Heat Exchanger Terminology Glossary
Confused about a term? Want to learn about a certain part or specific heat exchanger? View Sterling TT’s glossary of heat exchanger terminology to discover definitions for all the industry’s jargon.
Got more questions? Get in touch with Sterling TT to discuss your heat exchanger requirements. If you’re looking for a new heat exchanger, you might find out blog on ‘key considerations for bespoke heat exchangers‘ helpful.
| Air blast cooler | Air blast coolers use ambient air to cool fluids used in processes, such as lubricants. Is also referred to as a ‘fin fan cooler’ as a form of extended surface heat exchanger. |
| Ambient air | Ambient air describes air present in the existing environment. |
| Ambient conditions | Ambient conditions describe the conditions such as temperature, pressure, humidity and dust present in the environment. |
| Axial flow fans | To transport gas (air) using a motor and propeller. |
| Bar | The unit used to measure pressure. For example, compact shell & tube heat exchangers can safely refrain gases of pressures 5-10 bar. |
| Bonnet | A bonnet is a type of cover present at each end of a heat exchanger. |
| Bundle assembly | Describes the arrangement and assembly of tubes, tube sheets, baffles, spacers and tie rods (typically) in removable bundle heat exchangers. |
| CACA cooler | Closed Air Circuit Air-cooled cooler. CACA coolers are closed to prevent contaminants from entering the system and use air to remove excess heat. Also known as TEAAC coolers. CACA coolers use ambient air to indirectly cool the closed air circuit present in a machine. |
| CACW cooler | Closed Air Circuit, Water Cooled cooler. CACW coolers use water to indirectly cool the closed air circuit present in a machine. Also known as TEWAC coolers. |
| Closed circuit | A closed circuit refers to the air circulating in the machine. a closed environment in which external contaminants, such as dust, can’t enter the system. For example, CACA coolers and CACW coolers. |
| Compact shell & tube heat exchangers | A compact shell & tube heat exchanger is a smaller form of a shell and tube heat exchanger that optimises the heat transfer rate allowing for smaller heat transfer areas. |
| Computational fluid dynamics (CFD) software | Software that calculates specific fluid conditions through numerical and data analysis. It is used in heat exchanger manufacturing to calculate the dimensional requirements needed to achieve certain specifications. |
| Condensers | Condensers cool a gaseous substance past its dewpoint and into a liquid form. |
| Coolant | Coolant is the substance used in a cooler to reduce the temperature of the primary mediums. For example, water or hydrogen can both be coolants. |
| Core assembly | Core assembly refers to the arrangement and assembly of shell and tubes in fixed tube heat exchangers. See also – Tube sheet |
| Counterflow arrangement | The primary substance moves in the opposite direction of flow to the coolant or heating substance, leaving the tubes at opposite ends, achieving high efficiencies and low discharge temperatures. |
| Crossflow arrangement | The primary substance and coolant or heating substance move perpendicular to each other, such as in a fin heat exchanger. |
| Design pressure | Also referred to as the maximum allowed operating pressure, design pressure is used to calculate the thickness and other elements of heat exchanger design to ensure it can withstand maximum pressures during operation. |
| Dewpoint | The atmospheric temperature (varying according to pressure, etc.) at which a substance condenses from gaseous form to liquid. |
| Economiser | Economisers are a type of heat exchanger that recovers heat from flue gases, such as in boilers. The heat can then be used to pre-heat other fluids used in the process. |
| End plate | A cover that is fixed onto the end of the heat exchanger, particularly in bonnet assemblies. |
| Enhanced fins | Enhanced fins use more complex surface profiles to maximise the surface area between the mediums, increasing the heat transfer coefficient since gas has a poorer heat transfer rate than fluids. |
| Extended finned surface | See ‘Finned tubes’. |
| Fin fan cooler | See ‘Air blast cooler’. |
| Finned tubes | Also known as ‘fins’ or ‘extended surfaces’, finned tubes increase the surface area at the lower transfer side involved in the heat transfer process. They are most often used when a gas is present. |
| Flue gases | Gases that exit into the atmosphere via a flue. They are commonly found in boilers, for example, and, on a larger scale, in power stations. |
| Fouling | Fouling describes deposits of unwanted material building up within the heat exchanger. This could be sediment from the substance being heated or cooled, scaling, incrustation of the process fluids, or even biological growth in some specific processes. |
| Gas coolers | Gas coolers remove excess heat from a gaseous stream, for example, CO2 cooling in a refrigeration system. |
| Gas-to-liquid heat exchangers | See ‘Condensers’. |
| Gasket | A gasket is applied between two surfaces of a heat exchanger to prevent leaks. |
| Heat exchanger | A heat exchanger is a device that transfers heat energy from one medium to another. |
