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The origin of the heat pipe concept

The concept of heat pipe originated from a patent filed by R.S. Gaugler, G.M Company, Ohio, USA in 1942.

However, a lot of research on heat pipes began in the 1960s. In 1963, Grover launched a series of heat pipe research at Los Alamos Research Institute in New Mexico, USA. The research content included the use of working fluids such as lithium, sodium, and silver, and the capillary structure was made of metal wire into a grid structure.

 

In the 1970s, heat pipes began to be widely used in space components. At that time, the heat pipes designed at that time used metal as the working fluid, and the working temperature was above 10,000C, which was suitable for applications in non-gravity environments such as outer space components. Until Deverall and Kemme discovered low-temperature heat pipes using water as the working fluid, the application of heat pipes was further expanded to civilian uses, such as solar water heaters, car engine cooling, and even today's most common electronic component cooling.

 

The heat pipe is a mechanical element that uses the two-phase flow of the phase change of the working fluid to transfer heat. The heat pipe can be divided into an evaporating parts, a heat insulating part and a condensing part. When the secondary cold liquid attached to the tube wall of the evaporator absorbs external heat, it will heat and vaporize and generate a higher pressure called vapor pressure. This vapor pressure is the motive force that causes the vapor to flow to the condensing end (lower pressure), When the vapor flows to the condensing part, it will release latent heat and condense into a liquid. This liquid will finally return to the evaporating part by 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 components, and the use of latent heat can quickly transfer a large amount of heat, etc., which are the advantages of heat pipes.

 

A large number of heat pipes are used in notebook computers. Due to space constraints, the heat of the CPU cannot be directly dissipated. Therefore, heat pipe elements must be used to guide the heat from one end of the CPU to the other end, which is usually the side of the pen motor shell. The small fan next to the case dissipates the heat by convection. The heat conduction tool can of course use copper pipes (thermal conductivity coefficient 400W/mK) and aluminum pipes (200 W/mk), but the thermal conductivity coefficient is too low and the heat transfer speed is not fast enough. The heat pipe can be as high as 14,000 to 20,000 W/mK. Therefore, using the heat pipe as a heat conduction tool is very efficient, and it is now one of the indispensable heat conduction components for electronic heat dissipation.

 


Author

Professor Wei-Keng Lin

Education|Ph.D., University of Maryland

Occupation|Professor, National Tsing Hua University 

Specialty|Electronic package heat dissipation, Heat pipe, Loop heat pipes(CPL,LHP,PHP), Energy-saving design, Solar heat storage and cooling, Heat flow system, Cooling of electronic components, Two-phase flow, Heat transfer elements of artificial satellite and high-altitude flying object

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