| The fourth generation lighting source--LED is widely used in various lighting industries with its advantages of green environmental protection,energy saving,high efficiency and long life.With the rapid development of LED industry,LED develops towards the direction of high brightness,high integration and high power,but this also aggravates the heat dissipation difficulty of LED chips,leading to a sharp rise in junction temperature,which seriously affects the performance and working life of LED.Therefore,it is urgent to solve the heat dissipation problem that restricts LED development effectively.Array in this paper,by the high radiation type high power LED chip module and water-cooled radiator as the research object,analyzed the whole LED heat transfer process of water cooling,cooling bottleneck problem in the process of heat transfer,on the basis of the research of LED module encapsulation of the key factors influencing the module thermal resistance and the different types of water cooled radiator cooling performance.(1)For the LED module based on COB package,the thermal model of five different chip densities was studied by thermal simulation analysis(b=a,b=1.5a,b=2a,b=3a and b=4a,Where a is the chip diameter and b is the unit substrate diameter);the maximum thermal resistance of the aluminum nitride ceramic substrate is obtained by the finite element simulation calculation,and the optimum thickness of the substrate at different chip spacings is obtained.Taking the substrate of b=2a as an example,the numerical theory is used to derive the dimensionless expression of the maximum theoretical thermal resistance of the substrate.The maximum theoretical thermal resistance calculated by this method is less than 7% compared with the simulated value,which confirms the simulation analysis method.accuracy;The main research contents of this paper are as follows:(1)for the cob-encapsulated LED module,the thermal simulation analysis method is adopted to study the substrate thermal models with five different chip densities(b=a,b=1.5a,b=2a,b=3a and b=4a,where a is the chip diameter and b is the unit substrate diameter).Through the finite element simulation,the maximum thermal resistance of aluminum nitride ceramic substrate changes with its thickness,and the optimal thickness of substrate at different chip spacing is obtained.Taking the substrate with b=2a as an example,the dimensionless expression of the maximum theoretical thermal resistance of the substrate was derived by numerical theory,and the error between the calculated maximum theoretical thermal resistance and the simulated value was within 7%,which confirmed the accuracy of the simulation analysis method.(2)For three fin,five fin,seven fin and nine fin four finned water-cooled radiator,as well as the improvement of finned three pin fin scrambling and a porous flow,a total of six kinds of water-cooled radiator,based on ANSYS19.0 Icepak thermal simulation method,analyzed the influence factors of the radiator cooling and compared the performance of heat exchangers.The results show that when the number of fins increases,the maximum temperature and maximum temperature difference of the chip will decrease gradually,and the pressure difference will increase rapidly.Three pin fin scrambling best die temperature control,only 7.2 ?,but the differential biggest;The pressure difference of the multi-orifice water-cooling radiator is the best.Even if the pump flow reaches 25L/min,its pressure difference is only more than 1000 Pa.(3)The heat dissipation performance of the two typical water cooling radiators,the seven-fin type and the multi-hole flow channel type,was compared and analyzed at the same flow rate.Meanwhile,the temperature of the monitoring point measured in the experiment was compared with that obtained in the simulation,and the error was 3.5% and 2.9%,respectively,which confirmed the accuracy of the simulation analysis method. |
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