Heat Pipe History

The heat pipe was originally developed by Richard S. Gaugler of the General Motors Corporation, Ohio, USA in 1942. However, it was not until the 1960s that a great deal of research on heat pipes began. In 1963, George Grover embarked on a series of heat pipe studies at the Los Alamos National Laboratory in New Mexico, USA, using working fluids such as lithium, sodium and silver, and capillary structures made of a mesh of metal wires. In the 1970s, heat pipes became widely used in space components. At that time, heat pipes were designed using metal as the working fluid, with operating temperatures of around 10,000°C or more, making them suited to applications in gravity-free environments such as outer space components. It was not until J. E. Deverall and J. E. Kemme discovered low-temperature heat pipes using water as the working fluid that the application of heat pipes was further expanded to everyday applications such as solar water heaters, car engine cooling and most commonly today, electronic component cooling.

A heat pipe is a mechanical component that uses a two-phase flow with a change in the working fluid phase to transfer heat. Heat pipes can be divided into an evaporative section, an insulating section and a condensing section. When the subcooled liquid attached to the wall of the evaporative section absorbs external heat, it will heat up and vaporize the liquid and generate a higher pressure called vapor pressure, which is the driving force behind the flow of vapor to the condensing end (lower pressure). When the vapor reaches the condensing section, it releases latent heat and condenses into a liquid, which then returns to the evaporation section using the capillary force provided by the capillary structure of the heat pipe to form a cycle. It is worth noting that this cycle does not require additional fluid drive elements and that the use of latent heat allows for the rapid transfer of large amounts of heat, which are advantages of heat pipes. Heat pipes are widely used in notebook and laptop computers. Due to space constraints, the CPU cannot be directly cooled, so heat pipes must be used to conduct heat from one end of the CPU to the other. This is usually done by using a small fan on the side of the laptop case to dissipate the heat in a convective manner. Copper pipes (thermal conductivity of 400 W/m.K) and aluminum pipes (200 W/m.k) can be used for heat conduction, but the thermal conductivity is so low that the speed of heat transfer is not fast enough, whereas heat pipes can reach up to 14,000 to 20,000 W/m.K. Therefore, the heat pipe is a very efficient tool for heat conduction and is now one of the indispensable heat conduction components for electronic cooling.