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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 coolerAir 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 airAmbient air describes air present in the existing environment.
Ambient conditionsAmbient conditions describe the conditions such as temperature, pressure, humidity and dust present in the environment.
Axial flow fansTo transport gas (air) using a motor and propeller.
BarThe unit used to measure pressure. For example, compact tube heat exchangers can safely refrain gases of pressures 5-10 bar.
BonnetA bonnet is a type of cover present at each end of a heat exchanger.
Bundle assemblyDescribes the arrangement and assembly of tubes, tube sheets, baffles, spacers and tie rods (typically) in removable bundle heat exchangers.
CACA coolerClosed 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 coolerClosed 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 circuitA 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 tube heat exchangersA compact 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) softwareSoftware 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.
CondensersCondensers cool a gaseous substance past its dewpoint and into a liquid form.
CoolantCoolant 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 assemblyCore assembly refers to the arrangement and assembly of shell and tubes in fixed tube heat exchangers. See also – Tube sheet
Counterflow arrangementThe 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 arrangementThe primary substance and coolant or heating substance move perpendicular to each other, such as in a fin heat exchanger.
Design pressureAlso 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.
DewpointThe atmospheric temperature (varying according to pressure, etc.) at which a substance condenses from gaseous form to liquid.
EconomiserEconomisers 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 plateA cover that is fixed onto the end of the heat exchanger, particularly in bonnet assemblies.
Enhanced finsEnhanced 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 surfaceSee ‘Finned tubes’.
Fin fan coolerSee ‘Air blast cooler’.
Finned tubesAlso 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 gasesGases that exit into the atmosphere via a flue. They are commonly found in boilers, for example, and, on a larger scale, in power stations.
FoulingFouling 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 coolersGas coolers remove excess heat from a gaseous stream, for example, CO2 cooling in a refrigeration system.
Gas-to-liquid heat exchangersSee ‘Condensers’.
GasketA gasket is applied between two surfaces of a heat exchanger to prevent leaks.
Heat exchangerA heat exchanger is a device that transfers heat energy from one medium to another.
Heat transfer efficiencyMeasures the actual heat rate transferred compared to heat transferred in an ideal heat exchanger and expressed as a percentage.
Heat transfer rateThe amount of heat that is transferred per unit of time, for example, joules per second.
Hydrogen coolerA hydrogen cooler is a type of heat exchanger that uses hydrogen as the coolant.
Modular designA 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.
OFAFOil forced, air forced cooler. OFAF coolers use the forced movement of air and oil to aid heat dissipation in an oil-type transformer.
OFWFOil 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 passThis 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 pressureThe pressure that a heat exchanger usually operates at during normal running. Normally at least 10% below design pressure.
Parallel flow arrangementThe 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.
PreheaterA 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 streamProcess stream describes all substances that flow through the process equipment. It can be liquid or gas.
Range temperatureThe temperature difference of a fluid (or gas) as it moves through the heat exchanger
ReboilersShell 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 bundleWhen the tube bundle can be removed for maintenance or cleaning.
ShellSee ‘shell and tube heat exchangers’.
Shell and tube heat exchangersA 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 assemblyThe assembly in which the tube bundle sits in a shell and tube heat exchanger.
Shell headThe 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 sideShell 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 exchangerA 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 coolerTotally Enclosed Air to Air Cooled cooler. See ‘CACA cooler’.
Test pressureA test that checks for leaks that could occur on the heat exchanger joints, above both operating and design pressure.
TEWAC coolerTotally Enclosed Water to Air-Cooled cooler. See ‘CACW cooler’.
ThermosyphonsThermosyphons are devices with high thermal conductivity comprising of sealed tubes containing refrigerants. They allow heat to transfer without the need for pumps and fans.
TIRTest, 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 coolersTransformer 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.
TubeThe 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 sheetA 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 exchangersA 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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