Fraunhofer Institute for Physical Measurement Techniques IPM
Highly effective heat transfer
Heat pipes are fluid-filled tubes that can transfer large amounts of heat in a small area. Heat transfer in a heat pipe takes place via latent heat, i.e. the evaporation and recondensation of a fluid. This type of heat transfer is highly effective: Compared to a solid body of the same dimensions, a heat pipe transfers a greater amount of heat by a factor of 100 to 1,000. Heat pipes thus conduct heat more effectively than any other known material.
Heat pipes are used as standard components in computers, for example, where they protect processors and other components from overheating. But the need for highly effective electronics cooling is also increasing in e-mobility, building technology and aerospace due to technical progress and ever higher power densities. Here, too, heat pipes are increasingly being used for heat dissipation. There are many other potential areas of application – whenever large amounts of heat need to be dissipated and transferred in a small space.
Switchable heat pipes as heat switches
With the help of heat switches, heat flows can be switched on and off or regulated – very similar to what is possible with electrical switches. To be suitable for widespread use, for example for temperature control of components in electromobility, battery technology or mechanical engineering, thermal switches need to become more efficient and cost-effective. Conventional heat switch concepts have some disadvantages: The thermal resistance in the conductive »on« state is high, the switches are large and often complex in design, and they contain moving parts.
Fraunhofer IPM is collaborating with other Fraunhofer institutes on a new generation of thermal switches based on switchable heat pipes. The switchable heat pipes are compact and do not require any moving parts. Due to their simple design, these components can be integrated easily and promise significantly higher heat transfer capabilities.
We are pursuing a number of concepts to realize switchable heat pipes: For example, within the »Fraunhofer Cluster of Excellence Programmable Materials CPM« framework, so-called programmable materials are integrated into the heat pipes to trigger the thermal switching effect. Alternatively, flat pulsating heat pipes (PHPs) are equipped with additional external elements to make both switchability and controllability possible.
The switching effect based on these concepts has already been demonstrated at Fraunhofer IPM and is now being implemented in application-oriented heat pipe shapes, including the familiar cylindrical tubular heat pipe or the flat pulsating heat pipe.