The growing energy consumption in buildings is one of the major challenges to sustainable development, especially in countries such as Iran with diverse climates and high dependence on fossil fuels. Employing passive solar strategies such as the solar chimney, together with innovative technologies like thermochromic and electrochromic coatings, can play a significant role in reducing heating loads and improving thermal comfort. This study aims to investigate the performance of a hybrid system consisting of a solar chimney integrated with these smart coatings and to compare their effects during January 2022. The research was conducted in two cold Iranian climates: Tehran and Ardabil. The designed system comprised a vertical solar chimney with glazed façade, internal absorber surface, and inlet/outlet vents, simulated in DesignBuilder and EnergyPlus software. Input data included climatic datasets (EPW), building material properties, optical and thermal characteristics of the coatings, and window-to-wall ratios of 30% and 70%. Simulations were carried out for three consecutive days (10–12 January 2022) within the time interval of 09:00–15:00. Five main scenarios were defined: (1) a base model without solar chimney or smart coatings in a test room of 3 × 2.7 × 2.7 m³; (2) addition of a solar chimney with single glazing at 30% and 70% WWR; (3) replacement of single glazing with double glazing at 70% WWR; (4) application of thermochromic coating on the chimney glazing in Scenario 3; and (5) application of electrochromic coating on the glazing in Scenario 3. Results showed that thermochromic coating increased average indoor air temperature by 4.41 °C in Tehran and 6.06 °C in Ardabil, reduced daily heating demand by 22.5% and 24.9%, and improved thermal comfort indices. Overall, findings highlight the efficiency of integrating solar chimneys with smart coatings in cold Iranian climates, providing a basis for future research on combining these technologies with other building energy management systems.   

      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.

  This thesis, titled Designing a Green School in Kermanshah City with a Sustainable Ecological Self-Sufficiency Approach and Reducing Carbon Emissions, examines solutions for designing educational spaces with an emphasis on the connection between humans, culture, and the environment. The necessity of conducting this research stems from the increasing need to reduce energy consumption, optimize environmental behaviors, and promote cultural awareness among the new generation. Schools, as one of the most important educational and social spaces, play a fundamental role in shaping environmental attitudes and can become a platform for scientific education of the concepts of sustainability and environmental responsibility. The main goal of this thesis is to present a local model for designing a sustainable school in the Kermanshah region that, while reducing energy consumption and carbon dioxide emissions, also leads to improving students' cultural and environmental awareness.The design was carried out in two parts: physical and social. In the physical part, the focus was on the use of passive technologies, especially the Trombe wall enhanced with layers of phase-change materials and new materials such as concrete and recycled aluminum. In the social part, relying on the concept of cultural ecology, an attempt was made to design the spaces in a way that would strengthen the students’ sense of belonging, responsibility and environmental awareness. A review of the background of studies shows that sustainability approaches in school design often focus on technical and energy aspects, and the connection between culture, behavior and architecture has received less attention. However, new research shows that combining cultural considerations with energy-saving solutions can have a significant impact on thermal sustainability, quality of life and environmental behaviors.Accordingly, this thesis seeks to answer the question of whether it is possible to achieve an efficient model for self-sufficient schools in terms of energy and environmental culture by combining the principles of cultural ecology and design based on reducing dependence on fossil fuels

   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.

