Given the global energy crises and the importance

      Due to the significant share of the building sector in total energy consumption, investigating innovative methods to reduce energy use and enhance energy efficiency in this sector is of particular importance. One of the effective approaches in this regard is the use of phase change materials (PCMs) to improve the thermal performance of the building envelope. In this study, the performance of six types of phase change materials with five different thicknesses (ranging from 0.01 m to 0.05 m) was simulated using EnergyPlus software for a 48 m² residential building located in Kermanshah, during the period from November to March. The results showed that the building’s heating load, which was 3914.38 kWh in the reference case, decreased to 3601.94 kWh after incorporating PCM. The highest reduction in heating load, equal to 312.43 kWh, was achieved with paraffin RT21, which has a melting temperature of 21 °C, corresponding to 7.98% energy savings. Furthermore, it was found that increasing the PCM layer thickness beyond 4 cm had no significant effect on improving thermal performance, and the greatest impact of PCM occurred when it was applied to the inner layer of the building envelope.

   با افزايش روزافزون تقاضاي جهاني براي انرژي و نگراني‌هاي زيست‌محيطي ناشي از مصرف سوخت‌هاي فسيلي، توسعه و به‌كارگيري فناوري‌هاي نوين انرژي‌هاي تجديدپذير بيش از پيش ضرورت يافته است. در اين ميان، سيستم‌هاي فتوولتائيك حرارتي (PVT) كه توانايي توليد هم‌زمان برق و گرما را دارند، به عنوان راهكاري مؤثر براي افزايش بهره‌وري انرژي و كاهش انتشار آلاينده‌ها مطرح شده‌اند. در اين پژوهش با استفاده از نرم افزار تجاري شبيه سازيANSYS Fluent ، به تحليل و ارزيابي عملكرد حرارتي يك سيستم PVT مبتني بر سيال خنك‌كننده پرداخته شده است. در اين مطالعه، تأثير پارامترهاي مهمي همچون شدت تابش خورشيدي، دماي محيط، سرعت باد، دبي جرمي سيال خنك‌كننده و فاصله هوايي بين پوشش شفاف و پنل فتوولتائيك بر عملكرد سيستم بررسي شده است. مدل‌سازي با استفاده از روش حجم محدود و الگوريتم SIMPLE انجام گرفته و براي افزايش دقت، از روش Second Order Upwind در گسسته‌سازي معادلات بهره گرفته شده است. شبيه‌سازي‌ها در دو اقليم متفاوت كرمانشاه (با آب‌وهواي گرم‌تر و خشك‌تر) و بخارست (با آب‌وهواي خنك‌تر و مرطوب‌تر) انجام شد تا تأثير شرايط محيطي به‌صورت مقايسه‌اي مورد ارزيابي قرار گيرد. نتايج نشان مي‌دهد كه عملكرد حرارتي سيستم PVT به شدت تحت تأثير شرايط اقليمي است. در كرمانشاه، به دليل دماي بالاتر و رطوبت كمتر، توان حرارتي سيستم حدود ?.? درصد بيشتر بوده و به ???? وات مي‌رسد، در حالي كه در بخارست توان حرارتي ???? وات محاسبه شد. همچنين، گراديان دماي شديدي در ناحيه انتقال حرارت از پنل به سيال خنك‌كننده مشاهده شده كه اين افت دما در اقليم سردتر بخارست محسوس‌تر است. تحليل توزيع جريان هوا در بالاي پنل‌ها نشان مي‌دهد كه جابجايي طبيعي نقش مؤثري در تهويه و كاهش دماي سطح دارد، اما در اقليم گرم‌تر، اتلاف حرارت تابشي سهم بيشتري از اتلاف حرارت كل را به خود اختصاص مي‌دهد. علاوه بر اين، نتايج حاكي از آن است كه انتخاب بهينه پارامترهايي مانند سرعت سيال، فاصله هوايي و خواص ترموفيزيكي مي‌تواند بازده نهايي سيستم را به طور چشمگيري بهبود بخشد. استفاده از سيال خنك‌كننده علاوه بر افزايش راندمان الكتريكي سلول‌هاي خورشيدي، امكان بازيابي گرماي جذب‌شده را براي مصارف گرمايشي فراهم مي‌كند. بنابراين، سيستم‌هاي PVT در صورت طراحي بهينه و كنترل دقيق شرايط عملياتي، مي‌توانند به عنوان راهكاري كارآمد براي تأمين همزمان انرژي الكتريكي و حرارتي در ساختمان‌ها، به ويژه در مناطق خشك و نيمه‌خشك، نقش مهمي در توسعه پايدار و كاهش هزينه‌هاي انرژي ايفا كنند.

Abstract

In this numerical study, heat transfer and fluid flow in circular microchannels with porous and solid ribs were investigated. Water was used as the cooling fluid. A total of 23 circular ribs were analyzed across 8 porous and 6 solid cases in the microchannel. The rib volumes were kept constant across all cases, and in each case, increasing the inner diameter resulted in increased rib thickness. Due to the small size of the channel, laminar flow was used to avoid excessive pressure drop, with the Reynolds number ranging from 100 to 800. The Darcy–Brinkman–Forchheimer equations were applied to simulate the porous regions. The Nusselt number, pressure drop, and figure of merit (FOM) were calculated for all cases and compared. For the same inner diameter, solid ribs exhibited a higher pressure drop. The first solid case achieved the highest heat transfer among all cases. For the same inner diameter, porous cases demonstrated better FOM, with the first porous case having the highest FOM. This case was identified as optimal, as it provided satisfactory heat transfer without imposing excessive pressure drop on the system. The effects of porosity, permeability, and Al?O? nanofluid concentration were analyzed for the optimal case. Both solid and porous ribs improved the FOM compared to a ribless channel. For systems where both heat transfer and pressure drop are critical, porous ribs are a suitable choice. For systems where pressure drop is of greater concern, porous ribs are preferable. The third, fourth, and fifth solid cases, as well as the sixth, seventh, and eighth porous cases are recommended for systems prioritizing heat transfer performance.   

