Sharif Digital Repository

The natural gas liquid recovery is an important process in a gas plant to correct hydrocarbon dew point and earn profit. In this study, a natural gas liquid recovery unit operated based on the Joule–Thomson process was investigated and its performance was optimized. To improve the system performance, the plant configuration and intermediate pressure ratio were defined as the variables and maximization of the natural gas liquid recovery rate and maximization of exergy efficiency were defined as the objective functions. To improve the plant performance, the amount of natural gas liquid recovery rate should be increased. To achieve this goal, several scenarios for the intermediate pressure... 

A thermodynamic analysis was conducted on the Joule-Thomson (JT) process to improve separation performance and exergy efficiency of a three-stage throttling process in a natural gas liquid (NGL) recovery plant. The JT inversion curve (JTIC) along with the phase envelope diagram (PED) were used to study phase transition during the throttling process. Three different objective functions—maximization of NGL recovery rate, improvement of cooling performance, and minimization of the exergy destruction—were investigated in this study to increase the NGL recovery rate with minimum energy consumption. It was observed that the improvement of cooling performance did not always increase the NGL... 

In this study, six cubic equations of state (CEoSs) were used to predict the Joule-Thomson coefficient (JTC), specific heat capacity (SHC), inversion curve (IC) and outlet temperature of the Joule-Thomson (JT) valve parameters. The accuracy of each CEoS was evaluated from the comparison of experimental data with obtained results. Of the six CEoSs, three-paramter CEoSs— Esmaeilzadeh and Roshanfekr (ER), Harmen and Knapp (HK), and Patel and Teja (PT)— were more accurate than two-paramter equations— Nasrifar and Moshfeghian (NM), Peng-Robinson (PR), and Soave-Redlich-Kwong (SRK). Ironically, original SRK showed the optimum accuracy in estimation of JTC. In addition, the Joule-Thomson inversion... 

In this work, gas dehydration and natural gas liquid (NGL) recovery by the Joule-Thomson (JT) process, were investigated using the computational fluid dynamics (CFD) modeling approach. Droplet behavior inside the separator was analyzed by particle tracing and moisture diffusion methods. The modified separator reduced the water content of natural gas from 0.008 to 0.0029 kg/m3. In addition, the separation efficiency was increased by addition of internal components. One of the added internal components was an inlet deflector. Among different inlet deflectors, the reversed type one exhibited the highest separation efficiency. The separation efficiency improved from 6 to 10% in the original... 

In this study, the effects of several structural and operational parameters affecting the separation efficiency of supersonic separators were investigated by numerical methods. Different turbulence models were used and their accuracies were evaluated. Based on the error analysis, the V2-f turbulence model was more accurate for describing the high swirling turbulent flow than other investigated turbulence models. Therefore, the V2-f turbulence model and particle tracing model were selected to optimize the structure of the convergence part, the diffuser, the drainage port, and the swirler. The cooling performance of three line-type in the convergent section were calculated. The simulation... 

Background/Objectives: In this paper by utilizing frequency tracking electrical loads are shared on voltage source converters and then by applying a proposed-supplementary control system, frequency changes during changing electrical loads inside network is omitted. Methods/Statistical Analysis: Using decentralized control in Microgrids and sharing loads on power generation units respect to their nominal capacity are unavoidable approaches to have stable and operational network. Droop control in load sharing is known as practical and significant solution. In droop control, units output frequency, changes proportional to output active power that is not preferable. Simulation results in PSCAD... 

Learning a foreign language encompasses a process of trial and error that can lead to the progression of the learner's interlanguage, meaning that the learners make use of their language knowledge that receives feedback and brings about progress through diagnosis of the problems and being corrected by the teacher. Therefore, there exists a need to analyze the underlying reasons causing the students to remain taciturn with a low willingness to communicate (WTC) during a language class. There has been much work done investigating the role of the learner's stable personal characteristics (traits) along with their situational changes at a specific time (states) that influence the student's... 

Accurate system identification (SI) is essential for flight controller design of unmanned aerial vehicles and microaerial vehicles (MAVs). SI can be performed either in frequency or time domain using flight test data. As flight testing is often costly and may even lead to catastrophic events before some flight stability analysis is at hand, a low-cost 5 degree-of-freedom free motion platform (FMP) is designed and used for initial identification of MAVs via wind tunnel testing. A typical MAV is constructed as a test case and equipped with inertial sensors for testing and validation purposes. The proposed FMP allows for both rotational as well as translational motions that in turn provide for... 

Using 3-D scanned data to analyze and extract pore network plays a vital role in investigation of porous media's characteristics. In this paper, a new simple method is developed to detect pores and throats for analyzing the connectivity and permeability of the network. This automated method utilizes some of the common and well-known image processing functions which are widely accessible by researchers and this has led to an easy algorithm implementation. In this method, after polishing and quality control of images, using city-block distance function and watershed segmentation algorithm, pores and throats are detected and 3-D network is produced. This method can also be applied on 2-D images... 

In this paper, we try to recognize and distinguish different groups of arrhythmia using novel features which have been obtained from the heart rate's phase space in recent years. For this purpose, we used Triangular Phase Space Mapping (TPSM) and Parabolic Phase Space Mapping (PPSM). For recognition, we used three groups of 15 subjects using the Physionet database (Arrhythmia, Congestive Heart Failure (CHF), and Atrial Fibrillation (AF)) with Normal Sinus Rhythm (NSR). The obtained features discriminate arrhythmia from NSR by p