Theoretical study on effective thermal conductivity of salt/expanded graphite composite material by using fractal method

• Study on effective thermal conductivity of salt/EG composite by a fractal method.
• Multiple three-phase fractal units based on Serpinski carpet form a fractal model.
• Using this model gives a description of microstructures of salt/EG composite.
• Turning fractal units into resistance networks can predict thermal conductivity.
• Comparisons between model results and experimental data show a good agreement.

Fractal geometry has the advantage of describing the macroscopic behaviors of complex systems. Based on statistical self-similar theory, a theoretical study on the effective thermal conductivity of salt/expanded graphite (EG) composite material is conducted by a fractal approach. To allow the demonstration of more microstructural details, multiple fractal units which can represent three-phase media are employed to describe the complex microstructures of the composite. Turning these units into corresponding thermal resistance networks gives a set of predicted effective thermal conductivities that are fully comparable with the existing experimental results. Moreover, by use of this approach, factors that affect the heat conduction performance of the composite are analyzed, and it is found that the quantity of EG plays a dominant role, whereas the distribution of EG needs further attentions.