Heavy metals are among the environmental pollutants that human exposure to them through water and food can cause acute and dangerous poisoning. Water pollution with heavy metals is an existing and developing global problem. Heavy metals such as lead, copper, cadmium, arsenic, mercury, etc. are among the most common pollutants found in industrial wastewater. There are different methods for removing heavy metals, among these methods we can mention chemical precipitation, ion exchange, coagulation, reverse osmosis, electrochemical processes and surface adsorption. Most of these methods have disadvantages, and among them, surface adsorption is considered as an effective method for removing heavy metals. Bioabsorbents are one of the types of adsorbents that have been considered for the removal of heavy metals. In this research, in order to remove heavy metals cadmium and copper, aqueous solutions of melon peel modified with NaOH were used. FT-IR, SEM and ASS analyzes were used in order to determine the structure and identify and check the properties of the prepared biosorbent. In the following, the factors affecting the amount of removal such as pH, amount of adsorbent, contact time and initial concentration of the mentioned metals were investigated. ¬ 170 mg/L, 1.38 g/L adsorbent dose and 45 min contact time have been obtained. Experiment design was done using Design Expert software. R2 in this model for cadmium is equal to 0.9902, which indicates that 99.02% of the data are covered by the model, and the small difference with R2adj, which is equal to 0.9765, indicates the appropriate accuracy of the model. is Kinetic experiments showed that for both metal cations, the absorption capacity increased steeply during the first 20 minutes, and after that, this process slowed down and the absorption rate decreased. Until finally, the equilibrium state occurs after about 35 min for cadmium absorption and 40 min for copper absorption. Isothermal tests of Cd(II) and Cu(II) adsorption by NMPb biosorbent in a discontinuous and single-component system with the same conditions of pH equal to 5, adsorbent dosage of 1.56 g/L, temperature of 25?C and the time required to reach The balance was done. The maximum absorption capacity calculated using the Langmuir isotherm for the absorption of Cd(II) and Cu(II) in the single component system is equal to 310.4 and 136.0 mg/g, respectively. Also, according to the results, the Langmuir model for the absorption process of each of the metal cations is the most suitable model for fitting the laboratory data due to having the lowest values ??of the error function and the highest coefficient of determination R2.   

بيماري‌هاي ريه داراي آمار بالاي مرگ و مير در جهان هستند. دراين‌ميان آسم به عنوان شايع‌ترين بيماري شناخته‌مي‌شود و طبق گزارشات در سال ???? بيش از ?? ميليون نفر در آمريكا مبتلا به آسم بوده‌اند. بسياري از روش‌هاي درماني بيماري‌هاي ريوي و همچنين برخي بيماري‌ها، استنشاقي مي‌باشند، بنابراين شناخت رفتار ذرات استنشاقي (آلودگي‌ها و ذرات دارويي) همراه هوا درون مجاري تنفسي امري ضروري است. در مطالعه حاضر چهار نسل از ريه يك خانم ?? ساله سالم و غير سيگاري از تصاوير پزشكي سي تي اسكن استخراج شد. هندسه به 7 ناحيه تقسيم شد، سپس توسط شبكه بي‌سازمان با روش هموارسازي و با سلول‌هاي چندوجهي جهت حل عددي شبكه‌بندي گرديد. جهت شبكه‌بندي، ابتدا هندسه وارد محيط نرم‌افزار اسپيس‌كليم شده و در آن‌جا يكپارچه‌سازي هندسه انجام شد. سپس با استفاده از قابليت توپولوژي مجازي محيط انسيس مشينگ ، صفحات انتخاب شده و با گزينه تركيب سلول، تلفيق صفحات جهت ورود به محيط فلوئنت مشينگ انجام‌شد. سپس به وسيله استقلال حل از شبكه، شبكه مناسب انتخاب شد. از مدل آشفتگي k-?   براي شبيه‌سازي جريان آرام تا آشفته استفاده‌گرديد. ذرات با ديدگاه لاگرانژي و با استفاده از مدل فاز گسسته به ناحيه محاسباتي تزريق شد و مسيريابي و مدل‌سازي الگوي نشست در نواحي مختلف انجام شد. بر روي ساختار جريان در مجاري تنفسي براي نرخ‌هاي جريان مختلف و اثرات پديده‌هاي مختلف به‌وجودآمده در اين مجاري بر روي نشست ذرات بحث گرديد. الگوي نشست ذرات براي نرخ‌هاي مختلف جريان، به صورت منطقه‌اي و كلي به‌دست‌آمد و اثر نرخ جريان، اندازه و شكل ذرات بر ميزان نشست بررسي شد و در نهايت با استفاده از بهينه‌سازي و بهره‌گيري از روش پاسخ سطح و الگوريتم ژنتيك، حالت بهينه براي كمينه و بيشينه نشست ذرات در ناحيه درخت برونش به‌دست‌آمد. راندمان نشست بر حسب پارامتر برخورد نشان داد كه در تمامي نواحي مدل از جمله دهان- گلو، ناي و درخت برونشي، برخورد اينرسي نقش مهمي در نشست ذرات دارد. تحليل ساختار جريان سيال در مدل هندسه نشان داد كه جريان برگشتي، تشكيل گردابه و جت حنجره همگي بر ساختار جريان هوا و الگوي نشست ذرات اثرگذار هستند. ناحيه دهان-گلو داراي بيشترين كسر نشست به ازاي نرخ‌هاي جريان مختلف است. نتايج نشان داد كه تزريق به دو صورت تك ذره و استفاده از تابع توزيع بر ميزان نشست ذرات اثرگذار است. همچنين افزايش قطر ذرات باعث تغيير الگوي نشست ذرات شده و كسر نشست در ناحيه دهان-گلو افزايش يافت و شكل ذرات با اثرگذاري بر روي ضريب پسا، موجب تغيير الگوي نشست ذرات گرديد. از جمله نتايج ديگر اين بود كه بيشترين كسر نشست مربوط به ذرات كروي است. بررسي همزمان اثر قطر، شكل ذرات و سرعت ذرات و آناليز حساسيت نشان داد كه قطر با تاثير 60%، موثرترين پارامتر بر ميزان نشست ذرات است و پس از آن، ضريب شكل و سرعت قرار مي‌گيرند. در نهايت پيش‌بيني الگوريتم ژنتيك، بيشينه نشست ذرات در ناحيه درخت برونش را، 17% گزارش‌كرد، درحالي‌كه براساس نتايج عددي بيشينه نشست ذرات در ناحيه درخت برونش 20% گزارش شد. همچنين كمينه نشست ذرات توسط الگوريتم ژنتيك در ناحيه درخت برونش، 2/0 % گزارش گرديد، درحالي‌كه براساس نتايج عددي كمينه نشست ذرات در اين ناحيه، 24/0 % گزارش‌شد.   

