What is a shell-and-tube heat exchanger and how does it work?

Michaël Dreesen · 28 Oct 2026

60+ years of experience
120+ employees
Units up to 10 m diameter
Up to 1,000 tons

A shell-and-tube heat exchanger is a device that transfers thermal energy between two fluids without allowing them to mix. One fluid flows through a bundle of tubes, while the other flows around those tubes inside an outer cylindrical shell. The temperature difference between the two fluid streams drives heat from the hotter fluid to the cooler one across the tube walls.

This design is one of the most widely used heat transfer configurations in industrial processing because it handles high pressures, high temperatures, and aggressive media more reliably than most alternatives. The sections below address the most common questions about how these exchangers work, how they are built, and when material selection becomes critical.

How does a shell-and-tube heat exchanger transfer heat?

A shell-and-tube heat exchanger transfers heat by passing two fluid streams past each other through a metal barrier (the tube wall) without direct contact. One fluid travels through the interior of the tubes; the other circulates through the shell space surrounding those tubes. The temperature gradient between the two streams drives thermal energy from the hotter side through the tube wall to the cooler side by conduction and convection.

The efficiency of this transfer depends on several interacting factors: the surface area available for heat exchange, the velocity of both fluid streams, the thermal conductivity of the tube material, and the overall temperature difference between the two fluids at any given point along the exchanger.

In most industrial applications, the two fluids travel in opposite directions, a configuration known as counterflow. This arrangement maintains a more consistent temperature difference along the full length of the exchanger, which improves thermal performance compared to a parallel-flow arrangement where both fluids enter from the same end.

What are the main components of a shell-and-tube heat exchanger?

The main components of a shell-and-tube heat exchanger are the shell, the tube bundle, the tubesheets, the baffles, and the end headers or channel covers. Together, these elements direct both fluid streams, support the mechanical structure, and maximise the contact surface between the two fluids.

Shell: The outer cylindrical pressure vessel that contains the shell-side fluid and houses the tube bundle.
Tube bundle: A set of parallel tubes through which the tube-side fluid flows. The bundle determines the available heat transfer surface area.
Tubesheets: Thick plates at each end of the shell that hold the tubes in position and separate the two fluid streams. They are among the most mechanically demanding components in the assembly.
Baffles: Internal plates within the shell that direct the shell-side fluid across the tube bundle in a controlled path, increasing velocity and improving heat transfer.
Channel covers and headers: End enclosures that direct the tube-side fluid into and out of the tubes, and allow access for inspection and cleaning.
Nozzles: Inlet and outlet connections on both the shell and the channel for fluid entry and exit.

In demanding applications, the connection between the tubes and the tubesheets requires particular attention. Tube-to-tubesheet joints must be leak-tight under operating pressure and must accommodate differential thermal expansion between the tubes and the shell during temperature cycling.

What is the difference between shell side and tube side?

The shell side is the region inside the outer shell but outside the tubes, where one fluid flows around the tube bundle. The tube side is the interior of the tubes themselves, where the other fluid flows. Each side operates at its own pressure and temperature, and the two fluids are separated by the tube walls and tubesheets throughout the exchanger.

Deciding which fluid goes on which side is an engineering choice that affects both performance and long-term reliability. Several considerations drive this decision.

Pressure and corrosion considerations

Higher-pressure fluids are typically routed through the tube side, because tubes are more economical to design and fabricate for elevated pressures than a large-diameter shell. Corrosive or aggressive fluids are also commonly placed on the tube side, since it is less expensive to specify a premium corrosion-resistant material for the tubes and tubesheets than to construct the entire shell from that material.

Fouling and maintenance considerations

Fluids with a tendency to deposit scale or particulates are often placed on the tube side because the straight tube interior is easier to clean mechanically. The shell side, with its more complex flow path around baffles, is harder to access for mechanical cleaning and is therefore better suited to cleaner process streams.

What are the different types of shell-and-tube heat exchangers?

Shell-and-tube heat exchangers are classified primarily by how the tube bundle is constructed and how it accommodates thermal expansion. The most common configurations are the fixed tubesheet, the U-tube, and the floating head exchanger, each suited to different operating conditions.

