Editing Heat pipe (section)

{{Short description|Heat-transfer device that employs phase transition}}
{{Lead too short|date=February 2024}}
[[File:Laptop Heat Pipe.JPG|thumb|upright=1.3|A laptop computer heat pipe system]]

A '''heat pipe''' is a [[Heat exchanger|heat-transfer device]] that employs [[phase transition]] to transfer heat between two solid [[Interface (matter)|interfaces]].<ref name="Faghri_2016" />

At the hot interface of a heat pipe, a [[Volatility (chemistry)|volatile]] liquid in contact with a thermally conductive solid surface turns into a [[vapor]] by absorbing heat from that surface. The vapor then travels along the heat pipe to the cold interface and condenses back into a liquid, releasing the [[latent heat]]. The [[liquid]] then returns to the hot interface through [[capillary action]], [[centrifugal force]], or gravity and the cycle repeats.

Due to the very high heat transfer coefficients for [[boiling]] and [[condensation]], heat pipes are highly effective thermal conductors. The effective thermal conductivity varies with heat pipe length and can approach {{val|100|u=kW/(m⋅K)}} for long heat pipes, in comparison with approximately {{val|0.4|u=kW/(m⋅K)}} for [[copper]].<ref>{{cite web |title=Thermal conductivity of common metals, metallic elements and Alloys |url=https://www.engineeringtoolbox.com/thermal-conductivity-metals-d_858.html |website=www.engineeringtoolbox.com |access-date=October 15, 2020}}</ref>

Modern CPU heat pipes are typically made of [[Copper in heat exchangers|copper]] and use water as the [[working fluid]].<ref name="Jansson">{{cite journal |last1=Jansson |first1=Dick |year=2010 |title=Heat Pipes |journal=QEX |issue=Jul-Aug2010 |pages=3–9 |publisher=ARRL |url=http://www.arrl.org/files/file/QEX_Next_Issue/Jul-Aug_2010/Jansson.pdf |access-date=November 14, 2011 }}</ref> They are common in many consumer electronics like desktops, laptops, tablets, and high-end smartphones.