LED chips in LED lamps are electronic components with high heat flux density. During operation, due to their static and dynamic losses, a large amount of excess heat is generated, which is dissipated to the outside through the heat dissipation system to maintain the stability of their operating temperature. At present, the luminous efficiency of LEDs is still relatively low, resulting in an increase in junction temperature and a decrease in life. In order to reduce the junction temperature and increase the life span, it is necessary to attach great importance to the problem of heat dissipation. The heat dissipation design of the LED must start from the chip all the way to the entire heat sink, and every link must be given full attention. Improper design of any link will cause serious heat dissipation problems. Therefore, full attention must be paid to the design of heat dissipation.
The high-performance micro-groove group composite phase change heat transfer technology meets the heat dissipation requirements of high-power LED lighting. The technology is named "micro-groove group composite phase change integrated cooling technology". This technology has been successfully applied to LED lamps. The heat of LED chips can be distributed in the entire heat dissipation space instantly, extending the life of LED lamps and improving the luminous efficiency.
1. Micro-groove group composite phase change integrated cooling technology:
The heat generated by the LED chip is eventually dissipated into the air through the lamp housing. The general heat dissipation is: the heat generated by the LED chip comes out of its metal heat dissipation block, and then passes through the solder to the PCB of the aluminum substrate, and then passes through the thermal conductive glue to the aluminum radiator. The heat dissipation of LED lamps actually includes heat conduction and heat dissipation. There is a concept to understand first, that is, the difference between heat conduction and heat dissipation. Heat conduction is to transfer heat from the heat source to the surface of the radiator as quickly as possible, while heat dissipation is to radiate heat from the surface of the radiator to the air. First, the fastest heat must be exported, and then it must be most effectively dissipated into the air. The heat sink of the traditional radiator is aluminum fins, our heat sink is: micro-groove group phase change technology.
The micro-groove group phase-change cooling technology relies on technical means (such as equipment structure: micro-groove and other means) to turn the closed circulation cooling medium (if the medium is water) into a nano-scale water film. The thinner the water film, the ability to evaporate when heated The stronger, the stronger the latent heat exchange ability, the heat of the high-power electronic device is taken away by the steam.
Cooler system composition and working principle:
1. The composition of the cooler:
The system is mainly composed of four parts, namely a heat extractor, a condenser, a conveying pipeline, and a heat extracting medium (such as water, ethanol, etc.).
The heat extractor is generally made of imported aluminum alloy, and the inner cavity of the plate has many channels of the order of micrometers. Its function is to change the heat medium (such as water) into the required liquid film, heating power device and aluminum alloy according to the design requirements. The surface is in close contact, and its heat energy is transferred to the liquid film through aluminum heat, and the liquid film is instantaneously vaporized, and the heat energy is sent to the condenser for cooling through the pipeline. Due to the strong heat extraction capacity of the heat extractor, its thermal conductivity is greater than 106 W / (m * ℃), so the volume of the heat extractor can be made very small.
The condenser is usually made of imported aluminum alloy, the inner cavity of the plate has many channels of the order of millimeters, and the aluminum alloy plate has fins outside. The heat medium is sent to heat energy through the pipeline. It is responsible for convection heat exchange with outdoor air and Radiative heat exchange, the heat energy of the heat extraction medium is released through the condenser, and changes from the vapor state to the liquid state. The liquid heat extraction medium returns to the heat extractor by its own gravity, ready for the next heat energy exchange cycle.
