Square collage of coolers and heat exchangers supplied by Sterling Thermal Technology

What is a heat exchanger?

Heat exchangers are used everywhere, from in your home’s central heating to generating electricity, but what is a heat exchanger, and how do they work?

Sterling TT, an expert heat exchanger manufacturer, has broken down all the information.

Use the navigation below to skip to the information you’re looking for:

What is a heat exchanger?
How do heat exchangers work?
Types of heat exchanger
Common Applications
Designing heat exchangers
How are heat exchangers installed?
How are heat exchangers maintained?
Can heat exchangers be repaired?

Want to read more? Try our blog on the key considerations for bespoke heat exchangers.

What’s a heat exchanger?

Square collage of coolers and heat exchangers supplied by Sterling Thermal Technology

A heat exchanger is a device that enables effective heat energy transfer between two mediums without them mixing. It heats or cools something by transferring the heat energy through the process of conduction. For example, to keep a car engine cool.

What is a heat exchanger used for ?

Heat exchangers are used to give control over the temperature in various processes to improve efficiency, prevent overheating or other potential hazards, and to improve safety.

For example, an oil cooler cools down hot oil by passing cold water next to the hot oil tube. The heat from the oil is transferred into the cold water, reducing the temperature of the oil.

Wherever heat is being generated in a process, heat exchangers can be used to keep the process safe, as well as use the heat energy most efficiently. As there are so many different places they can be used, there are a lot of different varieties.

If you don’t understand any terms that we’re using, refer to our heat exchanger glossary

How do heat exchangers work?

Heat exchangers work differently according to the specific type. They use a combination of conduction and convection to move energy, in the form of heat, from one location or flow to another. They generally operate in a sensible heat range and occasionally engage the stored capacity of state change, enthalpy.

This could mean heating one medium by conducting heat into it. Alternatively, it could be cooling something by transferring heat from it into another medium, such as air or water. The goal is to improve efficiency or safety of a process. Some processes wouldn’t work at all without a heat exchanger.

Read how each of the common types of heat exchanger works below.

Different types of heat exchanger

There are many different types of heat exchanger from small heat exchangers used in car engines through to industrial ones used in nuclear power generation or in manufacturing.

Below are some of the most commonly used types of heat exchanger, including those which Sterling TT manufactures.

Shell and tube

Heat exchanger, shell and tube designed and manufactured by Sterling Thermal Technology

Shell and tube heat exchangers involve one tube which contains the medium that needs cooling or heating. This is surrounded by the ‘shell’ which contains the fluid that cools or heats the first medium.

There are a few different varieties of shell and tube heat exchangers including counterflow, parallel flow and cross flow.

It depends on the medium being cooled or heated as to which would work best. When we’re recommending a heat exchanger, we always discuss the application and goals to decide which variety will be most effective.

Finned Tube

photo of finned tubes designed and manufactured by Sterling Thermal TechnologyFinned tube heat exchangers maximise surface area to improve the speed and efficiency of the heat transfer. This is especially helpful when the fluid or medium has a very low thermal conductivity, such as air.

They consist of a stack of evenly spaced plates, which are the fins. The tubes are placed through pre-cut holes in the fins. Thanks to their large surface area, finned tube heat exchangers are sometimes referred to as extended surface heat exchangers.

Some common finned tube heat exchangers are gas coolers, for example.

Find out more about finned tube heat exchangers.


photo of an air cooled condenser showing the fan, designed and manufacture by Sterling Thermal TechnologyWith air-cooled heat exchangers, the fluid is cooled using air, commonly supplied through a fan. There are some occasions where no fan is used, and instead, the process relies on movement.

For example, air-cooled condensers use air to cool a gaseous process stream past its dew point, condensing it.

Plate Type

Plate heat exchangers are very similar to shell and tube heat exchangers. They maximise surface area through a stack of plates. On the whole, finned tube is used much more often now due to increased efficiency over standard plate type.

Common heat exchanger applications

Heat exchanger applications include power generation in power plants, heating and air con systems, refrigeration, manufacturing, food processing, chemical processing, car radiators and many others.

Heat exchangers are used in thousands of different places.

