جستجوی مقالات مرتبط با کلیدواژه « آب دریا » در نشریات گروه « فنی و مهندسی »

The purpose of this research is thermal analysis of a brushless permanent magnet motor with marine application. The advantages of brushless permanent magnet motors are creating high torque and power in proportion to their weight and size. But this issue leads to a large increase in engine temperature. Therefore, the design of the cooling system is essential for cooling and reducing the temperature of this engine. The engine has been thermal analyzed first without cooling system and then with different cooling systems. For the purpose of thermal analysis, the stator and the shell were first modeled and then simulated. The engine has been thermally analyzed first without cooling system and then with different cooling systems. In order to check the effect of the cooling system and choose an optimal and suitable cooling system for this engine, the maximum temperature in different cooling systems with the number of 4, 8 and 12 holes, the diameter of the holes various 3, 4 and 5 mm diameters and circular and oval cross-sections have been compared with each other and with the state without cooling system. The results showed that the temperature of this engine reaches about 416 ̊c without cooling system. Also, the cooling system with 8 circular 4 mm holes has been introduced as the most suitable cooling system for this engine.

Nowadays, decreasing access to sustainable water sources has pushed the water shortage to water stress and water crisis in some cases. This phenomenon has led to more and more researchers and craftsmans’ efforts to achieve cost-effective commercial processes for a sustainable supply of water. Reverse osmosis process showed suitable potential for supplying the human’s required drinking water among all the water treatment processes. However, this process needs economic studies in macro-industrial levels. Neka power plants’ reverse osmosis desalination of seawater has been designed for production of 6,000 m3/day desalinated water. Feed water of this plant is supplied from the Caspian Sea with total dissolved solids of 15,000 mg/L and electrical conductivity of 20,000 µS/cm. Based on the results, required capital cost of this plant is $6 million and annual variable cost of $1.232 million is needed for desalination plant operation. Final fixed price of the desalinated water has been calculated $0.684 per cubic meter of desalinated water with the consideration of 20 years’ plant life cycle. Break-even point of the desalination plant has been obtained less than 6 years and less than 2 years with sales price of 1 $/m3 and 2 $/m3 of desalinated water, respectively. Results show that reverse osmosis based desalination systems are a suitable replacement for conventional freshwater sources.

Desalination process of seawater by reverse osmosis method, has attracted more attention in recent years, due to its high efficiency, and about 62 percent of seawater is treated by this method. In this process energy recovery devices play an important role in reducing energy consumption and process costs, because on the one hand the energy consumption of high pressure pumps for feeding reverse osmosis membrane is high, and on the other hand 40 percent of feed water is treated with membrane and 60 percent is discharged as a high-pressure waste, which releases a lot of energy. The energy recovery device converts this hydraulic energy of the effluent into mechanical energy and transfers it to the feed pump as a shaft aid or uses it independently to transfer a part of the feed. The purpose of this research is to study energy recovery devices and compare them with each other to select a suitable energy recovery system.

Asphaltene precipitation, as stated in previous studies, plugs the pores in the porous media and causes various problems, including permeability reduction, wettability alteration, and ultimately reduces production. The results of this study showed that this surfactant is able to prevent asphaltene precipitation and is effective in different aqueous phases (DW, SW and CW). In addition to increasing recovery factor in the core flooding test, it was able to alter the wettability of the pores surface from oil-wet to intermediate.

In this research, the effect of current intensity on the corrosion resistance of Ti-6Al-4V alloy welded by Tungsten-inert Gas (TIG) method was investigated. For this purpose, 3 × 50 × 40 mm specimens were prepared and after preparing the surfaces, in a way but joint two-way single pass in vacuum chamber with inert argon with a flow rate of 70, 80 and 90 A were welded. Microstructural studies of base metal (BM), fusion zone (FZ) and heat affected zone (HAZ) were performed using optical microscopy and scanning electron microscopy (SEM). Then, in order to investigate the corrosion resistance of Ti-6Al-4V welded cross sections, the roots of the welded specimens were examined by potentiostatic polarization in seawater and 3.5% NaCl. The results showed that by increasing the welding current intensity from 70 to 80A, the grain size in the weld area as well as the corrosion rate of the weld area in Ti-6Al-4V alloy increased. By varying the flow intensity from 80 to 90A, the corrosion rate and grain size of the weld zone did not change significantly. The corrosion rate of Ti-6Al-4V alloy in 3.5% NaCl solution compared to seawater revealed that the corrosion rate of alloy in 3.5% NaCl solution is higher than its corrosion rate in seawater.

