What is a Heatpipe?
A Heatpipe is a sealed copper tube that is under vacuum, and can transfer heat rapidly away from the source. The High thermal conductivity enables a heat pipe to transfer, and dissipate heat to a more convenient location through a capillary action. This effect is similar to placing a paper towel in coffee, and watching the fluid rise up the paper towel. Heat pipes are available in various shapes and sizes.. The can be flat or round, and can be formed to fit most contours.
The use of a heatpipe for thermal management is a proven and widely applied technology. The modern concept of a capillary driven heat pipe was first invented by General Motors in 1962. NASA later adapted and further developed this concept. Heatpipes have become commonplace in some of today’s electronics systems. Computers, pipes along the Trans-Alaska Pipeline, nuclear reactors, heat-sensitive electronics aboard satellites and the International Space Station, all rely on heat pipes to manage thermal output effectively.
A heatpipe is a metal tube, sealed under partial vacuum, with an inner wick lining (capillary material) and a small amount of fluid. As heat is applied to the heatpipe’s surface, this causes the evaporator region to heat the fluid inside and change it into a vapor. This phase change from fluid to vapor creates pressure. As pressure increases, vapor will naturally flow into the cooler section. Heat is released as the vapor condenses back into a fluid. The fluid will then flow back into the warm region, where the cycle will repeat (as long as there is heat applied).
Many fluids can be used in heatpipes as the phase transition. In most applications, de-ionized water is selected as the working fluid due to its high latent heat, surface tension, thermal conductivity and boiling temperature. The negative pressure of the vacuum within heat pipes allows the water to boil and turn into steam at lower temperatures than normal. The internal wick can vary depending upon the application and orientation of the cooling device. The three most common methods are:
- Grooved - Low Cost, does not work well against gravity
- Wire Mesh - Most common method
- Sintered - Highest performance and cost
In this example a heatpipe was embedded into a heatsink so that the heat could be spread uniformly.
In this example a heatpipe was used to move the heat from a source to a remote radiator.
In this example the heatpipe and heatsink were nickel plated.