Heat pipe
A phase-change device that transfers heat with high efficiency.
A heat pipe is a heat-transfer device that employs phase transition to transfer heat between two solid interfaces. At the hot interface, a volatile liquid in contact with a thermally conductive solid surface turns into a vapor by absorbing heat, then travels to the cold interface and condenses back into a liquid, releasing latent heat. The liquid 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, with effective thermal conductivity varying with length and approaching values far exceeding copper.
- First capillary heat pipe patent
- 1942 by R. S. Gaugler of General Motors
- First use of term heat pipe
- 1963 by George Grover at Los Alamos National Laboratory
- Common working fluid for room temperatur
- water (298–573 K), ammonia (213–373 K), methanol (283–403 K), ethanol (273–403 K)
- Typical envelope material for water heat
- copper
- Example heat transfer capacity
- 3.7 kW at 1800 °F with 18 °F drop for a pipe 1 inch in diameter and 2 feet long
- First space application
- thermal equilibration of satellite transponders
Lore & Background
The general principle of heat pipes using gravity, classified as two-phase thermosiphons, dates back to the steam age. Angier March Perkins and his son Loftus Perkins created the Perkins Tube, which saw widespread use in locomotive boilers and working ovens. Capillary-based heat pipes were first suggested by R. S. Gaugler of General Motors in 1942, who patented the idea but did not develop it. George Grover independently developed capillary-based heat pipes at Los Alamos National Laboratory in 1963; his patent was the first to use the term 'heat pipe', and he is often referred to as 'the inventor of the heat pipe'.
Grover's suggestion was taken up by NASA, which led heat-pipe development in the 1960s, particularly for space flight applications due to low weight, high heat flux, zero power draw, and tolerance to zero gravity. The first space application was the thermal equilibration of satellite transponders, managing severe temperature discrepancies caused by alternating solar exposure and deep space cold. That cooling system was the first to use variable-conductance heat pipes to actively regulate heat flow or evaporator temperature. NASA also tested heat pipes using liquid sodium as the working fluid.
Starting in the 1980s, Sony began incorporating heat pipes into commercial electronic products in place of forced-convection and passive-finned heat sinks, initially in receivers and amplifiers. During the late 1990s, increasingly high-heat-flux microcomputer CPUs spurred a threefold increase in U.S. heat-pipe patent applications. As heat pipes evolved from a specialized industrial component to a consumer commodity, most development and production moved from the U.S. to Asia.
Reader's Guide
Heat pipes became a cornerstone of modern electronics cooling, particularly for CPUs in desktops, laptops, tablets, and high-end smartphones. Their ability to transfer large amounts of heat with minimal temperature drop and no moving parts made them ideal for applications where reliability and space are critical. The technology's adoption by NASA for satellite thermal management demonstrated its robustness in extreme environments, including zero gravity. In consumer electronics, Sony's integration of heat pipes in the 1980s marked a shift from traditional heat sinks, and the subsequent surge in CPU heat flux during the late 1990s drove widespread adoption. The move of production to Asia reflected the technology's transition from a specialized industrial component to a mass-market commodity. Heat pipes remain essential in managing thermal loads in devices where passive or active cooling alone is insufficient, and their design continues to evolve with advances in wick structures and working fluids.
Did You Know?
- A heat pipe one inch in diameter and two feet long can transfer 3.7 kW at 1800 °F with only an 18 °F temperature drop.
- The first use of the term 'heat pipe' was in a 1963 patent by George Grover at Los Alamos National Laboratory.
- NASA used heat pipes with liquid sodium as the working fluid for extreme conditions.
- Sony began incorporating heat pipes into commercial electronics in the 1980s, starting with receivers and amplifiers.
Frequently Asked Questions
What exactly is a Heat pipe in PC cooling?
A Heat pipe is a sealed tube that shuttles thermal energy from a hot component to a cooler area by exploiting the evaporation and condensation of a working fluid inside. It acts as an extraordinarily efficient thermal conductor, far outperforming a solid metal bar of the same dimensions.
How does the Heat pipe cycle work step by step?
At the hot end, a volatile liquid absorbs heat and flashes into vapor; that vapor migrates to the cold end where it condenses and releases its latent heat. The liquid then flows back to the hot end via capillary wicking, gravity, or centrifugal force, and the loop restarts.
Who is credited with inventing the Heat pipe?
The first capillary heat pipe patent was filed in 1942 by R. S. Gaugler at General Motors. The specific term "heat pipe" was not coined until 1963, when George Grover at Los Alamos National Laboratory popularized the name.
Why do enthusiasts prefer Heat pipes over plain copper blocks for CPU or GPU cooling?
Boiling and condensation carry far higher heat-transfer coefficients than simple conduction, so a thin pipe can move several kilowatts of heat with only a tiny temperature drop across its length. For instance, a one-inch-diameter, two-foot pipe can transfer roughly 3.7 kW while sustaining just an 18 °F gradient at 1800 °F.
What working fluids and envelope materials are standard in PC Heat pipes?
Copper is the go-to envelope metal for water-based heat pipes operating between roughly 298 K and 573 K. Other common fluids include ammonia (213–373 K), methanol (283–403 K), and ethanol (273–403 K), selected to match the target operating temperature range.
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