Iranian Journal of Chemical Engineering (IJChE)

Abstract Many industries produce large volumes of effluent which are made of oil and its derivatives; very common pollutants in the environment. The use of hydrophobic magnetic particles due to their low cost, low toxicity, and availability is one of the preferred methods for separating oil from water in oil spillage issues. This research aims at evaluating the effects of dopamine as a link in the hydrophobicity of carbonyl iron (CI) particles with stearic acid. In this connection, CI @ stearic acid and CI @ dopamine @ stearic acid have been synthesized. The FESEM analysis was used to observe the surface modification and structure of the particles. The magnetic properties of hydrophobic particles were also measured and the magnetic saturation of CI, CI @ stearic acid, and CI @ dopamine @ stearic acid were 200, 169, 131 emu/g respectively. Finally, the contact angle and adsorption capacity of two modified particles were measured. Based on the result, the static contact angles of water drops placed on the beds of the CI, CI @ stearic acid, and CI @ dopamine @ stearic acid were found to be 0°, 162.9°, and 168.24° respectively. The adsorption capacity range for CI@ stearic acid particles was 1.5 to 2.2 and for CI@ dopamine@ stearic acid particles was 1.8 to 3.2. Therefore, the result showed that dopamine had a good effect as a link to the hydrophobicity of carbonyl iron particles.

Abstract In this study, functionalized multi-walled carbon nanotubes using mixed acid treatment were synthesized using solvothermal method by TiCl4 as a precursor and the thermal conductivity enhancement of MWNT-TiO2 nanofluids  in  various  temperatures  were compared. The treated nanotubes have been characterized using Fourier Transform
Infrared Spectroscopy (FTIR). Hybrid materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that MWNTs are uniformly decorated with anatase nanocrystals. Temperature effects on thermal conductivity of MWNT-TiO2 nanofluids at different concentrations have been studied. The best result showed enhancement of thermal conductivity around 12.1% for the sample with 0.08 wt% of MWNT-TiO2 compared to distilled water at 36°C and 13.71% at 52°C. Also, zeta potential of 0.02 wt% nanofluids and particle size distribution
of nanoparticle were measured.

Abstract The coalescence of water droplets in oils may be enhanced by application of an electric field. This approach is commonly used in the crude oil and petroleum industry to separate water from crude oil extracted from oil well. By application of an electric field two patterns of drop-interface coalescence may occur: complete coalescence and partial coalescence. The former is obviously the desirable pattern for industrial coalescers. However in practice, the process of coalescence could actually produce smaller droplets which become more difficult to remove, and hence undesirable. This is caused by either necking, due to extensive elongation of the droplet, or reaction to a fast and energetic coalescence and is referred to as partial coalescence. The volume of the droplets formed in this way has been analyzed as a function of the initial droplet size, electric field strength and change in interface tension between two phases as a result of surface active agents. There is a considerable growth in secondary droplets volume. Expansion speed of the neck connecting the droplet and interface at the beginning of the pumping process has also been quantified and partial coalescence has been explained as a result of competition between pumping and necking processes. These results are useful in optimizing the electro-coalescence process.

Abstract In this work, the effects of air stream direction in the channels of indirect evaporative cooler (IEC) on system performance have been investigated. In addition, the dependence of system performance on outdoor air temperature and relative humidity has been studied to determine the allowable conditions for proper operation of the system, with respect to thermal comfort criteria. For this; the different types of IECs were investigated using the CFD technique. Several codes were defined in MATLAB for modeling the parallel flow, counter flow and cross flow layout. The CFD program was validated against theoretical data from the literature and good agreement between the prediction and measurement was achieved. The calculated results show that when the air relative humidity is lower than 70%, the system can prepare a good indoor condition even at 50oC, and a higher performance is achieved by using the IEC with counter current configuration. The results showed that IECs can be successfully used in hot and humid climates to fulfill the indoor thermal comfort conditions.