AbstractWith the increase in the number ofdistributed generation (DG) and renewable energy resource units (DG/RES) andtheir penetration in distribution networks, microgrids (MG) have become veryimportant. Future of the network stabilityis endangered by increasing the number of Distributed Generation (DG) andRenewable Energy Source (RES) units. The idea of the Virtual SynchronousMachine (VSM) has been raised to control the power electronic-based DG/RESconverters in order to have better integration with the grid. This thesisintroduces a new stabilizer design for VSM-based converters to guarantee thestability of the micro-grid (MG). In this regard, the Sliding Mode Control(SMC) theory, which is robust against the disturbances and uncertainties, isemployed to cope with the intermittent and nonlinear nature of DGs. The mutualoperation of the proposed inverter and MG stabilizer has the followingadvantages: (1) It provides a seamless and robust transition from thegrid-connected to the islanded mode. (2) It is universal, sharing the real andreactive power during islanded mode and acting as a grid-supporting inverter inthe grid-connected mode. (3) It mimics the behavior of the conventionalsynchronous generator resulting in better integration of DGs into the grid. (4)It can be used both in the voltage-controlled and the current-controlledVoltage Source Converters (VSC). (5) It obviates the need for the communicationlinks, Phase Locked Loop (PLL) and islanding detection process. Themathematical model of the whole system has been investigated. The simulationresults, conducted in the SIMULINK/MATLAB environment, confirm theeffectiveness of the proposed controller.Keywords: Microgrid; Sliding modecontrol; Virtual synchronous machine  

   In the process of additive manufacturing of metals, the ability to predict and control the microstructure can reduce the need for subsequent heat treatment. In this research, the numerical simulation of the additive manufacturing process of 316L stainless steel was studied. The ability to predict and control the microstructure of materials in selective laser melting (SLM) requires understanding the thermal conditions during the solidification process. In this research, process parameters were selected with transient thermal characteristics, i.e. temperature and cooling rate. The relationship between the cooling rate and the temperature gradient during local freezing, and the control parameters of the laser selective melting process were investigated, which were the control parameters of the laser scanning speed and the thickness of the powder layer. Also, solidification parameters, namely thermal gradient (G) and solidification rate (R) were investigated to predict the microstructure. In this project, the cooling rate and thermal gradient during solidification were calculated numerically by solving the relevant heat transfer equation using the finite element method in Comsol software, and then the results included the solidification parameters mentioned on the solidification map of 316L stainless steel alloy to predict the solidification microstructure. was imaged The results of this research (obtained using simulation) showed that the microstructure of 316L stainless steel produced by the selective laser melting (SLM) process will be columnar or cellular dendrites. Also, it was found that high laser scanning speed (i.e. speed of 1000 mm/s) leads to finer microstructure. Furthermore, the values of G × R increase from the bottom to the top of the melt pool geometry, leading to a finer structure in the top region. But the values of G/R decrease from the bottom to the top of the molten pool geometry. Also, in this research, it was found that the greater the thickness of the powder in each layer, the lower scanning speed should be used so that the laser heat flux can melt the powder and the sub-layer completely. By increasing the laser scanning speed from 200 to 1000 mm/s, the width decreases from 85 microns to 58 microns and the depth of the molten pool decreases from 23 to 13 microns, but the length of the pool increases from 93 to 97 microns.

     افزايشانتقال حرارت همواره يكي از موضوع­هاي موردعلاقه پژوهشگران بوده است و پديده جرياندوفازي جوشش در كانال‌هاي عمودي به دليل بالا بودن ضريب انتقال حرارت و استفاده دررآكتورهاي هسته­اي از اهميت ويژه­اي برخوردار است. در اين رآكتورها در صورت دفعنامناسب حرارت و افزايش دماي ديوار، قلب رآكتور دچار حادثه شده و اصطلاحاً شارحرارتي بحراني يا در نوع جريان مادون سرد جوشش انحراف از جوشش هسته­اي رخ داده كهتلاش­ به منظور پيش­بيني و بهبود آن به منظور جلوگيري از آسيب­هاي ناشي از رخ دادناين پديده بسيار ضروري به نظر مي­رسد. در پايان نامه حاضر جريان جوشش مادون سرد آبو فروسيال (نانوسيال مغناطيسي) در يك لوله­ي عمودي به طول 2 متر و قطر 15.4 ميلي­متر،تحت شار حرارتي ثابت روي ديوار به صورت دائم، در حالت دو بعدي با استفاده از نرمافزار Ansys Fluent به صورت عددي موردبررسي قرار گرفته است. براي شبيه­سازي مدل جريان دو فازي از مدل اويلرين، براي مدل­سازيفرآيند جوشش روي ديوار از مدل RPIو براي مدل­سازي آشفتگي از مدل SST k-?

