Thermal management is a crucial aspect of many modern electronic systems. Both terrestrial and space flight electronic devices and equipment, ranging from data acquisition units, to star trackers, cryocoolers, optical benches, and a large range of sensors and other instruments, can generate a large amount of heat that must be effectively managed to ensure reliable operation and prevent damage. Without proper waste heat removal, this vital equipment and scientific instruments can overheat, malfunction, and their lifetimes can be significantly shortened (which can be a “natural disaster” level of an expensive problem when working with satellites or particle accelerators).
As just about everyone reading this knows, there are two main types of thermal management products: passive and active. In this blog, we'll explore the differences between a passive thermal management product like a Thermal Strap, and an active thermal management product like a Heat Pipe or Vapor Chamber.
Passive thermal management products, like Thermal Straps, use conduction to transfer waste heat from the source to a heat sink. The straps themselves are made of materials that have a high thermal conductivity and can effectively transfer heat from one component to another (and depending on the operating temperature and thermal conductance requirements, certain materials are more beneficial than others, due to their density and material thermal conductivity across a range of operating temperatures).
They work by providing a direct thermal path between the hot component and the heat sink, allowing heat to be conducted away from the hot component and dispersed. Thermal straps are passive because they do not require a power source or any external control to function. We simply design the most efficient, lightest, and affordable (when possible) link between source and sink, using STP (CAD) files which detail the available envelope and interfaces within each thermal strap location (with the application’s requirements and operating environment in mind).
Just as there are significant disadvantages when it comes to products like Heat Pipes or Vapor Chambers, there are, of course, applications or circumstances in which a Thermal Strap is simply not your best option:
Active thermal management products, like Heat Pipes or Vapor Chambers, use a combination of conduction and convection to transfer heat from the hot source to a heat sink.
Heat Pipes contain a working fluid that vaporizes at the hot source, transfers heat through convection, and condenses at the heat sink. The condensed fluid then returns to the heat source, and the cycle repeats. This continuous cycle of vaporization and condensation allows Heat Pipes to transfer heat over large distances and provides a much higher heat transfer rate than Thermal Straps.
Vapor Chambers are a more advanced thermal management device that use phase change to transfer heat. They consist of a closed container filled with a working fluid, typically water or a water/glycol mixture, that is heated by the heat source. The working fluid changes phase from liquid to vapor as it absorbs heat, and the vapor then transfers heat to the heat sink through condensation. This phase change process results in a much higher thermal conductivity than conduction alone, making active Vapor Chambers more effective at transferring heat than a thermal strap. However, there are significant advantages and disadvantages of active systems like Heat Pipes and Vapor Chambers.
Thermal Straps, Heat Pipes, and Vapor Chambers all have their advantages and disadvantages. However, here at TAI, we don’t view Heat Pipes or Vapor Chambers as competing products. Instead, each have their place in the “thermal management tool box,” and they can even be complementary products.
Pictured: NASA engineer installing TAI's Copper Thermal Straps in the GEDI instrument, attaching strap assemblies to heat pipes.
For example, we often receive inquiries from aerospace engineers that require a substantial amount of heat transfer (for instance, some satellite applications have conductance requirements of as much as 30 – 100 W/K). While it is possible to remove this much heat with thermal straps alone (provided you have the interface area available—which is rarely the case), more often than not, in these cases, organizations like NASA will incorporate a system of Heat Pipes to transfer large amounts of heat over longer distances. Then, they rely on Copper and Graphite Thermal Straps from TAI, to mechanically decouple the Heat Pipe from the edge of a spacecraft or other important equipment and instruments like star trackers. In these cases, TAI can design Thermal Straps that either clamp directly to the Heat Pipe, as shown in the image, or we can design adapter brackets that attach to the pipes, thereby allowing a simpler and larger attachment interface for a thermal strap.
To learn more about our Thermal Strap products, contact TAI today. Our Engineering Team provides all front-end design services at no charge, and TAI offers the largest selection of custom and standard copper and graphite strap products in the industry, at the most affordable prices (and we’re happy to recommend some excellent Heat Pipe and Vapor Chamber manufacturers, if needed).