Editing Heat exchanger (section)

==Types==
By maximum operating temperature, heat exchangers can be divided into low-temperature and high-temperature ones. The former work up to 500–650°C depending on the industry and generally don't require special design and material considerations. The latter work up to 1000 or even 1400°C.<ref>{{Cite journal |last1=Mahmoudinezhad |first1=Sajjad |last2=Sadi |first2=Meisam |last3=Ghiasirad |first3=Hamed |last4=Arabkoohsar |first4=Ahmad |date=2023 |title=A comprehensive review on the current technologies and recent developments in high-temperature heat exchangers |url=https://www.sciencedirect.com/science/article/abs/pii/S1364032123003246 |journal=Renewable and Sustainable Energy Reviews |volume=183 |pages=113467 |doi=10.1016/j.rser.2023.113467 |bibcode=2023RSERv.18313467M |issn=1364-0321|url-access=subscription }}</ref><ref>{{Cite journal |last1=Kilkovsky |first1=Bohuslav |last2=Stehlik |first2=Petr |last3=Jegla |first3=Zdenek |last4=Tovazhnyansky |first4=Leonid L. |last5=Arsenyeva |first5=Olga |last6=Kapustenko |first6=Petro O. |date=2014 |title=Heat exchangers for energy recovery in waste and biomass to energy technologies – I. Energy recovery from flue gas |url=https://www.sciencedirect.com/science/article/abs/pii/S1359431113008454 |journal=Applied Thermal Engineering |volume=64 |issue=1 |pages=213–223 |doi=10.1016/j.applthermaleng.2013.11.041 |bibcode=2014AppTE..64..213K |issn=1359-4311|url-access=subscription }}</ref><ref>{{Cite web |last=Metz |first=Cathy |date=2022-10-17 |title=Considerations of high temperature shell & tube {{!}} Sterling TT |url=https://www.sterlingtt.com/2022/10/17/unique-considerations-high-temperature-shell-and-tube-heat-exchangers/ |access-date=2025-01-12 |website=Sterling Thermal Technology |language=en-GB}}</ref>

Double pipe heat exchangers are the simplest exchangers used in industries. On one hand, these heat exchangers are cheap for both design and maintenance, making them a good choice for small industries. On the other hand, their low efficiency coupled with the high space occupied in large scales, has led modern industries to use more efficient heat exchangers like shell and tube or plate. However, since double pipe heat exchangers are simple, they are used to teach heat exchanger design basics to students as the fundamental rules for all heat exchangers are the same.

1.	Double-pipe heat exchanger

When one fluid flows through the smaller pipe, the other flows through the annular gap between the two pipes. These flows may be parallel or counter-flows in a double pipe heat exchanger.

(a)	Parallel flow, where both hot and cold liquids enter the heat exchanger from the same side, flow in the same direction and exit at the same end. This configuration is preferable when the two fluids are intended to reach exactly the same temperature, as it reduces thermal stress and produces a more uniform rate of heat transfer.
 
(b) Counter-flow, where hot and cold fluids enter opposite sides of the heat exchanger, flow in opposite directions, and exit at opposite ends. This configuration is preferable when the objective is to maximize heat transfer between the fluids, as it creates a larger temperature differential when used under otherwise similar conditions.{{Citation needed|date=October 2023}}
 
The figure above illustrates the parallel and counter-flow flow directions of the fluid exchanger.
 
2.	Shell-and-tube heat exchanger

In a shell-and-tube heat exchanger, two fluids at different temperatures flow through the heat exchanger. One of the fluids flows through the tube side and the other fluid flows outside the tubes, but inside the shell (shell side).

Baffles are used to support the tubes, direct the fluid flow to the tubes in an approximately natural manner, and maximize the turbulence of the shell fluid. There are many various kinds of baffles, and the choice of baffle form, spacing, and geometry depends on the allowable flow rate of the drop in shell-side force, the need for tube support, and the flow-induced vibrations. There are several variations of shell-and-tube exchangers available; the differences lie in the arrangement of flow configurations and details of construction.

