Shell and tube heat exchanger is vital in the oil and gas sector. Their ability to handle high-pressure and temperature applications makes them become a top priority to be implemented. For companies, the reliability of heat exchangers is vital for ensuring the smooth operation of various processes. In this article, we will serve thorough information regarding shell and tube heat exchanger covering their definition, components, and how they work.
What Is Shell and Tube Heat Exchanger?
Shell and tube heat exchanger is a type of heat exchanging device constructed using a large cylindrical enclosure, or shell, that has bundles of tubing compacted in its interior. This heat exchanger is designed to transfer heat from one fluid to another fluid without them touching each other directly.
This category of heat exchanger is named after its design, which includes a shell (as a sizable pressure vessel) housing a group of tubes. Watch the video below for the illustration.
The tubes are enclosed by another fluid, such as water or air, and heat is transferred from the first fluid to the second fluid through the tube walls. Tube and heat exchangers have various applications, such as in air conditioning systems, refrigeration systems, and industrial processes that require heat transfer.
What Is The Industrial Use of Shell and Tube Heat Exchanger?
The industrial use of shell and tube heat exchangers, used in the chemical, food, oil and gas and other fields, is widespread. They are commonly employed in various industries for transferring heat between two fluids without direct contact. Some of the key industrial of shell and tube heat exchangers applications include:
- Heating and cooling processes in chemical plants
- Condensing and evaporating duties in refineries
- Heat recovery systems in power generation facilities
- HVAC systems in commercial and residential buildings
- Refrigeration systems in food processing plants
- Thermal management in oil and gas production facilities
Overall, shell and tube heat exchangers play a crucial role in optimizing thermal efficiency and maintaining temperature control across a wide range of industrial processes.
What Are The Components of Shell and Tube Heat Exchanger?
The components of a shell and tube heat exchanger can be broken down into the following parts:
1. Shell
The shell is the heat exchanger’s outermost part which holds the tube bundle. It is commonly a cylindrical container constructed from steel or other appropriate substances
2. Tubes or Tube Bundle
A collection of parallel tubes running along the length of the shell makes up the tube bundle. Depending on the specific use, the tubes can be composed of different materials, such as stainless steel, copper, or titanium. The diameter and thickness of the tubes are also important design parameters.
3. Tube Sheets
Tube sheets are sturdy sheets that act as a barrier between the tube bundle and the shell. They are commonly constructed using steel and are fused to the shell to ensure a firm and leak-free closure. The tubes are inserted through holes in the tube sheets and are either expanded or welded in position.
4. Baffles
Baffles are plates or rods that are placed inside the shell to regulate the movement of fluid around the tube bundle. These can be either longitudinal or transverse in orientation and are intended to enhance the effectiveness of heat transfer.
5. Inlet and Outlet Nozzles
The inlet and outlet nozzles serve as the entry and exit points for fluids in the heat exchanger. These connections are usually placed at opposite ends of the shell and are attached to the tubes and the shell using flanges or other types of fittings.
6. Expansion Joints
Expansion joints are flexible connectors that accommodate the tube bundle’s thermal expansion and contraction. Usually situated at the inlet and outlet of the heat exchanger, these joints are constructed using metal bellows or other flexible materials.
7. Support Structures
Support structures hold heat exchangers in position, ensuring a stable foundation. Support structures can be either temporary or permanent and may be made of steel or other materials.
What Are Some Types of Shell and Tube Heat Exchangers?
There are different types of shell and tube heat exchangers classified based on their design and intended use, as defined by the Tubular Exchangers Manufacturers Association (TEMA). These categories help in understanding the specific applications and requirements of each type:
1. Class B
These heat exchangers are designed for chemical processing applications. They are constructed with materials and configurations suitable for handling corrosive substances and demanding chemical processes. Class B heat exchangers are built to withstand the challenges posed by chemical environments.
2. Class C
This category encompasses heat exchangers intended for general commercial applications. These heat exchangers are versatile and can be used in various industries where moderate operating conditions are present. They are designed to efficiently exchange heat in common commercial settings.
3. Class R
Heat exchangers classified under Class R are specifically tailored for petroleum and large-scale applications. They are engineered to handle the rigorous demands of processing petroleum products, including high temperatures, pressures, and flow rates. Class R heat exchangers are robust and suitable for industrial-scale operations.
TEMA organizes shell and tube heat exchangers based on their components like the front end (head), rear end, and the shell. They use a chart with columns and rows to describe each type. To simplify identification, TEMA created a three-letter system (BEM, AEM, or NEN) for different designs of straight tube and fixed tube sheet heat exchangers.
