This research is conducted in two main stages. First, the behavior of a prismatic fuse-type damper is investigated and analyzed, and then its effect on the seismic performance of reinforced concrete structural frames under cyclic loading is evaluated. In many structures, especially in regions with high seismic hazard, controlling seismic response through energy dissipation systems such as dampers plays a crucial role. Prismatic fuse-type dampers, due to their high energy dissipation capacity and adequate deformability, are considered an effective solution for reducing the seismic vulnerability of structures. In this study, which is based on the use of two numerical analysis software packages, the damper is first modeled independently in Abaqus, and its load–displacement relationship is obtained. Subsequently, structural frames are modeled in SAP2000, and the damper behavior is introduced into the frame models in the form of a link element. The research methodology includes nonlinear numerical analysis of both the damper and the structural frames, which are performed separately using the aforementioned software. Finally, the performance of the frames equipped with dampers is investigated under cyclic loading to evaluate the effect of the damper on structural displacements and stiffness. The results of this study are expected to contribute to the improvement of design approaches for structures equipped with fuse-type dampers and to assist in selecting optimal materials for structural frames.

  Given the global energy crises and the importance

Abstract

   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.

   خاك‌هاي تورمي جزء خاك‌هاي مسئله‌دار هستند كه به‌طور وسيعي در سرتا سرجهان با آب‌وهواي مختلف از جمله ايران پراكنده ‌شده اند. در اينگونه از خاك‌ها تغييرات رطوبت، سبب تغييرحجم شديد و باعث آسيب و حتي خرابي سازه‌هاي واقع برروي آنها خواهد شد. يخبندان يكي از عوامل موثردر تغييرات رطوبت در مناطق سرد مي‌باشد و امروزه شناسايي و روش تثبيت جزء مسائل مهم در مهندسي ژئوتكنيك در مناطقي سرد (يخبندان فصلي) محسوب مي‌شود و همچنين در مناطق گرم خشك تغييرات رطوبت به‌علت تبخير در مناطق گرم بررسي رفتار خاك تورمي و روش تثبيت مناسب يك امر مهمي در دنيا مي‌باشد. به همين منظور هدف اصلي از تحقيق آزمايشگاهي مطالعه تأثير چرخه انجماد وذوب و سيكل تر و خشك بر روي چرخه انجماد وذوب بر خاك تورمي و خاك تورمي تبيت شده با سه ماده آهك، پودر متا و پودر آلفام مي‌باشد. و لذا براي دست يابي داده‌هاي اين تحقيق مجموعه از كار‌هاي آزمايشگاهي به شرح ذيل مد نظر مي‌باشد: 1- تثبيت خاك تورمي با آهك، پودر متا و پودر آلفا. 2- تاثير چرخه انجماد و ذوب بر پتانسيل تورم و پتانسيل فشار تورم و مقاومت فشار تك محوري (ucs) روي خاك تورمي تثبيت شده. 3-تاثير سيكل تر وخشك بر چرخه انجماد و ذوب روي خاك تورمي تثبيت‌شده.

Cooling of electronic equipment is a fundamental challenge in the electronics industry, so the development of new electronic systems depends on solving this challenge. In a Core I7 processor, more than 731 million transistors are accumulated in an area of 270 square millimeters, and their design thermal power reaches 140 watts. Removing this thermal load requires new methods. In recent years, the use of phase change materials in these systems has shown that these materials are effective in improving the thermal performance of heat sinks. Due to the increasing use of these materials, it is necessary to examine their thermal behavior in different conditions and to study the conditions where the presence of these materials leads to the improvement of the performance of heat sinks. These conditions depend on the geometry and materials of the heat sink components as well as its functional conditions. In this thesis, the thermal efficiency of a thermal heat sink equipped with a phase change material is investigated. The type of phase change material and its mass fraction in the presence of vanes and the arrangement of vanes are among the parameters that are studied. In addition, the efficiency of the heat sink may change over time depending on the amount and type of PCM, and therefore it is necessary to study this parameter over time. The results of this study can determine the conditions in which the presence of PCM leads to the improvement of the efficiency of the heat sink and introduce the appropriate limit for the use of PCMs. Also, in this study, it has been investigated that the presence of the valley in which wall of the heat sink has improved the performance of the heat sink in terms of cooling.  

