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). 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: Adding a non-condensable gas (NGS) that mixes with working fluid vapor and a reservoir, creates a Variable Conductance Heat Pipe (VCHP), where the effective thermal conductivity varies with the input power and heat sink conditions.
  • Diode: Diode heat pipes are designed to 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.

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

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

    Aluminum-ammonia systems are used for spacecraft thermal control.

  • High Temp Heat Pipes

    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 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.

Operations

New Advancements

  • Technologies

    Over the years ACT has developed many two-phase heat transfer technologies for future applications.

  • 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 Heat Pipes

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

  • High Temperature Heat Pipes

    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

    Heat pipe loops provide higher heat transport than heat pipes, with lower cost than LHPs.

  • Heat Pipe 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.