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
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)
- 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.
For most terrestrial applications Cu-H2O and Cu-Methanol are used.
Aluminum-ammonia systems are used for spacecraft thermal control.
Using liquid metal as the working fluid allows operation at temperatures up to 1,100 degrees C.
Wrap around heat exchangers create efficient operation to lower operating costs by pre-cooling incoming air.
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 Chambers are very high effective conductivity heat spreaders, as well as flux transformer, lowering the effective heat transfer rate at the heat sink.
Background physics to heat pipe operation including a video that demonstrates the two-phase heat transport.
Visit a gallery of heat pipes and related two phase heat transfer devices.
Learn about the various heat pipe limits that determine the maximum power (W) a heat pipe can move.
Use this tool to calculate a copper-water heat pipe's capability for your system.
Learn the basics on sizing and modeling with our heat pipes with our heat pipe design guide. You'll be able to integrate these devices into your project in no time!
Learn about the advantages, limitations, and trade-offs of various wick structures.
Working fluids are determined primarily by the ambient conditions, the thermodynamic properties of the fluid, and compatibility with the wick/envelope.
Discusses specialized heat pipes and their applications.
Discusses fundamental operating principles.
Learn how to integrate heat pipes into computer models.
A short history showing how heat pipe applications have expanded since the heat pipe was invented back in 1963.
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.
Over the years ACT has developed many two-phase heat transfer technologies for future applications.
Learn how ACT has extended the operating temperature range for water working fluid from 150 to 300°C.
ACT is developing new working fluids for the intermediate temperature range, between water and alkali metal working fluids.
Alkali metal working fluids with superalloy envelopes allow operation at temperatures up to 1100°C.
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.
PCHPs vary the amount of Non Condensable Gas (NCG) in their reservoir, allowing very tight temperature control (± 5 mK) over hours of operation.
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 provide higher heat transport than heat pipes, with lower cost than LHPs.
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.