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

   استفاده از مقاطع توخالي در اعضاي باربر سازه، مزيت كاهش وزن مخصوص را دارند؛ كه به سبب وزن كمتر، عملكرد بهتري را در مقابله با زلزله از خود نشان مي­دهند. الياف موادي ايده­آل براي استفاده در بتن و ملات­ها مي­باشند و استفاده از الياف در بتن سبب افزايش مقاومت در برابر آتش، سختي، افزايش مقاومت فشاري، خمشي و كششي و دوام مي­شود.پوشش­هاي FRP سبب افزايش ظرفيت باربري ستونها مي­شوند؛ و در سازه­هاي فرسوده واقع در مناطق لرزه­اي، به منظور بهبود شكل­پذيري و به تعويق انداختن شكست ناگهاني، كاربرد دارند. در اين پايان­نامه به بررسي و مقايسه مقاومت شعاعي و مقاومت در برابر حرارت بالا نمونه­هاي استوانه­اي توخالي بتني پرداخته مي­شود؛ بدين صورت كه نمونه هاي بتني، بتن اليافي و بتن با پوشش FRP به صورت استوانه­اي توخالي جدار نازك ساخته خواهد شد و سپس مقاومت شعاعي و مقاومت در برابر حرارت بالا نمونه ها اندازه­گيري و با يكديگر مقايسه مي­شوند.

  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  

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 .   

  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)

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

  This thesis examines the numerical and experimental performance of a metal foam heat sink in the free convection heat transfer. Metal foams are porcelain materials that used recently in the wide range application. This welcome is due to the appropriate thermo physical properties such as high volume ratio and high thermal conductivity. They are very lightweight because of their high porosity (0.9 and further).   The specimen used in this experiment is an aluminum foam (13 mm × 40 mm × 40 mm) of 92% porosity with 10 ppi. The experiments were carried out for heat sink inclination position of 0 °, 30 °, 60 °, 90 ° and 4, 8, 12, 16 watt power input. Numerical simulation was performed by finite element method and commercial software Comsol Multiphysics5.2. The heat transfer and fluid flow in the metal foam is expressed in terms of the macro volume theory based on the local thermal non-equilibrium condition (LTNE) for the energy equation. In this work, effect of foam geometric parameters, foam height, heat sink inclination angle and base temperature on the thermal performance of metal foam was investigated. The experiments results, show that the thermal performance of heat sink with increasing input heat flux decreases. For power input of 16 watts, the highest Nusselt number belong the inclination of 60 degrees (25.75).Comparison of thermal performance between horizontal and vertical heat sink indicates that the performance of horizontal heat sink is better than the vertical. The results of the numerical model show that the highest mean Nusselt number for all foam samples are in the horizontal position. It can be concluded that the average Nusselt number decreases with increasing porosity, and increases with decreasing in pore density. Influence of metal foam pore density of on the Nusselt number shows that in the samples with a 10 ppi and ppi 20 do not differ greatly, but the specimen with ppi 5 has a better performance. Comparison of Nusselt number in vertical(25.29) and horizontal(30.94) heat sink with 0.92% porosity and 5 ppi show that the mean Nusselt number in the horizontal position is %22.34 more than the vertical position. Comparison of Nusselt number of a metal foam heat sink ( 0.92% porosity and 10 ppi) with a flat plate in the horizontal position at the same base temperature (97.7 ?) indicated that the Aluminum metal foam increasing Nusselt number by %62.59. mean Nusselt number in the horizontal upward position is %29.52 more than the horizontal downward position

