Views: 36 Author: Site Editor Publish Time: 2021-06-22 Origin: Site
In practical applications, the ultra-thin heat pipe in the heat pipe heat sink is usually defined as a flat heat pipe with a thickness of less than 2.0 mm. Ultra-thin heat pipes are very thin and can dissipate heat directly to the surface of electronic components, so they are widely used in mobile or portable electronic devices such as smart phones, notebook computers, and smart watches. The thickness of the ultra-thin heat pipe is 1-2 mm and 0.8-1.2 mm, respectively, and the heat transfer capacity is above 20 W; for smart phones or smart watches, the thickness of the ultra-thin heat pipe is between 0.4-0.6 mm, and its heat transfer capacity Greater than 5 W. There are four main structural forms of ultra-thin heat pipes: flattened heat pipes, uniform temperature plates, flat micro heat pipes and ultra-thin loop heat pipes.
Flattened heat pipe
The flattened heat pipe is manufactured by directly flattening the traditional cylindrical heat pipe, and its structure and working principle are similar to the traditional heat pipe, as shown in Figure 1. In the axial direction, the flat heat pipe is generally composed of an evaporating part, a heat insulating part and a condensing part in sequence. The flattened heat pipe has a flexible manufacturing process, and the long flat structure enables it to achieve multiple heat sources and long-distance heat transfer, but it also has the shortcomings of small surface area and single shape. Flat heat pipes are mainly used for small mobile devices such as smart phones and tablet computers.
Homogeneous temperature plate
The homogenizing plate is a closed container with a plate-like structure. The inner wall of the container is covered with a wick structure. The evaporator and condenser are located on both sides of the closed container. The inner wick is the key to improving the heat transfer performance of the heat pipe. The capillary force produced provides power for liquid reflux, promotes the circulation of working fluid, and improves the heat efficiency of gas-liquid conversion. In addition, the uniform temperature plate has the advantages of light weight, flexible structure, strong thermal conductivity, etc., especially its large condensing area, so that the uniform temperature plate is widely used for heat dissipation of electronic equipment with high local heat flux.
Flat micro heat pipe
The flat-plate heat pipe is similar to the uniform temperature plate and consists of an evaporator, a liquid wick, and a condenser, and the whole is in the shape of a thin sheet. The difference from the uniform temperature plate is the heat pipe. The evaporator and the condenser are located on both sides of the wick and are in close contact with the wick. Thus, while inheriting the high temperature uniformity and high heat transfer capacity of the uniform temperature plate, the thickness of the flat plate is greatly reduced. Therefore, flat-plate micro heat pipes are mainly used for heat dissipation of electronic devices with high heat flux density.
Ultra-thin loop heat pipe
The composition and working principle of the ultra-thin loop heat pipe are similar to the traditional loop heat pipe. The classic loop heat pipe is composed of an evaporator, a compensation chamber, a steam channel, a condenser, and a liquid return channel, and it has a ring structure as a whole. The liquid absorption core structure is located in the evaporator and compensation chamber, and the rest of the loop elements are composed of smooth-walled tubes. The smooth-walled tubes can reduce the flow resistance of the working fluid backflow evaporator, which makes the ultra-thin loop heat pipe particularly suitable for long-distance heat transfer . The ultra-thin loop heat pipe has independent evaporator and condenser, therefore, not only can eliminate the entrainment effect, but also can transfer more heat. Therefore, the ultra-thin loop heat pipe can be used for thermal control of power batteries in addition to heat dissipation of mobile devices.