Thermal performance and energy efficiency of the composite clay and hemp fibers

Abstract

The purpose of this research is to demonstrate that incorporating hemp fibers into earth bricks can provide an adequate level of thermal comfort by enhancing the material's dynamic thermal characteristics. The main goal is to find the optimal thickness of a clay-hemp wall to attain the highest thermal inertia values. First, the flash method was used to estimate thermal diffusivity, and the state hot plate method was used to measure the thermal conductivity of a clay brick. Using the experimental data as input, computational analysis is performed to investigate the relationship between the thermal performance of composite materials and their microstructures, with the goal of predicting the effective thermal conductivity of the composite clay-hemp. Using the Random Sequential Addition algorithm, a two-phase, three-dimensional composite clay-hemp microstructure was produced. The effective thermal conductivity of these composites was assessed using the finite volume method. The predicted thermophysical characteristics were then utilized to simulate the transient heat transfer across clay-hemp walls. The results demonstrate that when the hemp volume fraction increased, the thermal conductivity, thermal diffusivity, and thermal volumetric capacity all decreased by approximately 52%, 27%, and 35%, respectively. Furthermore, incorporating hemp fibers improved the bricks' dynamic thermal characteristics. Finally, this study has revealed that a wall composed of clay-hemp bricks of 22 cm thick and an insulating layer of 6 cm thick allows for limiting the risk of overheating during the summer months (time lag between 10 and 12 h) while also satisfying the Moroccan Thermal Construction Regulation requirement for Marrakech city.