فهرست مطالب s. m. hosseinalipour
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In this paper, the performance of a hybrid humidification-dehumidification (HDH) desalination system is experimentally studied. The system operates as an Open-Air Closed-Water cycle and utilizes a solar air heater to heat the input air to the humidifier. An Ammonia absorption refrigeration cooling cycle is used to condense the humid air, producing fresh water. Parameters such as temperature and relative humidity were measured in different stages of the system by using humidity and temperature sensors, and the thermodynamic analysis was carried out using EES software. The effects of the mass flow rate and temperature of the inlet air flow on the rate of desalination, COP, GOR, and the efficiency of the humidifier and the dehumidifier were studied. The analysis proved that the highest rate of water production and GOR were 150 g/h and 1.2, respectively. It was also perceived that with an increase in the air mass flow rate, the rate of water production and COP increased, while GOR and the efficiency of the dehumidifier diminished. This is while the efficiency of the humidifier remains nearly constant. It was also concluded that an increase in the temperature of the input air, leads to a fall in the GOR, while the other parameters show an increasing trend. Following the economic analysis of the system, the CPL was found to be $0.16 /L.Keywords: Economic Analysis, energy analysis, Humidification-dehumidification, Solar System}
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In recent decades, global energy demand and environmental pollution have been steadily rising. The power sector is one of the major sources of global environmental pollution. Hence, it is necessary to pay more attention to renewable energy resources. In order to identify the best scenario for construction of a renewable power plant, it is necessary to examine all scenarios from all environmental aspects. Life cycle assessment methodology can be a useful tool for this purpose. In this research, life cycle of polycrystalline solar panel production in Iran is assessed. Primary energy consumption, global warming potential, acidification potential and eutrophication potential for panel and also cell manufacturing is assessed and the share of each panel component in all impact categories is presented. The primary energy demand is calculated as 15.4 MJ/WP and GWP, AP and EP are calculated as 1.4356 kg CO2-equiv. /WP, 0.006 kg SO2-equiv. /WP and 0.0013 kg PO43—equiv. /WP respectively. Transportation of panel components to the panel manufacturer is modeled in detail, results show that its contribution to life cycle primary energy consumption and environmental pollution is negligible. The results of this study can be used to identify critical points of the manufacturing life cycle and also to make decisions for the development of photovoltaics in Iran.Keywords: Life Cycle Assessment, Polycrystalline solar panel, GHG Emissions}
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امروزه در بسیاری از فرآیندهای صنعتی، برهم کنش حباب های گازی و قطرات نفتی نقش به سزایی در تعیین راندمان کلی سیستم بازی می کند. لذا شناخت پارامترهای اثرگذار بر این فرآیندها حایز اهمیت خواهد بود. از این رو، در مقاله حاضر به بررسی نقش اندازه قطره و حباب بر زمان تخلیه فیلم بینابینی به دام افتاده بین قطره و حباب پرداخته شد. ضمن این مطالعه شش سری آزمایش در شش اندازه مختلف مورد بررسی قرار گرفت و در طی آنها زمان مورد نیاز جهت تخلیه فیلم، زمان پوشش و زمان شکست فیلم که از جمله زمان های مشخصه فرآیند ایتلاف هستند، اندازه گیری شد. هر کدام از این سری آزمایش ها حداقل پنج بار تکرار شدند. نتایج حاکی از آن بودند که زمان تخلیه مستقل از اندازه قطره و حباب در حال تغییر است. علاوه بر آن، مشاهده شد که در هر اندازه قطره و حباب، زمان تخلیه ناشی از تکرارهای به دست آمده دارای پراکندگی های بسیار زیادی هستند که البته این پراکندگی ها ناشی از طبیعت پدیده مورد نظر بوده است و این بدان معنا است که پدیده های میکروسکوپیکی که در فیلم آب و بین سطوح مشترک قطره- حباب رخ می دهند، دارای اثرات بسیار زیادی بر تعیین زمان تخلیه هستند. همچنین ضمن این آزمایش مشخص شد که حجم فیلم به دام افتاده بین قطره و حباب، تاثیر چندانی بر زمان تخلیه فیلم آب بینابینی نخواهد داشت.
