Editing Heat exchanger (section)

=== 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.