Suchergebnisse

In this study, physical properties of nanofluids such as viscosity and thermal conductivity are investigated. Although there are many experimental and theoretical correlations and models available to predict these parameters, predictions are highly conflicting because the involved mechanisms are not fully understood. For instance, the predicted values of dynamic viscosity of 𝛾-Al2O3/water nanofluids (at a volume fraction of 0.001) by different models range between 0.0005623 and 0.0403 kg/m.s and thermal conductivity ranges within 0.866 and 1.551 W/m.K under the same conditions. In this work, 184 experimental data of thermophysical properties of various metal oxide nanoparticle including Al2O3, SiO2, TiO2, Fe2O3, MgO, and CuO at a temperature range of 30 to 65 oC, diameter range of 10 to 50 nm, and volume fraction between 0.004% to 2% were collected from various publications. In this work, artificial neural network (ANN) has been implemented. The parameters of thermal conductivity and dynamic viscosity have been correlated to nanofluid concentration, temperature, particle size and molecular weight. It has been found that the topography of )4, 4, 4) from the ANN provides about 2% and 1% cross-validating and testing error respectively. Additionally, a sensitivity analysis was performed and the effect of individual parameters was analyzed.

One of the most important absorbents used in the water and sewage industry and oil and gas industry is the activated carbon, which can be used to remove free chlorine from water and wastewater. If the important parameters of the process affecting the adsorption efficiency are not recognized and controlled, it can cause irreparable damage to downstream equipment and the environment. In the cooling towers system, excessive amounts of chlorine are often injected into the system, which can cause severe corrosion of the equipment and stop production. In this study, the removal of free chlorine from the circulating water of the cooling tower was examined by adsorption and in order to evaluate the effect of pH and water flow containing free chlorine and concentration in the inlet water, experiments were performed on a pilot scale. The adsorbent used in this research was PICA's Industrial Carbon Active. For this purpose, a tower with a fixed bed was first designed and built. The tower used 4,500 grams of activated carbon as an adsorbent. Experimental results showed that by passing 51549 liters of chlorinated water with free chlorine (at different concentrations and pH), 4058 g of chlorine was absorbed by activated carbon. Experimental results also showed that the lower the pH of the solution and the higher the flow rate of the solution, the higher the amount of chlorine adsorption by activated carbon. Also in this study, kinetic reaction of chlorine adsorption by activated carbon was investigated with Thomas, Adams – Bohart, and Yoon-Nelson Models, and the reaction rate constant K for the Thomas and Adams – Bohart models was Kb = KTh = 0.02037037 min-1 (R2=0.915), and for the kinetic models of Wang and Yoon – Nelson, KW=KYN = 0.022 min-1 was obtained and the time required to consume 50% of the adsorption bed was t1/2=258.09 min. The Wolburska kinetic model did not match well with the experimental data (R2=0.769).

Absorption of carbon dioxide as a greenhouse gas from a mixture of CO2 and N2 in a continuous falling film reactor (FFR) has been designed and developed. The reactor length and inner diameter were 1m and 0.021m, respectively. In this paper, the absorption of CO2 by DEA (Diethanolamine) in FFR is studied by means of COMSOL Multiphysics and Design expert. Design expert is used to developing an empirical equation for CO2 absorption when reacting with DEA. The simulation is performed with COMSOL Multiphysics for a second-order reaction and the velocity profile is considered the effect of shear stress. The result shows that the penetration depth of CO2 in the falling film reactor is 0.006mm and the absorption rate increases with increasing gas flow velocity and inlet CO2 concentration. Also, this study is performed on low Reynolds number (1 ≤ ReG ≤ 6 and 4 ≤ ReL ≤ 40 at 298 K) which has not been considered by other researchers.

In this work, novel Sodium benzyl sulfonate functionalized-bentonite (SBSB) adsorbent was synthesized through the reaction of bentonite with benzyl alcohol and chlorosulfonic acid. The prepared adsorbent was characterized using Low-angle XRD, FT-IR and TGA methods, and applied for the removal of calcium and magnesium ions from water solutions. The effect of contact time and initial hardness concentration on the hardness removal efficiency of the prepared adsorbents were studied. It was found that the adsorption was reached the equilibrium condition within about 60 min, and the maximum adsorption capacity (52.5 mg g−1) was achieved in the hardness of 150 mg L−1. Compared to pristine bentonite, the adsorption efficiency of SBSB was significantly enhanced, which is ascribed to the presence of benzyl sulfonate functional groups on its surface. The adsorption isotherm of calcium and magnesium ions on SBSB was described by Langmuir and its adsorption kinetic behavior followed pseudo-second-order model.