Sharif Digital Repository

In this study, the perturbed hard sphere chain equation of state is utilized to calculate the activity of water in binary and ternary solutions of polyethylene glycol (PEG), salt and water. The liquid density of the binary and ternary solutions is also predicted. To estimate the water activity in PEG-water binary systems, a linear correlation is obtained for the binary interaction parameter between water and PEG. Then, using this correlation and without introducing any additional binary parameters, the water activities are predicted in ternary solutions of water, salt and PEG with different molecular weights (MW). Our results show that the mean absolute average relative deviation (AARD %) of... 

Asphaltene precipitation and deposition is one of the main problems in some of the oil fields. The deposited asphaltene results in partial or total blockage of the wellstring and reducing or completely seizing oil production. Asphaltene deposition problems have been experienced in the field for a long time. Although, the asphaltene precipitation has been studied thoroughly and different parameters that effects this process has been investigated but little work has been carried out in the asphaltene deposition across the production system of flowing oil well. This paper introduces a new comprehensive model for description of asphaltene deposition behavior in wellstring. The mechanisms of... 

Hybrid renewable energy heat sources provide more sustainable energy resources with high maintenance for high-efficient power plants. Multigeneration systems driven by a hybrid renewable source are proved as cutting-edge technologies in recent studies. In this study, a novel multigeneration system driven by a hybrid biogas-geothermal heat source is proposed and simulated. To demonstrate the feasibility of the proposed multigeneration system, first and second laws analysis are employed as the most effective tools for performance assessment of the systems. It is found that the proposed multigeneration system can produce overall heating capacity, overall cooling capacity, net output power,... 

In this study, a thermal vacuum distillation amine reclaimer unit was industrially and theoretically investigated to remove HSS from a salty amine stream. The presence of ions in the salty amine solution limits application of computer simulation tools to study the process. A thermodynamic equivalent scheme was used for thermal vacuum distillation amine reclaimer, for first time and the simulation results were totally conformed to experimental and industrial data. The effect of critical parameters namely reclaimer vacuum pressure, re-circulation flow rate and HSS amount on performance of thermal amine reclaiming was investigated based on increasing amine solution quality, amine recovery,... 

Application of Cogeneration systems based gas turbine for heat and power production is increasing. Because of finite natural energy resources and increasing energy demand the cost effective design of energy systems is essential. CGAM problem as a cogeneration system is considered here for analyzing. Two new approaches are considered, first in thermodynamic model of gas turbine and cogeneration system considering blade cooling of gas turbine and second using genetic algorithm for optimization. The problem has been optimized from thermodynamic and Thermoeconomic view point. Results show that Turbine Inlet Temperature (TIT) in thermodynamic optimum condition is higher than thermoeconomic one,... 

In this paper, the application of neural networks for simulation and optimization of the cogeneration systems has been presented. CGAM problem, a benchmark in cogeneration systems, is chosen as a case study. Thermodynamic model includes precise modeling of the whole plant. For simulation of the steady sate behavior, the static neural network is applied. Then using dynamic neural network, plant is optimized thermodynamically. Multi layer feed forward neural networks is chosen as static net and recurrent neural networks as dynamic net. The steady state behavior of CGAM problem is simulated by MFNN. Subsequently, it is optimized by dynamic net. Results of static net have excellence agreement... 

Homogeneous charge compression ignition engines require a smart control system to regulate the input quantities of the engine in various operational conditions. Achieving an optimum combustion needs an appropriate system response for different engine loads and speeds according to the power acquired from the engine, as well as the amounts of emissions present in the exhaust. Therefore, performing a set of experimental tests together with numerical simulations in a wide range of conditions facilitates calibration of the input parameters of the engine. In this study, the effects of the thermodynamic parameters and the thermokinetic parameters on the engine output in the preliminary design stage... 

Asphaltene precipitation is a major assurance problem posing significant technical and economic loss on petroleum industry. To tackle this issue, various treatments have been proposed and applied by industry. Amongst, inhibiting or retarding the asphaltene precipitation has been understood as the most efficient approach. In this regard, blending crude oil with chemical additives could appreciably heighten its stability. Surfactants, owing to amphiphilic nature, could keep asphaltene dissolved in crude oil by precluding self-tendency of those particles to making agglomerates. Despite importance of this subject, there is still lack of sufficient experimental data to evaluate effectiveness of... 

In this study, the local composition based models such as the Wilson, the nonrandom two-liquid (NRTL), and the Wilson-NRF have been applied in correlation and estimation of density, viscosity, and surface tension of biodiesels. The thermodynamic models have been used in correlating the thermophysical properties for 215 experimental data points. These models have the interaction energy between each pair that is considered as adjustable parameters. To decrease the number of these adjustable parameters, it is assumed that the biodiesels are composed of two hypothetical components. The average absolute deviation (AADs) of the correlated density of biodiesels for the Wilson, the NRTL, and the... 

Phase identification is an important aspect of flash calculations which can affect the phase and chemical equilibria. A new simultaneous approach for reactive mixtures, based on τ-method which relies on modification equation for mole fraction summation, is introduced in this paper. In the proposed methodology, phase identification and solution of governing equations can be performed simultaneously and effectively. In addition, prior knowledge of the number of phases in advance is not required. Present methodology has been verified with the help of case studies and results are discussed in the present paper. The results indicate that the present method gives us information about presence of... 

The objective of this work is making comparison between thermodynamic models and data-driven techniques accuracy in prediction of hydrate formation pressure as a function of temperature and composition of gas mixtures. The Peng-Robinson (PR) and Patel-Teja (PT) equations of state are used for thermodynamic modeling and Artificial Neural Networks (ANNs) and Adaptive Neuro-Fuzzy Inference System (ANFIS) are used as data-driven models. The capability of each method is evaluated by comparison with the experimental data collected from literature. It is shown that there is a good agreement between thermodynamic modeling and the experimental data in most of the cases; however, the prediction...