   اين رساله به بررسي نقش انرژي خورشيدي در كاهش مصرف انرژي ساختمان پرداخته است، در قدم اول اين پژوهش به بررسي روشنايي طبيعي ساختمان پرداخت شد و با اختصاص دادن 30 درصد بازشو به پوسته هاي خارجي بنا مقدار روشنايي طبيعي مطلوبي كه در حد استاندارد LEED باشد براي ساختمان تامين گرديد. در قدم بعدي عايق كاري جدارهاي خارجي انجام گرديد و مشخص شد استفاده از عايق هاي حرارتي مي توانند نياز ساختمان به انرژي را كاهش دهند در همين راستا پنجره هاي ساختمان نيز از حالت تك جداره به دو جداره تغيير كرد و با احداث دو مدل سايبان بر روي پنجره ها تلاش شد كه مصرف الكتريسيته كه جهت خنك سازي بنا استفاده مي شد با اين راهكار كاهش يابد. همچنين با استفاده از ديوار ترومب و ايجاد تهويه طبيعي در ساختمان مقداري ديگر از انرژي مصرفي در ساختمان كاهش يافت و در آخر با هوشمند سازي تجهيزات الكتريكي ساختمان، استفاده از تاسيسات سرمايي و گرمايي با راندامان بالا و جايگزين كردن آنها با سيستم ها با كارايي كمتر مقدار مصرف انرژي را كاهش داد. در نهايت با قرار دادن سلول‌هاي خورشيدي بر روي بام بخش زيادي از انرژي مورد نياز ساختمان تامين و مقدار توليد كربن دي‌اكسيد بنا نيز منفي شده است. در انتهاي رساله اعتبارسنجي طراحي پژوهش صورت گرفت و ساختمان طراحي شده با ساختمان واقعي كه هر دو در يك اقليم و شهر قرار داشتند مقايسه شدند و نتايج نشان داد كه با استفاده از راهكارهاي استفاده شده در اين پژوهش مي توان مصرف برق ساختمان را 3 درصد افزايش و مصرف گاز را 86 درصد كاهش داد. كاهش كلي ساختمان با استفاده از راهكارهايي گفته شده 75 درصد مي باشد. اين رساله به بررسي نقش انرژي خورشيدي در كاهش مصرف انرژي ساختمان پرداخته است، در قدم اول اين پژوهش به بررسي روشنايي طبيعي ساختمان پرداخت شد و با اختصاص دادن 30 درصد بازشو به پوسته هاي خارجي بنا مقدار روشنايي طبيعي مطلوبي كه در حد استاندارد LEED باشد براي ساختمان تامين گرديد. در قدم بعدي عايق كاري جدارهاي خارجي انجام گرديد و مشخص شد استفاده از عايق هاي حرارتي مي توانند نياز ساختمان به انرژي را كاهش دهند در همين راستا پنجره هاي ساختمان نيز از حالت تك جداره به دو جداره تغيير كرد و با احداث دو مدل سايبان بر روي پنجره ها تلاش شد كه مصرف الكتريسيته كه جهت خنك سازي بنا استفاده مي شد با اين راهكار كاهش يابد. همچنين با استفاده از ديوار ترومب و ايجاد تهويه طبيعي در ساختمان مقداري ديگر از انرژي مصرفي در ساختمان كاهش يافت و در آخر با هوشمند سازي تجهيزات الكتريكي ساختمان، استفاده از تاسيسات سرمايي و گرمايي با راندامان بالا و جايگزين كردن آنها با سيستم ها با كارايي كمتر مقدار مصرف انرژي را كاهش داد. در نهايت با قرار دادن سلول‌هاي خورشيدي بر روي بام بخش زيادي از انرژي مورد نياز ساختمان تامين و مقدار توليد كربن دي‌اكسيد بنا نيز منفي شده است. در انتهاي رساله اعتبارسنجي طراحي پژوهش صورت گرفت و ساختمان طراحي شده با ساختمان واقعي كه هر دو در يك اقليم و شهر قرار داشتند مقايسه شدند و نتايج نشان داد كه با استفاده از راهكارهاي استفاده شده در اين پژوهش مي توان مصرف برق ساختمان را 3 درصد افزايش و مصرف گاز را 86 درصد كاهش داد. كاهش كلي ساختمان با استفاده از راهكارهايي گفته شده 75 درصد مي باشد.

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.   

