Travelling waves in a mixture of gases with bimolecular reversible reactions

Starting from the kinetic approach for a mixture of reacting gases whose particles interact through elastic scattering and a bimolecular reversible chemical reaction, the equations that govern the dynamics of the system are obtained by means of the relevant Boltzmann-like equation. Conservation laws are considered. Fluid dynamic approximations are used at the Euler level to obtain a close set of PDEs for six unknown macroscopic fields. The dispersion relation of the mixture of reacting gases is explicitly derived in the homogeneous equilibrium state. A set of ODE that governs the propagation of a plane travelling wave is obtained using the Galilei invariance. After numerical integration some solutions, including the well-known Maxwellian and the hard spheres cases, are found for various meaningful interaction laws. The main macroscopic observables for the gas mixture such as the drift velocity, temperature, total density, pressure and its chemical composition are shown.Comment: 13 pages, 2 figures, accepted on Physica

H2 from biofuels and carriers: A concerted homo-heterogeneous kinetic model of ethanol partial oxidation and steam reforming on Rh/Al2O3

Investigating bioethanol as a renewable energy source is crucial in the context of H2-based economy. Ethanol partial oxidation and steam reforming on Rh/Al2O3 represent promising processes that have already proved to be highly tangled reacting systems. In this work, a significant step forward has been done towards the development of an engineering tool that can capture all the relevant features of the process; a combined homo-heterogeneous kinetic scheme was developed and validated against experimental data, informative of the catalytic and thermal activation of the C2-alcohol. In particular, a 36-species reduced homogeneous scheme was developed, able to cap -ture observed trends with a limited computational load. On the other side, a macro-kinetic heterogeneous scheme with six molecular reactions (ethanol oxidative dehydrogenation, total oxidation, decomposition, dehydrogenation, steam reforming and acetaldehyde post -reforming) was tuned to accurately describe ethanol/O2 and ethanol/H2O reacting systems.& COPY; 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved

Development and testing of the Active Temperature, Ozone and Moisture Microwave Spectrometer (ATOMMS) cm and mm wavelength occultation instrument

We present initial results from testing a new remote sensing system called the Active Temperature, Ozone and Moisture Microwave Spectrometer (ATOMMS). ATOMMS is designed as a satellite-to-satellite occultation system for monitoring climate. We are developing the prototype instrument for an aircraft to aircraft occultation demonstration. Here we focus on field testing of the ATOMMS instrument, in particular the remote sensing of water by measuring the attenuation caused by the 22 GHz and 183 GHz water absorption lines. Our measurements of the 183 GHz line spectrum along an 820 m path revealed that the AM 6.2 spectroscopic model provdes a much better match to the observed spectrum than the MPM93 model. These comparisons also indicate that errors in the ATOMMS amplitude measurements are about 0.3%. Pressure sensitivity bodes well for ATOMMS as a climate instrument. Comparisons with a hygrometer revealed consistency at the 0.05 mb level, which is about 1% of the absolute humidity. Initial measurements of absorption by the 22 GHz line made along a 5.4 km path between two mountaintops captured a large increase in water vapor similar to that measured by several nearby hygrometers. A storm passage between the two instruments yielded our first measurements of extinction by rain and cloud droplets. Comparisons of ATOMMS 1.5 mm opacity measurements with measured visible opacity and backscatter from a weather radar revealed features simultaneously evident in all three datasets confirming the ATOMMS measurements. The combined ATOMMS, radar and visible information revealed the evolution of rain and cloud amounts along the signal path during the passage of the storm. The derived average cloud water content reached typical continental cloud amounts. These results demonstrated a significant portion of the information content of ATOMMS and its ability to penetrate through clouds and rain which is critical to its all-weather, climate monitoring capability

Sustainable Hydrogen Production via Sorption Enhanced Reforming of Complex Biorefinery Side Streams in a Fixed Bed Adiabatic Reactor

In this work, sorption enhanced steam reforming is explored as a potential solution for the valorization of gaseous streams recovered from biorefinery hydrogenation processes. The hydrogen content of such streams limits the hydrocarbon conversion in conventional steam reforming due to thermodynamic and kinetic constraints. A previously developed 1D dynamic heterogeneous model of an adiabatic reactor was thus applied to evaluate the effect of H-2 dilution on the performance indicators of the sorption enhanced reforming process. The mathematical model analysis highlights that despite of CO2 capture by the sorbent favorably modifies the thermodynamics of syngas production, H-2 dilution worsens the performance of the sorption enhanced reforming of model H-2/CH4 streams with respect to pure CH4. Results show a drop of 17% for CH4 conversion and a reduction of 15.4% of the captured CO2 on passing from pure methane to a H-2/CH4 feed with a 40/60 molar ratio. However, on increasing the heat capacity of the bed, by replacing part of the sorbent with an inert heat carrier, better performances are calculated for the H-2/CH4 feed matching the pure CH4 case. The presence of C2+ hydrocarbons is assessed as well and the results show a significant improvement in the reformer's performance; in the case of a stream composed of H-2/CH4/C3H8 with a molar ratio 40/45/15, the total hydrocarbon conversion grows to 92.8%, CO2 capture ratio to 82.6%, and H-2 purity to 95.6%. The positive effect is associated with thermal factors that promote the reaction kinetics. Thus, the suitability of the sorption enhanced reforming technology to H-2-rich and C-poor streams is strictly composition dependent; by cofeeding of C2+ hydrocarbons, the process turns into a remarkable solution for converting gaseous streams in pure H-2