  In this research, the effect ofroughness on thermal creep flow in microchannels has been investigated. Forthis purpose, a planar microchannel is considered in which a linear temperaturegradient is applied on the walls. In order for the wall temperature gradient tobe the only factor for creating the flow, the pressure at the inlet and outletof the microchannel is assumed to be the same. The dimensions of the channelare 0.2 x 1.2 µm, and different linear temperature gradients are applied to itswall. The flow is in the range of 0.002 ? Kn ? 0.2, that is, the slip flowregime. The governing equations, including continuity, Navier-Stokes and energyequations along with the velocity slip and temperature jump boundaryconditions, have been solved in the COMSOL Multiphysics software environment.Roughness is modeled using W-M fractal function, which is a completely randommodel. The effect of various fractal roughness parameters on thermal creep flowhas been investigated in detail, including relative roughness, 0 ? ? ? 4,fractal dimension, 2 < D < 1, and roughness density 1 ? Rd ? 5. Theresults show that the mass flow rate in rough microchannels is lower than thesmooth ones; And this decrease is more noticeable in higher Knudsen numbers.Therefore, in small Knudsen numbers and close to the continuum flow regime, theroughness effect is less important. For example, a high relative roughness of4% in near continuum flow with Kn = 0.002, leads to 15% decrease in mass flowrate; While the relative roughness as small as 0.5% in the Knudsen number of0.2 causes the mass flow rate to decrease by more than 27% compared to thesmooth channel. In general, it was observed that in different conditions, themass flow rate increases with the decrease of relative roughness, but there isa limit beyond which the flow behavior becomes independent of the roughnessheight, that is ? = 1%. So that, in the relative roughness of less than 1%, theflow is independent of the roughness parameters and the mass flow rate remainsalmost constant. In addition, it was found that the increase in roughnessdensity strongly reduces the mass flow rate, so that at high densities (Rd =5), the effect of thermal creep flow almost disappears. These last two featuresare specific to thermal creep flow and are not seen in pressure-driven andshear-driven flows.

The rapid economic growth in the world has led to anincrease in energy consumption during the last decades. According to recentstudies, the energy consumption of cooling and heating systems in buildings isabout 60%. As a result, any development in thermal system technology to lessenenergy consumption, especially in buildings, is welcomed. Phase changematerials (PCM) with high density for energy storage are one of the mosteffective ways to reduce energy consumption in buildings. In this thesis, usingDesign Builder version 7 software, heat transfer of a 4x4x3 electrical facilityroom located in Tehran city is simulated. Throughout these simulations, thethermal behavior of wall equipped with PCM layers has been examined. The various parametersof wall and PCM considered in the simulations include the thickness,conductivity coefficient, melting temperature of PCM material, and also heatgeneration within the room. The results showed that by increasing the thicknessof PCM, the amount of daily thermal load of the building decreases and as aresult, the thermal performance of the room is improved. By changing thethickness of PCM from 5 to 10 cm, the thermal performance coefficient of PCMincreases by 20-25% depending on the melting temperature of PCM. It is foundthat there is an effective thickness for PCM, after which increasing thethickness has a negligible effect on reducing the thermal load. As anotherresult, it was found that the conductivity coefficient has a small effect on thethermal performance coefficient so that for all the studied cases, the effectof conductivity changes in the range of 0.2 to 2 W/m2 °C on the thermalperformance coefficient is less than 13%. Also, the results showed that anincrease in the internal production of heat, leads to a decrease in the valueof the thermal performance coefficient, and in this case, the phase changematerial has a poor performance.  

Displacement of vents for the internal comfort of the building  

Controlling the heat generated by electronicequipment and microelectromechanical systems at high capacities is importantfor optimal performance and greater reliability. Open microchannel heat sinksare a new geometry of microchannels heat sinks that are important due to theirlower manufacturing cost and better heat transfer performance. In this research, heat transferand fluid flow characteristics of open microchannel heat sink in 17 differentgeometries, which includes 3 main shape of rectangular fins, plano convex fins andplano concave fins, that variable fins base heights varied from 0.4-0.7 mm, andin 2 shape of plano convex fins and plano concave fins on the same variablecurve range coefficients 0.20-0.5 for plano convex fins shape and 0.35-08 Forplano concave fins shape   on an equal finsbase height which the convective surface area and the materials that arerequired to build a heat sink are equal have been investigated. Openmicrochannel heat sink cooled by water fluid in   a laminar flow and single phase flow   that Reynolds number varied from 100-600 andheat flux 100-600 kWm2   that numericallyand in a three-dimensional geometry analyzed by Ansys Fluent software. At thesame heat flux, Reynolds number and fins base height, the Nusselt number of therectangular fins shape is less than the two shapes of plano convex fins andplano concave fins.in Comparison of two shapes of plano convexfins and plano concave fins in the lower fins height, the Nusselt number of theplano concave is more than plano plano convex and in the higher fins height,the Nusselt number of the plano convex is more than the plano concave. Despite the fact that at high heightsin the fins, where the Nusselt number of the plano convex fins shape is greaterthan the rectangular and plano concave   shape,but the plano convex pressure drop is less than these two shaps. The results show that at the end of the path, where theheat sink temperature is higher, in the plano concave model due to the moreconvective surface area at the end of the path has a lower critical temperatureand temperature non-uniformity. Despite the higher Nusselt number in plano convex finsshape in the curve coefficient of 0.80, 0.65 and 0.50 Compared to other plano concavefins shape in curve range coefficients of 0.35 and0.20, have a lower pressure drop than the above shapes.  

Choosing an optimal filteration system can reduce operating, repair and breakdown costs in many industries. If the suspended particles in the fluid are magnetic ones, magnetic filters can be used to separate them. Since internal magnetic filters are not able to separate FeS particles and other sub-micron particles, the use of high gradient magnetic filters is suggested as a solution. An important parameter in evaluation of these filters is the rate of adsorption of suspended particles in the liquid. Therefore, in this research, with the aim of COMSOL simulation software, the amount of particle adsorption and the effect of effective parameters on this parameter have been investigated. In both two-dimensional and three-dimensional simulations, a transverse configuration with a constant matrix diameter and a constant magnetic flux density is used. Important parameters of this research are the Reynolds number of the flow, the transverse distance of the rod matrices and the particle diameter. In three-dimensional analysis, according to the given variable parameters, the horizontal distance of the matrices and Reynolds number play an important role in the amount of particle adsorption, so that for horizontal distances greater than H = 1.4, the particle adsorption rate is significantly reduced, and the percentage Particle absorption is below 27%. It was observed that changing the particle diameter has less effect on the particle adsorption rate. The highest particle adsorption in the fluid occurs with the magnetic field strength of 1 Tesla with a rectangular arrangement for the horizontal distance H = 1.4 and the Reynolds number Re = 2, which has an adsorption rate of about 35%. The absorption rate of particles in the three-dimensional state is approximately one-half that of the absorption in the two-dimensional state. This can be explained due to the fact that all variables in two-dimensional and three-dimensional simulation were the same. Therefore, the same number of particles is considered in both geometries leading different values of adsorption.   