Fixed tubesheet: Both tubesheets are welded directly to the shell. This is the simplest and most compact design, but it provides no means of differential expansion between the shell and tubes. Expansion bellows in the shell are sometimes added to manage this. Suitable when temperature differences between the two streams are moderate.
U-tube: The tubes are bent into a U-shape and attached to a single tubesheet. The free end of each tube can expand independently, eliminating differential expansion concerns. The tube bundle can be removed for shell-side cleaning, but the U-bends are difficult to clean mechanically on the tube side.
Floating head: One tubesheet is fixed and the other is free to move axially within the shell. This configuration handles large temperature differences well and allows the bundle to be removed for cleaning on both sides. It is the most mechanically complex of the three but is widely used in demanding refining and chemical applications.

Beyond these three principal configurations, standards bodies such as TEMA (Tubular Exchanger Manufacturers Association) define a broader classification system using letter codes for shell type, front end, and rear end configurations. Design teams working to ASME, TEMA, and HTRI standards use these codes to specify exchanger geometry precisely.

What industries use shell-and-tube heat exchangers?

Shell-and-tube heat exchangers are used across virtually every sector of industrial processing where thermal energy must be transferred between fluid streams under controlled conditions. Their ability to handle high pressures, elevated temperatures, and aggressive media makes them the standard choice in technically demanding environments.

Common industries and applications include oil and gas processing, petrochemical and chemical production, power generation, mining and hydrometallurgy, pharmaceutical manufacturing, and food and beverage processing. Within chemical production specifically, they appear in processes ranging from purified terephthalic acid (PTA) production and acetic acid synthesis to brine purification and biofuel processing.

In hydrometallurgical operations such as high-pressure acid leaching for nickel and cobalt recovery, heat exchangers must handle highly corrosive process streams at elevated pressures, conditions that demand careful material selection and precision fabrication. The same applies to chlor-alkali processes and other electrolytic applications where aggressive chemical environments are the norm rather than the exception.

When does a shell-and-tube heat exchanger require special materials?

A shell-and-tube heat exchanger requires special materials when the process fluid is chemically aggressive, when operating temperatures exceed the reliable range of carbon steel or standard stainless steel, or when contamination of the process stream by corrosion products is unacceptable. In these situations, the choice of tube and shell material directly determines the service life and reliability of the equipment.

Common scenarios that drive the use of advanced materials include:

Highly acidic or oxidising media: Processes involving acetic acid, chlorine compounds, or concentrated oxidising agents often require titanium, zirconium, or Hastelloy alloys to resist corrosion at the tube and tubesheet surfaces.
Elevated temperature combined with corrosive conditions: At higher temperatures, corrosion rates accelerate, and materials that perform adequately at ambient conditions may degrade rapidly. Titanium Grade 9 tubes, for example, are used in PTA preheater applications where operating temperatures exceed the limits typically addressed by standard code allowables.
Halide-containing streams: Chloride-bearing fluids are particularly aggressive toward austenitic stainless steels and can cause stress corrosion cracking. Titanium and zirconium offer substantially better resistance in these environments.
Purity-critical processes: Where even trace contamination from corrosion products is unacceptable, inert materials such as zirconium or tantalum may be required regardless of the overall corrosivity of the stream.

Material selection also affects fabrication complexity. Exotic alloys such as zirconium and titanium require specialised welding procedures, controlled workshop environments, and qualified personnel. Tube-to-tubesheet expansion and welding in these materials demand particular care to avoid cracking and to maintain joint integrity under thermal cycling. These fabrication requirements are as important to long-term performance as the material properties themselves.

Where solid construction in a premium alloy would be prohibitively expensive, clad construction (combining a carbon steel structural shell with a corrosion-resistant inner layer) offers a technically sound and cost-effective alternative for the shell side of the exchanger.

How Coek Engineering approaches demanding shell-and-tube heat exchangers

Coek Engineering designs and manufactures custom shell-and-tube heat exchangers for applications where standard fabrication is not sufficient. The focus is on technically complex equipment: exchangers involving exotic materials, demanding operating conditions, precise tube-to-tubesheet requirements, or large-scale dimensions.

Relevant capabilities include:

Fabrication in titanium (including Ti Grade 9 and Ti Grade 2), zirconium, Hastelloy, tantalum, and other advanced alloys
Clad construction combining structural carbon steel with corrosion-resistant inner layers
In-house design engineering to ASME, TEMA, AD Merkblätter, and HTRI standards, including FEA, fatigue, thermal, and vibration analysis
References in PTA, acetic acid, brine purification, biofuels, and other chemically demanding processes
Large-scale manufacturing capacity at facilities in Geel and Genk, Belgium

Coek receives process requirements from EPC contractors, technology owners, and industrial end users and translates these into mechanically sound, manufacturable equipment. If your project involves a heat exchanger where material selection, operating conditions, or dimensional requirements go beyond what commodity fabricators can reliably address, contact Coek Engineering to discuss your specification.

