ندا عظيمي

In petroleum production processes, stable emulsions are extracted along with crude oil. The stability of these emulsions, primarily due to the presence of naturally occurring surface-active compounds in crude oil, leads to various operational and environmental challenges. Therefore, the effective separation of these emulsions is considered one of the critical and essential challenges in the petroleum industry. To provide an effective solution to this challenge, a hyperbranched polymeric demulsifier based on a polyester structure was synthesized in this study via direct polycondensation between a trifunctional polyalkylene glycol as the branching agent and a difunctional isophthalic acid. The hyperbranched structure, with a higher density of end-groups, enables multi-point and faster adsorption at the interface. A series of characterization analyses were performed to confirm the structure and the successful synthesis of the demulsifier, and the results verified the effectiveness of the synthesis process. The performance of the synthesized demulsifier in water-in-oil emulsion separation was evaluated under various operational conditions, specifically demulsifier concentrations ranging from 50 to 100 mg/L, temperatures from 40 to 70°C, and settling times from 10 to 60 minutes. Under the optimal conditions, including concentration of 90 mg/L, temperature of 70°C, and settling time of 50 minutes, demulsification efficiency of approximately 85% was achieved. In addition to its amphiphilic nature, the hyperbranched polymeric demulsifier exhibits acceptable separation performance due to its hyperbranched structure and favorable properties, including an appropriate molecular weight, relatively uniform structure, and high flexibility of the polymer chains. Subsequently, in order to further enhance the performance of the hyperbranched polymeric demulsifier and investigate the effect of magnetic nanoparticles on this system, magnetic graphene oxide nanoparticles were synthesized and incorporated into the system as a modifying agent. Under the previously determined optimal conditions and at a concentration of 0.025wt%, these nanoparticles increased the demulsification efficiency to 95.6%. In addition, the magnetic properties of the nanoparticles enabled their efficient recovery from the system, which not only reduced material consumption and operational costs but also demonstrated the potential for their reuse. Overall, the results of this study demonstrate that the synthesis of a hyperbranched polymeric demulsifier and its modification with magnetic graphene oxide nanoparticles provide a novel and innovative approach for the demulsification of water-in-oil emulsions. Furthermore, due to the high potential of this system in emulsion separation, the findings of this research can be utilized for industrial applications and further research studies in the petroleum industry.   

  atural convection inside a partitioned enclosure has attracted much attention in recent years due to its importance in engineering applications for weakening or enhancing the intensity of heat transfer. In this study, a vertical enclosure containing air partitioned by a row of horizontal flat insulating blades is investigated. The effects of effective variables on the steady laminar natural convection flow inside the partitioned enclosure are numerically studied. Different temperatures are considered for the side walls of the enclosure, while the other walls are insulated. The row of blades is unsymmetrical in two cases; in one case, the row of blades is moved away from the symmetry line of the enclosure and towards the hot wall, and in the other case, the row of blades is moved away from the symmetry line of the enclosure and towards the cold wall. The effective variables include the Rayleigh number (Ra) in the range of 103×7 and 1.45×104, the angle of inclination of the blades to the horizon (?) in the range of 0 to 180 o and the eccentricity (S) in the range of -1.5 to +1.5 mm. Based on the numerical results obtained, the heat transfer is particularly sensitive to the change in the angle of the blades (?) and has an oscillating trend towards it. In addition, the heat transfer increased with increasing the Rayleigh number (Ra). Also, the asymmetric arrangement of the blades inside the chamber reduces the heat transfer in the chamber by a maximum of 19% compared to the symmetrical arrangement (S=0). In fact, with a low-cost geometric change, a significant amount of heat transfer in the chamber is reduced.