| Heat transfer efficiency | Measures the actual heat rate transferred compared to heat transferred in an ideal heat exchanger and expressed as a percentage. |
| Heat transfer rate | The amount of heat that is transferred per unit of time, for example, joules per second. |
| Hydrogen cooler | A hydrogen cooler is a type of heat exchanger that uses hydrogen as the coolant. |
| Modular design | A concept to construct equipment from a standard range of basic units. A design of a heat exchanger where elements (modules) can be easily removed. It helps maintain and repair the heat exchanger. For example, steam air heaters lend themselves well to a modular design. |
| OFAF | Oil forced, air forced cooler. OFAF coolers use the forced movement of air and oil to aid heat dissipation in an oil-type transformer. |
| OFWF | Oil forced, water forced cooler. OFWF coolers force the movement of air and water to aid heat dissipation in an oil-type transformer. |
| One / two / four pass | This describes the number of times the tube-side medium passes through the tube bundle. In a one-pass heat exchanger, it travels through the tubes once. In a two-pass, it travels through half of the tubes and returns through the other half. In four-pass, it travels through a quarter of the tubes, then back and repeats. |
| Operating pressure | The pressure that a heat exchanger usually operates at during normal running. Normally at least 10% below design pressure. |
| Parallel flow arrangement | The primary substance moves in the same direction as the coolant or heating substance, exiting the tubes at the same end. Typically used with high difference in temperature conditions of the medium. |
| Preheater | A heat exchanger that increases the temperature of a gas or liquid before it is fed into another process. For example, an air preheater does this specifically for air. |
| Process stream | Process stream describes all substances that flow through the process equipment. It can be liquid or gas. |
| Range temperature | The temperature difference of a fluid (or gas) as it moves through the heat exchanger |
| Reboilers | Shell and tube heat exchangers with process fluid on one side, and steam or a mixture of steam and condensate on the other side. There are many design variations. See our reboiler page for details. |
| Removable bundle | When the tube bundle can be removed for maintenance or cleaning. |
| Shell | See ‘shell and tube heat exchangers’. |
| Shell and tube heat exchangers | A heat exchanger that has a shell with a bundle of tubes inside it. One fluid runs through the tubes, and another fluid flows over the tubes, and within the shell allowing for heat transfer between the two fluids. Find out more about shell and tube heat exchangers. |
| Shell assembly | The assembly in which the tube bundle sits in a shell and tube heat exchanger. |
| Shell head | The shell head is a section or dome that is fixed onto the shell pipe to prevent leaking. They can come in a variety of shapes according to the specific design considerations of the heat exchanger. |
| Shell side | Shell side refers to the part in a shell and tube heat exchanger in which the fluid flows over the tubes (as opposed to the tube side, where the fluid flows inside the tubes). |
| Single tube heat exchanger | A single tube heat exchanger contains one single tube within the tube design, rather than multiple. For examples, see air blast coolers, air preheaters, CACA coolers, CACW cooler, or steam air heaters. |
| TEAAC cooler | Totally Enclosed Air to Air Cooled cooler. See ‘CACA cooler’. |
| Test pressure | A test that checks for leaks that could occur on the heat exchanger joints, above both operating and design pressure. |
| TEWAC cooler | Totally Enclosed Water to Air-Cooled cooler. See ‘CACW cooler’. |
| Thermosyphons | Thermosyphons are devices with high thermal conductivity comprising of sealed tubes containing refrigerants. They allow heat to transfer without the need for pumps and fans. |
| TIR | Test, inspection and report. A TIR identifies problems with a heat exchanger and provides a solution in report format – as part of maintenance or repairs work. Find more information on our test, inspection and report page. |
| Transformer oil water coolers | Transformer oil water coolers are a form of shell and tube heat exchanger that also includes a double wall. They’re used to control the temperatures of transformers where ambient temperatures are too high. |
| Tube | The pipes through which substances flow in the heat exchanger. They can be made of various materials to improve the efficiency of heat transfer while minimising corrosion. |
| Tube sheet | A tube sheet is a plate that supports the arrangement of tubes in a heat exchanger. It can be fixed, floating or stationary. |
| U-tube heat exchangers | A U-tube heat exchanger is a type of shell and tube heat exchanger, named for its u-shaped tube. It’s a popular heat exchanger for the chemical industry, but has limited use particularly when sediment is present. |
Got more questions? Get in touch with Sterling TT to discuss your heat exchanger requirements.
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