In application to cool air with shell-and-tube technology (such as [[intercooler]] / [[charge air cooler]] for [[Internal combustion engine|combustion engines]]), fins can be added on the tubes to increase heat transfer area on air side and create a tubes & fins configuration. 
 
3.	Plate Heat Exchanger
 
A plate heat exchanger contains an amount of thin shaped heat transfer plates bundled together. The gasket arrangement of each pair of plates provides two separate channel system. Each pair of plates form a channel where the fluid can flow through. The pairs are attached by welding and bolting methods. The following shows the components in the heat exchanger. 
 
In single channels the configuration of the gaskets enables flow through. Thus, this allows the main and secondary media in counter-current flow. A gasket plate heat exchanger has a heat region from corrugated plates. The gasket function as seal between plates and they are located between frame and pressure plates. Fluid flows in a counter current direction throughout the heat exchanger. An efficient thermal performance is produced. Plates are produced in different depths, sizes and corrugated shapes. There are different types of plates available including plate and frame, plate and shell and spiral plate heat exchangers. The distribution area guarantees the flow of fluid to the whole heat transfer surface. This helps to prevent stagnant area that can cause accumulation of unwanted material on solid surfaces. High flow turbulence between plates results in a greater transfer of heat and a decrease in pressure. 
 
4.	Condensers and Boilers 
Heat exchangers using a two-phase heat transfer system are condensers, boilers and evaporators. Condensers are instruments that take and cool hot gas or vapor to the point of condensation and transform the gas into a liquid form. The point at which liquid transforms to gas is called vaporization and vice versa is called condensation. Surface condenser is the most common type of condenser where it includes a water supply device. Figure 5 below displays a two-pass surface condenser. 
 
The pressure of steam at the turbine outlet is low where the steam density is very low where the flow rate is very high. To prevent a decrease in pressure in the movement of steam from the turbine to condenser, the condenser unit is placed underneath and connected to the turbine. Inside the tubes the cooling water runs in a parallel way, while steam moves in a vertical downward position from the wide opening at the top and travel through the tube. 
Furthermore, boilers are categorized as initial application of heat exchangers. The word steam generator was regularly used to describe a boiler unit where a hot liquid stream is the source of heat rather than the combustion products. Depending on the dimensions and configurations the boilers are manufactured. Several boilers are only able to produce hot fluid while on the other hand the others are manufactured for steam production.

