Dispersions of oil in water are encountered in a variety of industrial processes leading to a reduction in the performance of the heat exchangers when thermally treating such two phase fluids. This reduction is mainly due to changes in the thermal and hydrodynamical behavior of the two phase fluid. In the present work, an experimental investigation was performed to study the effects of light oil fouling on the heat transfer coefficient in a double-pipe heat exchanger under turbulent flow conditions. The effects of different operating conditions on the fouling rate were investigated including: hot fluid Reynolds number (the dispersion), cold fluid Reynolds number, and time. The oil fouling rate was analyzed by determining the growth of fouling resistance with time and through pressure drop measurements. The influence of copper oxide (CuO) nanofluid on the fouling rate in the dispersion was also determined. It was found that the presence of dispersed oil causes a reduction in heat transfer coefficient by percentages depending on the Reynolds number of both cold and hot fluids and the concentration of oil. In addition, the time history of fouling resistance exhibited different trends with the flow rates of both fluids and its trend was influenced appreciably by the presence of CuO nanofluid. K E Y W O R D S copper oxide, dispersion, double-pipe heat exchanger, fouling, heat transfer, nanofluid, oil Heat Transfer-Asian Res.

The effect of impeller geometry on bubble breakage in a stirred tank was investigated for a range of impeller Reynolds number (Re) using a high speed imaging method. The bubble dynamic behavior and breakage mechanism were investigated for four different impeller geometries namely, two-flat blades impeller, four-flat blades impeller, four-twisted blades impeller, and two-pinned blades impeller. The performance of each geometry was investigated by determining the breakage probability and number of fragments (daughter bubbles) produced. The contributions of dominant breakage mechanisms for each geometry were specified and discussed by identifying the breakage locations relative to the impeller. Three main breakage mechanisms were observed, namely: bubble collision with the blade, bubble breakage by blade shear, and breakage by turbulent fluctuation away from the blade. The number of fragments by each breakage mechanism was specified for the entire range of Re. The four-flat blades impeller exhibited the highest breakage probability and produced the highest number of fragments. The Pinned blades gave a high performance compared to the smooth blades, especially at higher Re. This is considered to be due to the high turbulence level provided by this type of impeller. The twisted blades impeller showed low bubble breakage probability compared with the other geometries. Breakages by collision with the blades and by shearing effect resulted in a higher number of fragments compared to the breakages caused by turbulent fluctuations. The number of fragments produced by ‘collision with blade’ exhibited a higher dependence on Re than by ‘blade shear’ or by ‘turbulent fluctuations’.

Corrosion rate tests were carried out on carbon steel under concentration cells conditions of oxygen and sodium chloride. The effect of aeration in one compartment on the corrosion rate of both coupled metals was determined. In addition, the effects of time and temperatures on the corrosion rate of both coupled metals and galvanic currents between them were investigated. Corrosion potentials for the whole range of operating conditions under concentration cell conditions were also studied.   The results showed that under aeration condition, the formation of concentration cell caused a considerable corrosion rate of the Carbon steel specimens coupled in different concentrations of O2 and NaCl due to the galvanic effect. Aerating one compartment caused a noticeable increase in the corrosion rate of the coupled specimen in the other compartment due to the galvanic effect. Increasing temperature caused unstable trends in the free and galvanic corrosion potentials. Increasing the temperature led to an increase in the corrosion rate for both metals.

Both surface extension and nanofluid methods were used to enhance the heat transfer in a double pipe heat exchanger under turbulent flow conditions. Aluminum oxide nanoparticles were used with different concentrations(0.6-3 g/l)in hot water to increase the heat transfer rate on smooth tube and circular fins tube for a range of Reynolds number4240-19790. The simulation was also performed to predict the heat transfer coefficient and temperature profile for selected conditions in which COMSOL Multiphysics is used. The experimental results revealed that the heat transfer enhancement by both circular fin and nanofluid exhibited an increasing trend with Reynolds number and nanofluid concentration. The conjoint effect of Al2O3 of 3 g/l concentration and circular fin provided largest heat transfer enhancement of 53% for the highest Re investigated. Simulation results showed reasonable agreement with the experimental values of heat transfer coefficient. The simulation showed that the presence of nanofluid on finned surface influenced the temperature profile indicating the increased heat transfer rate.

The current education explores the magnetite aptitude by way of adsorbent in eliminating lead metal from simulated wastewater (SWW). The effect of magnetite dose, initial lead concentration, pH solution, and Adsorption time on the elimination procedure remained explored. The adsorbent remained considered through different instrumental methods (FTIR, SEM, and surface area analyzer) and was rummage-sale aimed at the elimination of Pb2+ metals from SWW. It remained initiate that the lead elimination touched 88.9 % through 0.3 g magnetite dose,75 min,2 ppm original concentration of lead thru pH = 6 at room temperature. The limits of adsorption were strong-minded aimed at heavy metals adsorption utilizing Langmuir and Freundlich isotherms. The consequences deliver robust evidence to support the adsorption mechanism hypothesis.

The massive scale of industrial development has resulted in environmental pollution in general and water contamination in particular. It is important at the present time to treat water for the purpose of eliminating or reducing pollutants, especially toxic pollutants, such as phenol compounds. In this study, zeolite (4A) was prepared firstly from the available and cheap materials using an inclined rotary disk. Then, physical, mechanical, and chemical properties were also studied. Experiments were conducted to determine these properties using local clay and the following results were obtained: Zeolite (4A) 70% and clay 30%, the time of calcination 3 h at a temperature of 850��C, breakage resistance of 17 Ib pounds, surface area 530-590 m2/g, grinding value 14% and moisture absorption ratio 30%. The prepared zeolite (4A) was used in the process of removing phenolic compounds (chlorophenol, nitrophenol) by the adsorption method. Different amounts of prepared zeolite (5g/l and 10g/L) will be used in the treatment process and different concentrations (2mg/L, 5 mg/L and 10 mg/L) of the pollutants Nitrophenol and Chlorophenol were used in the contaminated water tested. The removal process was carried out with a mixing speed of 200 rpm and pH (7.5-8.5). From the results of this study, we note that the highest percentage of Nitrophenol removal is (84.8%) when using an amount of zeolite (5g) and highest percentage of Nitrophenol removal is (95.5%) when using an amount of zeolite (10g) while that the highest percentage of Chlorophenol removal is (78.3%) when using an amount of zeolite (5g) and highest percentage of Chlorophenol removal is (0.894) when using an amount of zeolite (10g) it could be deduced that the percentage of the removal of nitrophenol was higher than that of chlorophenol because its solubility of chlorophenol in water is higher than the solubility of Nitrophenol.

Stability of nanofluids is one of the most important factors to ensure the most benefit of the properties of nanoparticles. Zinc oxide was used in the research with concentration between (0.2-1) wt. % with ethylene glycol base fluid. The stability of ZnO nanofluid was enhanced by adding two types of surfactants Tx-100 and Gum Arabic with concentration of (0.1-0.5) vol. % to stabilize the ZnO nanoparticles in the base fluid. The results showed that the Gum Arabic surfactant led to more stable fluid than that of Tx-100; this was shown from zeta potential and UV spectroscopy measurements. The thermal conductivity coefficient was also measured, and the results showed that the thermal conductivity increased with adding surfactant than without using a stabilizer.

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