This paper comprehensively studies the key issues of boundary condition setting, thermal resistance calculation, thermal load analysis and heat sink simulation modeling, and combines with laboratory temperature measurement to verify the accuracy of the simulation method. The results show that the method can accurately analyze the heat dissipation of indoor lighting LED lamps, and the simulation temperature error is about 4 °C. The simulation results have important reference value for the development and design of LED lamps.
0 Preface
LED is a semiconductor light-emitting device. Due to the current production level of LED chips , the input power of LED high-power products is only about 20%~30% converted into light energy, and the remaining 70% is converted into heat energy. The increase in junction temperature affects LED lifetime, light efficiency, color (peak wavelength), color temperature, light distribution, reliability, luminous intensity, forward voltage, etc., which are important factors affecting lighting quality.
In order to control the temperature rise of LED lamps and ensure the life and reliability of lamps, domestic and foreign scholars have done a lot of research on the heat dissipation design of LED lamps for lighting, especially the finite element fluid dynamics CFD simulation software for thermal simulation analysis. It can comprehensively analyze the heat conduction, heat convection and heat radiation of LED lamps, analyze and solve the temperature field and flow field inside and outside the LED lamps, which is very suitable for the current cooling simulation of LED lighting fixtures.
This paper will analyze the key problems in the simulation modeling of LED lighting fixtures from the aspects of boundary conditions (ambient temperature, gravity direction, etc.), thermal resistance calculation, thermal load distribution and form, thermal conductivity of thermal materials and emissivity. The accuracy of the model simulation results is verified by laboratory temperature measurements.
1 boundary conditions
1.1 Ambient temperature
The temperature field distribution of 5WHL-A60LED bulbs at ambient temperature of 20, 25, 30, 35, 40, 45 and 50 °C is simulated. The operating temperature of LED is shown in Fig. 1~3 (in the figure, Max indicates the maximum operating temperature of the LED, avg indicates the average operating temperature of the LED, the same as below), the average temperature of the heat sink, and the temperature change trend of the power supply temperature as the ambient temperature changes. As can be seen from the simulation results, the LED The maximum temperature and average temperature, the average temperature of the heat sink and the ambient temperature change linearly. That is, the higher the ambient temperature, the higher the maximum temperature of the LED and the average temperature of the heat sink. But the relationship between them is not a purely linear superposition, the scale factor is about 0.8.
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