===Shell and tube===
{{Main|Shell and tube heat exchanger}}

[[Image:Straight-tube heat exchanger 1-pass.svg|thumb|right|A shell and tube heat exchanger]]
[[File:Shell_and_tube_heat_exchanger.jpg|thumb|Shell and tube heat exchanger]]
Shell and tube heat exchangers consist of a series of tubes which contain fluid that must be either heated or cooled. A second fluid runs over the tubes that are being heated or cooled so that it can either provide the heat or absorb the heat required. A set of tubes is called the tube bundle and can be made up of several types of tubes: plain, longitudinally finned, etc. Shell and tube heat exchangers are typically used for high-pressure applications (with pressures greater than 30 bar and temperatures greater than 260&nbsp;°C).<ref name=":0">Saunders, E. A. (1988). Heat Exchanges: Selection, Design and Construction. New York: Longman Scientific and Technical.</ref> This is because the shell and tube heat exchangers are robust due to their shape.<br>Several thermal design features must be considered when designing the tubes in the shell and tube heat exchangers:
There can be many variations on the shell and tube design. Typically, the ends of each tube are connected to [[Plenum chamber|plenums]] (sometimes called water boxes) through holes in tubesheets. The tubes may be straight or bent in the shape of a U, called U-tubes.
* Tube diameter: Using a small tube diameter makes the heat exchanger both economical and compact. However, it is more likely for the heat exchanger to foul up faster and the small size makes mechanical cleaning of the fouling difficult. To prevail over the fouling and cleaning problems, larger tube diameters can be used. Thus to determine the tube diameter, the available space, cost and fouling nature of the fluids must be considered.
* Tube thickness: The thickness of the wall of the tubes is usually determined to ensure:
** There is enough room for corrosion
** That flow-induced vibration has resistance
** Axial strength
** Availability of spare parts
** Hoop strength (to withstand internal tube pressure)
** Buckling strength (to withstand overpressure in the shell)
* Tube length: heat exchangers are usually cheaper when they have a smaller shell diameter and a long tube length. Thus, typically there is an aim to make the heat exchanger as long as physically possible whilst not exceeding production capabilities. However, there are many limitations for this, including space available at the installation site and the need to ensure tubes are available in lengths that are twice the required length (so they can be withdrawn and replaced). Also, long, thin tubes are difficult to take out and replace.
* Tube pitch: when designing the tubes, it is practical to ensure that the tube pitch (i.e., the centre-centre distance of adjoining tubes) is not less than 1.25 times the tubes' outside diameter. A larger tube pitch leads to a larger overall shell diameter, which leads to a more expensive heat exchanger.
* Tube corrugation: this type of tubes, mainly used for the inner tubes, increases the turbulence of the fluids and the effect is very important in the heat transfer giving a better performance.
* Tube Layout: refers to how tubes are positioned within the shell. There are four main types of tube layout, which are, triangular (30°), rotated triangular (60°), square (90°) and rotated square (45°). The triangular patterns are employed to give greater heat transfer as they force the fluid to flow in a more turbulent fashion around the piping. Square patterns are employed where high fouling is experienced and cleaning is more regular.
* Baffle Design: [[Baffle (heat exchanger)|baffles]] are used in shell and tube heat exchangers to direct fluid across the tube bundle. They run perpendicularly to the shell and hold the bundle, preventing the tubes from sagging over a long length. They can also prevent the tubes from vibrating. The most common type of baffle is the segmental baffle. The semicircular segmental baffles are oriented at 180 degrees to the adjacent baffles forcing the fluid to flow upward and downwards between the tube bundle. Baffle spacing is of large thermodynamic concern when designing shell and tube heat exchangers. Baffles must be spaced with consideration for the conversion of pressure drop and heat transfer. For thermo economic optimization it is suggested that the baffles be spaced no closer than 20% of the shell's inner diameter. Having baffles spaced too closely causes a greater pressure drop because of flow redirection. Consequently, having the baffles spaced too far apart means that there may be cooler spots in the corners between baffles. It is also important to ensure the baffles are spaced close enough that the tubes do not sag. The other main type of baffle is the disc and doughnut baffle, which consists of two concentric baffles. An outer, wider baffle looks like a doughnut, whilst the inner baffle is shaped like a disk. This type of baffle forces the fluid to pass around each side of the disk then through the doughnut baffle generating a different type of fluid flow.
*Tubes & fins Design: in application to cool air with shell-and-tube technology (such as [[intercooler]] / [[charge air cooler]] for [[Internal combustion engine|combustion engines]]), the difference in heat transfer between air and cold fluid can be such that there is a need to increase heat transfer area on air side. For this function fins can be added on the tubes to increase heat transfer area on air side and create a tubes & fins configuration.

Fixed tube liquid-cooled heat exchangers especially suitable for marine and harsh applications can be assembled with brass shells, copper tubes, brass baffles, and forged brass integral end hubs.{{citation needed|date=December 2019}} ''(See: [[Copper in heat exchangers]]).''

