Hydrogen solubility in aromatic/cyclic compounds: Prediction by different machine learning techniques

A systematic procedure based on adaptive neuro-fuzzy inference systems (ANFIS), artificial neural networks, and least-squares support vector machines develop to estimate hydrogen solubility in aromatic and cyclic compounds. The key features of these models are determined through a massive trial-and-error process. The proposed intelligent models estimate hydrogen solubility as a function of critical properties and acentric factor of aromatic/cyclic compounds, temperature, and pressure. The ranking analysis based on seven statistical criteria indicates the priority of the ANFIS method over other paradigms. The proposed ANFIS model estimates 278 experimental hydrogen solubility in eleven aromatic/cyclic compounds by the absolute average relative deviation of 7.88%, the mean absolute error of 0.0023, the relative absolute error of 5.05%, mean squared error of 2.74 × 10^?5, root mean squared error of 0.0052, and regression coefficient of 0.99664. Moreover, the relevancy analysis justifies that the pressure is the strongest influential variable for the hydrogen solubility in aromatic/cyclic compounds.     

Mathematical model for iron corrosion that eliminates chemical potential parameters

Iron corrosion in acidic media is a natural phenomenon that converts elemental iron to a more chemically-stable form, i.e. its oxide and hydroxide. In this study, the iron corrosion process is modeled as a completely implicit problem, solved by a novel finite difference model to provide insight into the ionic aspects of corrosion behavior. This new mathematical model eliminates the chemical potential parameters from the corrosion process equations, thereby reducing the need for experimental determination of chemical potentials. The eliminatedchemical-potential-parameters model predicts and quantifies key parameters (concentrations of conjugate base ion, iron (II) ion, hydrogen ion, anodic and cathodic potentials, and the electrical current density) associated with the iron corrosion process in acidic solutions. The rigorous derivation and novel application of the eliminated-chemical-potential-parameters model and its results provide new insights into the iron corrosion process. The present model is also applicable in any industrial process which is associated with metal corrosion. The model helps to guide the design of future corrosion resistant systems, and various experimental studies pertaining to corrosion inhibition techniques.     

Thermo-mechanical simulation of ultrahigh temperature ceramic composites as alternative materials for gas turbine stator blades

The efficiency of the Bryton cycle strongly depends on the maximum temperature of the cycle. However, restrictions on metallurgical problems deprive engineers from the benefit of high temperatures. Ultrahigh temperature ceramics can be considered in such cases, instead of traditional materials like M152 superalloy. In this study, SiC reinforced HfB₂ and ZrB₂ ultrahigh temperature ceramics were proposed as gas turbine stator blades. The heat transfer and stress-strain equations were solved numerically by the finite element method to obtain temperature and stress distributions. The results showed that the maximum thermal stress occurs in vicinity of the cooling ducts where the temperature gradient is maximum. The maximum displacements of 1.2 mm (for HfB₂–SiC) and 1.14 mm (for ZrB₂–SiC) occur in the upper wall. It can be noticed that the ZrB₂–SiC made blade showed lower maximum stress and displacement than those for the HfB₂–SiC made one, as a result of lower expansion coefficient of ZrB₂–SiC system. The addition of SiC to monolithic HfB₂ and ZrB₂ ceramics decreases their thermal conductivity and following that, the temperature uniformity in blades reduces. Although the thermal stresses and the probability of failure in these stator blades enhance, the ZrB₂–SiC material presented the best performance among the other investigated samples. Both Coulomb-Mohr and Von Mises failure analyses were employed. It was understood that both blades made of HfB₂–SiC and ZrB₂–SiC composites simply withstand the applied stresses with the safety factors of about 1.5.     

Comparison of two different flow types on CO removal along a two-stage hydrogen permselective membrane reactor for methanol synthesis

Carbon monoxide (CO) is a gaseous pollutant with adverse effects on human health and the environment. Industrial chemical processes contribute significantly to CO accumulation in the atmosphere. One of the most important processes for controlling carbon monoxide emissions is the conversion of CO to methanol by catalytic hydrogenation. In this study, the effects of two different flow types on the rate of CO removal along a two-stage hydrogen permselective membrane reactor have been investigated. In the first configuration, fresh synthesis gas flows in the tube side of the membrane reactor co-currently with reacting material in the shell side, so that more hydrogen is provided in the first sections of the reactor. In the second configuration, fresh synthesis gas flows in the tube side of the membrane reactor counter-currently with reacting material in the shell side, so that more hydrogen is provided in the last sections of the reactor. For this membrane system, a one-dimensional dynamic plug flow model in the presence of catalyst deactivation was developed. Comparison between co-current and counter-current configurations shows that the reactor operates with higher conversion of CO and hydrogen permeation rate in the counter-current mode whereas; longer catalyst life is achieved in the co-current configuration. Enhancement of CO removal in the counter-current mode versus the co-current configuration results in an ultimate reduction in CO emissions into the atmosphere.     

Numerical simulation of cooling performance in microchannel heat sinks made of AlN ceramics

Microsystem Technologies - The problem of generating a high amount of heat in microelectronic equipment should be minimized properly. Allowing systems to run for long periods of time in high...