Following the reduction of fresh water resources and the growing need of society for these resources, the reduction of fresh water consumption in industries, especially the copper industry, is considered. In addition to water recycling, the use of seawater and treated water can be considered as alternatives. Since the highest water consumption of copper and molybdenum sulfide minerals processing is in the flotation unit, the purpose of this study is to investigate the changes of water quality on the efficiency of rougher flotation unit. The results showed that in similar operating conditions, the use of seawater reduces the recovery of copper sulfide minerals from 89.2% to 68.8%. However, the recovery of flotation when using treated water was 80.89% which is close to recovery when using well water (89.20%). Molybdenum recovery in both cases was approx. 100%, compared to 59 percent for seawater. Therefore, the use of treated water can be a good alternative to well water (current conditions).

The Persian Gulf is well known as one of the most aggressive environments in the world because of its high relative humidity, temperature, and concentration of chloride ions. Concrete structures are increasingly being deteriorated in this region. Therefore, Improving the durability of concrete structures in this environment is an important issue. Supplementary cementitious materials (SCMs) can be useful for concrete durability enhancement in such harsh environments. In this paper, the effect of silica fume on deterioration resistance to sulfate attack in seawater within simulated splash, tidal and submerged conditions have been studied in self-consolidating concretes and mortars containing silica fume (SF) with/without natural zeolite (NZ). To achieve this objective, self-consolidating concrete specimens and concrete equivalent mortars (CEMs) with/without 15% natural zeolite and 8% silica fume with a total binder content of 380 kg/m3 and a constant water to cement ratio of 0.45 were fabricated. limestone powder (LP) is also used as an inert filler in all SCC/CEMs. Additionally, both the conventional and SCC mixes were subjected to these durability tests to compare their performance. After 7 days of curing in a saturated calcium hydroxide solution, all of the specimens were subjected to three exposure conditions (tidal, splash, sub-merged) for 28, 90 and 180 days of testing ages. After taking fresh property testes of mortar/concrete samples by SP demand, slump flow, visual stability index, J-Ring, T50, V-funnel tests, several standard hardened property and durability tests were investigated by mortar/concrete compressive strength, chloride permeability, concrete electrical resistivity, mortar capillary water absorption and porosity tests. Moreover, the degree of sulfate attack was evaluated by measuring the expansion of mortar prisms. Traditionally, the extent of sulfate attack is quantified by the expansion of prismatic bars completely submerged in sulfate solution and this exposure regime used to evaluate sulfate attack is not typically representative of that encountered in the field. Wherefore, in this investigation, prismatic bars were placed in different conditions mentioned and exposed to simulated seawater solution then expansion values evaluated. In addition, a reduction in compressive strength of all specimens was denoted by the strength differential factor (SDF). Results demonstrated that the incorporation of SF with NZ mixes in different exposure conditions led to the lowest absolute value of SDFs in all of the simulated-testing environment. Conversely, the lowest level of compressive strength at all testing ages was obtained for ternary blended cements (PC+LP+SF). Therefore, it can be concluded that SF has a negative effect on the compressive strength of SCC exposed to Persian Gulf seawater solution. This is attributed to the Mg-oriented sulfate attack which was more deleterious in SF ternary blended cements. All in all, the results were obtained from a laboratory set-up and indicated that when the durability properties of the concretes in such environments were taken into account, the quarterly use of zeolite and silica fume (PC+LP+SF+NZ) provided the best performance in all exposures. Furthermore, self-consolidating concretes and mortars performed better than normal types. Besides, it is concluded that splash zones affect concrete specimens more harshly than other conditions.