Frequently Asked Questions

How do I know whether to choose a fixed tubesheet, U-tube, or floating head design for my application?

The decision comes down to three main factors: the temperature differential between your two fluid streams, the need to clean both sides of the exchanger, and your budget. If the temperature difference between shell and tube side is modest and only one side needs mechanical cleaning, a fixed tubesheet or U-tube design is usually sufficient and more cost-effective. If you are dealing with large temperature swings, heavily fouling fluids on both sides, or a chemically aggressive process that demands periodic bundle removal for inspection, a floating head exchanger is the more appropriate choice despite its added mechanical complexity.

What are the most common causes of premature failure in shell-and-tube heat exchangers?

The most frequent causes are flow-induced vibration of the tube bundle, stress corrosion cracking at the tube-to-tubesheet joints, fouling-driven underdeposit corrosion, and inadequate allowance for differential thermal expansion. Many of these failures trace back to the design or fabrication stage rather than to operational misuse — for example, baffle spacing that is too wide can allow tubes to vibrate under shell-side flow, eventually causing fatigue cracks near the tubesheet. Specifying a thorough vibration analysis and a correctly executed tube-to-tubesheet joining procedure during procurement significantly reduces these risks.

How does fouling affect performance over time, and what can be done to manage it?

Fouling deposits on tube surfaces act as an additional thermal resistance, progressively reducing heat transfer efficiency and increasing pressure drop across the exchanger. In practice, this means the exchanger may no longer meet its thermal duty well before the end of its intended service life. Managing fouling starts at the design stage by applying an appropriate fouling resistance factor, routing the more fouling-prone fluid to the tube side for easier mechanical cleaning, and selecting tube materials or surface finishes that resist deposit adhesion. Establishing a regular cleaning and inspection schedule based on actual operating data is the most reliable way to maintain performance over the long term.

When should I consider clad construction instead of solid exotic alloy fabrication?

Clad construction becomes attractive when the primary driver for using a premium alloy — such as titanium or zirconium — is corrosion resistance on the wetted surfaces, but the structural load is carried by a carbon steel substrate. If solid construction in the corrosion-resistant alloy would result in a disproportionate cost for a large-diameter shell, a clad shell (carbon steel with a bonded corrosion-resistant liner) delivers equivalent chemical protection at a significantly lower material cost. The trade-off is added fabrication complexity in the welding and inspection of the cladding interface, so this approach requires a fabricator with demonstrated experience in clad construction and the relevant code qualifications.

What information do I need to provide to get an accurate quote or design proposal for a custom heat exchanger?

At a minimum, a design team needs the process fluid identities and compositions for both sides, inlet and outlet temperatures, flow rates or heat duty, operating pressures, fouling tendencies, and any known corrosion constraints. Additional information that significantly improves the accuracy of a proposal includes the applicable design standards (ASME, TEMA class, AD Merkblätter), site or installation constraints such as maximum length or weight, and any previous exchanger history if this is a replacement unit. The more completely you can describe the process environment and operational context upfront, the less iteration is required to arrive at a sound technical specification.

Can shell-and-tube heat exchangers handle two-phase flow, such as condensing steam or boiling process fluids?

Yes, and in fact some of the most common industrial applications — steam condensers, reboilers, and vaporisers — involve two-phase flow on at least one side of the exchanger. Two-phase applications introduce additional design considerations, including the need to account for varying fluid density and velocity along the flow path, potential flow instability, and the management of non-condensable gases that can accumulate and reduce effective heat transfer area. These factors make thermal and hydraulic design more complex than for single-phase service, and they often influence the choice of exchanger orientation (horizontal versus vertical) and internal configuration.

How do TEMA and ASME standards relate to each other, and do I need to comply with both?

ASME and TEMA address different aspects of the same equipment. ASME Section VIII covers pressure vessel design and fabrication requirements — essentially the safety case for containing pressure — while TEMA standards govern the mechanical design details specific to heat exchangers, such as tubesheet thickness calculations, baffle design, nozzle load allowances, and fabrication tolerances. In most industrial projects, compliance with both is expected: ASME provides the pressure containment framework and TEMA fills in the heat-exchanger-specific engineering details that ASME does not cover. The applicable TEMA class (R, C, or B) is typically specified by the end user or EPC contractor based on the severity of the service.