Investigation On The Optimization Of Heat Transfer Of Fin Heat Sink Applied In COB Light Source

COB light sources have been extensively applied in industrial production,life lighting and other related fields.The temperature of COB is an important factor affecting its performance and lifetime,so the thermal management is extremely important for the working of COB.Among the various forms of thermal management for COB,natural convection heat dissipation with the fin heat sink is an efficient and inexpensive way to dissipate the heat generated by COB.However,there is often a mismatch between heat dissipation performance of fin heat sink and the demand of cooling capacity to dissipate heat resulting in high or insufficient heat dissipation input.Aiming at these problems,theoretical analysis,numerical simulation and experimental research are adopted to optimize the structural parameters and forms of fin heat sink.Based on analysis of classical heat transfer theory,the heat transfer process of fin heat sink is divided into five links.According to the thermal resistance analysis of simplified one-dimensional steady-state heat conduction process,the equivalent heat path diagram is established.The temperature distribution in the natural convection process of fin heat sink is obtained by experimental study.The calculation results of thermal resistance show that the thermal resistance at fin group accounts for more than 80%.It is necessary to focus on the heat transfer at the fin group for enhancement.Firstly,according to different calculation philosophies,the structural parameters of fin are optimized by theoretical calculation and analysis,including discrete calculation and random calculation.Discrete calculation is realized by discretely generating multiple sets of variables to solve the objective function value and conducting theoretical analysis.It mainly includes forward discrete computation and inverse discrete computation.The forward discrete computation realizes the evaluation of heat dissipation effects of fin heat sinks.It was found that surface temperature of COB showed a ’valley’ trend with the change of fin pitch and thickness under the fixed fin height.That’s,there is a superior area which includes the structure parameters of fin heat sink that makes the surface temperature of COB lower.The inverse discrete computation realizes the consideration of cost during the heat dissipation and the selection of fin heat sink.The results show that the equivalent mass heat transfer coefficient is more sensitive to the change of fin pitch compared to the fin thickness under the fixed fin height.Less raw materials are processed to achieve better performance of fin heat sink with the combination of large fin pitch and small fin thickness.As to different fin heights,the region of optimal structural parameter region has characteristics of narrow fin space and wide fin thickness for small fin height,while for large fin height,the region of optimal structural parameter shows reversely.Random calculation is realized by generating multiple groups of variables randomly to solve the objective function and carrying out directional optimization,which is realized by genetic algorithm.The structural parameters of fin heat sink obtained by random computation-genetic algorithm not only can achieve the lowest surface temperature of COB among fin heat sinks of same mass,but also achieve the lowest amount of materials among fin heat sinks of same surface temperature.That’s to say,it can achieve lower surface temperature of COB while using less materials.What’s more,the changes in the forms of fin heat sink improve the airflow organization in long and narrow parallel channels of original fin heat sink and strengthened its natural convection greatly.There are three structural forms:structure of removed material,structure of additional material and structure of new forms.The results of numerical simulation show that the slotted structure of removed material,the chimney structure of additional material and the staggered structure of new forms have certain effects on the performance of fin heat sink which lower the maximum temperature on the surface of COB compared to the conventional commercial fin heat sink on the market.The maximum surface temperature of COB can be effectively reduced when the material manufacturing cost is greatly reduced or slightly increased.The structural parameters of all kinds of forms have important effects on the enhancement of performance.