Aerosols are very small solid particles or liquid droplets suspended in a gas phase. It is very important to study aerosols evolution and its relevant processes including coagulation, deposition, condensation, and source reinforcement. It seems even more essential in issues such as nuclear reactor containments contamination and its environmental effects. On the other hand, Analytical solution of the governing aerosol evolution equations is not possible except in some limited cases. In this research direct simulation Monte Carlo (DSMC) method is employed to develop a numerical computer code which simulates coagulation and deposition processes in multicomponent aerosols with different densities. The coagulation and deposition processes are simulated based on Brownian motions and diffusion of particles, respectively. The effects of gravity are considered for both processes as well. Sectional method, which is the common technique in simulation of aerosols evolution, is used to validate the ability of our DSMC code in modeling coagulation and deposition processes. The comparison results in a well agreement between two methods. Furthermore, the evolution of nuclear aerosol of Uranium dioxide enriched with water particles is investigated using the validated DSMC code. The Uranium dioxide particles, ranged from 0.01 to 0.04 micrometers in diameter, are distributed in a cubic repository of one meter edge length. Then water particles are added to the aerosol and the evolution of Uranium dioxide particles including mass distribution variations as well as deposition and coagulation of suspended particles are studied. The water particles, which have the same size in each study, are ranged from 0.012 to 0.551 micrometers in diameter. It is observed that increasing the water particles diameter results in decrease of uranium dioxide particles deposition; such that for water particles with mean diameter 0.55 micrometers, the uranium dioxide particles are mainly suspended. On the other hand, due to coagulation of small particles over the time, remaining suspended particles have much larger diameters (70 times greater than initial size in average). These features can be beneficial in many ways such as tra  orting and deposition controlling of aerosols as well as using larger hole filters (less flow restriction) in case of air purification of nuclear repositories. Finally, taking a closer look at the deposition process, an estimated relation is used to improve the simulation of the coagulation. We call this method modified deposition rate DSMC in contrast to common DSMC. This modification results in more realistic simulation with completely different results compared to common DSMC. Another disadvantage of the prevalent DSMC is using estimated deposition rates in modeling diffusional deposition which does not take advantage of the prominent feature of the DSMC method that is particle tracking. However, simulating diffusional deposition by means of estimated deposition rates fail to use the ability of DSMC method in particle tracking. Therefore, a new scheme for simulation of diffusional deposition is proposed which is based on movement and position of particles and hence more accurate. The results of this method are close to modified deposition rate DSMC.

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.

Rotary Regenerative Air Preheater (RRAPH) is one of the main equipment for energy recovery in the steam boiler of the power plants. In the present study, Ljungstrom air preheater of the Bisotoun Thermal power plant has been investigated with the aim of optimizing its thermal performance. In this regard, with Computational Fluid Dynamics (CFD), three-dimensional simulation of the rotary air preheater was performed to solve the continuity, momentum and energy equations in porous medium. Considering the structure of the plates of the Ljungstrom matrix, the use of the porous medium assumption is acceptable. The results of simulation show acceptable accuracy in comparison with the experimental results which is achieved from Bisetoon power plant data. In this research, the effect of rotational speed on the efficiency of air preheater in variety of loads and mass flow rates for both without leakage and with leakage conditions was investigated. The results of the present study show that the impact of the rotational speed on the performance of RRAPH is in the range of 0.5 to 4 rpm, and after this increase in speed does not have a significant effect on efficiency. The present study also shows that leakage has a significant effect on reducing the efficiency of the RRAPH in all thermal loads and rotational speeds. In the following, the optimum rotary speed was studied in different loads, mass flow rate of air and flue gas. For this purpose, both without leakage and with leakage have been studied. Results show, the efficiency of the power plant was almost constant for various thermal loads, and performance is only increasing with increasing rotating speed. On the other hand, with considering leakage effect, the maximum RRAPH efficiency is related to the power plants nominal load (320 MW). One of the most important and limiting factors in increasing the speed of rotation is the dew point temperature forms acid. Therefore, in this study, this index was extracted for optimal rotary speeds in different thermal loads. In the following, the effect of material change on the efficiency of RRAPH was investigated. According to the results, for both without leakage and with leakage the best thermal performance is related to the stainless steel, which has the lowest thermal diffusivity, lowest thermal performance is related to the copper, which has the highest thermal diffusivity.  

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.

  Due to the growing need of the industry for energy and the increasing price of fuel and limited energy resources, it is significant of optimizing energy consumption and preventing its loss in industries. The exergy method is a powerful and effective tool for analyzing the energy system of industrial processes. The purpose of exergy analysis is to determine the location of exergy loss and its amount in a process. In this study, the exergy and energy analysis were carried out for amine sweetening unit of Ilam Gas Refinery. Since the temperature change of the environment plays a major role in the amount of waste and exergy efficiency of the components, in this study, the changes in these parameters have been investigated by changing the ambient temperature from 10 to 40 oC. According to energy analysis, most energy losses occur in air coolers, and both air coolers in this unit together causing 87% of energy dissipation. In this study, components are specified with the highest and lowest amount of exergy loss. The results of the exergy analysis show that the air cooler 1 at 10 °C and the filter 1 at 10 °C have the lowest and the highest exergy efficiency, respectively. At all temperatures, the highest exergy losses occur in the amine recovery tower and the lowest losses occur in filter 3. By increasing the ambient temperature, the maximum change in exergy efficiency occurs in air coolers.

