8/13/2019 109659385-7-Hex (1)

1/38

PMTSB 2006

Unfired pressure vessel classifications

Unfired PressureVessel

Drums Storage vessel Reactor Columns Separators Exchangers

Surge drum

Accumulator

Resin & filter

Storage

Atmospheric

Pressure

Radial flow

Axial flow

Radial & axial

Single bed

Multi bed

Fractionation

Distillation

Separation

Liquid-solid

Liquid-liquid

Gas-liquid

Gas-solid

Filter

Reboiler

Evaporator

Condenser

Cooler

Plate

Catalyst drum

8/13/2019 109659385-7-Hex (1)

2/38

PMTSB 2006

Heat exchangers

What are they for..

For exchanging heat, of course.

Most importantly, to recover and reuse generated heat,rather than merely exchanging heat

8/13/2019 109659385-7-Hex (1)

3/38

PMTSB 2006

Heat exchangers

How do they work..

By transferring the heat from a hot medium to anothercolder medium, without mixing the fluids

In most exchangers, heat is transferred by means ofconduction through the fixed walls of the exchangers

This process relies on the thermal conductivity of a solidmaterial and those of the fluids

8/13/2019 109659385-7-Hex (1)

4/38

PMTSB 2006

Heat exchangers

How do they work..continued

When designing exchangers, consider the following;

Thermal conductivity of tubes

Corrosion resistance

Heating surface areasTurbulence of fluid must be as high as possible becausethermal conductivity of fluid varies in direct proportionto the fluid turbulence

Fluid flow rate

8/13/2019 109659385-7-Hex (1)

5/38

PMTSB 2006

Heat exchangers

How do they work..continued

Generally, the thermal conductivity of a substance is lowerwhen it is in vapor phase or gas phase, than when it is inliquid phase

8/13/2019 109659385-7-Hex (1)

6/38

PMTSB 2006

Heat exchangers

Figure 6.1: Heat exchanger nomenclatures

How do they look like..

8/13/2019 109659385-7-Hex (1)

7/38

PMTSB 2006

Heat exchangers

Figure 6.1: Heat exchanger nomenclatures

How do they look like..

8/13/2019 109659385-7-Hex (1)

8/38

PMTSB 2006

Heat exchangers

How do they look like..

Figure 6.2: Heat exchangerclassifications, as per TEMA

8/13/2019 109659385-7-Hex (1)

9/38

PMTSB 2006

Heat exchangers

How do they look like..

Shell & tube bundle exchangers

The most widely used type of exchangers

A bundle is enclosed inside a shell

Fluids never come into contact with each other Tubes are attached to tubesheet by welding, brazing, or

rolling

8/13/2019 109659385-7-Hex (1)

10/38

PMTSB 2006

Heat exchangers

How do they look like..

Shell & tube bundle exchangers

Baffle plates

For causing the fluid flow inside the shell side to come into

contact with as much tube surface as possible, hence moreheat transfer will take place

They also provide support to the tubes

8/13/2019 109659385-7-Hex (1)

11/38

PMTSB 2006

Heat exchangers

How do they look like..

Shell & tube bundle exchangers

Fixed tubesheet

Both ends of the tube bundle are rigid little expansion of

the tubes Used when temperature difference between two fluids is

small

8/13/2019 109659385-7-Hex (1)

12/38

8/13/2019 109659385-7-Hex (1)

13/38

8/13/2019 109659385-7-Hex (1)

14/38

8/13/2019 109659385-7-Hex (1)

15/38

PMTSB 2006

Heat exchangers

How do they look like.

Figure 6.6: Tube passesarrangements

8/13/2019 109659385-7-Hex (1)

16/38

PMTSB 2006

Heat exchangers

How do they look like.

Figure 6.7: An exampleof a tubesheet

8/13/2019 109659385-7-Hex (1)

17/38

PMTSB 2006

Heat exchangers

How do they work..

Reboilers

Installed at bottom of columns

Used to provide boilup for distillation and similar towers

They generate pressure required to push the vapor up the column Vapor pressure generated must overcome pressure drop inside

column

8/13/2019 109659385-7-Hex (1)

18/38

PMTSB 2006

Heat exchangers

How do they look like..

Reboilers

Figure 6.8: Varioustypes of reboilers

8/13/2019 109659385-7-Hex (1)

19/38

PMTSB 2006

Heat exchangers

How do they work..

