Sharif Digital Repository

Unfortunately, energy demands and destruction of the environment from uncontrolled manipulation of fossil fuels have increased. Climate change concerns have resulted in the rapid use of new, alternative combustion technologies. In this study, reactivity controlled compression ignition (RCCI) combustion, which can simply be exploited in internal combustion (IC) engines, is investigated. To introduce and identify extra insightful information, an exergy-based study was conducted to classify various irreversibility and loss sources. Multidimensional models were combined with the primary kinetics mechanism to investigate RCCI combustion, incorporating the second law of thermodynamics. The... 

Anaerobic digestion (AD) is a green technology that has been applied for many years. One of the main problems in this process is controlling these bioreactors to maximize methane production. A supervisory control strategy has been proposed to improve the methane production rate in an anaerobic digestion process while minimizing the risk of process failure in the presence of several drastic feedstock changes. The inner loop consisted of a feedback control that manipulated the feed flow rate for achieving the desirable methane production rate. A rule based control strategy was used as supervisory control loop. This controller received the total volatile fatty acids concentration in the reactor... 

Using zero liquid discharge systems is one of the efficient methods to reduce the negative environmental impact of the brines of the desalination systems and also to recycle the industrial wastewaters for reuse. Due to the simple fabrication process, low maintenance cost, intensive to inlet water quality, and the ability to use renewable and low-grade-heat, modified humidification-dehumidification systems may be a proper choice for the zero liquid discharge applications. Thus, in the present study, the energy, exergy, exergoeconomic, and exergoenvironmental assessment of three advanced brine recycle humidification-dehumidification systems for zero liquid discharge operation are... 

Over the past decades, drastic growth in the installed capacity of seawater desalination systems has increased the energy consumption and brine discharge to the environment. However, using renewable energies and zero liquid discharge systems for minimizing these challenges is limited due to the higher fresh water cost of the systems rather than that of the conventional systems. In this research, a bubble-column humidification-dehumidification zero liquid discharge system is coupled with a multiple-effect distillation/vapor compression system in a novel way to overcome the high water cost of conventional zero liquid discharge systems. Further, the base system and the solar-powered system is... 

Discharging unconventional water sources having a high content of inorganic compounds is extremely destructive to the environment. In this research, four novel semi-open-air and closed-air configurations of brine-recycle humidification-dehumidification (BRHDH) systems with zero liquid discharge (ZLD) approach are presented to treat unconventional waters cost-effectively. Bubble-column humidifiers and dehumidifiers are used to have a low initial expenditure, and system multi-staging is implemented to reduce the operating expense of the configurations. The configurations are evaluated for high saline brine treatment using comprehensive energy, exergy, exergoeconomic, and exergoenvironmental... 

Lignocellulosic materials are recalcitrant to bioconversion, due to their rigid physiochemical structure. In this work, the effects of Fe2O3–TiO2 and NiO–TiO2 nanoparticles (NPs) and FeCl3 and NiCl2 salts, on the anaerobic digestion (AD) of wheat straw have been investigated. For this purpose, metal oxide-TiO2 NPs were synthesized and fully characterized. Results showed that addition of 0.252 mg of NiO–TiO2/g total solids (TS) to batch assays resulted in increase of soluble chemical oxygen demand (COD) and 67% increase in volatile fatty acids (VFAs) concentration compared to control tests during the first 4 days of experiments. These results indicate that hydrolysis and acidogenesis rates... 

The purpose of this study is to apply managerial economics and methods of decision analysis to study the optimal pattern of innovation activities for development of new energy technologies in developing countries. For this purpose, a model of energy research and development (R&D) planning is developed and it is then linked to a bottom-up energy-systems model. The set of interlinked models provide a comprehensive analytical tool for assessment of energy technologies and innovation planning taking into account the specific conditions of developing countries. An energy-system model is used as a tool for the assessment and prioritization of new energy technologies. Based on the results of the... 

This paper presents the results of a research project performed to study the ranking of systems and components of the Tehran research reactor, important to safety, using a level 1 probabilistic safety assessment (PSA). The occurrence of an imbalance condition, i.e. a lack of equilibrium between heat generation and heat removal without reactor scram, was defined as the "Top Event". A fault tree technique was used to study all scenarios leading to the top event, the probability of which was shown to be 9.5E-5. It has been concluded that, objects falling onto the reactor core; operator error to shutdown the reactor while safety flapper open; and simultaneous opening of water outlet valves, are...