Micro heat pipe technology solves the problem of LED cooling

     Compared with traditional light sources, LED also has the advantages of long life, fast response, potential high luminous efficiency, small size and narrow spectrum. But in essence, among these many advantages, the potential high luminous efficiency, small size and narrow spectrum are the most critical, which makes LED different from traditional light sources and broadens its applications in various fields. However, due to its small size and high luminous efficiency, LED still has the problem of heat dissipation, which is an obstacle to its application. If the heat of the LED chip cannot be dissipated, it will accelerate the aging of the chip, and may also lead to the melting of solder, making the chip invalid.

     At present, the main methods used to solve the thermal problem of power LED lighting systems are: adjusting the LED spacing, natural convection cooling , installing fans or liquid cooling forced air  cooling, heat pipe and loop heat pipe cooling, etc. With the development trend of LED integration with high density and high heat flow, it is necessary to realize rapid cooling  by means of efficient heat transfer of heat pipe.

     The micro heat pipe is a heat transfer element with extremely high thermal conductivity. It transfers heat through the evaporation and condensation of the liquid in the fully enclosed vacuum tube. It uses the fluid principle such as gross absorption to achieve the effect similar to the refrigeration of a refrigerator compressor. It has a series of advantages, such as high thermal conductivity, excellent isothermal property, variability of heat flow density, reversibility of heat flow direction, long-distance heat transfer, constant temperature characteristics (controllable heat pipe), thermal diode and thermal switch performance, and the heat exchanger composed of heat pipe has the advantages of high heat transfer efficiency, compact structure, small fluid resistance loss, etc

      From the point of view of heat transfer, the biggest difference between the micro heat pipe and the conventional heat pipe is that the specific surface area of the wall per unit steam flow in the micro heat pipe is greatly increased, so that heat transfer can be enhanced. Flat plate micro heat pipe array, that is, multiple simultaneously formed and completely independent micro heat pipes are combined (not just micro channel array heat pipes). Each micro heat pipe is disconnected, and the internal surface of each micro heat pipe can have micro grooves and other microstructures to enhance heat transfer.

   Compared with the existing flat plate heat pipe and single micro heat pipe, the flat plate micro heat pipe array has the following characteristics: first, multiple micro heat pipes in parallel solve the problem of small heat transfer capacity of micro heat pipes due to micro scale; Second, the internal structure greatly increases the area of phase change heat transfer. Because the aluminum wall between the micro heat pipes has a good thermal conductivity, it can transfer part of the heat from the heating surface to the opposite micro groove surface, and phase change occurs on the entire circumference of the micro heat pipe. Whether in evaporation section or condensation section, the heat dissipation capacity of unit steam flow is greatly enhanced. Third, the wall between the micro heat pipes acts as a "reinforcing rib" in the structure, greatly enhancing the pressure bearing capacity of the flat plate micro heat pipe array. Fourth, the flat plate micro heat pipe array has a flat shape, which can easily fit with the heat exchange surface. It overcomes the shortcoming that the conventional round section gravity heat pipe needs to add a special structure to fit closely with the heat exchange surface, and reduces the interface contact thermal resistance.

     The flat plate micro heat pipe array is a kind of thermal conductive element with superconducting thermal performance. Its apparent thermal conductivity is more than 5000 times that of the same metal material, and it is 10 times that of the traditional round heat pipe with the same sectional area. Each micro heat pipe in the flat plate works independently, and the pressure bearing capacity is more than 10 times that of the traditional round heat pipe. It is difficult to mechanically destroy the micro heat pipe. The temperature difference per meter is less than 1 ℃, which can almost be considered as an isothermal body; The heat release area of micro heat pipe array is large, and the temperature of aluminum fin, substrate and heat pipe is basically the same.

   The micro heat pipes can be randomly combined into a flat plate micro heat pipe array of a certain width, and the micro heat pipes can be arbitrarily bent, and the heat transfer effect has no obvious change at a lower heat flux. U-shaped micro heat pipe array is a bending form of micro heat pipe array with good heat transfer performance proved by experiments. The micro heat pipe array can basically solve the heat dissipation problem of various LEDs because of its high efficiency of heat absorption, transmission and heat release, and flexible deformation combined with fins.