دوماهنامه مهندسی شیمی ایران
پیاپی 80 (امرداد و شهریور 1394)

Nanofluids are suspensions of nanoparticles in base liquid and can be employed to increase heat transfer rate in various applications. In this work forced convective heat transfer coefficient of Al2O3/Ethylene Glycol nanofluid have been investigated experimentally in the double-pipe and plate heat exchangers. Experimental results indicate that heat transfer coefficient increases with nanoparticles concentration as well as operating temperature. Considerable deviations for high operating temperatures and nanoparticles concentration were observed from comparison of experimental and semi-empirical correlations’ results. The nanofluid Nusselt number for different nanoparticles concentrations as well as various operating temperatures was obtained and shown the enhancement up to maximum 50% using nanoparticles.

The purpose of this study is mathematical investigation of aggregation adsorption isotherm models in a five parameter equation. This equation can cover Langmuir isotherms, Freundlich, Hill, Redlich-Peterson, Sips, Toth, Koble-Corrigan, Khan and Radke-Prausnitz in the form of an equation. The mentioned equation were fitted with experimental data using some common numeric analytical software and the results were compared with the corresponding values other forms of nonlinear isotherms.In order to find the best isotherm for better matching with the experimental data, the error analysis methods such as sum of squares and the correlation coefficient were used. The experimental data used in this study, the best results were for experimental data of the adsorption of aniline, phenol, methylene blue, and cadmium. The mentioned equation with having the lowest sum of squared errors and the highest correlation coefficient is an appropriate equation for fitting the experimental results. The results confirm that increasing the number of parameters in an equation lead to the better fitting of experimental data.

In this work, the influence of substituted fullerene on the pour point and rheological behavior of a waxy crude oil sample was investigated. The compositional analysis of crude oil was performed and then the influence of the substituted fullerene on the viscosity and pour point of waxy crude oil was evaluated. The results show that the substituted fullerene reduces the pour point of the waxy crude oil is in all concentrations. Also, the results indicate that viscosity reduces by increasing the concentration of substituted fullerene at constant temperature and shear stress. While viscosity increases by decreasing the temperature of crude oil. It is obvious that by increasing the shear rate the viscosity decreases dramatically. Results show that the shear rate has considerable effect on decreasing viscosity particularly at temperatures below the pour point.

Improving the combustion efficiency is influenced by reduction of Metal particles agglomeration. Due to particles size dependent properties, many studieshave been done on nanoparticles and their applications including the energetic composites.Studies show that the agglomeration mechanism does not depend on the individual properties of initial particles but related totemperature of metal fuel ignitioncomparing withthe decomposition temperature of carbonaceous elements. Therefore metal nanoparticles due to theirlow ignition temperature and very small particle size influence on quality and quantity of agglomeration respectively.

Analysis of pollutants in water samples is very important. In recent years, separation technology based on magnetic materials has received considerable attention. These magnetic nanoparticles are not target selective and are unsuitable for samples with complicated matrices. Therefore, a suitable coating is essential to overcome such limitations. Surface modification stabilizes the nanoparticles and prevents their oxidation. This article dealing with the application of surfactant modified magnetic nanoparticles, to the separation and the preconcentration of pollutants in water samples. The magnetic extraction method is not only convenient, economical and highly efficient, but it also overcomes problems with conventional solid-phase extraction such as packing of sorbent into the column and time- consuming loading of large volume samples.

In this paper, multitube reactor with a fixed bed catalyst to produce Phthalic anhydric using Computational Fluid Dynamics (CFD) has been studied. Therefore, based on the reaction kinetics,phthalic anhydride conversion and temperature changes during reactor length have been modeled in FEMLAB softwareby applying the appropriate boundary conditions. The CFD simulation results show good agreement with operationdata in Farabi petrochemical companyfor conversion to the desired product as well as the formation of hot spot locations along the reactor. Phthalic anhydride conversion rate and temperature distribution along the reactor for different operating parameters such as feed flow rate, feed concentration, inlet temperature and wall temperature has been studied. The results show that the hot spot due to high rate of reaction has been located nearby the entrance of reactor. Salt bath temperature is an important factor in the operation of o-xylene oxidation reactor. So that, even 1ºC increasing in salt bath temperature, create higher reaction rate, result in enhancement in o-xylene conversion.

Improving mechanical, thermal and abrasion resistance of different polymer nanocomposites with nanodiamond particles have been interested for researchers in recent years. This review article is focused on nanodiamond, its production and preparation from nature briefly, synthesis and preparation of its polymer nanocomposites. In most of these nanocomposites, thermal, mechanical and abrasion resistance properties were improved by use of nanodiamond in polymer matrix. As an example: tensile strength of poly vinyl alcohol based nanocomposite with 5% nanodiamond increased from 95 MPa to 124 MPa and its tensile modulus from 3.7GPa to 10.6GPa. The tensile strength is also increased by 20% in epoxy resin/nanodiamondnanocomposites. Thermal degradation temperature of polypropylene and ethylene-propylene dien monomer elastomeric blend was increased about 46˚C by using of 5% nanodiamond in their composition. Obvious increasing in mechanical,thermal and abrasion properties were also observed forpolyurethane elastomer and rubber compoundsby applying only 1% and 3%nanodiamond respectively.