Components: press-pack or screw-mounted types
Applications: Power conversion, traction drives, UPS, broadcasting, military electronic.

Operating principle:

A heat pipe is a leaktight enclosure containing a liquid in equilibrium with its vapor and totally free of air or any other gas. Its operating principle is based on the phase change in the coolant it contains. In the hot, or evaporator, zone, the fluid evaporates and the vapor travels to the cold, or condenser, zone to condense. Return of the liquid is usually by gravitational flow, on the principle of the thermosiphon.

Product description:

The heat pipe consists of three parts:

- the "evaporator", an aluminum or copper block on which the components to be cooled are mounted.

- the "condenser", a finned aluminum or copper battery.

- the "adiabatic zone", consisting of copper tubes linking the evaporator to the condenser. Ceramic can be added to that connection for systems requiring insulation.

Types of fluids used in a heat pipe:

The type of fluid to use depends on the environment in which the heat pipe is installed.

When no dielectric insulation is required, the coolant in the heat pipe may be water or methanol:
- Under severe conditions, with temperatures running from -25°C to +40°C, methanol is used.
- Under normal conditions, with temperatures from 0°C to 40°C, water is used.

If dielectric insulation is required, the coolant is a fluorocarbon (FC72 or HFE 7100 or similar).

Advantages to a heat pipe:

A heat pipe offers high thermal performances. It serves as intermediary cooling in power electronics between air and water. Its thermal efficiency is due to high internal heat exchange factors in both boiling and condensation (which can be further increased by grooving the tubes). It can transfer heat over long distances with no need for a liquid loop, which is energy intensive and less reliable.

- Developing a large heat exchange surface with the air at the condenser helps reduce thermal resistance in comparison to air cooling systems, limited by conduction in the fins.

- Separating the electronic part from the finned part makes it possible to position power electronics components in a leaktight enclosure and the heat exchange area with the air outside that enclosure.

- Extracting high flows in a confined space results in very compact electronic systems that can be dielectrically insulated from their environment by using ceramic in the adiabatic zone and a dielectric coolant.

- Very low thermal inertia. The heat pipe starts operating almost instantaneously whenever even a slight difference in temperature between the evaporator and the condenser occurs in the tubes. This means the heat pipe can follow the power cycle in the electronic part rapidly and limit temperature peaks under the components.

- Consistent temperature on the plate and therefore under the components increases their reliability and durability.

- No maintenance is required, as these systems are highly reliable and robust.