Heat Pipe Resources

Advanced Cooling Technologies, Inc. (ACT) is a leader in Heat Pipe (HP) products and technologies. ACT manufactures a large variety of heat pipes, HP heat sinks and HP assemblies for a wide range of applications. In fact, ACT is the only US manufacturer that routinely delivers HPs for terrestrial electronics cooling (copper-water), on-orbit satellite thermal management (aluminum-ammonia) and high temperature calibration equipment (liquid metal). In addition, ACT is a leader in developing new functionality and increased performance with emerging heat pipe technology.

This Heat Pipe Resource page contains the most extensive information on heat pipes and related technology available anywhere on the web, including Fundamentals, Limits, Wicks, Working Fluids and Envelopes, Different Kinds of Heat Pipes, and Advanced Developments.

An Overview of the Technology

Illustration of Heat Pipe operation.

Figure 1. Illustration of Heat Pipe operation.

A heat pipe is a two phase heat transfer device with a very high effective thermal conductivity.  It is a vacuum tight device consisting of an envelope, a working fluid, and a wick structure.  As shown in Figure 1, the heat input vaporizes the liquid working fluid inside the wick in the evaporator section. The saturated vapor, carrying the latent heat of vaporization, flows towards the colder condenser section.  In the condenser, the vapor condenses and gives up its latent heat.  The condensed liquid returns to the evaporator through the wick structure by capillary action.  The phase change processes and two- phase flow circulation continue as long as the temperature gradient between the evaporator and condenser are maintained.

Benefits of these devices include:

  • High Thermal Conductivity (10,000 to 100,000 W/m K)
  • Isothermal
  • Passive
  • Low Cost
  • Shock/Vibration tolerant
  • Freeze/thaw tolerant

Please click on the icons below to learn more about heat pipes.

If you are designing a thermal system and simply want to learn more about heat pipes for cooling, use the links in the Operation Section. If you still have questions, contact us and an engineer will be in contact with you.

Read more about heat pipes in our Heat Pipe FAQ.  See a full video and transcription about the basics of heat pipes and their advantages.

Product Links

Electronics Cooling

For most terrestrial applications Cu-H2O and Cu-Methanol are used.

Aerospace

Aluminum-ammonia systems are used for spacecraft thermal control.

High Temperature

Using liquid metal as the working fluid allows operation at temperatures up to 1,100 degrees C.

HVAC / Energy Recovery

Wrap around heat exchangers create efficient operation to lower operating costs by pre-cooling incoming air.

HiK™ Plates

ACT’s HiK™ (High Conductivity) plates are heat spreaders with embedded HP to increase the effective thermal conductivity for conduction cooled cards and electronics enclosures

Vapor Chamber Assemblies

Vapor Chambers are very high effective conductivity heat spreaders, as well as a flux transformer, lowering the effective heat transfer rate at the heat sink.

Heat Pipe FAQ

Frequently asked questions about basic heat pipe fundamentals.

Operations

How do they work?

Background physics including a video that demonstrates the two-phase heat transport.

Gallery

Visit a gallery of two phase heat transfer devices.

Performance

Learn about the various limits that determine the maximum power (W) a heat pipe can move.

Calculator

Use this tool to calculate a copper-water heat pipe's capability for your system.

Design Guide

Learn the basics on sizing and modeling with our heat pipe design guide. You'll be able to integrate these devices into your project in no time!

Wick Structures

Learn about the advantages, limitations, and trade-offs of various wick structures.

Fluid Selection / Compatibility

Working fluids are determined primarily by the ambient conditions, the thermodynamic properties of the fluid, and compatibility with the wick/envelope.

Different Types of Heat Pipes

Discusses specialized heat pipes and their applications.

Fundamentals

Discusses fundamental operating principles of heat pipes.

Modeling

Learn how to integrate heat pipes into computer models.

History

A short history showing how applications have expanded since the heat pipe was invented back in 1963.

Webinars

ACT’s thermal management video tutorials, including two-phase heat transfer, heat sinks, LED thermal management, and thermal storage. Transcriptions of the videos are available.

New Advancements

Advanced Heat Pipes and Loop Heat Pipes

Advanced Heat Pipes and Loop Heat Pipes including new working fluids, passive thermal control with variable conditions, and freeze/thaw tolerance.

High Temperature Water Heat Pipes

Learn how ACT has extended the operating temperature range for water working fluid from 150 to 300°C.

Intermediate Temperature Working Fluids

ACT is developing new working fluids for the intermediate temperature range, between water and alkali metal working fluids.

High Temperature

Alkali metal working fluids with superalloy envelopes allow operation at temperatures up to 1100°C.

Vapor Chambers

ACT has developed vapor chamber heat spreaders that can accept heat fluxes up to 500 W/cm2 over a 4 cm2 area and transform the heat flux so that it can be removed with conventional cooling methods.

Pressure Controlled Heat Pipes (PCHPs)

PCHPs vary the amount of Non Condensable Gas (NCG) in their reservoir, allowing very tight temperature control (± 5 mK) over hours of operation.

Loop Heat Pipes

LHPs are passive, two-phase heat transport devices that can transfer higher amounts of heat over longer distances than conventional heat pipes.

Heat Pipe Loops (HPLs)

HPLs provide higher heat transport than heat pipes, with lower cost than LHPs.

Life Tests

Life tests are conducted to verify that the envelope, wick, and working fluid in a two-phase heat transfer device are compatible, allowing for long term operation.

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