Abstract    Industrial processes that involve the heating and cooling of a variety of fluids flowing through the ducts are very extensive and today represent some of the most common and important processes in engineering. Actually, in heat engineering, forced convection is probably one of the most effective and widely used heat transfer tools. Metals in their solid form have much higher thermal conductivity than fluids, which is why it is expected that fluids containing metallic suspended particles or metal oxide will have higher thermal conductivity than pure fluids. In the present work, the effect of magnetic field on the fluid flow and heat transfer of a nanofluid in the tube is experimentally studied, and the nanofluid is a type of Fe3O4   magnetic nanofluid with distilled water base fluid. After designing the experimental apparatus, experiments conducted to investigate the effect of the main operating variables such as voltage applied to an electric field applied with an alternating current (V), nanofluid concentration (C) and the intensity of the inlet fluid flow to the sub-field (Q) on the difference between the inlet and outlet temperature of the nanofluid. The channel crossing was selected based on the design of the experiments using response surface methodology based on the Box-Behnken model. The values of the variables in the study of the effect of applied voltage are 40, 80 and 120 volts, concentration of nanoparticles in solution of 0, 0.02 and 0.04   gL   and fluid flow intensity of 180, 360 and 540 L

چكيده اين پژوهش به بررسي عددي تاثير امولسيون حاوي مواد تغيير فاز دهنده ميكروكپسول شده بر روي انتقال حرارت جا بجايي در جريان آشفته، درون يك لوله افقي با شرط مرزي شار حرارتي ثابت مي پردازد. براي اين منظور، امولسيوني بر پايه آب حاوي غلظت هاي مختلف ميكروكپسول با هسته ميريستيك اسيد به عنوان ماده تغيير فاز دهنده بررسي شد. همچنين تاثير غلظت ميكروكپسول ها بر روي عدد ناسلت ، ضريب هدايت حرارتي، ضريب اصطكاك و دماي لوله مورد مطالعه قرار گرفت. براي انجام تحقيقات، مسئله شامل لوله و شار ثابت و امولسيون تغيير فاز دهنده در نرم افزار كامسول شبيه سازي شد . نتايج نشان داد كه افزودن ميكروكپسول هاي تغيير فاز دهنده به آب منجر به افزايش عدد ناسلت، ويسكوزيته و انتقال حرارت جابجايي در تمامي رينولدزها مي شود . همچنين مشخص شد با افزايش كسر حجمي اين افزايش همچنان ادامه دارد اما ضريب اصطكاك هم افزايش مي يابد كه منجر به ايجاد اختلاف فشار مي شود . در اين پژوهش علاوه بر موارد گفته شده مقدار ضخامت ميكروكپسول ها نيز مورد بررسي قرار گرفت كه مشخص شد با كاهش اين ضخامت با بيشتر شدن حجم ماده تغيير فاز دهنده، ميزان اثرگذاري امولسيون بر انتقال حرارت هم افزايش مي يابد .   

چكيده در مطالعه حاضر به بررسي عددي انتقال حرارت جابجايي طبيعي در حفره مربعيمتخلخل اشباع شده از نانوسيال آب اكسيد آلومينيوم پرداخته شده است. هندسه موردبررسي شامل يك حفره مربعي با دو دايره داخلي است . دماي دايره ­هاي داخلي ثابت،گرم و سرد مي­باشد. دماي ديواره هاي عمودي به صورت سينوسي تغيير مي­كند هاي افقي نيز عايق مي­باشند. نانوسيال به صورت تك فاز مدل سازي شده است. برايجريان سيال در محيط متخلخل نيز از مدل دارسي برينكمن فورچهيمر استفاده شده است. نتايجتحقيق شامل بررسي اثرات پارامترهاي عدد رايلي، عدد دارسي، درصد حجمي نانوذرات،عدد ناسلت ميانگين، عدد ناسلت محلي، پروفيل­هاي سرعت و دماي بي بعد و خطوط جريانفاصله بين مركزهاي دايره­هاي داخلي، و استفاده از نانوذرات مختلف و همچنين اختلاف فاز ديواره­ها بر رويجابحايي طبيعي   خطوط جريان و دماي بي بعد به سمت نيمه بالايي ديواره سرد و نيمه پاييني ديواره گرم متمايل مي­شود.مي­باشد. نتايج نشان داد افزايش عدد رايلي و دارسي سبب بهبود انتقال حرارت جابجايي و به تبع آن باعثافزايش عدد ناسلت و سرعت جريان در محفظه مي­شود. با افزايش عدد رايلي و بهبود افزايش كسر حجمي نانوذرات باعث افزايش لزجت نانوسيالو كاهش سرعت نانوسيال در محفظه مي­شود و افزايش نيروي شناوري مي­شود. افزايكسر حجمي نانوذرات در اعداد رايلي و دارسي تاثيرات متفاوتي بر روي عدد ناسلتميانگين دارد در اعداد رايلي كوچك و دارسي بالا افزايش كسر حجمي نانوذرات سببافزايش عدد ناسلت مي­شود اما با افزايش عدد رايلي از تاثير افزايش كسر حجمي نانوذرات كاسته شده و در برخي از اعداد رايلي و دارسي مختلف تاثير متفاوتي بر انتقال حرارت و عدد ناسلت دارد.افزايشو دارسي سبب كاهش عدد ناسلت مي­شود. افزايش فاصله بين دايره­هاي داخلي در اعداداختلاف فاز ديواره سرد سبب افزايش عدد ناسلت ديواره گرم مي­شود. از بين نانوذراتاستفاده شده نانوذرات مس به دليل داشت هدايت حرارتي بيشتر، عملكرد بهتري در بهبودانتقال حرارت دارند  