      Abstract The present study investigates and analyzes the energy and exergy of solar desiccant cooling systems with the aim of providing thermal comfort in residential buildings with high internal loads in three cities: Ahvaz, Bushehr, and Rasht. Considering the increasing energy demand in buildings and the environmental challenges arising from the consumption of fossil fuels, the use of innovative and sustainable systems in air conditioning has become more important than ever. Accordingly, desiccant cooling systems, which operate based on moisture absorption, have been introduced as an efficient solution for optimizing energy consumption and reducing environmental impacts. The results indicate the high potential of desiccant cooling systems. In this research, a maximum COP (Coefficient of Performance) of 0.404 was recorded for the system at temperatures of 15°C. Additionally, at temperatures of 35°C and 45°C, the COP decreased to 0.32 and 0.33, respectively, indicating better performance of this system at lower temperatures. The analyses also emphasize that the cooling capacity at temperatures ranging from 28°C to 40°C in Bushehr varies between 18.2 to 20.6 kW, and in Ahvaz between 19.5 to 21.5 kW. This research, while providing a roadmap for selecting optimal design parameters, hopes to offer practical solutions for ensuring thermal comfort in hot and humid regions. Overall, the results suggest improved performance of air conditioning systems and achieving thermal comfort in residential buildings through the use of desiccant materials and solar energy. Key words: Solar Desiccant Cooling, Thermal Comfort, Energy and Exergy Analysis, Residential Buildings, Hot and Humid Climates   

  One of the most important sources of energy for the

   In recent years, fluidized beds have garnered attention across various industries due to their advantageous characteristics, such as uniform temperature distribution, effective phase mixing, and high heat transfer rates. One effective method to enhance the efficiency of these beds is the use of a pulsed inlet. This technique improves the homogeneity of the bed and eliminates inactive and stagnant zones (dead zones) within the particles by varying the inlet air flow. Despite extensive research on the simulation of conventional fluidized beds, the study of pulsed bed systems has been relatively limited. In this thesis, the gas-particle two-phase flow in a spouted fluidized bed with a rectangular geometry and pulsed air inflow was numerically investigated. The simulation was carried out using a combination of Computational Fluid Dynamics (CFD) and the Discrete Element Method (DEM). To reduce computational costs, the geometry was defined as quasi-two-dimensional with a depth of 6 particles. The modeling was performed in a transient state, where a specific number of particles were initially placed at a certain height within the bed, and then gas was injected into the bed at a specified pulsed velocity. In this study, the pulses were applied in three waveforms: square, sinusoidal, and sawtooth, with frequencies of 1, 4, and 10 Hz. The results showed that when fluidizing (side) gases were present in the bed, applying a pulsed inlet in the spout positively impacted the elimination of dead zones and the circulation of particles across all three frequencies and waveforms. It was demonstrated that a frequency of 10 Hz and a square waveform yielded the best results. For instance, in a spouted fluidized bed at 10 Hz, the particle travel distance improved by 12.81%, 5.99%, and 5.97% for square, sinusoidal, and sawtooth waveforms, respectively. Similarly, improvements of 55%, 35%, and 30% were observed in the reduction of dead zones. In rectangular beds, it was found that the removal of fluidizing gases had significant negative effects on particle circulation and increased the dead zones, with the proportion of dead zones rising from 0.5% to 7.7% of the total particles. Finally, to examine the effect of fluidizing gases, different configurations with varying spout and fluidizing gas velocities were investigated. In these configurations, the spout velocity was gradually decreased while simultaneously increasing the fluidizing gas velocity, keeping the total inlet gas flow constant. The results showed that in two configurations where the fluidizing gas velocity reached its maximum, the dead zones were completely eliminated, particle mixing improved, and homogeneity in particle distribution increased. In the optimal gas inlet configuration, applying a square pulsed inlet at 10 Hz resulted in a 1.55% improvement in the average particle travel distance. In this study, it was demonstrated that by applying a pulsed flow and adjusting the inlet gas velocities, the hydrodynamic performance of the bed can be improved without the need for changes in the system geometry or the total inlet flow rate.

