
one end, flow parallel to each other in the same direction, and
leave together at the other end
• This arrangement has the lowest exchanger effectiveness
among single-pass exchangers for given overall thermal
conductance andfluid
flow rates and fluid inlettemperatures
• In a parallel flow exchanger, a large temperature difference
between inlet temperatures of hot and cold fluids exists at the
inlet side, which may induce high thermal stresses in the
exchanger wall at theinlet

7. counter flow Heat Exchanger
2) Counter flow
• In a counter flow or counter current exchanger, the two fluids flow
parallel to each other but in opposite directions within the core
• The counter flow arrangement is thermodynamically superior to
any other flow arrangement
• It is the most efficient flow arrangement, producing the highest
temperature change in each fluid compared to any other two-
fluid flow arrangements for a given overall thermal
conductance fluid flowrates and fluid inlet temperatures
• The maximum temperature difference across the exchanger
produces minimum thermal stresses in the wall for an equivalent
performance compared to any other flow arrangements

8. Cross flow Heat Exchanger
3) Cross flow
• In this type of exchanger, the two fluids flow in directions normal to
each other
• Thermodynamically, the effectiveness for the cross flow
exchanger falls in between for the counter flow and parallel flow
arrangements
• The largest structural temperature difference exists at the
‘‘corner’’ of the entering hot and cold fluids
• This is one of the most common flow arrangements used for
extended surface heat exchangers, because it greatly simplifies
the header design at the entrance and exit of each fluid

9. Cross flow Heat Exchanger

10. Heat Exchangers

11. Tubular Heat Exchangers
Tubular heat exchangers consist of circular tubes, one fluid
flows inside the tube and the other on the outside
The heat transfer takes place across the wall of the tube
Types of tubular heat exchangers
1) Concentric tube or double pipe
2) shell and tube

12. Concentric tube or double pipe
Two set of concentric pipes, two connecting tees, and a
return bend
A device whose purpose is the transfer of thermal energy
between two fluids
Common applications – Boilers, Coolers, Condensers,
Evaporators
Common design consist of two fluids separated by a
conducting medium

13. Concentric tube or double pipe

14. Shell & Tube Heat Exchangers
 Shell & tube type heat exchangers are built of tubes (round or rectangular
in general) mounted in shells (cylindrical, rectangular or arbitrary shape).
 Many variations of this basic type is available.
 The differences mainly in the detailed features of construction and
provisions for differential thermal expansion between the tubes and
the shell.
Tube
outlet
Tube
inlet
Shell
outlet
Shell
inlet

15. Plate heat exchangers
 Types
1) Flat plate type
2) Spiral plate type

16. plate type

17. Flat plate type

18. Spiral plate type