Loop Thermosyphon

Loop Thermosyphon


A Loop Thermosyphon (LTS) is an ideal solution for any system that can leverage gravity assist fluid return. LTS are routinely found in Power Electronics applications where customers mount IGBTs and other high-power density devices directly to an evaporator plate and have the ability to remotely locate the condenser or heat sink above the components. ACT systems are fielded in a variety of industries including medical, energy/utility, automation and HVAC systems.

The principle operation is similar to a heat pipe or thermosyphon where heat generated by components causes liquid within the attached cold plates to evaporate.  The expansion of this fluid as it changes phase from liquid to vapor creates a stirring motion that increases convection and subsequently, heat transfer efficiency. The system takes advantage of the latent heat of the fluid which allows for such high heat transfer rates. A Loop Thermosyphon can move larger amounts of heat compared to a similar-sized heat pipe or thermosyphon because there is no counterflow (liquid and vapor moving in opposing directions). The “loop” aspect makes this possible by designing a discrete vapor line to the heat sink, condensing within the heatsink, and liquid returning down a separate fluid line.

A loop thermosyphon is a scalable technology, with products built from less than 100W to upward of 75,000W. It’s an ideal choice for electronics and Power Electronics applications because of its passive operation, di-electric working fluid options, and high performance. The geometric design flexibility is also critical to most system engineers. Loop thermosyphons can move heat very large distances and can incorporate important features on the evaporator, condenser and fluid lines to allow for easy integration.



ACT has experience working collaboratively with customers to thermally analyze, mechanically design, prototype, test and implement loop thermosyphon solutions

A few past projects tailored to our customers’ needs:

Loop Thermosyphon

Power Electronics Cooler

  • Industry: Power Conversion
  • Power: 5-15 kW
  • Key Features: Patent-pending evaporator plate to allow for direct mount of multiple IGBTs on both sides. Di-electric fluid for electrical isolation.



Loop Thermosyphons

Flexible Line, IGBT Cooler

  • Industry: Industrial Power Electronics
  • Power: 5-15 kW
  • Key Features: Dielectric, flexible coolant lines for remote mounting of condenser. Direct mount, patent-pending custom evaporator design. Multiple condenser configurations available



Loop Thermosyphon for a Medical Application

  • Power: ~1000W
  • Key Features: All aluminum design; High heat flux evaporator design (~40 W/cm2); eliminating the need for a chiller



Single IGBT Cooler

  • Application: Solid-state transformer
  • Power: ~1000W
  • Key Features: All Aluminum construction; Patent pending custom evaporator design


HVAC Heat Exchangers

  • Industry HVAC Energy Recovery
  • Power: Scalable > 100kW
  • Configurations:

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