1. HEAT EXCHANGERS

2. OUTLINE Definition & classification of heat exchangers
Heat exchangers according to construction
Plate heat exchangers
Extended surface heat exchangers
Tubular heat exchangers
Heat exchangers according to phase change
Condensers
Evaporators

3. WHAT IS A HEAT EXCHANGER?
They are devices specifically designed for the efficient transfer of heat from one fluid to another fluid over a solid surface.

4. WHAT ARE HEAT EXCHANGERS USED FOR?
They have the function to transfer heat as efficiently as possible. Heat exchangers are widely used in :
refrigeration
air conditioning
space heating
electricity generation
chemical processing

5. CLASSIFICATION OF HEAT EXCHANGERS
Heat exchangers may be classified according to the following main criteria:
Recuperators and regenerators
Transfer processes: direct contact and indirect contact
Geometry of constructions: tubes,plates and extended surfaces
Phase change mechanisms: condensers and evaporators
Flow arrangements: parallel, counter and cross flow

6. RECUPERATORS Hot steam A recovers some of the heat from stream B.
The conventional heat exchangers with heat transfer between two fluids.
Hot steam A recovers some of the heat from stream B.

7. REGENERATORS
Storage type heat exchangers. The same flow passage (matrix) is alternately occupied by one of the two fluids.
Thermal energy is not transfered through the wall.

8. 1. Direct contact type heat exchangers:
TRANSFER PROCESSES
1. Direct contact type heat exchangers:
Heat transfer between the cold and hot fluids through a direct contact between these fluids.
Examples: Spray and tray condensers,cooling towers

9. 2. Indirect contact type heat exchangers:
Heat energy is exchanged between hot and cold fluids through a heat transfer surface.
The fluids are not mixed

10. 1. Paralel Flow Heat Exchangers:
FLOW ARRANGEMENTS
1. Paralel Flow Heat Exchangers:
Two fluid streams enter together at one end, flow through in the same direction, and leave through at the other end

11. 2. Counter Flow Heat Exchangers:
Two fluid streams flow in opposite directions.

12. 3. Cross Flow Heat Exchangers:
The direction of fluids are perpendicular to each other.

13. BASIC CRITERIAS FOR THE SELECTION OF HEAT EXCHANGERS
Process specifications
Service conditions of the plant environment, resistance to corrosion by the process
Maintenance, permission to cleaning and replacement of components
Cost- Effectiveness
Site requirements, lifting, servicing,capabilities

14. GASKETED PLATE SPIRAL PLATE LAMELLA
PLATE HEAT EXCHANCERS
GASKETED PLATE
SPIRAL PLATE
LAMELLA

15. Limited to below 25 bar and 250ºC
Plate heat exchangers have three main types : gasketed ,spiral heat exchangers and lamella
The most common of the plate-type heat exchangers is the gasketed plate heat exchanger

16. GASKETED PLATE HEAT EXCHANGER
The most common of the plate-type heat exchangers is the gasketed plate heat exchanger

17. SPIRAL PLATE HEAT EXCHANGER
Ideal flow conditions and the smallest possible heating surface

18. LAMELLA
Consisting of cylindrical shell surrounding a number heat transfering lamellas.
Similar to tubular heat exchanger

19. ADVANTAGES
Plate heat exchangers yield heat transfer rates three to five times greater than other types of heat exchangers.
The design of the plate heat exchanger allows to add or remove plates to optimize performance, or to allow for cleaning, service, or maintenance with a minimum of downtime.
Plate exchangers offer the highest efficiency mechanism for heat transfer available in industry.

20. DISADVANTAGES
Plate exchangers are limited when high pressures, high temperatures, or aggressive fluids are present.
Because of this problem these type of heat exchangers have only been used in small, low pressure applications such as on oil coolers for engines.

21. 2. EXTENDED SURFACE HEAT EXCHANGERS
- PLATE FIN HEAT EXCHANGER
- TUBE FIN HEAT EXCHANGER

22. PLATE FIN HEAT EXCHANGER
For gas to gas applications.
Widely used in cryogenic, energy recovery, process industry, refrigeration and air coditioning systems.

23. TUBE FIN HEAT EXCAHNGER
For gas to liquid heat exchangers.
Used as condersers in electric power plant, as oil coolers in propulsive power plants, as ir cooled exchangers in process and power industires.

24. TUBULAR HEAT EXCHANGERS
are so widely used because the technology is well established for making precision metal tubes capable of containing high pressures in a variety of materials.
There is no limit to the range of pressures and temperatures that can be accommodated.

26. SHELL AND TUBE HEAT EXCHANGERS

27. SHELL AND TUBE HEAT EXCHANGERS
are the most commonly used heat exchangers in oil refineries and other large chemical processes.
are used when a process requires large amounts of fluid to be heated or cooled.
provide transfer of heat efficiently.
use baffles on the shell-side fluid to accomplished mixing or turbulence.

28. SHELL AND TUBE HEAT EXCHANGERS
tube : strong, thermally
conductive, corrosion
resistant, high quality
outer shell : durable, highly
strong
inner tube : having effective
combination of durability,
corrosion resistant and
thermally conductive
APPLICATIONS:
Oil refining,
Vapor recovery systems,
Permanent engines,
Industrial paint systems.

30. U - TUBE HEAT EXCHANGERS
heat exchanger systems consisting of straight
length tubes bent into a U-shape surrounded by a
shell.

31. U - TUBE HEAT EXCHANGERS
Both initial and maintenance costs are reduced by
reducing the number of joints.
They have drawbacks like inability to replace
individual tubes except in the outer row and inability to
clean around the bend.