Lithium-ion batteries, as primary energy sources in electric vehicles, energy storage systems, and high-power electronic devices, face significant challenges related to temperature rise and thermal management. Increased internal battery temperature not only reduces efficiency and service life but also poses serious safety risks such as thermal runaway, fire, and electrode damage. Therefore, developing effective methods to control temperature, delay critical temperature rise, and homogenize heat distribution is a fundamental aspect of lithium-ion battery design and performance improvement. One advanced approach in thermal management is the use of phase change materials (PCM), which have the capacity to store and release latent heat and can prevent rapid temperature increases by absorbing the heat generated by the battery. This thesis investigates and analyzes the performance of various phase change materials including paraffin, vaseline, and their composites with conductive additives such as graphite, copper oxide, and alumina+CuSO?, evaluating their effects on the thermal behavior of lithium-ion batteries comprehensively. In this study, more than 23 different phase change material compositions with varying ratios of paraffin and vaseline and different amounts of conductive additives were examined. The experiments included recording the battery temperature rise time, heating rate, and heat distribution uniformity at different voltages, along with comparing thermal behavior with and without conductive additives. These data enabled precise analysis of the impact of different PCM compositions on battery thermal management and identification of optimal mixtures. The results showed that pure paraffin compounds, due to high latent heat capacity, extended the temperature rise time but exhibited non-uniform temperature distribution and hotspot formation on the battery surface because of low thermal conductivity. Pure vaseline, though structurally stable and reducing PCM leakage, had a higher heating rate and lower heat storage capacity. With the addition of graphite and other conductive additives, heat transfer improved and temperature distribution became more uniform. Compositions containing graphite and copper oxide or alumina+CuSO? showed the longest critical temperature time and lowest heating rates, providing optimized thermal performance along with suitable mechanical stability. Also, paraffin–vaseline mixtures with graphite achieved a good balance of thermal energy storage, structural stability, and temperature uniformity and were suitable for moderate charge-discharge cycles. Ranking analysis revealed that the best thermal performance was related to PCM base compositions with conductive additives, while pure vaseline and pure paraffin without additives showed the lowest efficiency in thermal management. Findings indicate that selecting the optimal PCM composition combined with conductive materials is crucial for achieving stable thermal management, enhancing safety, and prolonging the lifespan of lithium-ion batteries. This thesis serves as a scientific and practical guide for designing advanced thermal management systems in electric vehicles and industrial applications of lithium-ion batteries, highlighting the importance of intelligent PCM and conductive additive combinations in improving battery thermal performance.   

Ejectors, as essential devices in industrial processes, play a vital role in energy transfer and fluid suction. In this thesis, the performance of an air ejector experimentally investigated by Tang Liu and co-workers was studied using Computational Fluid Dynamics (CFD) in a two-dimensional axisymmetric model. The main objective of the study was to analyze the effects of nozzle throat diameter and mixing chamber diameter on the entrainment ratio, the influence of primary and secondary flow pressures on entrainment ratio and critical back pressure, and to compare the simulation results with experimental data, which showed good agreement. Velocity, pressure, and Mach number contours were plotted and analyzed under different operating conditions. The results indicated that increasing the nozzle throat diameter reduces the entrainment ratio but raises the critical back pressure. Enlarging the mixing chamber diameter increases the entrainment ratio while decreasing the critical pressure. Moreover, the maximum entrainment ratio was observed with a larger mixing chamber and a smaller nozzle. The effects of primary and secondary flow pressures on mass flow rate and entrainment ratio were also investigated. It was found that, for all geometries, an increase in primary flow inlet pressure increases the primary mass flow rate, whereas the entrainment ratio or entrained mass flow initially rises and then decreases. The increase in secondary mass flow rate was attributed to higher nozzle exit velocity at elevated primary pressures, which enhances suction. However, beyond a certain limit, further increases in primary pressure cause excessive expansion of the converging-diverging nozzle flow, blocking the secondary stream, as confirmed by Mach number contours. Furthermore, with a constant nozzle throat diameter, higher primary flow pressure results in an increased maximum entrainment ratio and a higher corresponding optimum primary pressure. In contrast, with a fixed mixing chamber diameter, increasing the nozzle throat gradually decreases the maximum entrainment ratio and lowers the optimum primary pressure. It was also observed that ejectors with smaller nozzle throats require higher secondary pressures to initiate operation. Results further revealed that, when the nozzle size is fixed and the mixing chamber diameter gradually increases, the minimum secondary pressure required for startup increases, and the entrainment ratio grows more rapidly with increasing secondary pressure. Conversely, with a fixed mixing chamber diameter, reducing the nozzle throat diameter leads to a faster rise in entrainment ratio with increasing secondary pressure. Finally, recommendations for future research were proposed, including three-dimensional simulations, multiphase flow analysis, multi-parameter optimization, investigation of working fluid effects, and transient flow studies. The findings demonstrate that numerical simulation is a powerful tool for analyzing and optimizing high-performance industrial ejectors.  

