Heat-Transfer Analysis Of Metal Foam And Optimization Design Of Heat Dissipation Structure

With the rapid development of industrial equipment and aerospace technology,design and preparation of high-performance engineering materials become more important.As a new kind of Ultra-light Cellular Materials,metal foam can be used in compact heat exchangers for air borne equipments,heat sinks for power electronics in the thermal management due to its predominate performance,such as low-density,large surface area in a limited volume,high thermal conductivity of the cell edges and the ability to mix the cooling fluid by promoting eddies.Therefore,it is a theoretic and application issue to study how the foam properties affect the heat-transfer performance by using effective macro equivalent models.As the development of the electronic equipment toward integration and miniaturization and the increasing of the power density,thermal management becomes one of leading problems that limit the development of the electronic equipment.It is desired to develop electronic equipments with a better thermal structure and internal flow field which can improve the heat dissipation capability,reduce the important component' temperature and increase the stability and life.For the background mentioned above,heat transfer analysis of open-cell metal foam and thermal structural optimization design of electronic equipment are discussed in this paper.The main work includes:(1) A new method for forced-convection heat transfer of open cell metal foam: Transfer Matrix Method.This chapter focuses on the forced-convection heat transfer of open cell metal foam.A transfer matrix method for heat transfer performance of open-cell metal foam under the forced convection is presented.The transfer matrix method bases on cube cell model and considers metal foam as structures with periodic micro cells.With in-depth heat transfer analysis on micro structure and considering the change of fluid temperature simultaneously,the relationship between integral heat transfer performance and the size of the micro structure is obtained.Compared with the fin analogy model,the new method eliminates the error generated by modal simplification and gives a precise analysis.The integral heat-transfer coefficient is calculated.The results show that the transfer matrix method is able to predict the heat transfer efficiency accurately.(2) Heat dissipation design of CPU chip.In order to solve the problem that the temperature of CPU chip is too high,the distribution of the high-thermal conductivity materials of CPU chip based on constructal theory and topology optimization is discussed. The optimization problem considers volume of high-thermal conductivity materials as objective function and the allowable temperature as constraint condition.The temperature field and flow field of electronic equipment are simulated by commercial software.The results suggest that the design of topology optimization can improve the temperature condition of CPU chip and save high-thermal conductivity materials.(3) Struetal design of Led lamp radiating crust.With the requirement of structural optimization design for a lamp radiating crust in practical application,the simulation of the temperature and flow field of Led lamp is carried out.The deficiency of the preliminary design is found out.Several kinds of design proposals are proposed to lower the temperature and reduce the weight of the Led lamp.The results show that the new design can lower the operating temperature and reduce the weight of Led lamp.The work of this dissertation is supported by the National Key Basic Research Program of China(No.2006CB601205),the National Natural Science Foundation of China through the Grant No.s(90605002,10721062,90816025) and the program for new century excellent talents in university of china.