فهرست مطالب seyed mohsen peyghambarzadeh

In this paper, the molecular diffusion coefficient is calculated by obtaining experimental data of gas diffusion in stagnant solvent and using mathematical models based on Fick's second law. The purpose of this paper is to calculate the ethylene diffusion coefficients in n-methyl pyrrolidone (NMP) solvent at initial pressures of 600, 800 and 1100 kPa and temperatures of 278.1, 298.1 and 328.1 K using two available models. Although similar to previous researches, the experimental results from both models showed that the diffusion coefficients increase with increasing temperature, the type of dependence on temperature as DAB = A.Tn has been different from the researchers' point of view. To examine, the experimental results were compared with the predictions of Wilke-Chang model, in which n = 5.65, and Diaz model, in which n =8.5. The dependence of the molecular diffusion coefficient on temperature in the two experimental models is different, and the prediction of the Diaz model had better agreement to the experimental data of this study.

The pressure decay of ethylene due to diffusion into the stagnant liquid of N-methyl-2-pyrrolidone (NMP) is evaluated at temperatures of 278.15, 298.15, and 328.15 K, and at three initial pressures of about 0.6, 0.8, and 1.1 MPa. Then, an available graphical method named the initial model is implemented to calculate the diffusion coefficient. Some corrections on the initial model are applied as follows: 1) in the infinite series of the solution to Fick’s second law, more terms are considered. 2) the equilibrium pressure is considered a tuning parameter to eliminate the requirement for an inaccurate experimental measurement. The proposed model is proven to be more reliable and valid for a whole range of pressure decay data including the early times. Due to the large differences between the results of the initial and the proposed models, the Wilke-Chang relation is considered a basis for comparison. This comparative study shows that the results of the Wilke-Chang relation are more compatible with the proposed model.

The flow patterns and pressure gradient of a two-phase mixture of water/super high viscous oil in a horizontal pipe were experimentally investigated. The mixture containing oil with a viscosity of 67 cP and density of 0.872 g/cm3, and pure water flows through an acrylic pipe with a length of 6m and a diameter of 20 mm. Superficial velocities of water and oil were in the range between 0.18–1.2 m/s and 0.18–0.95 m/s, respectively. Six flow patterns were identified. The stratified flow became visible at low velocities of oil (<0.42 m/s) and water (<0.26 m/s) and bubbly flow patterns happened at low superficial oil velocities (Uso = 0.18–0.22 m/s). The dispersion of oil in water (DO/W) occurred at high superficial water velocity (Usw =0.79 – 1.2 m/s) at low or moderate superficial oil velocities (Uso = 0.18 –0.53 m/s). Dispersion of water in oil (DW/O) appeared from superficial oil velocity of higher than 0.69 m/s. The effect of oil viscosity on flow structure was assessed by comparing the present work with the available data and this revealed that the extent of dual continuous patterns reported by other systems containing low viscosity oil is 5% higher than the results of the present study. The effect of oil viscosity on the pressure gradient was also investigated. The pressure gradient values obtained in this study were 80% greater than other studies at similar superficial oil and water velocities. The experimental pressure gradient was also compared with the values predicted by the Al-Wahaibi correlation and two-fluid model. The Al-Wahaibi correlation agreed reasonably with the experimental results, with an average absolute error of less than 9%, while the error of the two-fluid model was 30%.  Based on the results, a clear overview of the flow patterns and pressure drop with detailed information was presented.