===Plate===
{{Main|Plate heat exchanger}}
[[Image:Plate frame 1.svg|thumb|right|Conceptual diagram of a plate and frame heat exchanger]]
[[Image:Plate frame 2.png|thumb|right|A single plate heat exchanger]]
[[Image:PHE Trieste 013.jpg|thumb|right|An interchangeable plate heat exchanger directly applied to the system of a swimming pool]]
Another type of heat exchanger is the [[plate heat exchanger]]. These exchangers are composed of many thin, slightly separated plates that have very large surface areas and small fluid flow passages for heat transfer.  Advances in [[gasket]] and [[brazing]] technology have made the plate-type heat exchanger increasingly practical. In [[HVAC]] applications, large heat exchangers of this type are called ''plate-and-frame''; when used in open loops, these heat exchangers are normally of the gasket type to allow periodic disassembly, cleaning, and inspection. There are many types of permanently bonded plate heat exchangers, such as dip-brazed, vacuum-brazed, and welded plate varieties, and they are often specified for closed-loop applications such as [[refrigeration]]. Plate heat exchangers also differ in the types of plates that are used, and in the configurations of those plates. Some plates may be stamped with "chevron", dimpled, or other patterns, where others may have machined fins and/or grooves.

When compared to shell and tube exchangers, the stacked-plate arrangement typically has lower volume and cost. Another difference between the two is that plate exchangers typically serve low to medium pressure fluids, compared to medium and high pressures of shell and tube.  A third and important difference is that plate exchangers employ more countercurrent flow rather than cross current flow, which allows lower approach temperature differences, high temperature changes, and increased efficiencies.

===Plate and shell===
A third type of heat exchanger is a plate and shell heat exchanger, which combines plate heat exchanger with shell and tube heat exchanger technologies. The heart of the heat exchanger contains a fully welded circular plate pack made by pressing and cutting round plates and welding them together. Nozzles carry flow in and out of the platepack (the 'Plate side' flowpath). The fully welded platepack is assembled into an outer shell that creates a second flowpath (the 'Shell side'). Plate and shell technology offers high heat transfer, high pressure, high [[operating temperature]], compact size, low fouling and close approach temperature. In particular, it does completely without gaskets, which provides security against leakage at high pressures and temperatures.

===Adiabatic wheel===
A fourth type of heat exchanger uses an intermediate fluid or solid store to hold heat, which is then moved to the other side of the heat exchanger to be released. Two examples of this are adiabatic wheels, which consist of a large wheel with fine threads rotating through the hot and cold fluids, and fluid heat exchangers.

===Plate fin===
{{Main|Plate fin heat exchanger}}
This type of heat exchanger uses "sandwiched" passages containing fins to increase the effectiveness of the unit. The designs include crossflow and counterflow coupled with various fin configurations such as straight fins, offset fins and wavy fins.

Plate and fin heat exchangers are usually made of aluminum alloys, which provide high heat transfer efficiency. The material enables the system to operate at a lower temperature difference and reduce the weight of the equipment. Plate and fin heat exchangers are mostly used for low temperature services such as natural gas, [[helium]] and [[oxygen]] liquefaction plants, air separation plants and transport industries such as motor and [[aircraft engine]]s.

Advantages of plate and fin heat exchangers:
* High heat transfer efficiency especially in gas treatment
* Larger heat transfer area
* Approximately 5 times lighter in weight than that of shell and tube heat exchanger. {{citation needed|date=August 2023}}
* Able to withstand high pressure

Disadvantages of plate and fin heat exchangers:
* Might cause clogging as the pathways are very narrow
* Difficult to clean the pathways
* Aluminium alloys are susceptible to [[Liquid metal embrittlement#Mercury embrittlement|Mercury Liquid Embrittlement]] Failure

=== Finned tube ===
The usage of fins in a tube-based heat exchanger is common when one of the working fluids is a low-pressure gas, and is typical for heat exchangers that operate using ambient air, such as automotive [[Radiator (engine cooling)|radiators]] and [[Heating, ventilation, and air conditioning|HVAC]] air [[Condenser (heat transfer)|condensers]]. Fins dramatically increase the surface area with which heat can be exchanged, which improves the efficiency of conducting heat to a fluid with very low [[thermal conductivity]], such as air. The fins are typically made from aluminium or copper since they must conduct heat from the tube along the length of the fins, which are usually very thin.

