In this paper, a comparison of exergetic models between two hot air engines (a Gamma type Stirling prototype having a maximum output mechanical power of 500 W and an Ericsson hot air engine with a maximum power of 300 W) is made. Referring to previous energetic analyses, exergetic models are set up in order to quantify the exergy destruction and efficiencies in each type of engine. The repartition of the exergy fluxes in each part of the two engines are determined and represented in Sankey diagrams, using dimensionless exergy fluxes. The results show a similar proportion in both engines of destroyed exergy compared to the exergy flux from the hot source. The compression cylinders generate the highest exergy destruction, whereas the expansion cylinders generate the lowest one. The regenerator of the Stirling engine increases the exergy resource at the inlet of the expansion cylinder, which might be also set up in the Ericsson engine, using a preheater between the exhaust air and the compressed air transferred to the hot heat exchanger.

This research article explores the potential of using agave Americana fibers (AAFs) to enhance the physical and mechanical properties of concretes. The study investigates the impact of AAFs on concrete mix proportions in detail. Different concrete compositions are systematically created by integrating AAFs into them. The chemical structure, crystallinity, morphology, and tensile strength of extracted AAFs are examined, revealing a low cellulose content and a crystallinity index of around 41.34%. The microstructural analysis highlights the rough surface morphology of the extracted AAFs. The research also evaluates how AAFs affect concrete density, water uptake, and flexural and compressive strengths across various mixtures. The results show that incorporating AAFs in a horizontal position can increase the flexural resistance by up to 99% and the compressive resistance by up to 86% without chemical reactions occurring with mud-lime concrete. However, it is worth noting that using AAFs with cement can affect fiber durability due to the alkaline environment. As the alkali concentration increases, the fiber mechanical resistance decreases. Therefore, it is recommended to use AAFs with noncement concrete for improved sustainability and durability. Overall, this study advances our understanding of eco-friendly and resilient concrete materials.

Modern materials science has made significant progress in creating new materials and processes for waste recovery. One such advancement involves the development of a new porous composite material made from clay and an environmentally sustainable eggshell powder. In this study, the dynamic behavior of water vapor during desorption and adsorption processes within this composite material was investigated. The moisture diffusivity coefficient was determined within the clay/eggshell powder composite material. The drying kinetic data were analyzed using various models such as Newton, Page, and Wan and Singh. The static gravimetric vapor adsorption/desorption experiments were conducted at different temperatures (30, 40, 50, 60, and 70 °C) to depict the material's capacity for absorbing and releasing moisture over time. The experimental isotherm data were fitted using different mathematical models (Guggenheim, Anderson, and De Boer, Peleg, Adam and Shove, Oswin, and Modified Henderson). The findings suggest that integrating eggshell powder with clay can significantly influence the behavior and characteristics of the resultant material. The combination of eggshell powder and clay reduces moisture sorption and accelerates the drying process. Consequently, this affects the porosity, permeability, and response to humidity changes.