A network landscape model: stability analysis and numerical tests

Versão dos autores para este artigo.A Network Landscape Model (NLM) for the evaluation of the ecological trend of an environmental system is here presented and investigated. The model consists in a network of dynamical systems, here each node represents a single Landscape Unit (LU), endowed by a system of ODEs for two variables relevant to the production of bio-energy and to the percentage of green areas, respectively. The main goal of the paper consists in testing the relevance of connectivity between the LUs. For this purpose we consider rst the Single LU Model (SLM) and investigate its equilibria and their stability, in terms of two bifurcation parameters. Then the network dynamics is theoretically investigated by means of a bifurcation analysis of a proper simpli ed di erential system, that allows to understand how the coupling between di erent LUs modi es the asymptotic scenarios for the single LU model. Numerical simulations of NLM are performed, with reference to an environmental system in Northern Italy, and results are discussed in connection with SLM.GNFM - INdAM; FC

Short-Term Wind Speed Forecasting Model Using Hybrid Neural Networks and Wavelet Packet Decomposition

Wind speed is one of the most vital, imperative meteorological parameters, thus the prediction of which is of fundamental importance in the studies related to energy management, building construction, damages caused by strong winds, aquatic needs of power plants, the prevalence and spread of diseases, snowmelt, and air pollution. Due to the discrete and nonlinear structure of wind speed, wind speed forecasting at regular intervals is a crucial problem. In this regard, a wide variety of prediction methods have been applied. So far, many activities have been done in order to make optimal use of renewable energy sources such as wind, which have led to the present diverse types of wind speed and strength measuring methods in the various geographical locations. In this paper, a novel forecasting model based on hybrid neural networks (HNNs) and wavelet packet decomposition (WPD) processor has been proposed to predict wind speed. Considering this scenario, the accuracy of the proposed method is compared with other wind speed prediction methods to ensure performance improvement

A BGK model for reactive mixtures of polyatomic gases with continuous internal energy

Versão dos autores para esta publicação.In this paper we derive a BGK relaxation model for a mixture of polyatomic gases with a continuous structure of internal energies. The emphasis of the paper is on the case of a quaternary mixture undergoing a reversible chemically reaction of bimolecular type. For such a mixture we prove an H-theorem and characterize the equilibrium solutions with related mass action law of chemical kinetics. Further, a Chapman-Enskog asymptotic analysis is performed in view of computing the first-order non-equilibrium corrections to the distribution functions and investigating the transport properties of the reactive mixture. The chemical reaction rate is explicitly derived at the first-order and the balance equations for the constituent number densities are derived at the Euler level.The paper is partially supported by the Italian National Group GNFM of INdAM and by the Portuguese Funds FCT Project UID/MAT/00013/2013. One of the Authors (AJS) thanks the Italian institution for the financial support given in her visiting professor program in Italy.info:eu-repo/semantics/publishedVersio

Analyzing the impact of demand response and reserves in islands energy planning

Small Islands usually rely on fossil fuels for their energy supply and face common challenges such as high energy costs and carbon dioxide emissions. For these reasons they represent interesting cases for analysing the transition towards a clean and secure energy system. Nevertheless, integrating non-dispatchable Renewable Energy Sources in the power grid causes stability issues and this is particularly true for island grids. Such issue is not fully considered in long-term energy planning; indeed, an important factor that should be considered in order to ensure the reliability of the grid are Reserves. There are different types of Reserves depending on the reactiveness/response time and the duration of the service. In this paper, primary and secondary reserves have been analysed in order to plan the long-term energy transition of the small island of Favignana, Italy by means of the new version of H2RES, a Linear Programming single-objective optimisation model able to provide a long-term capacity investment and dispatching optimisation. It has been found that biomass generators are favoured to both photovoltaic and wind turbines for their ability to provide reserves and also decrease the unpredictability of the supply. Batteries and Electrolysers are also used mostly for reserve provision

Warm-Dense Molecular Gas in the ISM of Starbursts, LIRGs and ULIRGs

The role of star formation in luminous and ultraluminous infrared galaxies is a hotly debated issue: while it is clear that starbursts play a large role in powering the IR luminosity in these galaxies, the relative importance of possible enshrouded AGNs is unknown. It is therefore important to better understand the role of star forming gas in contributing to the infrared luminosity in IR-bright galaxies. The J=3 level of 12CO lies 33K above ground and has a critical density of ~1.5 X 10^4 cm^-3. The 12CO(J=3-2) line serves as an effective tracer for warm-dense molecular gas heated by active star formation. Here we report on 12CO (J=3-2) observations of 17 starburst spirals, LIRGs and ULIRGs which we obtained with the Heinrich Hertz Submillimeter Telescope on Mt. Graham, Arizona. Our main results are the following: 1. We find a nearly linear relation between the infrared luminosity and warm-dense molecular gas such that the infrared luminosity increases as the warm-dense molecular gas to the power 0.92; We interpret this to be roughly consistent with the recent results of Gao & Solomon (2004a,b). 2. We find L_IR/M_H2 ratios ranging from ~10 to ~128 L_sun/M_sun using a standard CO-H2 conversion factor of 3 X 10^20 cm^-2 (K km s^-1)^-1. If this conversion factor is ~an order of magnitude less, as suggested in a recent statistical survey (Yao et al. 2003), then 2-3 of our objects may have significant contributions to the L_IR by dust-enshrouded AGNs.Comment: 15 Pages, 2 figures, Accepted for Publication in Ap