ACT is a leading provider of Phase Change Material (PCM) heat sinks for military, aerospace and industrial thermal management applications.
How Do Phase Change Material Heat Sinks Work?
PCM Heat Sinks can absorb thermal energy (heat) with minimal temperature rise during the solid to liquid phase transition. During this phase transition, the latent heat (J/kg) is at least one (1) to two (2) orders of magnitude higher than the sensible energy that can be stored by the specific heat of a material in its solid or liquid phase. Figure 1 illustrates this phenomena by plotting the temperature rise of a PCM over time with a steady-state energy input.
In practice, a PCM is contained in a hermetically sealed enclosure and used to maintain the temperatures of critical heat generating components over a given period of time.
Ideal Applications for Phase Change Material (PCM) Heat Sinks
- Applications such as missiles that have finite mission life can utilize PCM energy storage to replace complex active thermal management solutions.
- PCM Modules are also used in systems having pulse mode operations by storing the heat during the “on” cycle and dissipating the heat (as the PCM refreezes) during the “off” cycle.
- PCM is an emerging technology in the Spacecraft market for thermal control. PCM has the ability to store more thermal energy in a smaller package, with less mass when compared to some of the more traditional thermal solutions, therefore is attractive to the booming space market.
Although the concept of storing heat by melting a phase change material is fairly simple, there are numerous practical challenges that must be addressed to obtain a volume or mass optimized, fully functional and highly reliable PCM heat sink design. ACT has the expertise and experience in all areas from initial evaluation, through prototyping to full volume production of PCM heat sinks.
How do I select a Phase Change Material (PCM) for my heat sink?
The first consideration when designing a PCM heat sink should be the PCM’s melt temperature. Typically, the PCM is selected to provide a melting temperature that is several degrees lower than the maximum component temperature throughout the mission. Paraffin waxes are common because they are available with a wide range of melt temperatures. The second consideration is the energy that must be stored and the duration. The combination of these two factors, along with the thermal properties of the PCM, will ultimately determine the amount of PCM required in your system.
Read More on PCM Selection advice
Phase Change Material (PCM) Heat Sink Design Considerations
The challenge with many PCM Heat Sink Designs is the poor thermal conductivity of the PCM. For example, paraffin waxes typically have thermal conductivities of less than 1 W/m-K. This is remedied by adding internal features to increase the overall effective thermal conductivity of the enclosure. ACT is experienced with fins, heat pipes and metal foams as options for these internal structures.
Thermal Simulations of Phase Change Material (PCM) Heat Sink Systems
ACT has expertise in analyzing PCM systems and accurately predicting transient responses. In-house analytical tools in combination with computational fluid dynamics (CFD) software are leveraged for thermal simulations involving PCM.
In most cases, a dynamic specific heat is created to capture effects during multiple stages.
ACT has developed a PCM heat sink calculator that provides a temperature profile as a function of time for up to three Phase Change Materials. It also estimates the mass and volume and volume for the PCM heat sink. *Note that this calculator assumes a general fin thickness. ACT develops custom solutions with the optimal fin thickness for each application’s unique requirements.
Critical Manufacturing of Phase Change Material Heat Sink Systems
Since 2015, ACT has been designing and manufacturing PCM Heat Sinks for some customers from the most high-profile defense suppliers, to innovative high-profile disrupters in the commercial sector (customers and project details confidential). Our depth of experience in not only the design but also the manufacturing of custom PCM Heat Sink solutions positions us to be your trusted partner of choice for PCM Heat Sinks.
ACT has developed the necessary manufacturing technologies required to produce high-quality, high-reliability PCM heat sinks. Some of these manufacturing technologies include
- PCM project evaluation and thermal design
- PCM heat sink prototyping and production
- Unique brazing techniques of complex PCM structures
- Precision charging of PCM
- Safe and reliable sealing of the PCM assembly