The first letter in the code describes how the front end stationary head is connected to the shell and channel—either bolted (B) or welded (W). The second letter indicates the type of shell, including inlet/outlet positions, presence of baffles, and distribution plates. The third letter specifies the rear end head type and how the shell connects to the second tube sheet—bolted (B) or welded (W).
For example, a BEM heat exchanger has a bonnet header, a one-pass shell, and a fixed tube sheet, all identified using the TEMA system for clear categorization and understanding of different heat exchanger designs.
Understanding these classifications helps in selecting the appropriate shell and tube heat exchanger for specific industrial needs, ensuring optimal performance, reliability, and longevity in heat exchange processes.
How Many Types of Shell and Tube Heat Exchanger?
Essentially, there are three main types of shell and tube heat exchangers that are commonly used:
1. Fixed Tube Sheet Exchanger (L, M, and N Type Rear Headers)
In this design, the tube sheet is welded to the shell, resulting in a simple and economical construction. While the tube bores can be cleaned mechanically or chemically, the outside surfaces of the tubes are generally inaccessible except for chemical cleaning. Expansion bellows may be necessary to accommodate large temperature differences between the shell and tube materials, but they can be a source of weakness and failure.
2. U-Tube Exchangers
In a U-Tube exchanger, the front header types may vary, and the rear header is typically an M-Type. U-tubes allow for unlimited thermal expansion, and the tube bundle can be removed for cleaning. However, internal cleaning of the tubes by mechanical means is difficult, making this type suitable only for applications where the tube side fluids are clean.
3. Floating Head Exchanger (P, S, T, and W Type Rear Headers)
In this type of exchanger, the tubesheet at the rear header end is not welded to the shell but allowed to move or float. The tubesheet at the front header end is of a larger diameter than the shell and is sealed similarly to the fixed tubesheet design.
Thermal expansion can be accommodated, and the tube bundle can be removed for cleaning. The S-Type Rear Head is the most popular choice for the rear header. Floating head exchangers are suitable for high temperatures and pressures but are generally more expensive compared to fixed tubesheet exchangers.
How Does Shell and Tube Heat Exchanger Work?
Shell and tube heat exchanger works by transferring heat between two fluids, such as liquids or gasses. The fluids are separated by a solid barrier and flow through separate channels. One fluid travels through tubes while the other flows around the tubes in the shell.
While the fluids flow through their channels, the heat is transferred from the hotter fluid to the cooler fluid through the barrier because of temperature differences and the barrier’s conductive properties of the solid barrier.
The shell and tube design provides a large surface area for heat transfer, making it an efficient method to carry the heat between fluids. Furthermore, the tubes can be removed for cleaning or replacement without affecting the shell, which makes it easy to maintain and clean.
What Are The Advantages of A Shell and Tube Heat Exchanger?
The advantages of a shell and tube heat exchanger include its simple design, robust characteristics, and relatively low purchase and maintenance costs. This type of heat exchanger is widely used in various cooling applications due to these benefits.
The simple design of a shell-and-tube heat exchanger makes it versatile and suitable for a range of cooling needs. It is commonly used to cool hydraulic fluid and oil in engines, transmissions, and hydraulic power packs. Additionally, with the right choice of materials, these heat exchangers can also be used to cool or heat other mediums such as swimming pool water or charge air.
One of the significant advantages of shell-and-tube heat exchangers is their ease of service, especially models with a floating tube bundle design where the tube plates are not welded to the outer shell. This makes maintenance and cleaning more accessible, contributing to efficient operation and extended lifespan. Furthermore, the cylindrical design of the housing provides excellent resistance to pressure, making shell-and-tube heat exchangers suitable for a wide range of pressure applications in various industries.
PetroSync’s Shell and Tube Heat Exchangers training course is a five-day course that aims to provide you with a thorough understanding of the ASME/ TEMA codes and standards related to mechanical design engineering, maintenance, repair, and testing of shell and tube heat exchangers.
We emphasize the importance of comprehending both the stated and implied requirements of the codes. You will also learn about the practical application of these code/standard rules and mechanical design formulas under different design conditions and services. Compared to other codes and standards like BS/DIN, ASME Section VIII/TEMA are easier to use and commonly adopted guidelines.
The course will help you gain confidence in carrying out the design, maintenance, and testing of shell and tube heat exchangers, as well as in strength calculations and assessing the integrity of existing exchangers.
The course will also provide case discussions to illustrate how to adopt code rules for different types of exchangers and service conditions. Let’s improve your heat exchanger performance by maximizing your mechanical design, operation, and maintenance knowledge with PetroSync!
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