Pressure gradient of a two phase mixture in a horizontal pipe were experimentally investigated for water/super viscose oil mixtures. The mixture contained oil having a viscosity of 67 cp and density of 0.872 g/cm3, and pure water, flowing through an acrylic pipe having a length and diameter of 6 m and 20 mm, respectively. A high speed digital camera has been used to record visual information. Superficial velocities of water and oil were in the range between 0.18–1.2 m/s and 0.18–0.95 m/s, respectively. The experimental pressure gradient has been compared to the Al-Wahaibi correlation and two-fluid model. The absolute average error for the “two-fluid model” and Al-Wahaibi correlation have been calculated for 30% and 12%, respectively. In this investigation, a new modified correlation is developed on the basis of the Al-Wahaibi correlation, that predicts the values of pressure gradient with an absolute average error of about 9%. The pressure gradient correlation was validated extensively against 11 independent data sources. To our knowledge, this is the best pressure gradient furmola that is published for oil–water flow which includes wide range of operational conditions including fluid properties, pipe diameters and pipe materials. One of the advantages of the new proposed formula is that it also performs well for super viscosity oils.

In this paper, a cascade solar water sweetening still with the capability of installing latent heat thermal energy storage system (LHTESS) was fabricated, and the Glauber salt as a phase change material (PCM) was used in the thermal reservoir for thermal energy storage. Application of weir on the cascade edge leads to force water flow on the absorption sheet and increases the residence time in the apparatus. Thermal performance of the still with (LHTESS) and without thermal energy storage system (WLHTESS) were analyzed at different days. Results showed that the amount of sweet water productivity in WLHTESS is higher than that of LHTESS at the sunny days. However, after the sunset, the amount of produced sweet water in the LHTESS is considerably greater than of the WLHTESS. Furthermore, results showed that increasing the flow rate of sour water from 50 to 150 ml/min for the WLHTESS decreased the sweet water production from 423 to 252 ml/m2 day and for LHTESS from 396 to 235 ml/m2 day.

It was shown that the concept of drag-reducing in the pipe flow with the aid of macromolecules is of great importance in practical engineering applications. In this study, the drag-reducing the performance of three biological macromolecules including guar gum (GG), xanthan gum (XG), and carboxymethyl cellulose (CMC) was compared with three synthetic macromolecules including polyethylene oxide (PEO), polyacrylamide (PAM), and polyacrylic acid (PAA). Results showed that all the macromolecules enhanced the DR% except for GG. DR% for almost all of the macromolecules deteriorated with increasing fluid flow rate. On the other hand, DR% enhanced with increasing the pipe diameter for the synthetic polymers but this effect is not obvious for biological polymeric solutions. Maximum DR was 44%, which occur at 1000 ppm concentration of XG at 30 °C and flow rate of 6 l/min and diameter ½ inch. Finally, a new correlation was developed for the prediction of friction coefficient based on the Prandtl-Karman relation with the newly adjusted slope which is a linear function of polymer concentration. This correlation was in excellent agreement with the experimental data.

This study aimed to investigate the air pollution caused by volatile organic compounds (VOCs) with an emphasis on benzene, toluene, ethylbenzene, and xylene (BTEX). Due to surface evaporation from the storage tanks of the largest petroleum and chemical product terminal in the export port of the southwestern Iran, the field measurements of the emission sources were performed using the TANKs 4.0.9d software, and VOC emission modeling was performed using the PHAST software. Among 36 point sources (32 external floating roof tanks and four internal floating roof tanks), the emission rates of the VOCs of the storage tanks were determined using the TANKs 4.0.9d software in the area of 3.8 km2 during 12 months (March 2017-January 2018). The highest rate of VOC emissions from the tanks was observed in July, with the highest temperature and wind speed in the region. According to the results, the total emission rate of the VOCs from the storage tanks was 881.74 ton/year, and the highest emission rate was observed in the external floating roof tanks (865.7 ton/year; 98.18%). The contribution of the internal floating roof tanks was 16.04 ton/year (1.81%), and the highest and lowest VOC emission rates in the export port were observed in the light naphtha tank No. 67 and jet naphtha storage tank (56.73 and 4.18 ton/year), respectively. In addition, the highest and lowest BTEX emission rates from the storage tanks were observed in the gasoline tank No. 62 and jet naphtha tanks No. 93 and 94 (0.37 and 0.05 ton/year), respectively.