The main construction types of finned tube exchangers are:

* A stack of evenly-spaced metal plates act as the fins and the tubes are pressed through pre-cut holes in the fins, good thermal contact usually being achieved by deformation of the fins around the tube. This is typical construction for [[Heating, ventilation, and air conditioning|HVAC]] air coils and large [[Vapor-compression refrigeration|refrigeration]] condensers.
* Fins are spiral-wound onto individual tubes as a continuous strip, the tubes can then be assembled in banks, bent in a serpentine pattern, or wound into large spirals.
* Zig-zag metal strips are sandwiched between flat rectangular tubes, often being [[solder]]ed or [[Brazing|brazed]] together for good thermal and mechanical strength. This is common in low-pressure heat exchangers such as water-cooling [[Radiator (engine cooling)|radiators]]. Regular flat tubes will expand and deform if exposed to high pressures but flat [[Micro heat exchanger|microchannel]] tubes allow this construction to be used for high pressures.<ref name=":1" />

Stacked-fin or spiral-wound construction can be used for the tubes inside shell-and-tube heat exchangers when high efficiency thermal transfer to a gas is required.

In electronics cooling, [[heat sink]]s, particularly those using [[heat pipe]]s, can have a stacked-fin construction.

===Pillow plate===
{{Main|Pillow-plate heat exchanger}}
A [[pillow plate heat exchanger]] is commonly used in the dairy industry for cooling milk in large direct-expansion stainless steel [[bulk tank]]s. Nearly the entire surface area of a tank can be integrated with this heat exchanger, without gaps that would occur between pipes welded to the exterior of the tank. Pillow plates can also be constructed as flat plates that are stacked inside a tank. The relatively flat surface of the plates allows easy cleaning, especially in sterile applications.

The pillow plate can be constructed using either a thin sheet of metal welded to the thicker surface of a tank or vessel, or two thin sheets welded together. The surface of the plate is welded with a regular pattern of dots or a serpentine pattern of weld lines. After welding the enclosed space is pressurised with sufficient force to cause the thin metal to bulge out around the welds, providing a space for heat exchanger liquids to flow, and creating a characteristic appearance of a swelled pillow formed out of metal.

===Waste heat recovery units===
{{unreferenced section|date=March 2017}}
A [[waste heat recovery unit]] (WHRU) is a heat exchanger that recovers heat from a hot gas stream while transferring it to a working medium, typically water or oils. The hot gas stream can be the exhaust gas from a gas turbine or a diesel engine or a waste gas from industry or refinery.

Large systems with high volume and temperature gas streams, typical in industry, can benefit from steam [[Rankine cycle]] (SRC) in a waste heat recovery unit, but these cycles are too expensive for small systems. The recovery of heat from low temperature systems requires different working fluids than steam.

An organic Rankine cycle (ORC) waste heat recovery unit can be more efficient at low temperature range using [[refrigerant]]s that boil at lower temperatures than water. Typical organic refrigerants are [[ammonia]], [[pentafluoropropane]] (R-245fa and R-245ca), and [[toluene]].

The refrigerant is boiled by the heat source in the [[evaporator]] to produce super-heated vapor. This fluid is expanded in the turbine to convert thermal energy to kinetic energy, that is converted to electricity in the electrical generator. This energy transfer process decreases the temperature of the refrigerant that, in turn, condenses. The cycle is closed and completed using a pump to send the fluid back to the evaporator.

===Dynamic scraped surface===
Another type of heat exchanger is called "[[Dynamic scraped surface heat exchanger|(dynamic) scraped surface heat exchanger]]". This is mainly used for heating or cooling with high-[[viscosity]] products, [[crystallization]] processes, [[evaporation]] and high-[[fouling]] applications. Long running times are achieved due to the continuous scraping of the surface, thus avoiding fouling and achieving a sustainable heat transfer rate during the process.