At home

Around the home, they’re commonly found in central heating combi boilers and help to heat and cool down the water efficiently and safely. They’re also found in your refrigerator, ensuring it stays at a stable, cool temperature.

Public Spaces

You’re also likely to have benefited from heat exchangers in public places. Your local swimming pool would be much colder without a heat exchanger helping to keep the water warm.

Car engines produce a lot of heat and this needs to be managed effectively to prevent dangers. Cars often use a combination of fans and air flow, with fins to dissipate heat, and the use of a coolant fluid.


Heat exchangers are also used widely in different industrial applications. This includes power generation, the manufacture and storage of food, chemical engineering, and even in the running of air and marine transport, for example.

Sterling TT works with a range of industries to provide specialist heat exchangers. Find out more about the markets we serve.


Even in the defence sector, we find heat exchangers. They are installed, for example, on the navy surface and auxiliary ships as well as on submarines. They cool nuclear submarine propulsion motors.

Design & manufacturing heat exchangers

How are heat exchangers designed?

Heat exchangers are designed according to the specific requirements of where they’ll be used. Different processes bring different challenges, so it’s essential to have a suitable heat exchanger that performs well under the pressures of the specific process.

When designing, we consider the specific goals and challenges of your process. From this, we then design the heat exchanger taking into account:

  • Primary fluid type temperature and flow rate
  • The goal of the heat transfer and whether you want to reuse heat energy in the process
  • The secondary fluid type’s temperature and flow rate
  • The appropriate materials – for example, to maximise efficiency while minimising corrosion
  • Your budget and cost considerations

If you’d like to discuss your project, simply get in touch with Sterling TT.

Common materials used in heat exchangers

Selecting the materials used in a heat exchanger is a pivotal part of the design. They need to be heat conductive whilst withstanding any corrosive properties of the mediums involved. Some materials will wear or get dirty faster than others, so upkeep and durability is another consideration.

Conductive metals

The vast majority of heat exchangers rely on conductive metals. For example, copper and steel are popular choices. However, they’re only suitable for applications up to a certain temperature and where the fluids involved won’t react with the metals.

While conductive metals are most common, in some applications ceramics or especially designed plastic polymers can be a better alternative.


The fluids used in the process are an important element. We design heat exchangers suitable to have seawater, oil, water or water-glycol as the coolant. We select the best option according to both your resources and the other medium involved.

We can also design heat exchangers for use with more corrosive fluids such as acids, chlorinated salt water and other chemicals. If these are being used, we carefully consider the appropriate materials to prevent corrosion.


Air is also commonly used in heat exchanger systems. It has a low thermal conductivity and, therefore, often works well with an extended surface heat exchanger such as our enhanced fin heat exchanger.

Installations and aftermarket & service support

How are heat exchangers installed?

For heat exchangers in devices around the home, they’ll be installed during the manufacturing or installation of the item.

However, with industrial heat exchanges, installations can be more complex as the devices are often bigger or involve more challenging mediums.

An experienced engineer installs the heat exchangers that Sterling TT designs and manufacturers. This ensures that they are correctly installed and are functioning effectively.

How are heat exchangers maintained?

Maintaining a heat exchanger well helps to increase its lifespan. However, this starts in the design process.

When we design a heat exchanger, we take into account the materials and any corrosion or build-up that might occur, as well as the placement of the heat exchanger and whether it is easily accessible for regular maintenance. We also consider how essential it is to your process and whether maintenance will lead to downtime.

From this, we design the heat exchanger to best suit your maintenance capabilities and recommend the appropriate maintenance schedule, such as cleaning.

We have a full aftercare service to ensure your heat exchanger lasts as long as possible.

Can a heat exchanger be repaired?

photo to illustrate aftersales serives at Sterling Thermal TechnologyMany companies prefer to repair an old heat exchanger rather than replace it due to cost considerations. Heat exchangers can usually be repaired, particularly if breaks are minor and if the heat exchanger is otherwise well maintained.

There are occasions where damage isn’t repairable, but a qualified engineer will always advise accordingly and with your budget in mind.

Find out more about our heat exchanger repair and aftermarket services.

Looking for more information about heat exchangers? Explore our website or get in touch for advice on your specific project. Why not read our blog on the key considerations for bespoke heat exchangers?

    This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.