Due to the increase in population and as a result of the increase in economic activities in the world, the demand for water consumption has increased significantly. Seawater covers two-thirds of the earth's surface, so it makes sense to use these resources to provide drinking water and could be an important component in solving the problem of water scarcity. In addition, existing technologies for water treatment to meet There are certain water quality requirements, so reusing used water to address water shortages can be further explored. In recent years, organic metal frameworks have received much attention due to their interesting chemistry and potential applications. In the science of separation, researchers have extensively studied organic-metal frameworks for gas separation and water treatment. In this paper, the aim is to investigate the possibility of using organic-metal frameworks for membrane desalination. Therefore, after a brief introduction of organic-metallic frameworks, several methods for preparing membranes of organic-metallic frameworks, water desalination techniques and methods of application of organic-metallic frameworks and finally membranes of organic-metallic frameworks for different applications of water Such as desalination, nanofiltration, ultrafiltration and microfiltration are considered. The use of organic-metal frameworks as membranes in water treatment is still in its infancy compared to other applications such as gas separation.

Today, fuel is produced from non-renewable and limited sources, and since it is not possible to recover or produce these sources, replacing sources such as seawater can eliminate this problem for years. In recent years, jet fuel production from carbon dioxide (CO2) and hydrogen (H2) in seawater has been considered. Fuel production involves two stages of separation of hydrogen and carbon dioxide from water, as well as the synthesis of Fischer-Tropsch (FT) to produce jet fuel. In this research, different methods of hydrogen and carbon dioxide production from seawater have been introduced and their strengths and weaknesses are discussed. It has also been evaluated by examining the Fischer-Tropsch reaction, and the overall costs of the fuel production process in the oceans and seas. The results show that it takes 3 to 6 dollar to produce a gallon of fuel this way.

In the present study, in an efficient and selective method, Thorin as a reagent was used by forming colour in the alkaline water–acetone media for direct spectrophotometric determination of lithium ion in the coastal seawater of Chabahar bay. Affective factors on the lithium-thorin complex formation reaction such as reaction time, concentration of thorin and the percent of potassium hydroxide and acetone were studied and optimized. Under optimum conditions, the limit of detection, linearity range relative and standard deviation of method were obtained as 0.039 mg/L, 0.10-1.3 mg/L, 9.11% (n =7), respectively and the average concentration of lithium in seawater of Chabahar Bay was estimated as 0.173 mg/L. Furthermore the effect of different depth on the dispersal of lithium in Chabahar Bay was investigated. The results showed that there were no significant differences among Li concentrations in different depths

Clayey soils usually have low bearing capacity, high compressibility, shrinkage and swell characteristics. Several methods have been adopted to improve the geotechnical properties of such soils. Soil stabilizing by chemical materials is one of the most common methods for treating fine grained soils. Lime has been used to improve some mechanical and plastic properties of fine grained soils since many years ego. In recent years some studies has been also carried out to investigate the influence of adding pozzolany materials on the geotechnical properties of lime – treated clayey soils. Geotechnical behavior of clayey soils depends on chemistry of pore fluid. When drinking water is used to provide the needed moisture of soil in the laboratory, it will be lead to incorrect interpretation in engineering properties of soil where specific water such as sea water is utilized. Therefore, if the undrinkable water has been used to provide soil moisture, it is necessary to examine the behavior characteristics of the materials by the same water. For example, presence of some sulphates in the soil stabilized with lime leads to problems such as reduction of strength and increase of swelling in clay. In this laboratory study, effect of sea water on strength of stabilized kaolinite has been investigated by conducting several unconfined compression tests. The specimens were prepared at fore percentage of lime and pozzolan (i. e. 0%, 1%, 3%, 5%) by weight of dry soil and distilled water and three saline water which were taken from Caspian Sea, Persian Gulf and Urmia Lake. for every combination, weight of each material was determined exactly based on the optimum moisture content and maximum dry density which is obtained from the standard proctor compaction test. Clay and lime and pozzolan were mixed in dry condition properly and then water was added gradually. Afterwards, the mixtures were kept in plastic bags for 24 hours. Weight of each specimen was determined in accordance with given specific volume and obtained maximum dry density from compaction test. This weight was divided into four portion and each portion was compacted in 20 mm layer in a PVC mold. The specimens were cured in a oven having a temperature about 35 C for 3, 7 and 14 days. After each curing time a extruder was used to remove the specimens from the molds with constant rate vertically to avoid bending and formation of tensile cracks. Then the specimens were immediately tested under strain controlled at constant loading rate of 1. 0 mm per minute, according to requirements of ASTM D 2166. For each combination, three specimens were examined to assure repeatability of results. The results of conducted experiments indicate that unconfined strength of samples without additives (lime and pozzolan) prepared by sea water are higher than specimens containing distilled water. For the samples containing Urmia lake water, the unconfined strength were higher than the other samples. Also, for the specimens in which additive has been used, the strength of the samples containing Caspian Sea and Persian Gulf water were more than that with distilled water and the strength of samples containing Urmia lake water was less because of differences in the concentration of salts existed in the water. Finally, the results show that water minerals are higher in Urmia lake water, Persian Gulf and Caspian Sea, respectively.