   Experimental study of the effect of using phase change materials in heat pipe condensers for cooling of electronic components

   Identification of two-phase flows and its Taylor bubble characteristics is one of the most important parameters designing industrial installations for intermittent gas-liquid two-phase flow. Also, it is important to know the characteristics of two-phase flow in order to improve the exploitation of oil wells and to optimize the process of maintenance and repair of flow transmission lines with the purpose of cleaning pipelines along with reducing its costs in the oil and gas industries and in chemical and electronic chip cooling industry. The purpose of this research to analyze bubble flow patterns, achieve two-phase flow patterns of water and air using numerous experimental tests and investigate the effect of pulsating gas flow on the characteristics of the Taylor flow field (Taylor bubble length and velocity) under different two-phase inlet conditions air and water done in the form of an upward parallel flow. The range of studied apparent velocity Gas and Liquid phase is 0.12-0.28 m/s and 0.05-0.25 m/s, respectively, and the pulsating gas flow frequency is 0.25-0.4 Hz. In this study, by examining more than 100 different apparent velocities for the phases, three patterns of bubble, slug and churn were observed and a map of the two-phase flow pattern of water and air was drawn. Also, the effect of pulsating gas flow on the length of the Taylor bubble was investigated in 150 different experiments, and the results of this study showed that with the increase of the pulsating gas flow and the frequency, the stability of the Taylor bubble flow increased and the length of the Taylor bubble decreased significantly. So that at the frequencies of 0.25, 0.5, 1, 2 and 4 Hz, respectively, the maximum bubble length was observed at the liquid velocity of 0.12 m/s and gas velocity of 0.25 m/s are 455.5, 367, 313.1, 286.3 and 244.2 mm.   Also, at a constant frequency, the length of the Taylor bubble increases with the increase of the apparent velocity of the gas phase. For example, at a constant frequency of 1 Hz and a liquid velocity of 0.12 m/s, the bubble length increased from 147.8 mm to 1.313 mm when the gas velocity increased from 0.10 to 0.25 m/s. In addition, in this research, with the help of image processing, the movement speed of the Taylor bubble was measured and determined for 15 different apparent speeds using the speed measurement technique. Comparison of the obtained linear equation with previous studies showed that the relationship has a good fitting accuracy. The results of the present work proves that the pulsating gas flow technique enables the control of the gas-liquid Taylor bubble flow pattern and the stability of the motion of the Taylor bubbles, which will be very useful for future industrial applications in gas-liquid reactions.

Abstract: Due to the limitations of mineral resources on the earth and the distant horizon for long-term life on this planet, preservation and maintenance of materials against damage and destruction becomes very important in industrial societies. On the other hand, the growing process of industrialization of human life has increased the share of industrial sectors in the financial portfolio of governments, and governments are forced to send a large amount of their financial resources to the industrial market every year in order to reach the desired level of industry. Abrasion is one of the main destructive events in the fluid transfer sector in industries. Especially when two-phase and multi-phase fluid flows are involved. Obviously, the countries where the transfer of refinery, power plant, oil and gas fluids is considered their vital artery are more involved in this phenomenon in their industries than others. Today, software simulations compete strongly with laboratory research. Because laboratory research, despite all its inherent advantages and advantages, has disadvantages such as high costs. On the other hand, the increasing power of computer systems for analysis and simulation is a powerful support. This research is a simulation with the help of numerical methods, in which a 90 degree elbow is considered as a sample piece (which is one of the most damaged industrial connections). To carry out the desired simulation, a computational fluid dynamic model has been used along with the discrete cell method. The continuous fluid and the particles injected into the flow at the elbow inlet were simulated in different geometries. The final simulation model includes McLaury's Erosion model based on the validation results. Particles are tracked by Lagrangian method along with random collisions of Grant-Tabakoff recursive model. To ensure the correctness of this choice, another validation has been used in this section. Considering that particle momentum plays an important role in Erosion, in this research, it has been tried to make the injected particles lose their momentum by rotating the water flow lines. Therefore, changes were made in the same direction in the knee geometry. The result of this research shows that changing the geometry of the elbow reduces the momentum of the particles when they collide with the internal surfaces to the extent that it increases the life of the elbow by about 8 times in the case of using internal spiral blades. Key word: Erosion, elbow, helical blades, computational fluid dynamics, Euler Lagrange, particle tracking   