   نفت خام سنگين به دليل ويسكوزيته بالا، محتواي بالاي آسفالتين و رزين و دشواري در فرآورش همواره يكي از چالش‌هاي اصلي صنايع پالايشي محسوب مي‌شود. يكي از رويكردهاي نوين براي بهبود فرآورش اين برش‌ها، بهره‌گيري از پديده كاويتاسيون و انرژي آزادشده از انفجار حباب‌ها به‌عنوان منبعي براي تغيير خواص نفت سنگين است. در اين تحقيق، شبيه‌سازي عددي پديده كاويتاسيون در يك اجكتور در مقياس آزمايشگاهي با استفاده از ديناميك سيالات محاسباتي انجام شد. هندسه اجكتور در نرم‌افزار انسيس ديزاين مدلر طراحي و شبكه‌بندي آن در انسيس مشينگ انجام شد. شبيه‌سازي جريان سه‌فازي (آب، بخار و نفت سنگين) و پديده كاويتاسيون با استفاده از مدل جريان مخلوط در انسيس فلوئنت انجام گرديد. شرايط مرزي شامل فشار ورودي آب Pa 2.000.000 و دماي   K298 و فشار ورودي نفت سنگين Pa80000 و دماي   K353 بود، در حالي كه فشار خروجي برابر با Pa 101325 تعيين شد. دبي ورودي نفت در شرايط مرزي فوق به ترتيب Kg/s4709171/0 بود و حداكثر سرعت در گلوگاه اجكتور m/s 39/ 63 گزارش شد. داده‌هاي به‌دست‌آمده از فلوئنت شامل فشار و حجم بخار توليدي (m³/s 104×33/7) به نرم‌افزار متلب منتقل شد و با بهره‌گيري از معادله ريلي پلست، ديناميك فروپاشي حباب‌ها و انرژي آزادشده از انفجار آن‌ها محاسبه گرديد. دما و فشار حباب حين فروپاشي به ترتيب،   K98/4722 و bar 2827 انرژي آزادشده از يك حباب در اين فرآيند J 10-10 833× /1بود كه به عنوان بار حرارتي به جريان نفت سنگين اعمال شد. تحليل نتايج نشان داد دانسيته نفت پس از كاويتاسيون از Kg/m³1/903 به 1/880 كاهش يافت و ويسكوزيته ازKg/m·s 2467/0 به 0754/0 كاهش يافت، كه بيانگر تغيير قابل توجه در خواص ترموديناميكي نفت سنگين است. بر اساس نتايج به‌دست‌آمده، بهره‌گيري از كاويتاسيون و طراحي بهينه اجكتور مي‌تواند رويكردي مؤثر براي بهبود فرآيندهاي شكست مولكول ها و سبك‌سازي برش‌هاي سنگين نفت باشد. چارچوب روش‌شناسي ارائه‌شده، امكان تحليل همزمان هيدروديناميكي، ديناميكي و اثرگذاري انرژي آزادشده از كاويتاسيون بر نفت را فراهم مي‌آورد و مي‌تواند مبناي توسعه تحقيقات آينده در بهينه‌سازي فرآيندهاي پالايشي قرار گيرد.

  One of the major challenges in photovoltaic (PV) panels

   Lithium-ion batteries are the powerhouse of the digital electronic revolution in this modern society. However, a critical issue is the thermal management of these devices' batteries to ensure rapid charging or discharging, safe operation, and efficient performance by regulating their temperature within the optimal range. Nevertheless, existing battery thermal management methods, including air and liquid cooling (known as active cooling), not only occupy significant space but also struggle to overcome battery cooling at high temperatures due to their heavy weight and limited energy consumption, leading to reduced vehicle efficiency. In contrast, passive cooling methods, referred to as phase change material (PCM)-based battery thermal management technology, have demonstrated favorable performance by saving weight and energy consumption. However, the low thermal conductivity and leakage of PCMs have limited their application in battery thermal management. In this thesis, the thermal modeling of a battery using a heater was experimentally investigated. Additionally, several battery thermal management systems, including PCMs with three different mass percentage ratios composed of paraffin and beeswax, and carbon-based aerogel/PCM composites, were fabricated. The results showed that using a PCM composed of 75% paraffin and 25% beeswax alone increased thermal performance by up to 56% compared to the other two ratios. Furthermore, using raw aerogel/PCM composed of 25% paraffin and 75% beeswax resulted in a 31% increase in thermal conductivity compared to the PCM alone. However, black aerogel/PCM composites showed acceptable performance across all ratios and resulted in a 46% increase in thermal conductivity. Overall, the use of a black aerogel/PCM composite composed of 25% paraffin and 75% beeswax was considered the optimal thermal management system due to its highest thermal conductivity.

