超重条件下泡沫石墨-石蜡相变传热实验研究

基于高热导率多孔材料骨架强化传热的相变蓄冷器具有热容量大、换热效率高、控温稳定、环境适应性强等优点，在航空航天领域具有广泛的应用前景。多孔介质内固-液相变换热过程中，由于相变换热产生的相变工质密度差在加速度的驱动下造成的液相浮升力变化，将引发更为复杂的固-液相变流动与换热不稳定性特征。设计搭建了离心环境条件下的多孔介质内固-液相变换热实验研究装置，实验获得了不同加速度大小和方向下多孔介质内固-液相变换热特性。结果表明，高导热泡沫石墨-石蜡相变蓄冷能够实现界面较低升温速率温控，同时加速度方向对于相变蓄冷装置整体换热效率及换热均温性存在显著影响。当加速度方向与热流方向反向或垂直时，加速度驱动液相储能工质局部自然对流将促进整体换热效率，而加速度方向与热流方向同向时换热效率降低，并且上述差异将随着加速度的提升而进一步扩大。

Experimental investigation on phase change heat transfer of paraffin composited with porous graphite under supergravity

The phase change regenerator based on the high thermal conductivity porous material framework to enhance heat transfer has the advantages of large heat capacity, high heat exchange efficiency, stable temperature control, and strong environmental adaptability. It has a wide range of application prospects in the aerospace field. During the solid-liquid melting process in the porous media, the buoyancy variation derived from the density difference of the liquid phase driven by the acceleration would induce more complex flow and heat transfer instability during the solid-liquid phase change. In this study, an apparatus for studying solid-liquid phase change of the paraffin composited in porous media was set up, and the heat transfer characteristics of paraffin melting in porous graphite under different accelerations were obtained. The results showed that, the temperature of the thermal load can be better controlled by the phase change heat transfer of paraffin composited with porous graphite, and the general heat transfer efficiency and the nonhomogeneous thermal diffusion of the phase change energy storage device were remarkably affected by the accelerating direction. When the direction of acceleration is opposite or perpendicular to the direction of heat flow, the local natural convection of liquid phase driven by acceleration will promote the overall heat transfer efficiency of the phase change energy storage module, while the overall heat transfer efficiency will be suppressed when the direction of acceleration is in the same direction as the direction of heat flow. Besides, the temperature difference under different accelerating direction was enlarged with the increase of the acceleration.