Study On Heat Dissipation Structureoptimization Of Power Electronic Device And Equipment

With the continuous improvement of the level in aerospace science technology, space power technology with high reliability and high power density has become the key technology anticipated highly. Power electronic device and equipment must be developed to miniaturization and light weight as the core of the power supply system. The special working environment and the higher requirements for the volume, weight and life of the power supply makes the cooling problem more serious. It makes the thermal structure design of the power electronic device more prominent.The thermal optimization method of effecting factor of MCM is deeply studed in this paper. The calculation method of thermal resistance for forced air cooling heat sink, the calculation method of transient temperature of heat sink and the thermal structure and optimization method of high power density power electronic devices in forced air cooling are also analysised in this thesis.Main factors effecting thermal performance of MCM is analysised using finite element method. A regression equation describing the relationship of structure parameters and material properties with the maximum chip junction temperature of MCM is made based on the response surface methodology. Quantitative analysis of the effect of four design parameters on the maximum chip junction temperature of MCM is studied. The four design parameters are the thickness of the substrate, thermal conductivity of the substrate, thermal conductivity of the thermal grease, and convection heat transfer coefficient, respectively. The thermal stress distribution of MCM after optimization is simulated with ANSYS. The regression equation provides a simple and fast method for initial thermal design of MCM.The design method and selection basis of fans and heat sink in forced air cooling system are studied, the general design method of forced air cooling heat dissipation system is summarized. Based on that the thermal resistance is the most key parameter characterizing the cooling capacity of heat sink, the thermal resistant equicalent circuit method of thermal resistance for forced air cooling heat sink is proposed in this paper. The validity and accuracy of the method is verified with simulation and related experimental results. It lays a foundation for the thermal structure of heat sink and the objective function is minimizing thermal resistance of heat sink.Aiming at the sitution that power electronics device is may in cycle switch state or switching of different working condition. The transient thermal model of forced air cooling system is established based on the principle of conservation of energy. A method calculating surface temperature of heat sink is derived. The transient calculation method of surface temperature of heat sink is proposed in this paper when the total loss of power devices remains the same and the power layout is changed. And the equivalent design method of heat sink after changing the power layout is proposed. The method is verified by simulation and experiment results to be accurate. The transient thermal analysis makes the cooling system more reasonable and comprehensive.The influence of structure parameters on the cooling capacity is analysised, thermal resistance, pressure drop and weight are object function, and the thermal optimization procedure of the heat sink is studied in this paper. The entropy generation minimization based on the second law of thermodynamics is used to study the thermodynamic losses caused by heat transfer and pressure drop. The fin parameters are optimized by genetic algorithm.The performance metrics before and after optimization is verified with simulation. The method is is convenient for thermal-mechanical design of forced air cooling system. Base on the optimization of structure the thermal structure optimization methods includes reasonable shape of cooling hole and using wind cover are proposed. The simulation results show that the temperature rise of heat sink is lower and the cooling effect is better after optimizing the air duct.The response surface thermal structure optimization taking MCM as an example in power electronics device can guide the optimal choose of design parameters and the package process. The purpose is to reduce the maximum junction temperature and lay the foundation for the system level thermal design. The optimization of the cooling system based on the entropy generation minimization has two functions. On the one hand, the junction temperature is reduced, the performance and reliability of the device is improved. On the other hand, the volume and weight of the cooling system is reduced. It provides ideas and methods for the miniaturization and lightweight of the electronic equipment.