Cupronickel 90-10 is one of the most applicable Cu-based alloys which possess suitable corrosion resistance and strength and is employed extensively in marine industries particularly in the boilers and heat exchangers. Generally, the tubes of water cooling systems especially those use seawater as cooling medium are made of this alloy. In this paper, the causes of premature failure of a cupronickel (90-10) condenser tube used in a cooling system of an oil refinery in the south of Iran have been studied by different microscopical and analytical methods, e.g. X-ray fluorescence spectroscopy (XRF) and X-ray diffraction (XRD). The results showed that pitting corrosion on the internal surface of the tube was the main cause of its failure which was a consequence of the stagnant of the tube by external solids and preparation of an appropriate environment for the activity of microorganisms, hence, microbial corrosion.

As a consequence to global warming and climate change all around the world and irregular consumption of underground water resources, the societies are being faced to a serious dangers named water scarcity. Population growth, need to food security, climate changes and agricultural needs have forced the societies to search for appropriate alternatives for fresh water resources. Unconventional water resources are known as one of the most important alternatives for fresh water on the earth. One of the most sources of unconventional waters is saline or brackish water. Considering the great amount of saline water on the earth, water desalination can be a fruitful method to overcome the crisis of water scarcity. Water desalination technologies will be categorized into two main groups of thermal and membrane technologies. In this paper, at first the most important and most applicable desalination technologies around the world are studied, then the influences of desalination technologies regarding energy and economy have been evaluated. At the end, the examples of desalination units in different parts of the world have been studied.

The cooling systems are widely used in power plants, manufacturing industries and refineries for the sake of reducing system heats and an increase in operational efficiency. Copper is widely used in cooling systems due to its high thermal conductivity. Corrosion of copper is one of main problems in these industries. The use of corrosion inhibitors is a common method to control the corrosion in cooling systems. Various inhibitors are usually used to protect the different metals in cooling systems. The synergistic or antagonistic effect of inhibitors on each other may be influenced on inhibition efficiency. The inhibition effect of 1H-benzotriazole (BTA) on corrosion of copper has been investigated in simulated sea water in the presence and absence of sodium molybdate (SM) using weight loss, Tafel polarization and electrochemical impedance spectrometry (EIS) methods. The results indicated that adsorption of BTA and SM on copper surface obeyed from Langmuir adsorption isotherm. The adsorption energy values for BTA and SM on copper surface was obtained -33.88 and -21.22 kJ/mol, respectively. The absorption of sodium molybdate promoted the stability of surface oxides on copper surface which in turn has a synergistic effect on the inhibition effectiveness of BTA. The inhibition of SM and BTA has been attributed to stabilize the effect of surface oxides and the formation of a protective complex layer, respectively.

Investigation of Persian Gulf seawater corrosion effect on the carbon steels and welded pieces used in construction of metallic storage tanks is important from this point of view that this investigation may result in using this seawater to do hydro test of these tanks. If the results of this evaluation be positive, it will have lots of economic and environmental advantages. In order to achieve this target in this study, at first a 15 mm thickness plate of ASTM A283 Grade C low carbon steel was welded by E7018 electrode then quality controlled by radiography test and its microstructure evaluated by macro and micro etch tests and also hardness test was done for it. Furthermore chemical composition, pH, conductivity and SRB amount within the water has been measured too. Then corrosion rates for each one of these mentioned steel and electrode in Persian Gulf seawater were measured by electrochemical method of linear polarization resistance and also immersion test. Then corrosion product and corroded surface were analyzed by EDS and SEM methods. Results of polarization and immersion tests proved that E7018 electrode is anode compared to ASTM A283 Grade C steel and this result was confirmed by SEM images.

