Modeling and measuring of the thermal properties of insulating vegetable fibers by the asymmetrical hot plate method and the radial flux method: Kapok, coconut, groundnut shell fiber and rattan

Abstract

This article presents two methods dedicated to the determination of the thermophysical properties of natural fibers grown in almost all countries of the world. Experimental measurements were carried out on four dry natural plant fibers of low density: kapok fibers; groundnut shell fibers; rattan fiber and coconut fibers. The thermal effusivity has been estimated by a transient method (the asymmetrical hot plate method). With experimental measurement of the specific heat capacity by Differential Scanning Calorimeter (DCS) which made it possible to deduce the thermal conductivity of such fibers. The thermal properties estimated by this method are then compared to the results obtained by radial flux flow method, a steady state method that directly measures the thermal conductivity. The experimental results compared by these two methods are in good agreement (relative error<5%). The thermal conductivities of kapok fibers (λ=0.045Wm−1K−1) and coconut fibers (λ=0.055Wm−1K−1) obtained all showing that they can be used as substitutes for synthetic insulating materials such as polyester fibers (λ=0.045Wm−1K−1) or glass wool (λ=0.04Wm−1K−1). Also the thermal conductivities of kapok and coconut fiber measured correspond with the results obtained by other measuring methods in the literature. This can then help us infer that the quadrupole 1D model developed to estimate the thermal properties of bulk fiber is valid and can allow a good estimation of thermo-physical properties. Therefore, the thermal conductivity of groundnut shell fibers and cane fibers is estimated in the order of λ=0.093Wm−1K−1 and λ=0.072Wm−1K−1 respectively.