Heat Pipes for Thermal Management

Advanced Cooling Technologies, Inc. (ACT) is a leader in heat pipe products and technologies. ACT manufactures a large variety of heat pipes, heat pipe heat sinks and heat pipe assemblies for a wide range of applications. In addition, ACT is a leader in developing new functionality and increased performance with emerging heat pipe technology.

How Are Heat Pipes Used?

Heat Pipes which have also be termed heatpipes or even thermal pipes, are used across a wide range of markets and applications, and we’re known for producing high-quality copper heat pipes. In fact, ACT is the only US manufacturer that routinely delivers heat pipes for terrestrial electronics cooling (copper-water), on orbit satellite thermal management (aluminum-ammonia) and high temperature calibration equipment (liquid metal heat pipes). Navigate through the products section below for more information on any of these highly reliable products.

An Overview of Heat Pipe 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.

Common Types of Heat Pipes

There are several types of heat pipes available, including:

  • Vapor chamber: These flat heat pipes are typically used when heat fluxes and high powers are applied to smaller evaporators, as well as for enabling heat flow through very thin devices.
  • Variable conductance: VC heat pipes are equipped with two additions that are not included on standard heat pipes: a non-condensable gas (NGS) that mixes with working fluid vapor and a reservoir.
  • Diode: Diode heat pipes differ from conventional heat pipes in that they transfer heat in one direction and insulate it in the opposite direction.
  • Loop heat pipe (LHP): An LHP is a passive two-phase device that is capable of transferring higher power over longer distances.

The benefits of a standard heat pipe include:

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

More Information 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.

See a full video and transcription about the basics of heat pipes and their advantages.

Product Links

  • Copper (Cu) Heat Pipes

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

  • Aerospace Heat Pipes

    Learn more about aluminum-ammonia heat pipes used for spacecraft thermal control.

  • High Temp Heat Pipes

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

  • HVAC / Energy Recovery

    Wrap around heat pipe 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 heat pipes 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 flux transformer, lowering the effective heat transfer rate at the heat sink.


  • How do heat pipes work?

    Background physics to heat pipe operation including video that demonstrated the two-phase heat transport.

  • Heat Pipe Gallery

    CCHPs VCHPs Loop Heat Pipes heat Pipe Loops Vapor Chambers ACT Heat Pipe Gallery

  • Heat Pipe Performance

    The amount of power (W) a heat pipe can move is determined by several variables. Learn about the various heat pipe limits that govern overall performance.

  • Heat Pipe Calculator

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

  • Design Guide

    Learn the basics on how to size and model your heat pipes with our heat pipe design guide. You'll be able to integrate heat pipes into your project in no time!

  • Wick Structures

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

  • Fluid Selection / Compatability

    Heat pipe fluids are determined primarily by the ambient conditions and thermodynamic properties of the fluid.

  • Different Types of Heat Pipes

    In addition to the standard, Constant Conductance Heat Pipe (CCHP), there are a number of specialized heat pipes.

  • Heat Pipe Fundamentals

    Learn about the fundamentals of how heat pipes operate.

  • Heat Pipe Modeling

    Learn how to integrate heat pipes into computer models.

  • Heat Pipe History

    Go back to 1963 when the heat pipe was discovered and view how heat pipe applications have expanded since

  • Webinars

    ACT’s thermal management video tutorials, including heat pipes, heat sinks, LED thermal management, and pumped single and two phase cooling. Transcriptions of the videos are available.

New Advancements

  • Technologies

    Over the years ACT has developed many heat pipe related technologies for future applications.

  • High Temperature Water Heat Pipes

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

  • Intermediate Temperature Heat Pipes

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

  • High Temperature Heat Pipes

    Superalloy heat pipes with alkali metal working fluids operate 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

    Pressure Controlled Heat Pipes (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

    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

    Heat pipe loops combine elements from heat pipes and Loop Heat Pipes (LHPs) to provide higher heat transport than heat pipes, with lower cost than LHPs.

  • Heat Pipe Life Tests

    Heat pipe life tests are conducted to verify that the heat pipe envelope, wick, and working fluid are compatible, allowing for long term operation.