Heat Pipes: simple and efficient two-phase heat transfer devices

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Loop Heat Pipe

Technology abstract

An Italian SME working in the Space field is offering efficient thermal control solutions based on the use of Heat Pipes. Heat Pipes are simple, reliable and low-cost devices capable of transferring heat by exploiting the transition of phase of a working fluid and capillary forces that allow the motion of the fluid in a piping system, without requiring pumps or external actuators. Heat Pipes can be used for the passive thermal control of different devices for space and ground applications.

Technology Description

Heat Pipes essentially consist of metal tubes that transfer thermal power in an efficient way thanks to the evaporation and condensation of a working fluid. These systems are capable of transporting large quantities of heat with a very small temperature difference between the hot and cold interfaces. Heat Pipes are passive devices: in fact, the fluid motion is obtained by exploiting the capillary forces that are developed in the interaction between the fluid and the Heat Pipe structure without requiring actuators like pumps.
The company offers three main types of Heat Pipes which differ for the geometrical layout and the maximum amount of thermal power that they can transfer: Axially Grooved Heat Pipes, Loop Heat Pipes, and Pulsating Heat Pipes.

Axially Grooved Heat Pipes consist of tubes that can transfer about 200 W for short distances (<1 m).

Loop Heat Pipes are composed of a closed loop piping which transmits heat from a hot area (evaporator) to a cold area (condenser). They can transfer high amount of heat (higher than 500 W) for long distances (>1 m).

Pulsating Heat Pipes are composed of a closed loop piping that can be embedded in structures. They can be used to transfer or to spread heat on surfaces.

Given their simplicity and their good performance, they have been used in space and ground applications, for example for the thermal control of electronics devices, computer systems, and for domestic and industrial energy applications. In particular Axial Heat Pipes and Loop Heat Pipes have already been used in space applications, while Pulsating Heat Pipe performance is still under investigation.
The company has a consolidated know-how and experience in the design, development and characterization of Heat Pipes. The design is performed using numerical models developed and validated by the company. This technology has been demonstrated by means of tests performed on Ground and on board the International Space Station (Thermal Exchange, 2016-2017).

Innovations & Advantages

Heat Pipes represent candidates for the thermal control of devices in different applications, thanks to their low complexity, operational flexibility and limited maintenance requirements. Compared to the traditional heat transfer systems, two-phase heat transfer devices can improve the thermal management thanks to their efficiency, lightness, flexibility, reliability and ease of construction.

Further Information

One of the most critical drivers in the development of the Heat Pipes is the working fluid, which affects the performance and the operative temperature of the system. A lot of fluids which have very good performance are toxic (e.g. ammonia); then their utilization in environments with human presence has been limited for safety reasons. The company has been working on low toxicity fluids to overcome this limit and to allow a broader application of this technology.

Current and Potential Domains of Application

Thermal Transport Solution in different domains: Automotive, Computer systems, Defence, Domestic and Industrial Energy, Electronics & Opto-electronics, Renewable energy, Space