32. U - TUBE HEAT EXCHANGERS
Examples : reboilers, evaporators and Kettle
type.
They have enlarged shell sections for
vapor-liquid separation.

33. FIXED TUBE HEAT EXCHANGERS
have straight tubes that are secured at both
ends to tube sheets welded to the shell.

34. FIXED TUBE HEAT EXCHANGERS
They are the most economical type design.
They have very popular version as the heads
can be removed to clean the inside of the
tubes.
Cleaning the outside surface of the tubes is
impossible as these are inside the fixed part.
Chemical cleaning can be used.

35. FLOATING HEAD HEAT EXCHANGER
one tube is free to float within the shell and the other is fixed relative to the shell.

36. FLOATING HEAD HEAT EXCHANGERS
A floating head is excellent for applications
where the difference in temperature between the
hot and cold fluid causes unacceptable stresses
in the axial direction of the shell and tubes.
The floating head can move, so it provides the
possibility to expand in the axial direction.
Design allows for bundle to be removed for inspection,
cleaning or maintenance.

37. FLOATING HEAD HEAT EXCHANGERS
Examples : kettle boilers which have dirty
heating medium.
They have the most highest construction cost of
all exchanger types.

38. DOUBLE-PIPE HEAT EXCHANGERS
They consist of one pipe concentrically located inside a
second, larger one.
Cold and hot liquid respectively
flows in the gap of inner pipe
and sleeve pipe.
Structure is simple and heat
transmission is large.

39. DOUBLE-PIPE HEAT EXCHANGERS
utilize true counter-current
flow which maximizes the
temperature differences
between the shell side and
tube side fluids.

40. DOUBLE-PIPE HEAT EXCHANGERS
When the process calls
for a temperature cross,
it is the most efficient
design and will result in
fewer sections and less
surface area.

41. DOUBLE-PIPE HEAT EXCHANGERS
ADVANTAGES:
Operates in true counter current flow permitting extreme temperature cross.
Economically adaptable to service differentials.
Ideal for wide temperature ranges and differentials.
Provides shorter deliveries than shell and tube due to standardization of design and construction.

42. PHASE CHANGE HEAT EXCHANGERS
2.Condensers
1.Reboilers
(Evaporaters)

43. 1)REBOILER
to generate vapor to drive fractional distillation separation
Most Common Reboiler’s Types
Kettle Reboilers
Forced Recirculation Reboilers
Thermosiphon Reboiler

44. Kettle Reboilers

45. Major factors influence reboiler type selection:
Plot space available
Total duty required
Fraction of tower liquid traffic vaporized
Fouling tendency
Temperature approach available
Temperature approach required

46. Kettle Reboilers Disadvantages Advantages
All the dirt collects and non volatiles accumulate
Shell side is difficult to clean
Difficult to determine the degree of mixing
Oversize shell is expensive
Advantages
Insensitive to hydrodynamics
High heat fluxes are possible
Can handle high vaporization
Simple piping
Unlimited area

47. Thermosiphon Reboiler

48. Thermosiphon Reboiler
operate using natural circulation with process flow on the shell side
process flow on the tube or shell side in vertical units.
not require a pump for recirculation
have sensible heat transfer followed by nucleate boiling.

49. Forced Recirculation Reboilers

50. Forced Recirculation Reboilers
These reboiler types have two mechanisms of heat transfer: sensible heat transfer followed by nucleate boil-ing.
Process flow is typically on the tube side of a standard exchanger in the vertical position.

51. 2)CONDENSERS b) Air- Cooled Condensers Water-Cooled Condensensers
Horizontal shell and tube
Vertical shell and tube
Shell and coil
Double pipe
b) Air- Cooled Condensers
Phases:
de-super-heating
Condensing
Subcooling

52. Single-Pass Condenser

53. SELECT AN WATER-COOLED CONDENSER
…IF:
1. Adequate water supplies are available from tower, city or well sources.
2. Water supply is of good quality.
3. Heat recovery is not practical or unimportant.
4. Plant ambient temperatures consistently exceed 95°F.
5. Ambient air is polluted with large dust and dirt particles.
ADVANTAGE & DISADVANTAGES
1. Offer lower capital investment.
2. Operates more efficiently on hot summer days.
3. Easier to operate.
4. Does not offer summer ventilation.

54. SELECT AN AIR-COOLED CONDENSER
...WHEN:
1. Adequate water supply not available from tower or well sources.
2. Water supply is not of good quality.
3. Heat recovery is practical and important.
4. Plant ambient temperature will not consistently exceed 95°F.
5. Ambient air is not polluted with large dust and dirt particles.
ADVANTAGE & DISADVANTAGES
1. Somewhat more costly to purchase and operate.
2. Gives less cooling on hot summer days.
3. Consumes more electricity.
4. Offers summer ventilation and winter supplement heating.

55. OUTLINE Definition & classification of heat exchangers
Heat exchangers according to construction
Plate heat exchangers
Extended surface heat exchangers
Tubular heat exchangers
Heat exchangers according to phase change
Condensers
Evaporators

56. REFERENCES
Andreone, C.F., Tubular heat exchanger inspection, maintenance, and repair, McGraw-Hill, NY, 1998
Couper JR,Penry W.R., Fair J.R., Walas S.M., Chemical Process Equipment, Elsevier Inc, 2005
Incropera,F.P.,Dewitt D.P., Fundamentals of Heat and Mass Transfer, 5th ed.,John Wiley & Sons Inc., NY,2000
Kakaç, S. Heat exchangers, CRC Press, Fla, 1998
Shah, R.K.,Psekulis D., Fundamental of Heat Exchanger Design, John Wiley &Sons Inc., NY,1999