  Drug delivery within the human body has a significant role in the treatment of many diseases. There are different methods for tra  orting a pharmaceutical compound to a specified part of the body among which magnetic drug targeting is of great attention.   A magnetic drug delivery system utilizes the magnetic field to tra  ort the magnetic nanoparticles as a means of a delivery vehicle. Therefore, it is possible to control the delivery of the drug in such a way that the particles of the drug to be focused adequately where necessary. This will accelerate the recovery of the disease and also prevent the destruction of healthy tissues by the drug. Cardiovascular diseases are one of the major causes of deaths of women and men in recent years which have different types. One of the most common cardiac diseases is abdominal aortic aneurysm. In this disorder, due to the weakening of the vessel wall and blood pressure, the aortic vessel in the abdominal region expands and may lead to tearing of the vessel. Usually, treatment of this disorder is aggressive and has a high risk. But an alternative approach based on embolization of aneurysm, brought up recently seems to be a cure for this disease. In this method, aneurysm region will be targeted by particles of demanded drug, using an external magnetic field. So the pressure on targeted vessel wall will reduce. In this thesis, the three-dimensional transient flow of blood and transfer of drug are simulated with Eulerian-Lagrangian approach in the region of abdominal aorta vessel suffering from an aneurysm. According to the physics of the problem, the oscillating velocity at the inlet with non-Newtonian fluid are considered for the blood flow and the effect of aneurysm geometry, magnetic field and specifications of drug particle are studied. The results indicate that an increase in the size of an aneurysm, vertical distance between aortic vessel and magnetic source and Reynolds number leads to a decrease in the efficiency of drug absorption. At the other hand increasing the strength of magnetic field, size of particles and magnetization of nanoparticles leads to increase in the capture efficiency. These findings can be used to design and develop the drug targeting systems for the human body.Keywords: Magnetic drug targeting, abdominal aortic aneurysm, magnetic nanoparticles, Eulerian-Lagrangian approach, non-newtonian fluid

    Numerical Analysis of the influence of the aspect ratio and angle of tube in vacuum tube solar collectors with modified structure

  Smart materials are a new term for materials with ability of understanding and processing environmental events and show an appropriate response to them. These materials are able to change in their dimensions, colors and energy in a reversible manner in response to the physical or chemical effects of the environment. In recent years, using intelligent materials has been expanded in a wide range of new technologies. Magnetolectroelastic materials are the most important types of these materials, which provide the ability to interact between magnetic, electrical and elastic properties in a single compound form. In this present research free vibration, static and dynamic response of functionally graded Magnetolectroelastic beam have been investigated for these materials. The studied beam has different support conditions and relations are based on two-dimensional elasticity theory. The equations of motion are extracted using the Hamilton principle and solved by finite element method. The mechanical, electrical, and magnetic properties of this beam vary in thickness according to the power low distribution. Finally, the accuracy of the responses was compared with the results of previous studies including the static and dynamic response of the system, the effect of various geometric parameters, auxiliary and volume fraction indices on natural frequencies were investigated. According to the results, it is observed that with increasing the volume fraction of functionally graded material, the natural frequency increases. In the static response study, with the increase of the volume fraction indices in different supporting conditions, the deviation of the middle of the beam decreases. The greatest divergence of the middle in the beam is with clamped-free boundary condition and the middle cavity deviation is reduced in beams with simply supported, clamped-simply and clamped-clamped boundary conditions, respectively. The solutions obtained from finite element solvers based on the two-dimensional elasticity theory are in good agreements with theory of beams.

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بررسي قابليت اطمينان شبكه هوشمند با لحاظ نمودن خودترميمي شبكه در حضور منابع توليد پراكنده

  The lightweight steel frame (LSF) structure, is a building system used primarily for short-term and intermediate-level buildings. Due to its plenty of advantages compared to other existing systems in construction, the use of this system is increasing. In this structure, cold formed steel sheets (CFS) are used to make thin-walled steel sections. These sections are galvanized steel sheets, which are formed using cold forming. In this system, CFS beams and columns are used as barrier members. The beams used in this system are often made up of 0.5 to 3 mm, which, Because of their low thickness, they are prone to buckling. This geometric feature affects their load-bearing capacity and makes it impossible to can not to use the load bearing capacity of the sections well. Therefore, using the method that increases the resistance buckling of beam, it can be used the load-bearing capacity more efficiently.An ideal method for achieving this goal is to create a bracing for the CFS beams by casting concrete around the web. the concrete can provide bracing for beam and improve the buckling resistanae of it. For this purpose, the ultra-lightweight-concrete encased cold-formed steel beams have been investigated. This concrete has a slight compressive strength and is often used as an insulating or filler material, but it has now been found to be structural performance.In this study, using finite element analysis, polystyrene aggregate concrete (PAC) encased CFS beams under four-point bending loading have been investigated. For this purpose, 2C and 2U cross-section beams with different geometric dimensions were modeled and investigated. The results showed that, using of PAC can provide full bracing for the steel beams and increase their ultimate strength capacity level by 43%. In addition, due to the lightness of this concrete, A slight load is added to the weight of the structure and the advantage of the lightness of the LSF structures is maintained.

  Today, despite significant advances in construction, many of the existing structures against earthquakes do not function properly. The inappropriate seismic behavior of these structures can lead to many fatal and financial damages. In order to prevent such damages, an appropriate and economical solution is to retrofit existing buildings.Considering the damage caused by earthquake in prone to earthquake, it has been observed that joints are one of the most important and vulnerable areas in concrete structures. Therefore, due to the importance of joints in the proper seismic performance of the structure, the behavior of concrete joints and their retrofitting methods against earthquakes has been investigated.In this study, the reinforcement of the external connections of the beam to the reinforced concrete column was investigated using FRP sheets and steel jacket. In this regard, for different makeup of FRP and steel jackets and for three concrete grades 25, 30, 35 Mpa, various parameters such as strength, hardness, energy absorption and ductility were calculated and evaluated.

