Heat Pipes & Assemblies

What’s a Heat Pipe, And How Does It Work?

A heat pipe is a cylinder-shaped device that transfers heat from one place to another by the vaporization and condensation of a liquid medium.

A heat pipe consists of three components – its sealed outer wall, called an “envelope,” a “wick” which condenses and provides a travel path for vapor, and a small amount of working fluid.

The fluid is processed under vacuum, which allows for a two-phase operation across a wide temperature range. During operation, applied heat boils the fluid, then pushes the fluid vapor to the cooler region of the heat pipe. This cooler region is known as the “condenser;” it’s usually coupled with a heat sink.

The fluid gives up its heat, and condenses back to a liquid, and is again absorbed in the “wick structure” – a grooved structure that uses capillaries to pump the fluid back to the evaporator.

The flow is continuous across the pipe – no motors nor pumps at work here… just pure physics!

What Impacts a Heat Pipe’s Performance?

  • Pipe Length & Diameter: The diameter and the length of the heat pipe affect the rate at which the vapor travels between the evaporator and the condenser.
  • Application: How & Where The Pipe is Being Used – not every heat pipe material is suitable for every application. For instance, when the application’s working fluid is liquid nitrogen, pipe vessel material of stainless steel is appropriate, but copper and nickel are not.
  • The Pipe’s Wick Structure: there are four types of wick structures utilized in heat pipes: groove, wire mesh, sintered powder metal, and fiber. The structures operate differently contingent on a number of factors such as pipe material and whether the wick is working with or against gravity.

Heat Pipe Specifics

Heat Pipe Features

  • Can operate over a wide temperature range: – 150° to +1,000°C (20°C – 250°C in water)
  • Are Freeze/Thaw Tolerant
  • Can work against gravity

Advantages of Practical Use of Heat Pipes

  • K(eff) ranges from 10,000 to 200,000 W/m-K
  • Continuous Passive Operation
  • Isothermality Characteristics
  • Quiet and Discreet Operation

Heat Flux Capabilities

Heat Pipes can operate with heat flux up to 50-75 W/cm(2), with custom wicks to 500W/cm(2)

Common Applications

  • Lighting Applications: Heat pipes used in common “luminaire” lighting designs to transfer generated heat from the device to a heat sink.
  • Automotive Applications: Automobile operations present several practical uses for heat pipes including the heat pipe as a device for controlling the catalytic converter temperature, warming of the catalyst bed, heating of the rear defogger and passenger compartment, and engine, oil and diecast cooling.
  • Heat Sink Applications: Heat pipes are used in desktops and laptops to decrease the device’s operating temperature for better performance. They are an ideal solution for CPU cooling to dissipate the associated heat from computer processors, especially in newly designed processors to accommodate for their enhanced power and faster operations.
  • Card Guide Applications: Heat pipes outfitted to a heat plate can be used to provide the highest level of heat transfer in the hottest areas, transferring heat to a “final” heat sink outfitted in the bottom of the card cage. The result – hot spots in the card guide are eliminated, and the overall temperature gradient gets reduced significantly.

KTK Specializes in High Power Heat Pipe Application

KTK Thermal Technologies has proven success working with customers to conceptualize, design and analyze thermal solutions for a variety of applications and industries – often with strict design requirements. We have taken on numerous projects that require expert thermal and mechanical design skills to turn prototypes into deliverable units.

Contact us to speak to a KTK team member about your project specifics today.

KTK has the knowledge and experience to help you solve your toughest thermal management challenges.