  Separation of gas-solid flows is an important process in many industries. Cyclone separators are the most common devices for separating solid particles from gas flows, which indicates the importance of studying and researching to increase their efficiency and reduce energy consumption by reducing the pressure drop. In this regard, the present study used an additional inlet to enter flow into the cyclone with the aim of increasing the separation efficiency of a standard gas cyclone. To find the optimal height, this additional inlet was added at four different heights along the length of the cyclone, including the heights of 0.95D, 1.4D, 1.5D and 1.95D (D is the diameter of cylindrical section of cyclone) and the results were obtained for two conditions of inlet flow distributions: Increasing the inlet flowrate and division the inlet flowrate. In the first case, in addition to the polluted air flow entered through the original inlet (that was equal to the flowrate of cyclone without an additional inlet), an extra flowrate (20% of flowrate of original inlet) was injected through the additional inlet. In other words, the total flowrate of the cyclone was 20% more than it in cyclone without additional inlet. In second case, part of the inlet flow (83.33%) was injected through the original inlet and part of it (16.67%) was injected through the additional inlet, so the total inlet flowrate was equal to it in cyclone without additional inlet. The Reynold stress turbulence model (RSM) was used to solve the Averaged Navier- Stokes equations and Eulerian- Lagrangian approach and discrete phase model (DPM) was applied to track particles with a uniform diameter of 0.5 to 1.8 micron as discrete phase. The results showed that, in both flow distribution cases, installing the additional inlet at a height of 0.95D has the most positive effect on the separation efficiency. The separation efficiency increased 28.8% in flowrate increasing case and 19.6% in flowrate division case for particles with diameter of 0.5 micron compared to cyclone without additional inlet. In addition, in both of the flow distribution cases, increasing the separation efficiency of sub-micron particles was greater than it of bigger particles.

     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-?

Displacement of vents for the internal comfort of the building  

   Proper design of solar panels and increasing their thermal performance is one of the most important issues of the day. In this dissertation, using Ansys Fluent 19.2 software, a three-dimensional solar chimney power plant for Kermanshah weather conditions and the effect of collector geometric dimensions such as collector height and radius, solar radiation and ambient temperature on mass flow rate, air pressure temperature In the chimney, the output power, thermal efficiency and total efficiency of the power plant as well as the distribution of temperature, pressure and pressure meters were examined. In this study, the collector height was 2 to 8 meters, the collector radius was 100 to 400 meters, the chimney height was 2 meters, the chimney radius was 4 meters and the sunlight was 400 to 1000 watts per square meter. Increased sunlight leads to increased mass flow in the chimney. Increasing the ambient temperature reduces the fluid flow and thus the output power. There is a direct relationship between heat flux and power output of the power plant so that with increasing (decreasing) solar radiation, the output power also increases (decreases) and the thermal efficiency of the solar chimney power plant increases. Increasing the collector radius increases the mass flow rate and thus the power output of the power plant, but increasing the collector height has an inverse relationship with power. As the collector radius or height increases, the total power plant efficiency decreases. Changing the collector radius from 100 meters to 400 meters for a solar flux of 800 watts per square meter increases the output power by 93.6%.    Keywords: Thermal performance, Chimney power plant, Solar energy, Numerical simulation