  AbstractIn the last three decades the use of geosynthetic materials for retaining walls and reinforcing slopes has increased significantly throughout the world. These materials have a very wide range of geotechnical engineering works due to their properties including corrosion and rust resistance, durability, flexibility and so on. The use of geosynthetics increases the resisting forces in the soil mass through tensile forces mobilized in these elements. As a result, there is a reduction in horizontal deformations and an increase in the general stability of soil structures. Geogrid is a member of the geosynthetic family, which is widely used for reinforcing due to the high rigidity and tensile strength and more interactions with soil particles. In the recent decades, several experimental and numerical investigations have been carried out to determine the bearing capacity of shallow foundations on soil reinforced by different types of materials. Recently A new type of geosynthetics called grid-anchor has been introduced to increase the load capacity of soil soils. Grid-anchor is made by changing the structure of the typical and adding polymeric anchors to it. Grid-anchor has great pullout strength than the common geogrid when it deals with the sandy soil. The basic difference between common geogrids and grid-anchor is existence of short anchors attached to the geogrid on one side which provides great pullout strength for grid-anchor that This can improve the performance of most of the structures that are reinforced with it. In this research, A series of model tests has been carried out to evaluate the effect of using grid-anchor on performance of soil reinforced retaining walls to evaluate the effects of offset distance of a strip footing on lateral displacements of the wall facing and bearing capacity of strip footing. The results of this study showing that by using of Greid Anchor to reinforcing retaining wall can be increase bearing capacity 5.6 time more than unreinforced condition and 1.5 time more than increase toward arming with Geogrid. Furthermor, The Greid Anchor can reduce the side walls displacement of the wall by 65% compared to unreinforced condition and 16% relative than the reinforcing position with the Geogrid. Also, the highest BCR(Bearing capacity ratio) in the distance b= 0.1H and the lowest amount WDR( wall displacement ratio) in the distance b= 0.4H toward by the edge of the wall.

The bulk of energy consumption and greenhouse gas emissions are attributed to buildings. The heating of water required for buildings consumes a considerable amount of energy. As a result, the use of solar water heaters can play an important role both in the storage of fossil fuels and in reducing air pollution and emissions of greenhouse gases. Many factors affect the thermal and economic performance of solar water heater systems. In this thesis, a forced-circulation solar water heater system has been simulated with flat plate collectors as well as a evacuated tube collectors. Given that the performance of solar systems is inherently dynamic and tend to vary over time, simulation has been done dynamically. The main objective of this thesis is to study the effect of hot water consumption patterns on the thermal and economic performance of solar water heaters. In addition, by applying different patterns of water consumption, appropriate values of collector mass flow rate and volume of hot water storage tank are determined based on the achievement of the highest thermal performance of the system. Moreover, the appropriate values of collector area are determined to achieve the most economic performance of the system. The results show that by choosing the consumption pattern that is almost identical to the hourly variations of the solar radiation, compared to other consumption patterns, system achieves the largest annual solar fraction in lower ratio of tank volume to collector area. Furthermore according to the results the hot water consumption patterns can have a significant effect on both the annual life cycle saving and the pay back time of the system. On the other hand, due to the low radiation from 6 to 10 AM and the heat loss of the storage tank over night, the auxiliary energy required during these hours, increases. This, in turn, will increase the cost of energy supply to the auxiliary system as well as the solar systems pay back time. Substitution of hot water consumption patterns with flat plate collectors for those employing evacuated tube collectors might increase the annual life cycle saving to a remarkable extent.

This research discusses photovoltaic cell modeling with two diodes. With respect to the problem parameters and available equations, seven parameters were recognized as unknown parameters. The parameters were determined by descending numerical sequence. A mathematical model was created using governing equations and a model was coded and prepared in MATLAB. The code was validated and the results were compared with the credible works carried out in this field. After being ensured of the validity of the code, different parameters effective in current and power were discussed in a photovoltaic array. Finally, optimization of problem parameters was discussed. To determine the important and effective parameters, the literature was referred to. Studying the literature revealed that most of the studies discussed and optimized the seven parameters to maximize the power generation. Consequently, this study discussed model optimization using the determined parameters, adopting an appropriate change interval, and applying meta-heuristic algorithms. Genetic algorithm and particle swarm algorithm have been used commonly and have been effective in this field. Therefore, the two algorithms were used and their results were presented. The remaining section discusses and evaluates the results.It was concluded form the results for examining radiation parameters that the major parameters on radiation include geographic location, day of year, and ambient temperature. Efficiency and power generation improve with the parameters increasing. Maximum power increases up to 6 times with the amount of radiation increasing from 200 W/m2 to 1000 W/M2. (Figure 1-6 shows the changes.)The study of the amount of radiation on different days of the year determined that the amount of power on the first day of summer was higher because the amount of radiation was maximal. Ambient temperature increases on summer days. The temperature rise improves PV efficiency. Temperature variations from 20 to 40 indicate an increase of power generation from 27 to 83 watts, which represents a 3-fold increase. According to reference [61], it was selected for optimization of parameters and its proportional interval. The results of genetic algorithm show that a maximum power of 74.27 watts could be generated.

In this study, natural convection flow in a micro enclosure is investigated using direct simulation Monte Carlo (DSMC) method. Argon molecules are used for gaseous medium. The sidewalls of the enclosure are subjected to various boundary conditions including adiabatic, constant temperature and symmetry where symmetry boundary condition simulates the flow in a long channel. The aspect ratio of the enclosure is set to AS = 2. The lower wall is heated to temperature TH and the upper wall is cooled to TL while the thermal ratio is preset to rT = TH/TL= 0.1. Similar problem for macro-scale channels which is known as Rayleigh-Benard problem is widely investigate. However, the micro enclosure problem which classified as rarefied flow is still under study. The Knudsen number is assumed in the range 0.001 ? Kn ? 0.12 and a wide range of 0.2 ? Fr ? 10000 is studied for Froud number. The results show that the thermal creep effect has an important role in formation of convective rolls in the enclosure. Unlike the channel flow where no vortex will appear in adequate low or high Froud numbers (based on Knudsen number), in enclosures we have vortexes in all Froud numbers at all Knudsen numbers due to thermal creep phenomenon.   It is shown that the heat transfer rate is the same for channel and enclosure at very small or very high Froud number. However, for mediate Froud numbers heat transfer rate decreases in enclosure as where the side walls resist against convective rolls. The bounds for the values of high or low Froud number depend on the Knudsen number. Finally, the ability of SBT collision scheme in simulation of Rayleigh-Benard convective flow is evaluated in this study. Comparing to NTC scheme which is conventional collision scheme for DSMC method, it is shown the SBT scheme is accurate enough to simulate the Rayleigh-Benard instability flow.

