In the present study, fully developed laminar flow with forced convection heat transfer of Al2O3/water and TiO2/water nanofluids inside a vertical tube subjected by constant heat flux from the wall was numerically analyzed using Ansys Fluent release 17.2. In this work, the single-phase model was proposed to simulate the water and nanofluids heat transfer characteristics; spherical nanoparticles with a constant diameter equal to 30 nm are used. The study has been carried out on a Reynolds number with ranges (400-2000) and nanoparticles volume concentration up to 1.5%. the results show that the average Nusselt number for nanofluid is higher than that the base fluid (water) especially for TiO2/water nanofluid, the Nusselt number increased with increasing Reynolds number and volume concentration in all cases. The enhancement ratio for nanofluids compared to water at different volume friction was studied; the higher improvement is about 3.51% for TiO2/water nanofluid with 1.5% volume fraction. Moreover, a study for pressure drop along vertical tube was discussed.
In recent years there has been increasing research interest in the removal of nitrogen-oxides from exhaust gases using a pulsed corona discharge reactor. The pulsed streamer corona produces energetic electrons that excite, ionize and dissociate gas molecules, and by forming radicals that enhance the gas-phase chemical reactions which reduce the pollutant’s concentration.In this paper a method is presented, where the reaction rates of the electron-molecule collision are determined. The model is based on calculation of the energy of free electrons in the time and space varying field, considering the mean free path and the energy-dependent reaction cross sections of molecules. Knowing the rates, it is possible to solve the reaction kinetic equations, and to get the time-evolution of by-products, and the decomposition ratio of the pollutant gases.
As it is well known, the non-thermal plasma discharge is an effective way to clean the flue and exhaust gases of hazardous pollutants, like sulphur-oxides, nitrogen-oxides. The decomposition ratio of these substances depends on the gas composition, concentration, energy distribution of fast electrons, and other parameters. For a detailed analysis of the phenomena, the first step is the mathematical description of corona pulses which determines the electric field. The second step is the determination of the electric field distribution inside the reaction chamber.In this paper the authors give an easy model for the pulsed corona current and a simplified model for the electric field by using the corona current and the displacement current pulse shapes. The result of the model is the space and time dependent field distribution, which is suitable for calculating the rate coefficients of chemical reactions.
Deterioration of concrete materials exposed to an aggressive solution is often characterized by the leaching of calcium and silicon compounds from the cement matrix. This paper presents the results of the study of concrete composites exposed to the various sulphate environments (sulphuric acid and magnesium sulphate solutions) under laboratory model conditions. The leaching of the calcium and silicon from concrete specimens has been studied during 180 days using X-ray fluorescence method for leachate analysis. As expected, sulphuric acid of pH3 was confirmed to have the most significant effect on the studied ions releasing. The released amounts of analysed ions were 192.2 and 9.6 times higher for calcium and silicon ions, respectively in H2SO4 with pH=3 when compared to fresh water. The concentration of released calcium was 2.6 times higher
During the production of natural gas one of the major problems is the formation of hydrate crystals in the pipeline. The forming hydrate crystals can form hydrate plugs in the pipeline. The hydrate plugs lengthen production outages and result in financial losses for the producer, because the removal of the plugs is a time consuming procedure. One of the solutions used to prevent hydrate formation is the injection of modern compositions to the gas flow. The modern compositions help to dehydrate the gas, thus, the size of hydrate crystals does not increase. The substances, used in low concentrations, have to be locally injected, at the gas well sites. Inhibitor dosing depends on the amount of gas hydrate present. In the article a neural network based predictive detection solution is presented, which uses four factors.
Authors:Messaouda Rais, Adel Boumerzoug, and Balint Baranyai
usually expressed by the CO 2 concentration in the space and the air ventilation rate [ 12 ]. This study presents the evaluation of a typical existing social house design in Algerian hot and dry climate region, which represent the major part of the
During the production of gas one of the major problems is the formation of hydrate crystals in the pipeline. The growing hydrate crystals can form hydrate plugs in the pipeline. The hydrate plug effect lengthens production outages and results in the loss of money of the maintainer, because the removal of the plug is a time consuming procedure. One of the solutions used to prevent hydrate formation is the addition of modern compositions to the gas flow. The modern compositions help to dehydrate the gas, thus, the size of hydrate crystal does not increase. The substances, used in low concentrations, have to be locally injected at the gas well sites. Thus, an injector unit is required for this purpose. The production-related aspect that the consumers expect much more flexibility from gas provider cannot be neglected because of the habits of the users and the appearance of energy-saving technologies are different. The first part of the article a newly developed injection system is introduced. To achieve optimal dosage, not only the hardware of injection system is important, but also the software. In addition to the traditional control, a preventive inhibitor dosing system can be developed, based on model driven system. The nature of the model highly influences the quality of control system. In the second part of the article a machine learning based predictive detection system is introduced
Authors:Jaroslav Hrudka, Štefan Stanko, and Michal Holubec
In the process of design and operation of sewerage system are used empirical formulas, which are in many cases, become obsolete and unusable when somebody can use nowadays modern technologies and materials. Therefore there is the possibility of using the mathematical models enormous importance for the enhanced environmental protection with the lowest operating and investment costs. In this modern method of analyzing of sewers has been designated as the first object, the object sedimentation tank. The purpose of the primary and secondary settling tank is to ensure the reduction of concentration the floating solids.
For the solution of research work has been chosen, after consultations with representatives of the Western Slovakia Water Company as interesting object of sedimentation tank located on the waste water treatment plant Nitra - Dolné Krškany.
Measurements on the object settlement tank situated at waste water treatment plant Nitra confirmed the expected speed parameters of the sewage in the tank. The velocity of wastewater is in the most cases very low, and even insignificant. However, finding that the sludge cloud has a non-standard form of a double wave gives the opportunity to optimize the operation of facilities sedimentation tank. The measured parameters are used as calibration parameters to input to the mathematical simulations, which are created by software ANSYS fluent.