2. Working principle:
Many micro-channels are processed on the inner surface of the capillary micro-groove compound phase change heat collector to form a micro-groove group structure. The micro-scale composite phase change is used to strengthen the heat transfer mechanism to achieve a high heat flux density and small volume in a narrow space. High-power devices take heat efficiently. The heat extracted from the capillary micro-groove group phase change heat collector is transported by steam to the remote high-efficiency micro-structure condenser through the steam circuit, and high-strength micro-scale steam is carried out on the surface of the micro-scale condensation tank group structure in the micro-structure condenser Condensation exotherms. The heat released by the condensation of the condenser can be quickly diffused to the structure surface of the micro-scale condensation tank group, and is conducted outward through the wall surface to the rib surface of the outer wall of the microstructure condenser, and the heat is released to the outside environment by convection heat exchange Go in the environment. The condensate passes through the condensate liquid circuit and flows back to the micro-groove group phase change heat collector under the effect of pressure gradient. Therefore, the closed loop of high efficiency and no power consumption of the system's own heat extraction and heat release is realized, and the purpose of device cooling is achieved. The heating surface of the micro-groove group composite phase change heat collector is in close contact with the power electronic device, and its inner surface is engraved with many composite phase change micro-channels, which are integrated into a composite phase change micro-groove group. There is a small amount of liquid working fluid with a certain latent heat of vaporization in the micro-groove group phase change heat exchanger. The liquid working fluid flows along the micro-grooves under the action of the capillary pressure gradient formed by the micro-groove group's own structure, and at the same time forms a high-strength micro-scale recombination of thin liquid film evaporation and thick liquid film nuclear boiling of the extended meniscus in the micro grooves. The phase change strengthens the heat exchange process, turns the liquid working fluid into steam, and utilizes the huge heat generated by the vaporization latent heat when the power electronic device is working, thereby reducing the working temperature of the device and controlling it within an ideal range. The micro-groove group composite phase change cooling system is composed of a small-sized heat extraction element (micro-groove group composite phase change heat collector), heat and fluid transportation pipelines, and a remote heat release element (remote microstructure condenser). Among them, the heat and fluid transportation pipeline includes a steam circuit that transports heat and a condensate circuit that transports condensate. The micro-groove group composite phase change heat exchanger and the remote microstructure condenser are connected to form a Externally closed micro-negative pressure circulation system. The huge heat extracted by the composite phase change heat collector of the micro-groove group is transported by the steam through the steam circuit to the remote microstructure condenser under the action of the evaporation and condensation pressure difference of the system, and the microscale condensation in the inner cavity of the microstructure condenser High-strength microscale steam condensation and heat release are carried out on the surface of the tank group structure. The heat released by the steam condensation is transferred from the surface of the micro-scale coagulation tank group structure through the wall surface to the rib surface of the outer wall of the microstructure condenser or the cooling water channel group on the outer wall (Note: the wall surface of the microstructure condenser condenses the external environment and The cooling water is separated from the microstructure condenser, the external environment and the cooling water do not contact with the condensate in the microstructure condenser), through air (natural or forced) convection heat exchange with the external environment or with the cooling water channel group The cooling water in the system undergoes single-phase forced convection heat exchange and is eventually lost to the external environment. The condensate flows back through the condensate circuit, with the help of gravity and the pressure gradient generated by the system's fine-scale tank group structure, back to the micro-groove group phase change heat collector. Therefore, the entire system forms a unidirectional flow with working fluid in the order of the micro-groove group composite phase change heat collector, steam circuit, remote microstructure condenser, condensate circuit, and then returning to the micro-groove group composite phase change heat collector. , Liquid-vapor-liquid phase heat extraction and heat release mode of power consumption-free cycle (passive cycle), to achieve the purpose of cooling the high-power power electronic devices that generate heat. Figure 1 is a schematic diagram of the cooling system.
Figure 1 Schematic diagram of micro-groove group composite phase change cooling system.
3. The difference with heat pipe
Similar in form to heat pipes, but it is essentially different in heat exchange mechanism, structure and performance:
1. Adopt a powerful micro-scale composite phase change to strengthen the heat transfer mechanism; the heat pipe is only ordinary liquid film evaporation;
2. The inherent heat transfer limit of heatless tube such as boiling, entrainment, capillary force, etc .;
3. The high contact thermal resistance and heat conduction thermal resistance when the high-power heat dissipation without heat pipe and the bulky and complicated problems of the device;
4. Problems of starting without heat pipe and working stability;
5. The heat extraction capacity per unit area at the same temperature is about 100 times higher than that of the heat pipe, and the system is simple, light and compact.
