Effective medium theory (EMT) for thermal conductivity is a method to estimate the effective thermal conductivity of a composite material that consists of two or more phases with different properties1. EMT can be used to model the thermal conductivity of materials that have anisotropic or heterogeneous structures, such as coiled aluminum sheets2.
The basic idea of EMT is to replace the composite material with a homogeneous medium that has the same macroscopic behavior as the original material. The effective thermal conductivity of the homogeneous medium is calculated by averaging the thermal conductivities and volume fractions of the constituent phases, taking into account the shape, size, orientation, and distribution of the phases. There are many different EMT models, each with different assumptions and approximations. Some of the most common EMT models are:
- Maxwell model: This model assumes that one phase is dispersed as spherical inclusions in another phase, and that there is no interfacial thermal resistance between the phases3.
- Bruggeman model: This model assumes that both phases are randomly distributed in a symmetric way, and that there is no interfacial thermal resistance between the phases4.
- Maxwell-Garnett model: This model assumes that one phase is dispersed as ellipsoidal inclusions in another phase, and that there is no interfacial thermal resistance between the phases5.
- Hasselman-Johnson model: This model modifies the Maxwell model by introducing an interfacial thermal resistance between the phases.
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