Lithium-ion batteries have a high energy density, but heat production due to electrochemical reactions and the internal resistance of the batteries increases their temperature. Battery thermal management system plays an important role in maintaining the performance of lithium-ion batteries. Phase change materials (PCM) are widely used in battery thermal management systems due to their low energy consumption, high temperature uniformity, and affordable price, but the low thermal conductivity of PCMs has made their use a challenge. One of the ways to increase the thermal conductivity of PCMs is to insert carbon-based materials such as carbon nanotubes and graphene in PCMs. Due to their high thermal conductivity, these materials lead to strengthening the heat transfer of PCMs.Carbon quantum dots are one of the carbon-based materials that are in the nano-size range and have features such as high surface area to volume, excellent electrochemical activity and the ability to precisely adjust the electrical structure. Therefore, in the present study, a heat management system based on PCM reinforced with carbon quantum dots was presented. The phase change agent consisting of beeswax and coconut oil with different weight ratios was prepared and their physicochemical properties were investigated. Carbon quantum dots were also synthesized by hydrothermal and heating methods using citric acid carbon source and their physicochemical properties were investigated using different methods. Physical and chemical characterization of carbon quantum dots was performed using infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques.Then, the effect of PCMs reinforced with quantum dot carbon on lowering the battery temperature was investigated. The results showed that the addition of quantum dot carbon to PCM leads to a decrease in temperature in the optimal range of battery performance (less than 40 ?C)  

  polymer materials are widely used in many household and industrial tools

  

Abstract

Copper is a critical mineral that, in optimal concentration, has a significant role in the health and quality of life of living beings. But at the same time, its deficiency or extra amount causes dysfunction of body's vital organs. So the Copper’s concentration measurement is an essential issue in the water safety monitoring field. As recommended by the World Health Organization (WHO) for the maximum allowable concentration of Cu2+ ions in drinking water is 1.5 mg / l. Conventional concentration measurement methods generally require professional performance and access to expensive tools. It shows the importance of developing low-cost, simple, and efficient methods for measuring copper ion concentrations. The use of microfluidic devices is a good option for analytical experiments due to its speed in analysis, reduction of sample consumption, reagents, solvents, and less waste generation. However, high production costs are an essential obstacle to the widespread use of these devices globally. The use of threads used in the textile industry can be considered as an effective solution to solve this problem. This study aimed to achieve a suitable geometry for microfluidic and find a suitable thread with fluid transfer capability to recognize copper ions. In this regard, by performing various experiments in several stages to investigate the micro-mixing due to the deformation of microfluidics based on different yarns with acid and base solutions, macro mixing with food colors, and finally, the detection of copper ions based on the color change resulting from the reaction of Potassium iodide with copper ions using a T-shaped microfluid based on nylon 66 grade 1880 denier yarn has investigated.Finally, through the reaction of copper with potassium iodide, microfluidic geometry's effect on the rate of fluid advancement in the mixing channel and the quality of fluid mixing based on polyester yarns have been investigated. The investigation results of the thread grade (microfluid channel diameter) change effect on the rate of fluid progress in this study show a direct relationship between increasing thread diameter and the rate of fluid progress. However, this increasing trend is not continuous, and with increasing the yarn grade from 1670 to 2200 deniers, the length of fluid advancement in the mixing channel decreased. In the experiment of double twist Nylon 6 and Nylon 66 yarns with grades 940, 1400, and 1880 Deniers in three types of microfluidics with T, ? and Y-shaped geometries, it was observed that the highest rate of progress has occurred in microfluid with double twist 1880 Denier Nylon 66 yarn. Then, using the reaction of potassium iodide with copper ion, polyester yarns with different scores in three types of microfluidic geometry were investigated, and the microfluid ?-shape still had the highest fluid advancement. In the process of investigating the effect of changes in the concentration of acidic and basic solutions on the rate of fluid advancement, it observed that with increasing concentration of solutions, the length of fluid progress in the mixing channel decreases, and the highest fluid advancement occurs in microfluid with T-shaped geometry. However, the double twisted Nylon 66 yarn, grade 1880, still has the highest rate of advancement. Finally, using a T-shaped microfluid based on nylon 66 yarn, grade 1880 denier, the color change resulting from potassium iodide with copper ion reaction was used to identify the Cu2+ ion. The first color change was observed when using a copper solution with a concentration of 0.002 M, and gradually with a gradual increase in concentration, different colors are observed.   

Photovoltaic cell performance enhancement using hybrid system /micro channel/phase change material   cooling system