Thermal Conductivity and Diffusivity Analysis of Gypsum Plaster and Coffee Grounds : CFD Simulations for Enhanced Insulation Performance

Abstract

Improving the thermal performance of buildings is a key challenge in the pursuit of sustainable development and energy efficiency. Traditional gypsum plaster, widely used in construction, provides limited thermal insulation, contributing to increased energy consumption. With growing environmental concerns, there is a rising interest in integrating natural or recycled materials into building components to enhance their thermal properties. This study investigates the potential of incorporating waste coffee grounds into gypsum plaster to develop composite materials with improved thermal insulation. The objective is to evaluate the influence of varying coffee ground content on the thermal behavior of the plaster. Composite samples containing 10%, 20%, and 30% coffee grounds by weight were prepared and analyzed. Thermal conductivity was measured using the steady-state hot plate method, while thermal diffusivity and specific heat capacity were determined using the flash method. Furthermore, Computational Fluid Dynamics (CFD) simulations were performed with ANSYS software to examine heat transfer and surface temperature distribution in walls constructed with these composites. The results demonstrate that increasing the proportion of coffee grounds significantly enhances thermal performance. The sample with 30% coffee grounds (SMP3) exhibited a thermal conductivity of 0.260 W/m·K, representing a 23% reduction compared to pure gypsum. Thermal diffusivity decreased by 30%. CFD simulations indicated a 30–50% reduction in thermal losses, translating into a 15–20% decrease in energy consumption for a typical 100 m² building. These findings confirm the viability of coffee ground–gypsum composites as a sustainable, cost-effective solution for improving building insulation, while simultaneously promoting waste reuse and reducing environmental impact.