In this article, the authors numerically investigate dynamic heat transfer related to free convection in porous and partially porous cavities, paying particular attention to the dependence of velocity and temperature fields on Rayleigh (Ra) number, porous layer permeability, and cavity aspect ratio (AR), the ratio between its height and width. Heat and fluid flows inside the cavity are described by using the generalized porous medium model, and the governing equations were numerically solved using the artificial compressibility version of the characteristic-based split scheme. The proposed model was first applied to the simulation of heat and fluid flows in a square porous cavity, and an excellent agreement was found between the results obtained and the data available in the literature. The analysis was then extended, here for the first time, to transient natural convection in partly porous cavities, with AR equal to 4:1 and 8:1 for different Ra and Darcy (Da) numbers. The mean Nusselt (Nu) number was calculated as a function of cavity geometrical characteristics, porous layer permeability, and fluid properties.

In this paper, the authors present an overview of biomass gasification modeling approaches with the aim of evaluating their effectiveness as a modeling tool for the design and optimization of polygeneration plants based on biomass gasification. In fact, the necessity to build plant operating maps for efficiency optimization requires a significant number of simulations, and non-stoichiometry equilibrium models may allow fast computations thanks to their relative simplicity. The main objective consists of the assessment of thermodynamic equilibrium models performance as a function of biomass type and composition to better understand in which conditions of practical interest such models can be applied with acceptable reliability. To this aim, the authors developed two equilibrium models using both a commercial software (referred as Aspen model) and a simulation tool implemented in a non-commercial script (referred as analytical model). To assess their advantages and disadvantages, the two models were applied to the gasification simulation of different biomasses, employing experimental data available from the scientific literature. The obtained results highlighted strengths and limitations of using equilibrium models as a function of biomass type and composition. For example, they showed that the analytical model predicted syngas composition with better accuracy for biomass types characterized by a low ash content, whereas the Aspen model appeared to fairly predict the syngas composition at different conditions of ER; however, its accuracy might be reduced if the properties of the treated biomass changed.

Public transport environments are thought to play a key role in the spread of SARS-CoV-2 worldwide. Indeed, high crowding indexes (i.e. high numbers of people relative to the vehicle size), inadequate clean air supply, and frequent extended exposure durations make transport environments potential hotspots for transmission of respiratory infections. During the COVID-19 pandemic, generic mitigation measures (e.g. physical distancing) have been applied without also considering the airborne transmission route. This is due to the lack of quantified data about airborne contagion risk in transport environments.

This study offers a detailed techno-economic assessment of Carbon Capture (CC) integration in an existing Waste-to-Energy (WtE) incineration plant, focusing on retrofit application. Post-combustion carbon capture using monoethanolamine (MEA) was modeled for various low-scale plant sizes (3000, 6000, and 12,000 t of CO₂ per year), using a process simulator, highlighting the feasibility and implications of retrofitting a WtE incineration plant with CC technology. The comprehensive analysis covers the design of the CC plant and a detailed cost evaluation. Capture costs range from 156 EUR/t to 90 EUR/t of CO₂. Additionally, integrating the CO₂ capture system reduces the overall plant absolute efficiency from 22.7% (without carbon capture) to 22.4%, 22.1%, and 21.5% for the different capture capacities. This research fills a gap in studying small-scale CC applications for the WtE incineration plants, providing critical insights for similar retrofit projects.