Evaluating the Thermal Conductivity of Three-phase Insulation Composite using Analytical and Numerical Methods

Sustainable insulation materials have been more attractive in the last two decades due to biodegradability, low embodied energy, availability, and non-toxicity. Those materials are primarily fabricated as composite materials using natural plant fibres. Then, the material contains three phases, i.e., fibre, binder, and air void. The volume fraction of each phase will decide the material’s insulation properties and can be analyzed using experimental, analytical, and numerical methods. Numerical and analytical methods are more attractive compared to experimental methods due to cost-effectiveness and less time consumption. However, only a limited number of studies have attempted to find the effective thermal conductivity (K
eff
) of a three-phase composite by these methods. In this study, the authors have suggested a plan to find the K
eff
of this composite using a numerical method and validated through the analytical techniques. This study, coir fibre was used as a fibre material and latex as a binder material. The results show that the numerical model should be changed based on the air void fraction. It was concluded that the close-pores structure model applies to the pore volume fraction of 0.65 and the open-pores structure model for pore fractions above 0.65 for numerical analysis.