Using shell and tube heat exchangers?
Shell and tube heat exchangers are one of the most common types of heat exchanger because of their versatility. They are highly customisable, with many different types for different applications. This includes different flow types, head configurations, tube plates and materials.
A plant, factory or other business might not have much flexibility in the type of shell and tube heat exchanger they need to use, but it can still be a bespoke configuration to provide the best solution to the specific process.
This article covers the function, parts, applications and benefits of shell and tube heat exchangers. If you have further questions, read one of the following articles:
- Types of shell and tube heat exchanger
- Designing bespoke heat exchangers
- Designing high-temperature shell and tube heat exchangers
- Heat exchanger maintenance guide
- Shell and tube products from Sterling Thermal Technology
If you’re looking for a heat exchanger for your process, get in touch.
What is a shell and tube heat exchanger?
Shell and tube units are a type of heat exchanger commonly used in industrial applications to transfer heat between fluids. The design consists of a shell (outer vessel) and a series of tubes (inner vessel) through which the fluids flow. Heat is transferred between the fluids through the walls of the tubes.
How they work
One fluid flows through the tubes, whilst the other fluid flows around the tubes inside a larger shell. Heat is transferred from the hot fluid to the cold fluid through the walls of the tubes, resulting in a temperature difference between the two fluids.
Depending on the design, there will be a different number of passes between the substances and different flows (e.g. counterflow, etc.) to suit the specific substances and requirements of the process.
Why are shell and tube heat exchangers popular?
Shell and tube heat exchangers have advantages over other options, such as their efficient heat exchange rates and how easily they adapt to suit a range of purposes. They can be designed with various custom features to best suit the specific process requirements, improving efficiency and providing flexibility.
For example, engineers can incorporate tubeplates into the design or add extended surface fins. They can be made from different materials according to the substances involved and the demands of the process. Read our blog on the materials used in industrial heat exchangers.
Industries and applications of shell and tube heat exchangers
Because shell and tube heat exchangers are extremely versatile and can be designed in multiple configurations, many industries use them.
These are just some of the industries that commonly use shell and tube heat exchangers.
- Chemical plants
- Oil plants and refineries
- Marine and Defence
- Energy production (including nuclear)
- Food processing and production
The number of industries that use shell and tube heat exchangers is extremely large because these heat exchangers can help with several different processes, including:
- Removal of process heat
- Preheating feed water or other liquid
- Condensing process vapour or steam
- Evaporating process liquid or steam
- Cooling hydraulic and lube oil
- Cooling turbines, compressors and engines
Parts of a shell and tube heat exchanger
It is in the unique design of each heat exchanger that the true versatility of the product can be seen. By designing each shell and tube heat exchanger to our customers’ requirements, we can ensure that the final product is ideally suited for the process and environment in which it will operate. It’s one of the reasons why heat exchangers are so commonly used.
Let’s examine some of the elements of the heat exchanger to understand the different design configurations.
The shell encases the tube bundle and other internal components.
One of the critical aspects of shell design is the materials of construction. The shell needs to be heat resistant and able to withstand temperature changes. In some processes, it must be corrosion-resistant. For example, shell and tube heat exchangers used in seawater or chemical processes often need to be corrosion resistant.
The tube bundle
The tube bundle holds the tube-side medium, which undergoes a change in temperature.
Various ways exist to customise the tubes and tube bundle of a shell and tube heat exchanger, including the type of material, the diameter, the number of passes and the tube shape (e.g. U-tubes).
The tube bundle can be removable in some assemblies.
The tube pitch is the distance between the centre of one tube to the centre of the adjacent tube.
It is typically measured as the perpendicular distance between the tubes and is an important design parameter that affects the heat transfer efficiency and pressure drop in the heat exchanger. Tubes can be arranged in triangular or square configurations for different purposes.
The tube pitch is an important parameter that must be carefully selected during the design of a shell and tube heat exchanger to ensure optimal performance and reliability.
