What is a Heat Exchanger?
A Heat exchanger is a device to transfer heat from one fluid (Liquid/Gas) to another. There are various types of heat exchangers used in process piping. Shell and tube heat exchanger is the most widely used heat exchanger. Fig 1 shows the typical working principle of a shell and tube heat exchanger.
Basic Components of Shell and Tube Heat Exchanger
Typically a Shell and Tube Heat Exchanger consists of two-compartment / section one is shell side and other is channel/tube side
- Shell side section consists of the following components: Shell, Cover, Body Flange, Nozzles, Saddle support.
- Channel / Tube side section consists of the following components: Channel, Cover, Body Flange, Nozzles, Tube Sheet and Tubes (Tube Bundle)
Tube Bundle (Fig. 3) consists of the following components
- Tube sheet
- Tie rods and Spacers
- Sliding strips
Tube Pattern (Fig. 4)
The tube shall be placed with a min. c/c distance of 1.25 times the tube outside diameter of the tube. When mechanical cleaning of the tube is specified then min. A cleaning lane of 6.4 mm shall be provided.
Type of Shell and Tube Heat Exchanger
TEMA Exchanger Type
- R – Refinery and Petrochemical Application
- C – General Process Application
- B – Chemical Process Application
TEMA Heat Exchanger applicable Criteria
- Inside diameter 2500 mm
- Product of nominal diameter (mm) and design pressure (kPa) of 5 x 106
- design pressure of 3000 psig
Fixed Tube Sheet Heat Exchanger (Fig. 5)
Floating Head Heat Exchanger Removable Bundle (Fig. 6)
Stationary Tube sheet with removable tube bundle (Fig. 7)
Stack Types of Configuration
In this, two or three heat exchangers placed one above other. This is termed as 1 shell in parallel and 2 or 3 Shells in series. Refer Fig. 8.
Design codes used for Heat exchangers
- API 660 / ISO 16812 ( Shell and Tube heat exchangers for general refinery service )
- ASME SECT.VIII Div.1 (UHX) or Div.2, PD 5500, EN 13445, AD 2000 Merkblatt.
- TEMA -Tubular Exchanger Manufacturers Association
- Shell DEP 22.214.171.124 and DEP 31.21.01.30
Software for used Thermal Design
- HTRI – Heat Transfer Research Institute
- HTFS – Heat Transfer Research and fluid flow service
Design of Shell and Tube Heat exchangers
- MIN. SHELL THK.(Fig. 9) as per TEMA for class – R\
- Baffle clearance, Baffle spacing and thickness as per TEMA table RCB -4.3
- Tie rod size and nos. as per TEMA table R- 4.71 for class – R
- PERIPHERAL GASKET: The min. width of the peripheral ring gasket for external joints shall be 10 mm for shell sizes up to 584 mm and 12 mm for all larger shell sizes.
- PASS PARTITION GASKET: The min. width of the gasket web for pass partition of the channel shall not be less than 6.4 mm for shell sizes up to 584 mm and 9.5 mm for all larger shell sizes. Gasket joint shall be confined type
- Shell and Head design is done as per selected Pressure vessel Design Code such as ASME, EN or AD
- The most widely used design code across the world is ASME Sect. VIII Div.1 & 2
- Body / Girth Flange Design as per Appendix -2 of ASME Sect. VIII Div.1
- The tube sheet design is Mandatory as per UHX of ASME Sect. VIII Div.1
- The tube sheet is designed for the following three cases.
- Tube side pressure (Pt) acting and Shell side pressure (Ps) is Zero
- Shell side pressure (Ps) acting and Tube side pressure (Pt) is Zero
- Shell side pressure (Ps) acting and Tube side pressure (Pt) acting
- Please consider the effect of Vacuum in above load cases
- Tube sheet Design formula based on the theory of Flat Plates
Material of Construction most widely used:
- Carbon steel and Cladding Plates
- Stainless Steel
- Duplex Stainless steel
- Tubes – Carbon steel, Stainless steel, Duplex stainless steel, Exotic material such as copper, Inconel, Titanium
Application of Heat Exchangers
Shell & Tube Heat Exchangers find their application in the following Industries-
- Refinery and Petrochemical
- Oil and Gas
Few more resources for You..
Shell & Tube Heat Exchanger Piping: A brief Presentation
An article on Plate Heat Exchanger with Steam
A typical Check List for Reviewing of Shell & Tube Heat Exchanger Drawings
A brief presentation on Air Cooled Heat Exchangers
Basic Considerations for Equipment and Piping Layout of Air Cooled Heat Exchanger Piping
Reboiler Exchanger and System Type Selection