Reboilers

Kettle type

Tube bundle inside an oversize shell which provides large

vapor space above the bundle This large vapor space is where liquid and gas phases are

separated and then withdrawn separately

8/13/2019 109659385-7-Hex (1)

20/38

PMTSB 2006

Heat exchangers

How do they look like..

Reboilers

Kettle type

Figure 6.9: A kettle type reboiler

8/13/2019 109659385-7-Hex (1)

21/38

PMTSB 2006

Heat exchangers

How do they work..

Reboilers

Thermosyphon

The fluid will circulate at a rate which the pressure lossesin the system are just balanced by the availablehydrostatic head

The driving force for circulation round the system is thedifference in density of the cold liquid at the bottomcolumn base and inlet piping, and the hot two-phase fluid

in the upper exchanger tubes and outlet piping Top tubesheet at same level as liquid level inside tower

8/13/2019 109659385-7-Hex (1)

22/38

PMTSB 2006

Heat exchangers

What are they for..

Evaporators

To remove solvent by vaporization from solids that are notsoluble

Used to produce concentrated liquid

8/13/2019 109659385-7-Hex (1)

23/38

PMTSB 2006

Heat exchangers

How do they work..

Evaporators

Circulation of flow may be natural or forced with pumps

Forced circulation evaporators are for viscous and foulingservices but also more expensive

Most evaporators use natural circulation

8/13/2019 109659385-7-Hex (1)

24/38

PMTSB 2006

Heat exchangers

How do they look like..

Evaporators

Figure 6.10: A few types of evaporators

8/13/2019 109659385-7-Hex (1)

25/38

PMTSB 2006

Heat exchangers

How do they look like..

Evaporators

Figure 6.11: Other examples of evaporators

8/13/2019 109659385-7-Hex (1)

26/38

PMTSB 2006

Heat exchangers

What are they for..

Condensers

To reduce vapor temperature to the point of condensationi.e. vapor transforms into condensate

8/13/2019 109659385-7-Hex (1)

27/38

PMTSB 2006

Heat exchangers

How do they work..

Condensers

When freezing can occur, condensation is normallyperformed on the shell side to prevent clogging

When condensing mixtures whose lighter components aresoluble in the condensate, tube side condensation ispreferred because drainage is less complete and allowscondensation to take place at higher temperatures

8/13/2019 109659385-7-Hex (1)

28/38

PMTSB 2006

Heat exchangers

Figure 6.12: Varioustypes of condenser

How do they looklike..

Condensers

8/13/2019 109659385-7-Hex (1)

29/38

PMTSB 2006

Heat exchangers

How do they look like..

Condensers

Figure 6.13: A badly clogged seawater condenser

8/13/2019 109659385-7-Hex (1)

30/38

PMTSB 2006

Heat exchangers

What are they for.. exposed tube bundles

Air coolers

Cooler when a hot fluid is cooled to a lower desiredtemperature by transfer of heat to water

Air cooler when a hot fluid is cooled by air

8/13/2019 109659385-7-Hex (1)

31/38

PMTSB 2006

Heat exchangers

How do they work.. exposed tube bundles

Air coolers

Since air is not as good as water in removing heat, theprocess of exchanging heat is further enhanced byinstalling fins outside the tubes

The process fluids flows through finned tubes and coolingair is blown across them with fans

Air cooler is easier to maintain than water cooler becauseair is not corrosive and unlikely to foul

8/13/2019 109659385-7-Hex (1)

32/38

PMTSB 2006

Heat exchangers

How do they look like.. exposed tube bundles

Air coolers

Figure 6.14: Two types ofair coolers

8/13/2019 109659385-7-Hex (1)

33/38

PMTSB 2006

Heat exchangers

How do they look like..

Plate heat exchangers

Figure 6.15: A plate heat exchanger being serviced

8/13/2019 109659385-7-Hex (1)

34/38

8/13/2019 109659385-7-Hex (1)

35/38

PMTSB 2006

Heat exchangers

How do they look like..

Plate heat exchangers

Figure 6.17: Fluid flow inside a plate heat exchanger

8/13/2019 109659385-7-Hex (1)

36/38

PMTSB 2006

Heat exchangers

How do they look like..

Figure 6.18: Various tubefins constructions

8/13/2019 109659385-7-Hex (1)

37/38

PMTSB 2006

Heat exchangers

How do they look like..

Figure 6.19: Various tube fin attachment constructions

8/13/2019 109659385-7-Hex (1)

38/38