  Thermoelectric devices produce electricity if a temperature gradient is applied to them (direct effect), and vice versa, by applying an electric current generate temperature (inverse effect).These devices are composed of a number of n-type and p-type semiconductor junctions connected electrically in series and thermally in parallel. If an electric current is applied to a thermoelectric cooler, heat is transferred from one side of the thermoelectric cooler to the other side. Therefore, one face of the thermoelectric cooler is cooled and the opposite face is heated. This study aims to investigate the effect of Piezo-fan boundary conditions on the efficiency of thermoelectric refrigerators. Piezoelectric fans are vibrating beams, disks, or plates whose vibratory motion is actuated using a piezoelectric material. Typically they consist of a flexible fan blade to which the piezoelectric element is bonded. By applying an alternating input signal to the piezoelectric element, beam begins to oscillate and induce a flow in the surrounding fluid. This could be used enhance heat transfer. Numerical results show that the maximum convection heat transfer coefficient in which fan tip to the wall distance is 1.5 mm and the wall is experiencing a constant thermal flux of 650 W/m2 is 73.55 W / m2.K. The boundary conditions imposing on thermoelectric elements affect their efficiency and by altering it the temperature of the insulated end could reach 73.66 Kelvin relative to ambient temperature. The results show that using a cooling system consisting of a heat sink and Piezo-fan on the hot end could meet the refrigerators thermal requirements. Depending on the heat sink type and the Piezo-fan configuration, the refrigerators performance would be different. Namely, a cooling system consisting of a pin-fin heat sink and a vertical arrangement of Piezo-fans has increased the refrigerators effective electric current range by 6.5% and has increased the maximum temperature drop by 8.4% with the cooling flux to be 20,000 watts W/m2.

  This paper introduces design and application of a novel hybrid sun-wind-tracking system. This hybrid system employs cooling effect of wind, beside the advantages of tracking sun for enhancing power output from examined hybrid photovoltaic cell. The principal experiment focuses on comparison between dual-axes sun-tracking and hybrid sun-wind-tracking photovoltaic (PV) panels. The deductions based on the research tests confirm that the overall daily output power gain was increased by more than 49.83%, compared with that of a fixed system. Moreover, an overall increase of about 7.4% in the output power was found for the hybrid sun-wind-tracking over the two-axes sun tracking system.

In recent years, studies on microelectromechanical systems have shown that there are considerable opportunities for microsensors based on mechanism like piezoelectric. Microelectromechanical systems objective in miniaturization, multiplicity, creation and integration of microelectronic systems. Today microelectromechanical systems have numerous application in vehicles, military industries, medicine, sensors and actuators. New technologies have led to increase in use of piezoelectric materials. One of the recent changes is using piezoelectric materials as sensors and microsensorS in microsystems. Piezoelectric are a category of smart materials which can be used in electric energy harvesting from environment. Using these materials as sensors has grown popular due to lack of need for an external source. These materials can be used frequently in strain gauges, active biomedical materials, switches, pressure and vibration sensors, accelerometers, flow detectors and vibration and ultrasonic controllers. In the present thesis, speed sensor design and manufacture using piezoelectric polymer and wind energy harvesting via these materials are studied. Piezoelectric polymer is used as cantilever beam inside the low-speed wind tunnel. Standard DC circuit is used to convert piezoelectric alternating voltage to direct voltage using an operational amplifier too boost the piezoelectric output voltage. By performing various tests on the sensor, the relationship between piezoelectric output voltage and wind speed was obtained. The result of sensor tests indicated this relationship can be approximated with a first degree function. The amount of harvested energy from wind is also tested in different speeds. Peak power and power density were obtained with speed of 15m/s and optimal resistance of 2200 as 7.38 mW and 134.2 mW/cm3 respectively. Finally, the produced voltage and harvested energy can be used for wireless sensor networks, sensors and also for place in which changing batteries are not possible.