Numerical analysis of entropy generation in a turbulent diffusion flame

Thermodynamic irreversibilities generated by the combustion process are evaluated and analyzed numerically. The numerical simulation is performed for a reference case study for which experimental data are available in the literature: diffusion flame properties in a common burner configuration are studied by the Fluent software with the standard k–ε turbulence model and two-step chemical reaction. The study quantifies the contribution of each mechanism to entropy generation, i.e., friction, heat conduction, species diffusion, and chemical reaction. The chemical reaction and heat conduction are found to be the major sources of entropy production. Preheating of air reduces thermodynamic irreversibilities within the combustor.     

Green chemicals and process to graft cellulose fibers

The treatment of additive-free hand sheet paper samples with cold plasma was carried out and showed that cellulose can be chemically linked with reactive natural products, namely myrcene (My) and limonene (LM). Contact-angle measurement and X-ray photoelectron spectroscopy (XPS) were used to ascertain the occurrence of the grafting. Indeed, the contact-angle value of a drop of water deposited at the surface of paper increased from 30° for unmodified substrate to about 105 and 107°, for LM- and My-treated samples, respectively. In fact, LM- and My-treated surfaces were rendered totally apolar. Indeed, the polar contribution to the surface energy decreased from about 23 mJ/m² for pristine samples to practically zero for treated ones. The treated surfaces displayed water-barrier properties; the penetration of the liquid was reduced significantly after LM and My treatments. The XPS spectra showed that the modification with LM and My gave rise to very significant change in the O/C ratio, as well as in the intensity of the C1 peak assigned to aliphatic carbon sequences.     

Sobolev type spaces in quantum calculus

In this paper q-Sobolev type spaces are defined on Rq by using the q-cosine Fourier transform and its inverse. In particular, embedding results for these spaces are established. Next we define the q-cosine potential and study some of its properties.     

Estimate of the Fourier–Bessel Multipliers for the Poly-axially Operator

We prove the analogue of H?rmander–Mikhlin multiplier theorem for the multidimensional Fourier–Bessel transform associated with the Poly-axially operator.     

Modification of cellulose fibres with organosilanes: Under what conditions does coupling occur?

Different cellulose substrates and organosolv lignin were treated heterogeneously with organic solutions of trialkoxysilanes bearing variable function on the forth substituent. It was shown unambiguously for the first time that Si-OR does not react with the hydroxy groups of cellulose even at high temperature, whereas it condenses with the phenolic OH of lignin. The addition of moisture to these systems induces the partial hydrolysis of the siloxane moieties and the ensuing silanol groups can then react with the cellulose OH, but only at high temperature. Using the latter systems and a siloxane bearing a polymerizable function, it was possible to attach poly(methylmethacrylate) chains to the surface of cellulose fibres through a two-step procedure.     

Rigorous Bounds for the Föppl—von Kármán Theory of Isotropically Compressed Plates

Summary. We study the F?ppl—von Kármán theory for isotropically compressed thin plates in a geometrically linear setting, which is commonly used to model weak buckling of thin films. We consider generic smooth domains with clamped boundary conditions, and obtain rigorous upper and lower bounds on the minimum energy linear in the plate thickness σ . This energy is much lower than previous estimates based on certain dimensional reductions of the problem, which had lead to energies of order 1+σ (scalar approximation) or σ ^2/3 (two-component approximation). Received August 7, 2000; accepted September 8, 2000 %%%Online publication November 15, 2000 Communicated by Robert V. Kohn     

Optimization of Combustion Efficiency Using a Fuel Composition Based on CH4 and/or H2

Russian Journal of Applied Chemistry - In this paper, we investigate the exergy analysis of the combustion chamber supplied by different fuel compositions based mainly on methane and/or hydrogen in...     

The aid of calorimetry for kinetic and thermal study

Journal of Thermal Analysis and Calorimetry - Phosphoric acid, a non-renewable chemical, is used in different industries. Production of this chemical from natural phosphate can be done by two...     

Renewable energy resources and workforce case study Saudi Arabia: review and recommendations

Journal of Thermal Analysis and Calorimetry - Energy is linked to the most economic and social issues which affect sustainable development of countries. To diversify its economy sources, Saudi...