Second, the characteristics of micro-groove group composite phase change LED high-power light source cooler:
1. Super thermal conductivity:
The micro-groove group phase change cooling technology has super thermal conductivity, and its thermal conductivity is 10,000 times that of the aluminum substrate. This technology can send the heat of the LED chip to each heat dissipation surface of the aluminum substrate with an infinite area in time.
Thermal conductivity is greater than 106 W / (m * ℃). Copper is an excellent conductor and an excellent thermal conductor. The thermal conductivity of copper is about 400 W / (m * ℃). The thermal conductivity of MGCP is higher than that of copper. It has super thermal conductivity. A solid copper rod with a length of 60cm and a diameter of 1.3cm is used to deliver 200W of thermal energy at an operating temperature of 100 ° C. The temperature difference between the two ends of the copper rod is as high as 70 ° C; the MGCP heat collector is made of half of the weight of the above copper rod. At a working temperature of 100 ° C, 200W of thermal energy is transported, and the heat transport distance is also 60cm away. Its temperature has only dropped by 0.5 ° C. The experiment shows that MGCP technology has super thermal conductivity.
2. Super cooling ability:
The heat flux density has reached 400W /, its capacity is 1000 times higher than that of water cooling, and about 100 times higher than that of heat pipes. The heat extraction capacity is 100 times higher than that of forced water cooling and 1000 times higher than that of forced air cooling.
At 1 standard atmospheric pressure, the boiling point of water is 100 ° C, 1Kg of water is heated from 99 ° C to 100 ° C, and the required thermal energy is 4200 joules; 1Kg of 100 ° C water absorbs heat and turns into steam at 100 ° C, but the temperature does not change, but The amount of heat absorbed is 2.26 million joules. Water cooling is sensible heat exchange, and the heat exchange heat is low, MGCP technology is latent heat exchange, and the heat exchange ability is super strong. It takes only 4200 joules of heat to heat 1Kg of water at 1 ℃. The temperature of 1Kg of water at 100 ℃ changes from 100 ℃ to 100 ℃. There is no change in temperature, but the amount of heat absorbed is 2.26 million joules. The difference between the two is more than 500 times. Therefore, There is a huge difference in heat exchange capacity between the two.
3. Cooling without power consumption:
Passive heat dissipation, no fan or water pump, no energy consumption for cooling, no power operation, energy saving. MGCP technology is the ingenious use of the energy of high-power power electronic devices to evaporate the heat medium to generate kinetic energy and potential energy. The steam flows to the condenser to radiate heat and condense into a liquid. The high-power power electronic device is closely attached to the heat collector, thereby realizing a closed cooling cycle without external power.
4. Light weight and small size:
The weight is less than 25% of the existing radiator, and the volume can be as small as 20%.
5. High reliability:
The device is simple and compact, with stable operation and no startup problems. Its reliability is much higher than that of fans, water cooling and heat pipe radiators.
6. Low cost and environmental protection:
The cost of the product is less than the radiator of the fan, water cooling and heat pipe; the phase change working fluid is environmentally friendly, and the amount is small without consumption.
7. Utilization of waste heat:
The heat (waste heat) generated by high-power power electronic devices can be converted into 50 ℃ ~ 60 ℃ hot water for daily life, replacing electric water heaters and achieving energy saving.
LED lighting technology is still developing rapidly. With the advancement of technology, the micro-groove composite phase change technology has matured. Many LED lighting companies in China are gradually putting it into use. I believe that this technology will be used in the near future. Step into more high-power LED lighting manufacturers who are troubled by heat dissipation, and truly solve the heat dissipation problem.
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