Heat exchanger: Shell And Tube Heat Exchanger

avpatil159@gmail.com
SHELL & TUBE
HEAT EXCHANGER

Basic Heat Exchanger Equation
The general relation reflects the heat transfer across a surface is:
Where,
)()( cicochohih HHMHHMQ 
Q = U A (LMTD)

Dimensionless Number
• Nusselt Number
• Reynolds Number
• Prandtl Number

Why Shell and Tube Heat
Exchanger?
• Relatively inexpensive
• Available in many sizes
• Compact design
• Available in many different materials
• Can be designed for high pressures without excessive cost
• Design principles well known
• Many different manufacturers
• Well-developed fabrication facilities.

Types of STHE
• Fixed tube-sheet
• U-tube
• Floating-head

Fixed Tube sheet heat exchangers

U-tube heat exchanger

Floating head heat exchanger

Components of STHE
• Shell
• Shell cover
• Tubes
• Channel
• Channel cover
• Tube sheet
• Baffles
• Support plates
• Floating head cover
• Nozzle
• Tie-rods
• Spacers
• Impingement plate

Shell
Dimensions
• Line pipe dimensions shall be used for carbon steel shells up to a
nominal shell diameter of 18-20 inches
• For shells rolled from plate and with a shell diameter above 20 mm the
nominal diameter is the shell inside diameter.
• During the design stage one should follow standard HTRI shell
dimensions unless detailed information is available with the designer.
Orientation
• Horizontal in General
• Limited space or certain process requirements – Vertical Orientation
• For thermo siphon re-boilers, vertical orientation is preferred to
horizontal orientation, even if the heating medium is fouling.

Types of SHELL
E-Type Shell F-Type Shell

G-Type Shell H-Type Shell

J-Type Shell K-Type Shell
X-Type Shell

Pressure Drop of Different
Shell Types
F shell 8 x ΔPE shell
G shell 1 x ΔPE shell
H shell 1/8 x ΔPE shell
J shell 1/8 x ΔPE shell
X shell <1/100 x ΔPE shell

Tubes
• The smallest tube diameter generally produces the most heat transfer
area per unit volume in a given shell and most efficient heat transfer.
• 19.15 mm tubes are commonly used for clean services.
• For very clean services, 15.875 mm tubes are sometimes used.
• For gases, boiling, condensing or two phase flow 19.05 mm to 31.75 mm
tube ODs are required.
• For vertical tube side vacuum falling film evaporators tubes with outside
diameter upto 2 inches are used.

Selection of Tube

Tube sheets
• Tubes are held on both the ends called tube sheets.
• The tube sheet thickness varies from 1 inches (25 mm) for low pressure
and low shell diameter applications up to over 12 in. (300 mm) in high
pressure and large shell diameters.

Tube to tubesheet joint
• Tubes are expanded into grooves in tube sheet or welded to them.
• Welded joints are preferred in sever conditions like high pressures (80
kg/cm2 g) or when handling toxic or inflammable fluids where leakage
are not permitted.

Typical Tube sheet

Tube Layout Pattern
Typical Tube pitch = 1.25 x tube dia.

Tube-side Passes
Multiple passes are used to
• Increase tube-side velocity and taking maximum advantage of
available pressure drop
• Reduce overall length
• Allow U-tube/floating head designs

Pass partition arrangements

Baffles
• Baffles provide the framework to support and secure the tubes and
prevent vibration
• Baffles redirect the shell side flow across the tube bundle

Types of Baffle

The construction of the bundle provides multiple fluid pathways
C C
B BF
A -Tube-to-baffle hole leakage E - Baffle-to-shell leakage
B - Main cross flow F - Pass-partition bypass
C -Bundle-to-shell bypass
Shell Side Fluid Stream Analysis

Impingement Plate
Purpose:
To protect the uppermost tubes located just below the shell-side inlet nozzle against
direct impingement.
Such impingement can cause erosion, cavitations and/or vibration.
TEMA Standards specify an impingement protection is required for following cases:
• Inlet nozzle ρV2 is greater than 2232 kg/m s2 for non-corrosisve, non abrasive
single pass fluid.
• Shell side condensation is specified
• Shell side boiling is specified and the inlet nozzle ρV2 is greater than 744kg/m s2
• for all saturated vapors and liquid-vapor mixtures (there are chances of carrying
liquid droplets.)
Types
• Circular plate
• Rectangular plate
• Rods

Standard Dimensions for
impingement plate
•Minimum height under nozzle (Hmin) = D/4,
•Minimum width of the impingement plate (Wmin) = D + 50 mm,
•Length of the impingement plate L = D + (50 ~ 70 mm), where D is the nozzle
inside diameter.

The figure below shows the height under nozzle measurement for different cases

Nozzle
• Inlet and outlet nozzles are sized for pressure drop and velocity
considerations.
• The total nozzle pressure drop for either shell side or tube side
should not exceed about 25% of total.
• Nozzle pressure drop is dominating in case of condensers (due to
pressure recovery in condensers).
• For liquid flow nozzle rhoV2 should be limited to 3000 kg/m s2.
• For gas flow, nozzle velocity should be less than 20% of acoustic
velocity.
• Thermo wells, pressure indicator connections, safety and relief
valves, product drains, vents, block valve are other miscellaneous
nozzles.

Nozzle Locations
• Nozzle orientation should be decided in consideration of process
requirements, mechanical construction and requirements from plot plan.
• Following samples can be used as a good reference.

 Temperature
 Pressure
 Viscosity
 Fouling and cleaning
 Corrosion
 Flow rate
 Temperature range
Allocation of Fluids - Parameters

Brushes and cages

Codes & Standards: TEMA R/C/B
The mechanical design, fabrication, inspection and testing of shell and
tube type heat exchangers shall be applied in accordance with the
following sections of “TEMA” standard
• TEMA Class R: Sever requirements for petroleum and related
processing applications
• TEMA Class C: Moderate requirements for commercial and general
process applications
• TEMA Class B: For chemical process service

Heat exchanger: Shell And Tube Heat Exchanger

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Heat exchanger: Shell And Tube Heat Exchanger

Similar to Heat exchanger: Shell And Tube Heat Exchanger (20)

Recently uploaded

Recently uploaded (20)

Heat exchanger: Shell And Tube Heat Exchanger