  The Ti-6Al-4V alloy with good tribiological characteristics, low elastic modulus, high strength to weight ratio and the Co-Cr-Mo with excellent resistance to corrosion and erosion, are practical as metal bio-materials in artificial joints. The Co-Cr-Mo alloy leads to reduced corrosion in the thigh joint and the Ti-6Al-4V alloy easily pairs up with surrounding bones and is therefore preferred for thigh stem. To build such a bimetal system, given the disparity of welding parameters, connection is a big hurdle. Different welding methods such as fusion welding, laser welding, hard and soft soldering, and penetration bonding for simillar and disimillar bonding of these alloys have been used. In this study, the transient liquid phase   rocess has been used for the Ti-6Al-4V/Co-Cr-Mo dissimilar system in order to address the shortcomings of other welding methods and access mechanical properties comparable with base metal. In this method, samples were cut as cylinders with 8 mm in diameter and 5.7 mm in height and their surfaces were prepared for bonding. An copper interlayer was placed between the two surfaces as covering on cobalt sample, and a constant pressure of 1 MPa was applied to the samples using fixture. Next, the bonding set was exposed to heating in under-pressure stove with the different temperatures of 925, 950 and 975, considering the eutectic temperature of Ti-Cu (about 875 °C), for 5 to 120 minutes. On the connected samples, cross section cut was performed and the substructure was studied using optical microscope. Results suggested that as a result of the bonding, 3 zones of DAZ (diffusion-affected region), ASZ (athermally solidified zone), and ISZ (isothermally solidified zone) appear in the bonding point, with the length of these zones differing depending on conditions of performing the bonding, and as joint temperature and duration increases, the athermally solidified zone can be removed, thus leading to progressed isothermally solidification during the bonding. Cut test was used to investigate mechanical strength of the samples, with the maximum shear strength equal to 350 MPa, which is around 50% of the base metal, obtained for the bonding made at 950 °C and in duration of 2 hours. Also, the failure level of the samples was identified with the X-ray diffraction test and failure level combination was considered. Type of failure and elements present in different phases of sample cross-sections were investigated using scanning electron microscopy. Elements constituting present elements were identified via the EDS test, and element changes in the sample were obtained with linear analysis. Keywords: transient liquid phase (TLP), Ti-6Al-4V, Co-Cr-Mo, evaluation of microstructure, mechanical properties, copper interlayer  

  The present work is aimed at energy and exergy analysing of a IX-SAHP system considering the effects of the pressure drop associated with the ?ow of R134a refrigerant through the condenser, evaporator and connection pipes and the flow of Ethylene glycol through the collector, using Homogeneous method for two-phase pressure drop inside horizontal pipes. This system mainly employs a collector with a surface area of 5.5 m2, a hot water tank with the volume of 150 L, an electrical rotary-type hermetic compressor and a thermostatic expansion valve. The effect of various parameters, including solar radiation, ambient temperature, collector surface area, compressor speed and number of collector cover has been studied on the thermal performance of the system. The simulation results have good agreement with experimental results and they indicate that with the increase in ambient temperature (Ta) from -5 to 30 °C, for a given solar radiation of 700 W.m-2, the system COP and collector ef?ciency (?C) increases from 2 to 3.5 and from 35.8 to 58.8%, respectively. With the increase in radiation intensity (IT) from 350 to 1200 W.m2, for a given ambient temperature of 20 °C, the system COP increases from 2.1 to 5.5 and collector ef?ciency decreases from 71.4 to 45.6% and also with increasing ambient temperature, solar radiation and compressor speed, the pressure drop in the condenser, collector and evaporator increases.

  AbstractIn this thesis, a model has been introduced to simulate the capture efficiency of 3D high gradient magnetic filters for the separation of iron sulfide particles from the amine solution in the sweetening gas process. The geometry of the filter consists of a matrix of rods located in a channel with a square cross section. In order to study this problem, initially the Navier-Stokes equations coupled with Ampere equation are solved numerically in a 2D geometry. Having the flow field, the problem of particle capturing has been studied due to Lagrangian viewpoint and the effects of governing parameters including the particle diameter, fluid velocity and the geometrical parameters of the matrix have been investigated. Finally, the results of 2D analysis have been extended to simulate the particle capturing in a 3D filter. The 2D numerical simulations have been performed with COMSOL MULTIPHISICS 5.0 based on the finite element method and the extension of results to the 3D case has been carry out with proper code in MATLAB. This code interpolates or extrapolates the 2D results for any cases rather than those simulated in COMSOL. It has been demonstrated that the capture efficiency of filters with triangular configuration is higher than the rectangular one in the same conditions because the triangular configuration provides a better fluid mixing. However, the difference between capture efficiency of these two filters decreases with the increase in fluid velocity or distance between the matrices or decrease in particle diameter. Also, it has been demonstrated that the capture efficiency of these filters is directly related to the particles diameter and reversely dependent to the fluid velocity and the distance between the matrices. In addition, the performance of these filters are investigated in the case of non-uniform distribution of particles in the inlet. In order to demonstrate a useful graph, the performance contours of the 3D filter in the operational conditions are presented in terms of Reynolds number and the distance between the matrices. These counters show that the capturing efficiency of 60% will maintained when the dimensionless distance between the matrices is less than 1.2 independent of the Reynolds number.   Keywords: Magnetic filter, Capture efficiency, High gradient magnetic separation, Particle tracing

  Nowadays,it has been proven that improvement of   pavement surface texture charactristics and surface drainage condition is an important matter in safety improvement and decreasing of accidents rate specially in wet weather condition. Researches on the relationship between pavement surface charactristics and accidents rate date back to the 1960s, but there is no research done in the field of surface drainage.     This research has proposed a system that has the ability to simulate the saturated situation and assessing of pavement surface drainage with a high speed and precision.To do so, an innovative device is presented to simulate the saturation condition of pavement surface and acquire photo from drainage process of pavement surface after saturation.The proposed system is based on image processing methods.     The preprocessing and enhancement of images was performed using image processing techniques.Then the Morphological features of the images were extracted and the rate of surface drainage progress was evaluated by three indices extracted from the images. Finally, pavements were ltr">The results of the pavement surface drainage system as the first system in this field can be used in safety assessment systems in both project and network level to enhance road safety specially in wet weather condition.