Analysis of the heat dissipation performance of U-shaped flat plate micro-heat pipe LED radiator

Light-emitting diode (LED) lighting has been increasingly prominent in the global market in recent years, due to the high luminous efficiency. Generally, the integrated LEDs products can inevitably generate a lot of heat, leading to the extremely high local temperature. However, LED cooling heat pipes in practical applications often face some challenges, such as insufficient contact thermal resistance and heat transfer area. In this study, a heat sink was designed to transfer the heat inside the LED out in time for the long life of the products. Micro heat pipe array (MPHA) was used to explore the impact of the structure on heat dissipation performance using computational fluid dynamics (CFD) software. Two models were established to compare with the experiment. The results show that the maximum error between the simulated and experimental values reached 39.62% at 0.5 m/s. Among them, the simulated value under forced convection was in good agreement with the experimental value, with the maximum error of 11.85%, indicating the accurate simulation. The heat dissipation of LEDs was varied greatly under the action of heat sinks with different structures. Moreover, the better uniformity of temperature was achieved in the U-shaped flat-plate micro heat pipe. Furthermore, the maximum difference of temperature was only 0.6℃ for the MHPA in the vertical direction at an input power of 50W. The better uniformity of temperature was promoted the expansion of the heat exchange area, thus improving the heat transfer capacity of MHPA. The radiator was optimized to enhance the convective heat transfer rather than the heat dissipation. The verified model was used to simulate and analyze the five influencing factors (fin type, inlet wind speed, fin height and fin spacing) on the heat dissipation of LED heat sources. Research results show that the saw-shaped fins shared the larger area of effective heat conduction and better heat dissipation, compared with the traditional straight fins and W-fins. The better performance and heat transfer were achieved under 0.5 m/s or 3 m/s conditions. The convective heat transfer also increased, as the inlet wind speed increased. The heat dissipation under 3m/s conditions was much better than 0.5 m/s. However, the stable temperature drops of the LED heat source gradually slowed down, as the wind speed increased. The economic factors were considered in actual applications, such as the power consumption of the fan. It is necessary to select the wind speed the most suitable for the application scenario. Therefore, the smaller fin spacing and higher fin height of radiator structure can increase the effective heat transfer area and the heat dissipation performance of the heat sink. An orthogonal experiment was designed to determine the best working conditions and structure. The optimal combination was achieved in the forced convection and structure with an inlet wind speed of 3.5 m/s, a fin height of 12 mm and a spacing of 8 mm. The finding can provide new ideas to design the heat dissipation of lighting equipment for the service life and stability of LEDs. © 2024 Chinese Society of Agricultural Engineering. All rights reserved.