Thermo, Volume 2, Issue 2 (June 2022) – 2 articles

The production of biogas by means of the anaerobic digestion process is becoming increasingly attractive in the green economy context. When municipal organic waste is used to produce biogas, a further positive effect on urban waste disposal is obtained. Starting from the anaerobic digestion model n.1, an accurate analysis of the temperature effects on the anaerobic digestion process in a plug flow reactor is performed. This paper aims at presenting a comprehensive and integrated one-dimensional biological and thermal model for a plug flow reactor. Partial differential equations with respect to time and space are considered to model the heat transfer between the reactor and the internal heat exchanger and between the reactor and the environment. In this scope, a suitable simulation code was developed in MATLAB and validated using the data available in literature. The results of the calculations show that temperature plays a crucial role in the anaerobic digestion process, since it strongly affects the kinetic rates of the microbial species and the methane production. The results obtained in terms of temperature fields and biogas production are compared with the ones available in literature, dealing with a continuously stirred tank reactor. The comparison is conducted considering that both reactors process a volumetric waste flow rate of $20 {\mathrm{m}}^3/\mathrm{d}$ and have the same structural characteristics. The plug flow reactor resulted better performance with a produced biogas flow rate equal to $2300 \mathrm{N}{\mathrm{m}}^3$/year. Full article

The wide category of organic materials containing polymers had a great impact on the last middle century, and continues to nowadays, thus affecting our daily behaviors. The need to investigate their durability has grown, which may be necessary in the successful completion of the application for which these materials were designed, and to mitigate their impact on the environment. The aim of this Special Issue was to allow researchers, in both Industry and Academia, to show their current research in material properties finalized to the lifetime prediction. Full article