Channels or heads
Shell and tube manufacturers can use many different types of heads. For example, if frequent maintenance of the heat exchanger will be required, a removable cover channel might be most suitable. Bonnet heads are perhaps the most commonly used on shell and tube heat exchangers that don’t require frequent maintenance.
Tube sheets can add greater flexibility and ensure the heat exchanger can meet more challenging environmental demands.
A fixed tube sheet is a ‘standard’ design used when there are no significant operating challenges.
On the other hand, a double tube sheet, for example, is used where the substances involved must not mix. This is common in chemical operations, among others. The tube sheet design creates an evacuation route for any leaking substance, triggering an alert.
For more information, read ‘heat exchanger tube sheets for challenging operations’.
An expansion joint (also known as bellows) allows the shell and tube heat exchanger to adapt to changes in temperature, expanding or shrinking as the material gets hotter or colder.
Heat exchangers that handle wide temperature ranges need expansion joints to prevent stress on other elements, which could otherwise lead to damage.
Baffles direct the flow of the substances within the heat exchanger, helping to achieve the most effective velocity for a high heat transfer coefficient. Designing the correct baffle for the product parameters can improve efficiency, reduce fouling and make the equipment fitter for its purpose.
In some configurations, baffles also support the tubes to prevent sagging or damage from vibration.
Extended surface fins
Extended surface fins can be integrated into shell and tube designs to improve efficiency and make the product more compact and/or more economical. They increase the surface area of the exterior side of the tube to enhance the balance of the heat transfer coefficients.
Find out more about enhanced heat exchangers with extended fins.
Basic shell and tube heat transfer calculations
One of the most important equations the describes the function of a shell and tube heat exchanger is:
Q = U x A x ΔTm
- Q is the rate of heat transfer.
- U is the overall heat transfer coefficient.
- A is the heat transfer area.
- ΔTm is the log mean temperature difference between the hot and cold fluids.
With this equation, we can calculate the heat transfer rate in a heat exchanger. It is commonly used in the design and analysis of heat exchangers, allowing engineers to optimise the performance and efficiency of the heat exchange process.
For example, we could use this equation to calculate the surface area required in our heat exchanger to cool a material to a required temperature. In this case, we would rearrange the equation to:
A (surface area) = Q / (U x ΔTm)
Getting a heat exchanger that meets your needs
Several factors must be considered to design a shell and tube heat exchanger that meets your needs.
- Identify your specific process fluids and operating conditions. This will determine the appropriate design and material selection for your heat exchanger.
- Ensure that the materials used are appropriate and high quality. This will depend on your application, such as requiring corrosion-resistant alloys for harsh environments.
- Consider your future needs and potential expansion plans. You want your heat exchanger to accommodate changes in your process.
- Know your budget. Balance your needs with the price and delivery time while ensuring that you get a product that meets your quality standards.
- Work with a reliable manufacturers and suppliers. They should have a s good reputation, experience, certifications and positive customer reviews.
Standards for shell and tube heat exchangers
Like all heat exchangers, shell and tube heat exchangers are subject to multiple standards and regulations. TEMA, or Tubular Exchanger Manufacturers Association, is the most widely used standard for shell and tube heat exchangers.
However, there are other industry codes and regulations related to the pressure vessels used in heat exchangers, including:
- ASME (American)
- EN13445 (European)
- CODAP (France)
For more information, visit our heat exchanger standards page.
Versatility and flexibility
Shell and tube heat exchangers are the most common variety of heat exchangers currently used in the industry sector, thanks to their efficiency and cost-effectiveness. Their design configurations are extremely versatile and flexible, so each heat exchanger can be customised to suit its purpose.
Sterling TT is specialised in designing and manufacturing bespoke heat exchangers for industrial applications. Want to know more? View our shell and tube heat exchanger page, or get in touch today by filling the below form.