کلید واژگان: ائتلاف قطره- حباب, مدل تخلیه فیلم, زمان تخلیه, حباب, قطره, جریان سه مولفه ای}Nowadays, the interaction between gas bubbles and oil droplets plays an important role in the efficiency of many industrial processes. Therefore, it is of great importance to study the influencing factors on these processes. So, in the present paper, the effect of droplet and bubble size on the drainage time of the trapped intervening film between droplet and bubble was investigated. Six series of experiments were conducted for various sizes and three characteristic time scales including drainage time, coverage time, and rupture time were measured. Each of these experiments was repeated at least five times. The results showed that the drainage time changed independently of the droplet/bubble size. Moreover, it was observed that due to the nature of the phenomenon, the measured drainage times in each equivalent size are notably scattered, which means that the microscopic interactions in the water film and between bubble-droplet interfaces have significant impacts on the drainage time. Also, in the current experiment, it was found that the volume of the intervening film between droplet and bubble has no vital role in the drainage time of the mediate water film.
Keywords: Bubble-Dropet Coalescence, Film Drainage Model, Drainage Time, BubbleDroplet, Three-Component Flow} -
دعاوی تاخیرات بخش غیرقابل اجتنابی از فرایند ساخت محسوب می شوند. کارفرمایان در پی بهره برداری به موقع از پروژه های ساخت هستند تا انتفاع شان از سرمایه گذاری انجام شده به تعویق نیافتد، از طرفی پیمانکاران نیز پیشنهاد قیمت خود را با فرض تکمیل کارها در دوره ی معینی از زمان ارائه می کنند و اگر این دوره ی زمانی طولانی تر شود، هزینه های آن ها نیز افزایش می یابد. اما با توجه به ماهیت پروژه های ساخت و مواجهه با رویدادها و شرایط غیرقابل پیش بینی و یا قصور عوامل ساخت، پروژه ها با تاخیرات روبه رو می شوند؛ لذا با توجه به اهمیت زمان و هزینه برای هریک از طرفین، طرح ادعاهای مالی برای جبران خسارت ها قابل انتظار است. هدف کلی این نوشتار، بحث و مقایسه ی مفاد جبران خسارت ناشی از تاخیرات در شرایط عمومی پیمان و شرایط قراردادهای بین المللی (J C T پانویس{j o i n t c o n t r a c t s t r i b u n a l (J C T)}، I C E پانویس{i n s t i t u t i o n o f c i v i l e n g i n e e r i n g (I C E)}و فیدیک) است. این نوشتار به طورخاص به کاستی های شرایط عمومی پیمان از دیدگاه جبران خسارت ناشی از تاخیرات می پردازد.
کلید واژگان: تاخیر, شرایط عمومی پیمان, ادعا}Time is an extremely important issue in construction. Together with cost and quality, it is a primary objective of project management, and a major criterion by which the success of a project is judged. In practice, projects are required to be completed by a certain date, and, in the case of commercial projects, this usually means as soon as possible. Time is also of fundamental importance to the contractor in that he must assess his performance capabilities and resources in order to carry out and complete the work within a given time. Whilst both the employer and the contractor would prefer the certainty of a fixed completion date, delays are an inevitable part of the construction process. With regard to the importance of time for project parties, most construction contracts include provisions for delay to oblige the responsible party to pay damages. Contractors would normally want to be paid as much as possible, and for as little risk as possible. Conversely, owners will want to pay as little and as late as possible, and possibly, and/or forcibly, transfer all risk, expense and cost to the contractor. In the event of one of the party incurring those costs, he will certainly look for reimbursement from the other party. For years, there have been a number of construction disputes involving delay in construction projects. So, most standard-form international construction contracts currently in use contain detailed provisions, under which the contractor can claim against the employer for any losses suffered if the work is disrupted due to certain specified causes. From the viewpoint of indemnifying damages, Iranian General Conditions of Contracts have shortcomings, and the risks of increasing costs for delays are not apportioned fairly in its provisions. For renovation, indemnifying damage provisions, and a fair apportioning of incurring costs, a comparative comparison between the general conditions in Iran and international conditions are used in this article. The general purpose of this paper is to discuss and compare conditions of contract provisions for recovering delay damages in Iran and international standards (JCT, ICE and FIDIC). In particular, the paper focuses on the shortcomings of the Iranian General Conditions of Contracts, regarding the recovery of delay damages. The result of research shows that reconsideration of the indemnifying contractor and owner damage provisions of Iranian General Conditions of Contracts is necessary. One of the most important results of the research is the high level risk of Iranian General Conditions of Contracts in the case of owner delays, since few events for recovery of owner damage are predicted in the Iranian General Conditions of Contracts. Also, no mechanism for claiming recovery of owner damage from the contractor is predicted in the Iranian General Conditions of Contracts.
Keywords: Delay, General Conditions Of Contract, Cllaim}
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