Research And Analysis On Heat-Release Technology Of High-Power Led Array

As a new generation of semiconductor light source, High-power white light LED array has been increasingly widespread concerned with long life, low energy consumption, a variety of advantages. At present, the heat flow density of the high-power white light LED array has reached100W/cm2, but it can only transfer about20%of electric energy into light energy, the rest of80%is converted into heat energy. Unless the heat is timely and effectively dissipated, it will lead to the exorbitant chip temperature, so as to reduce the photons quantity that the chip directly emitted, decrease the light-extraction efficiency, and influence the chromatic ity and color temperature of the white LED, as a result of affecting the quality of light source, accelerating device ageing and shortening service life. Therefore, the heat dissipation become an important problem to be solved for the high power LED array.The heat dissipating technology of high power LED array has been analysed and researched in this paper, the microchannel heat sink based on liquid cooled was designed, and the structure is optimal analysed and simulated as well. According to the physical meaning of thermal resistance, the relation between the thermal resistance and the channel width, the cooling fluid flow velocity of the microchannel heat sink has been derived through the heat transfer and fluid mechanics theory, on this basis, the optimization of the channel width and the coolant flow rate are obtained applying the theoretical optimization and MATLAB simulation analysis, the cooling efficiency of the microchannel heat sink is improved greatly in this paper.Because the theoretical analysis is a simplified analytical model, and in order to be able to accurately and visually represent the cooling performance of microchannel heat sink, the computational fluid dynamics software FLUENT is used for simulation in this paper. First, under the same power of the heat source, the air-cooling radiator and water-cooling radiator of the high power LED array, whose distribution of temperature fields are simulated and analysed, and compared with those of the microchannel heat sink in the cooling effect, which shows the superiority of microchannel heat sink. Then, the channel width and the cooling fluid flow velocity of the microchannel heat sink are simulated and optimized. Simulation results show that when the overall size of the radiator is fixed, the smaller the width of the channel and the larger the cooling area, the higher the cooling efficiency in a certain range. But, the decrease of the channel width will also affect the cooling effect, due to the cooling fluid dynamic viscosity increased. When the radiator channel width is0.1mm, the cooling effect is best.Regarding to the coolant flow rate, the temperature distribution of the microchannel heat sink obviously decreases with the increase of the flow velocity, the cooling effect is enhanced. But the coolant flow can not be increased unlimitedly, because the greater the coolant flow rate, the greater the inlet pressure required and the frictional resistance loss of the channel. In actual application, the maximum pressure of the water pump can provide is also considered, when the cooling water flow rate is1m/s, the radiator cooling effect is best. When the microchannel width is0.1mm, cooling water flow rate is1m/s, the minimum thermal resistance of the microchannel heat sink can reach0.019W/℃.Finally, aimed at the phenomenon of uneven distribution of temperature on the surface of the high power LED array, the microchannel heat sink with variable width is presentd in this paper, and the simulation of its temperature field is analysed. The results show that the problem of the temperature in central being much higher than that on the edge of the high power LED array is effectively solved, and the temperature distribution tend to be more uniform.