===Phase-change===
[[Image:Kettle reboiler.svg|thumb|right|Typical kettle reboiler used for industrial distillation towers]]
[[Image:Surface Condenser.png|thumb|right|Typical water-cooled surface condenser]]

In addition to heating up or cooling down fluids in just a single [[phase (matter)|phase]], heat exchangers can be used either to heat a [[liquid]] to evaporate (or boil) it or used as [[Condenser (heat transfer)|condensers]] to cool a [[vapor]] and [[Condensation|condense]] it to a liquid. In [[chemical plant]]s and [[Petroleum refinery|refineries]], [[reboiler]]s used to heat incoming feed for [[distillation]] towers are often heat exchangers.<ref>{{cite book|author=Kister, Henry Z.|title= Distillation Design|edition=1st |publisher=McGraw-Hill|year=1992|isbn=978-0-07-034909-4|title-link= Distillation Design}}</ref><ref>{{cite book|author1=Perry, Robert H.  |author2=Green, Don W.|title=Perry's Chemical Engineers' Handbook|edition=6th| publisher=McGraw-Hill|year=1984|isbn=978-0-07-049479-4|title-link=Perry's Chemical Engineers' Handbook}}</ref>

Distillation set-ups typically use condensers to condense distillate vapors back into liquid.

[[Power plant]]s that use [[steam]]-driven [[turbine]]s commonly use heat exchangers to boil [[water]] into [[steam]]. Heat exchangers or similar units for producing steam from water are often called [[boiler]]s or steam generators.

In the nuclear power plants called [[pressurized water reactor]]s, special large heat exchangers pass heat from the primary (reactor plant) system to the secondary (steam plant) system, producing steam from water in the process. These are called [[Steam generator (nuclear power)|steam generators]]. All fossil-fueled and nuclear power plants using steam-driven turbines have [[surface condenser]]s to convert the exhaust steam from the turbines into condensate (water) for re-use.<ref>[http://www.epa.gov/oar/oaqps/eog/course422/ce6b3.html Air Pollution Control Orientation Course] from website of the Air Pollution Training Institute</ref><ref>[http://kolmetz.com/pdf/ENERGY%20EFFICIENCY%20IMPROVEMENT.pdf Energy savings in steam systems] {{webarchive|url=https://web.archive.org/web/20070927225000/http://kolmetz.com/pdf/ENERGY%20EFFICIENCY%20IMPROVEMENT.pdf |date=2007-09-27 }} ''Figure 3a, Layout of surface condenser'' (scroll to page 11 of 34 PDF pages)</ref>

To [[Energy conservation|conserve energy]] and [[cooling capacity]] in chemical and other plants, regenerative heat exchangers can transfer heat from a stream that must be cooled to another stream that must be heated, such as distillate cooling and reboiler feed pre-heating.

This term can also refer to heat exchangers that contain a material within their structure that has a change of phase. This is usually a solid to liquid phase due to the small volume difference between these states. This change of phase effectively acts as a buffer because it occurs at a constant temperature but still allows for the heat exchanger to accept additional heat. One example where this has been investigated is for use in high power aircraft electronics.

Heat exchangers functioning in multiphase flow regimes may be subject to the [[Ledinegg instability]].

===Direct contact===
Direct contact heat exchangers involve heat transfer between hot and cold streams of two phases in the absence of a separating wall.<ref>Coulson, J. & Richardson, J. (1983), Chemical Engineering – Design (SI Units), Volume 6, Pergamon Press, Oxford.</ref> Thus such heat exchangers can be classified as:
* Gas – liquid
* [[Miscibility|Immiscible]] liquid – liquid
* Solid-liquid or solid – gas

Most direct contact heat exchangers fall under the Gas – Liquid category, where heat is transferred between a gas and liquid in the form of drops, films or sprays.<ref name=":0" />

Such types of heat exchangers are used predominantly in [[air conditioning]], [[humidification]], industrial hot [[water heating]], [[water cooling]] and condensing plants.<ref>Hewitt G, Shires G, Bott T (1994), Process Heat Transfer, CRC Press Inc, Florida.</ref>