  در پايان­نامه حاضر جريان پايا و گذراي خون در مدل

Unfortunately, nowadays many patients suffer from abnormalities in their nervous system. For some of those patients, brain surgery is the only chance of survivale. In that case, the surgeon needs a clear and high-resolution (temporally and spatially) picture of the brain which shows the locations of the brain abnormalities. Lack of such picture may lead to unsuccessful brain operation by the surgeon and removal of healthy brain tissues (instead of brain tumors). The mostly used techniques for brain imaging are: EEG and fMRI. EEG imaging has a good time resolution, but it has a poor spatial resolution while fMRI imaging has a good spatial resolution, but it has a poor time resolation. Therefore, combination of EEG and fMRI can be a powerful non-invasive imaging tool for providing both spatial and time resolution. Obtaining EEG and fMRI data simultaneously is a non-invasive approach to study and investigate the electrophysiological and hemodynamic aspects of the brain functions. Despite the time-varying nature of both measurements, their relationship is usually to be time-invariant. In general, the combination of EEG and fMRI involves two important challenges: firstly, simultaneous data acquisition, secondly data integration. In this study, the main focus is on the data integration. The motivation of this research is to increase the accuracy of existing methods by introducing a new method for combining EEG and fMRI in which the maximum information is retained. In this regard, the Dynamic Regional Phase Synchrony (DRePS) criterion and methods for measuring phase synchrony in multichannel EEG signals are deployed. The methodology was applied to a data set composed of behavioral, EEG, and fMRI data acquired from human subjects performing a perceptual decision making task. The data set is publicly available at https://osf.io   under a Data Use Agreement. The proposed methodology can be used as a neuroimaging tool for studying epilepsy as well as neuro-vascular coupling and cognitive studies. It can also be deployed to get better constrain solutions of the inverse problem of source localization of  EEG  activity.

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

  شبيه­سازي جريان­هاي چند فازي و مطالعه نشست ذرات

   It is very time consuming to use deterministic methods for test generation as they use backtrack. The simulation-based test generation methods only analyze the circuit in forward path and this has made them popular. Random Test Generation Methods, which are among simulation-based methods, need a short time for test generation, but the number of test vectors produced in random methods is high. A suitable solution to reduce the number of these vectors is through using the Fault Coverage Index to evaluate the competency of test vectors and trimming test vectors that are inadequate. But calculating the Fault Coverage Index for each test vector requires a fault simulation that is a time consuming process. Also, the genetic algorithm can reach a very compact test set because of the optimized search it performs over a large space of test vectors. But this method, which is simulation based, again requires the time consuming simulation of fault as it uses the fault coverage index as a fitness function. The main purpose of this thesis is to reduce the test generation time in simulation-based methods by maintaining their quality for combinational circuits. The idea behind this thesis is to study the competency of test vectors using a new index based on Probabilistic  ystem that is fast and low-cost to calculate. To evaluate the accuracy of the proposed competency index, the concept of statistical correlation was used. The results showed that there is a correlation between the proposed competency index and the Fault Coverage Index for all circuits and the correlation was greater than 0.7 for 6 circuits out of 10 ISCAS85 circuits, which indicates high correlation.   The results of using the proposed competency index in simulation-based test generation methods showed that the basic method of trimming test vectors can be accelerated to 86% on average by maintaining the quality of test generation and the basic method of test generation based on genetic algorithm can be accelerated to 49.85% on average with an additional test vector.

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  

Numerical Study of Magnetic Field Effect on Convection Heat Transfer of Nanofluid Flow in a Microchannel  

  Investigation of thermal performance of a direct-expansion solar-assisted heat pump water heater system using N2O refrigerant

  Abstract:Worldwide, the building sector is responsible for about 30% of the green gas emissions and about 40% of the energy consumption. So, improving building performance can play a crucial role to cope with climate changes and resources depletion. Optimization methods can be more effective in finding the optimal building design after eliminating the less important variables using global sensitivity analysis and thereby reducing the search space. Firstly, in this thesis to identify those input variables that have a large impact on annual energy consumption of an existing office building and thermal comfort of its occupants, to assist building energy engineers and policymakers to decide on the best strategies in retrofitting proce   two different sensitivity analysis methods, namely one-factor-at-a-time (OFAT) and analysis of variance (ANOVA), have been applied to outcomes of a validated model of the studied office building. These output variables were the annual electricity and gas consumption and average absolute PMV. The variables chosen as inputs that could be changed easily for the building, they were: heating and cooling set points, air infiltration and ventilation rates, supply water temperature for heating and cooling, and overall heat transfer coefficient of external walls. Then by building simulation based optimization, has been tried to reduce building's energy need, while maintaining thermal comfort in acceptable range. Because this task involves direct coupling of the optimization algorithm to a simulation model, it is computationally intensive. To overcome this issue, this thesis has described an optimization methodology based on a combination of regression models and a Multi-objective Evolutionary Algorithm (NSGA-II) that has applied for the case study. The optimization results shows that the applied method, while maintaining occupants' thermal comfort in acceptable zone, can decrease building's annual gas and electricity consumption 88.1% and 39.2%, respectively.  Keywords: building energy consumption; occupant thermal comfort; sensitivity analysis; one factor at a time (OFAT); analysis of variance (ANOVA); surrogate regression model; multi-objective optimization (NSGA-II)