Water based CuO nanofluids at low concentrations were used to improve the heat transfer performance and also decrease the water consumption in an experimental cooling tower. Nanofluids were prepared at the concentrations lower than 0.2 wt.% and stabilized completely. Then, the experiments were conducted at different water circulating flowrates and different water return temperatures. Air flowrate was considered to be constant at all the experiments. Results showed that using nanofluid improved the cooling performance and enhance the temperature difference between the water supply and return in the cooling tower in comparison with pure water. For example, using CuO nanofluid at the concentration of 0.2 wt.% and at the return temperature of 41 oC and water to air flow rate ratio (L/G) of 0.8 decreased the water outlet temperature from the cooling tower up to %21 compare with pure water, and decrease the water loss up to %16. Results showed that using nanofluid decreased the water loss due to evaporation considerably, and therefore, it is possible to design the cooling tower in smaller size on the basis of this heat transfer enhancement.

In this paper, the radiation section of ethylene dichloride (EDC) cracking furnace, considering the chemical reaction, was numerically modelled using computational fluid dynamics (CFD). This study investigated the influence of some parameters such as mass flow rate, the inlet temperature of fluid into the radiation section, and heat flux on the conversion and changes in velocity, pressure, and temperature of the fluid along the coil passes, as well as the outlet stream of the coil. Then, the modelling results were compared with a series of industrial data of an industrial EDC cracking furnace. The results showed that considering the variable heat flux boundary condition is more compatible with the industrial data rather than the constant heat flux boundary condition. Increasing the feed inlet temperature to the furnace, increased the EDC conversion due to the endothermic nature of the thermal cracking reaction. Furthermore, reducing the inlet mass flow rate led to a significant increase in the conversion, temperature, and mass fraction of the products due to an increase in residence time.

In this study, the solubility of CO2 in DEA in the presence and absence of choline chloride was reported at different temperatures of 276.15, 298.15, 313.15, and 333.15 K, and pressure range of 4-15 bar. The solubility of CO2 was evaluated using the pressure decay method in a batch isochoric stirred absorption cell. Also, the design of experiments performed with Qualitek-4 software using the Taguchi method. Henry’s law constants at three different temperatures were calculated from the correlation of solubility data. Results showed that increasing the initial pressure and DEA concentration and also decreasing the temperature, increases the solubility of CO2. Optimum operating conditions to maximize the amount of CO2 absorption including the temperature of 276.15 K (minimum level), the initial pressure of 15 bar (maximum level), the concentration of DEA of 40 wt.% (maximum level), and the concentration of choline chloride of 5 wt.% (middle level). Also, Qualitek-4 software predicted the amount of solubility at the optimum conditions which was 7.5% different from the measured value.

Fouling is a common, fundamental and costly problem in heat transfer systems, which reduces thermal efficiency of equipment, increases the energy loss and causes strong damage to the heat transfer equipment in various industries. The main causes of fouling on the heat transfer surfaces are salts with inverse temperature-solubility in the fluid which calcium sulfate is one of the most important of them. In this paper, the effect of calcium sulfate fouling on the heat transfer coefficient in subcooled flow boiling was investigated. The fouling mass of calcium sulfate on the heat transfer surface was also calculated. In the experiments carried out in this study, flow rate (2.5–11.5 l/min), solution concentration (1.75–2.2 g/l), bulk fluid temperature (55–75 ℃), and heat flux (8-95 kW/m2) were variables at the mentioned ranges. The results showed that the maximum deviation in the uncertainty analysis was related to the difference between the inlet and outlet temperature of the fluid, followed by the temperature difference between the wall temperature and the bulk fluid temperature. Also, the analysis of the experimental data revealed that increasing the salt concentration, the bulk temperature, and the heat flux of the solution, the mass of deposited calcium sulfate on the heat transfer surface increases with time, resulting in a decrease in the heat transfer coefficient. Careful analysis of the experimental data also showed that the solution concentration has more important role than the heat flux and the fluid bulk temperature in fouling formation.