{| class="wikitable"
|-
! Phases<ref>Table: Various Types of Gas – Liquid Direct Contact Heat Exchangers (Hewitt G, Shires G & Bott T, 1994)</ref>
! Continuous phase
! Driving force
! Change of phase
! Examples
|-
| Gas – Liquid
| Gas
| Gravity
| No
| Spray columns, [[Packed bed#Packed column|packed columns]]
|-
|
|
|
| Yes
| [[Cooling tower]]s, falling droplet evaporators
|-
|
|
|Forced
|No
|Spray coolers/quenchers
|-
|
|
|Liquid flow
|Yes
|Spray condensers/evaporation, jet condensers
|-
|
|Liquid
|Gravity
|No
|[[Bubble column reactor|Bubble columns]], perforated tray columns
|-
|
|
|
|Yes
|Bubble column condensers
|-
|
|
|Forced
|No
|Gas spargers
|-
|
|
|Gas flow
|Yes
|Direct contact evaporators, submerged combustion
|}

=== Microchannel ===
Microchannel heat exchangers are multi-pass parallel flow heat exchangers consisting of three main elements: manifolds (inlet and outlet), multi-port tubes with the hydraulic diameters smaller than 1mm, and fins. All the elements usually brazed together using controllable atmosphere brazing process. Microchannel heat exchangers are characterized by high heat transfer ratio, low refrigerant charges, compact size, and lower airside pressure drops compared to finned tube heat exchangers.{{citation needed|date=April 2021}} Microchannel heat exchangers are widely used in automotive industry as the car radiators, and as condenser, evaporator, and cooling/heating coils in HVAC industry.{{Main|Micro heat exchanger}}
'''Micro heat exchangers''', '''Micro-scale heat exchangers''',  or '''microstructured heat exchangers''' are heat exchangers in which (at least one) [[fluid]] flows in lateral confinements with typical dimensions below 1&nbsp;mm. The most typical such confinement are [[microchannel heat exchanger|microchannels]], which are channels with a [[hydraulic diameter]] below 1&nbsp;mm. Microchannel heat exchangers can be made from metal or ceramics.<ref>{{cite journal | author = Kee Robert J. | year = 2011 | title = The design, fabrication, and evaluation of a ceramic counter-flow microchannel heat exchanger | journal = Applied Thermal Engineering | volume = 31 | issue = 11| pages = 2004–2012 | doi=10.1016/j.applthermaleng.2011.03.009| bibcode = 2011AppTE..31.2004K |display-authors=etal}}</ref> Microchannel heat exchangers can be used for many applications including:
* high-performance aircraft [[gas turbine engines]]<ref>{{cite journal |author1=Northcutt B. |author2=Mudawar I. | year = 2012 | title = Enhanced design of cross-flow microchannel heat exchanger module for high-performance aircraft gas turbine engines | journal = Journal of Heat Transfer | volume = 134 | issue = 6| page = 061801 | doi=10.1115/1.4006037}}</ref>
* [[heat pumps]]<ref>{{cite journal |author1=Moallem E. |author2=Padhmanabhan S. |author3=Cremaschi L. |author4=Fisher D. E. | year = 2012 | title = Experimental investigation of the surface temperature and water retention effects on the frosting performance of a compact microchannel heat exchanger for heat pump systems | journal = International Journal of Refrigeration | volume = 35 | issue = 1| pages = 171–186 | doi=10.1016/j.ijrefrig.2011.08.010}}</ref>
* [[Microprocessor]] and [[microchip]] [[cooling]]<ref>Sarvar-Ardeh, S., Rafee, R., Rashidi, S. (2021). Hybrid nanofluids with temperature-dependent properties for use in double-layered microchannel heat sink; hydrothermal investigation. Journal of the Taiwan Institute of Chemical Engineers. cite journal https://doi.org/10.1016/j.jtice.2021.05.007</ref>
* [[air conditioning]]<ref>Xu, B., Shi, J., Wang, Y., Chen, J., Li, F., & Li, D. (2014). Experimental Study of Fouling Performance of Air Conditioning System with Microchannel Heat Exchanger.</ref>