<  gt;شبيه سازي كامپيوتري ديوار ترومپ براي گرمايش ساختمان مسكوني</P>

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.

بررسي كارايي حرارتي مبدل صفحه ايي با استفاده از نانو سيال

In this thesis, numerical simulation of fluid mixing has been performed for non-Newtonian flow under the effect of electric filed (Electroosmotic flow). This problem is of great importance as a frequent process in advanced and progressive technology of Lab-on-Chips and has numerous applications introduced in medical and biochemical areas. One of the major purposes of this field is to design high performance micromixers so that ideal mixing can be achieved in minimum time and energy consumption. In this study, the effects of governing parameters on mixing performance have been investigated in a flow field consisted of combined electroosmotic and pressure driven flows in presence of physical hurdles and zeta-potential heterogeneities. The simulations have been conducted for 2D geometry using finite element method by means of commercial code COMSOL Multiphysics 5.2a. Nernst-Planck equations have been used for the modeling of electric double layer (EDL) and the distribution of ions. The results indicate that several factors such as dilatant fluid behavior, adverse pressure gradient, zeta-potential heterogeneities as well as height of hurdles can have augmentative effects on the mixing performance. It is found that increasing the length of the hurdles has small effects on mixing performance while the location of the hurdles along the channel hardly changes the mixing quality. It is also seen that the effect of patches’ arrangement on the mixing is mostly depended on the magnitude of the zeta-potentials of the patches. The results showed that among the various effective parameters, the best choice for increasing the mixing quality is to increase the value of zeta-potential of the patches, because the mass flow rate passing the micromixer has no reduction and it is almost constant. This is a key characteristic because any reduction in mass flow rate is undesirable and deteriorates the performance of micromixer.

  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.

In this work the thermal performance of a two-stage DX-SAHP for high temperature condensing in the rang of 60-100 °C with considering the effects of he pressure drop associated with the flow of R134a refrigerant through the condenser,collector/ evaporator and connection pipe is analyzed numerically.the Homogeneous method for two phas pressure drop inside horizontal pipes is used to calculate the two phase refrigerant pressure drop.This system employs a bare flat plate solar collector with a surface area of 5.5 m2 ,a hot water tank with the volume of 150 L,two rotary-type hermetic compressors,two thermostatic expansion valves and a flash chamber.The effect of various parameters, including solar radiation, ambient temperature, collector surface area, compressor speed,wind speed and number of collector cover has been studied on the thermal performance of the system.The results show that the hours of system operation, during different months in the climate of Kermanshah, vary between 44 to 144.4 hours and the monthly average COP and the solar collector efficiency vary between 4.4 to 7.66 and 55.1 to 79.63 percent respectively.also the thermal performance is compared for two-stage and single-stage DX-SAHP at the Kermanshah climate. the results show that the performance of two-stage DX-SAHP is better than that of single-stage system.monthly average COP and the solar collector efficiency for the two-stage DX-SAHP vary between 4.389 to 7.768 and 71.44 to 100.3 percent respectively and for single-stage vary between 3.92 to 6.05 and 66.25 to 96.12 percent respectively.also the hours of system operation, during different months for two-stage DX-SAHP is less than that of single-stage system