Application Studies Of Phase Change Heat Dissipation Technology Under The Periodic Thermal Load

With the continuous development of science and technology,the characteristics of miniaturization and high integration of electronic components become more and more obvious,which makes the heat dissipation requirement of electronic equipment for radiators is getting higher and higher.Phase change heat dissipation technology has the advantages of small size,low energy consumption and high reliability,so it is widely used in the field of heat dissipation of aerospace electronic equipment and various kinds of civil electronic devices.In this thesis,aiming at the problem of the mismatch between the time of the intermittently working electronic components at the working/shutdown stage and that of PCM absorption/release of energy,the heat transfer characteristics of phase change radiator under the periodic thermal load are analyzed by research means combining theory,simulation and experimental.Firstly,a thermal analysis method for phase change heat transfer problem with the boundary conditions of periodic thermal load is established based on the correlation theory of phase change heat transfer.The heat transfer characteristics of the phase change heat dissipating unit under the periodic thermal load with different power is simulated by the ANSYS simulation software,and the change regulation of the temperature of heat source and PCM internal with time is obtained.The experimental study on phase change heat dissipation is carried out for phase change heat dissipating unit.It is verified that the effectiveness of the simulation method and experimental device through the comparison between experimental results and simulation results.Secondly,an index,namely effective working time length parameters,for evaluating the work efficiency of a phase change radiator is innovatively proposed based on the characteristics of periodic work of the phase change radiator,and its theoretical formula is derived according to the one-dimensional mathematical model and its approximate analytical solution of the phase change heat transfer problem with the boundary conditions of periodic thermal load.On this foundation,the influence of six parameters,such as PCM thickness and convection heat transfer coefficient,on the heat dissipation performance of phase change heat dissipating unit under periodic thermal load is studied by theoretical and simulation analysis methods.Thus,the influence rules of various factors on the melting time,the solidification time and the effective working time length parameters are summarized.Finally,the fin structure is optimized by simulation analysis for the straight fin and the needle fin radiators filled with PCM in the fins in order to improve work efficiency.The fin structure form with better heat dissipation performance is obtained.Then a single-period and multiperiod experiment of phase change heat dissipation was carried out based on the two structures of the fin radiator.It is verified that the effective working time length parameters is effective in evaluating the effective working time of phase change radiator under the periodic heat load.