The inhibition behavior of 1H-benzotriazole on corrosion of mild steel and Aluminum alloy 1050 in single and couple modes was investigated in sea water by immersion, Tafel polarization and electrochemical impedance spectrometry methods. The results indicated that an increase in inhibitor concentration cause to enhance in inhibition efficiency for both MS and AA1050 in single mode. In this case, the use of 0.01 M BTA caused to 50 and 70 percent reduction in corrosion rate of mild steel and AA 1050, respectively. BTA adsorbed on both MS and AA1050 surfaces physically according to the Langmuir adsorption isotherm. BTA was adsorbed on mild steel surface chemically when mild steel coupled to AA1050 which in turn caused the corrosion rate of mild steel to reduce more than 95 percent with respect to reference sample.

Aluminium 5xxx alloys excellent properties make them suitable for many industrial applications. The corrosion behavior of this alloy family in industrial environments such as sea water is the main focus of many researches. Due to need for joining large segments of this alloys, the effect of single as well as multipass (double and triple pass) gas metal arc welding (GMAW) on microstructure and corrosion behavior of Al5083-H321 alloy was studied. For this purpose, ER5183 filler metal was used. Microstructures were evaluated using optical and scanning electron microscopy (SEM). Corrosion measurements were performed using open circuit potential test, immersion test in 3.5%NaCl solution and polarization tests. Results indicated that the corrosion resistance of the two passes weldment was improved in comparison with the base metal and its icorr and Ecorr were equal to 0.087´10-6 (µA/cm2) and -0.4395 (V), respectively.

Nowadays, seawater usage in mineral processing has become a fairly topical issue. Due to rapid population growth and industrial development, the amount of fresh water is decreasing rapidly, so that fresh water is a critical component, especially in many industrialized arid countries, such as Iran. One of the main methods of mineral processing is flotation process that occurs in aquatic environments and consumes large volumes of water. The purpose of this paper was to investigate the use of sea water in the Cu-Mo ores froth flotation. In the experimental work, seawater was utilized as process water in the laboratory rougher flotation tests and compare the results with fresh water. The ore sample was porphyry Cu-Mo ore, which was delivered from Sarcheshmeh Copper complex. Results show that recovery of copper maintained almost the same level in both mediums. However, lime consumption was observed to be increased significantly under flotation conditions in seawater. In addition, the floatability of molybdenum was affected negatively above the pH 9.5-10. Recovery reduction of molybdenum was suggested to occur due to the magnesium hydroxide complexes and magnesium hydroxide precipitates, which began to form in seawater in higher pH levels. The experimental work showed that the conventional flotation of Cu-Mo ore conducted in seawater has serious conflicts, when pyrite is depressed with lime.

Air entrainment in liquids via a fluid jet, is a complex phenomenon that has important applications in industry and the environment. The impact of a vertical laminar water jet translating over the quiescent pool of water at constant velocity was studied empirically, and the penetration depth as well as distribution of the bubbles formed by this jet was measured for both fresh and sea water with two different optical methods. This experiment was conducted at different flow rates (corresponding to different vertical velocities). In each case, the jet was moved at different horizontal velocities relative to the pool surface. As the jet started its horizontal translation, air began entering the pool from the bottom of the point of impact. Bubbles penetration depth was measured through a high-speed imaging technique, and pulse shadowgraphy was used for measuring the bubbles distribution. Increasing the vertical velocity of the jet while simultaneously decreasing the horizontal velocity of the same led to increased bubble penetration depths, and similar results were obtained for fresh water and sea water. This result was obtained in spite of the fact that the number and size of the bubbles formed in sea water were dramatically different from those formed in fresh water. Moreover, the significant role of buoyant forces in the distribution of the bubbles was obvious. The penetration depth and distribution of the bubbles were measured and reported for various jets with different diameters at different vertical and horizontal velocities.