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    Investigation of effective parameters on the performance of the helium liquefaction cycle

    , Article International Journal of Heat and Technology ; Volume 37, Issue 4 , 2019 , Pages 1009-1018 ; 03928764 (ISSN) Larijani, M. A ; Eslami, M ; Afshin, H ; Sharif University of Technology
    International Information and Engineering Technology Association  2019
    Abstract
    Due to its unique properties, helium has wide application in different industries and scientific fields, which has turned it into a strategic material. Helium liquefaction plants include wide temperature range from 300 k to 4.2 k, so these plants have high energy consumption. A lot of studies have done to optimize the operation of these cycles. In this research, an exergy analysis is performed for a liquid helium production plant. The optimal performance of 3 and 4 stage cycles is extracted using parametric study and the results are compared with those of Collins dual-expander cycle. The results show that by increasing the number of cooling stages, not only the compressor optimum discharge... 

    Investigation of effective parameters on the performance of the helium liquefaction cycle

    , Article International Journal of Heat and Technology ; Volume 37, Issue 4 , 2019 , Pages 1009-1018 ; 03928764 (ISSN) Larijani, M. A ; Eslami, M ; Afshin, H ; Sharif University of Technology
    International Information and Engineering Technology Association  2019
    Abstract
    Due to its unique properties, helium has wide application in different industries and scientific fields, which has turned it into a strategic material. Helium liquefaction plants include wide temperature range from 300 k to 4.2 k, so these plants have high energy consumption. A lot of studies have done to optimize the operation of these cycles. In this research, an exergy analysis is performed for a liquid helium production plant. The optimal performance of 3 and 4 stage cycles is extracted using parametric study and the results are compared with those of Collins dual-expander cycle. The results show that by increasing the number of cooling stages, not only the compressor optimum discharge... 

    Design and Optimization of Helium Recovery Process from Natural Gas

    , M.Sc. Thesis Sharif University of Technology Azimi, Sajad (Author) ; Afshin, Hossein (Supervisor) ; Farhanieh, Bijan (Co-Supervisor)
    Abstract
    Helium is a valuable substance that is widely used in industry and medicine because of its unique properties. Due to the increasing demand for helium in the global market, several helium extraction units have been launched in the world in recent years; Nevertheless, there is still a significant gap between projected global helium production capacity and demand. Today, natural gas is known as the main source of helium on the earth. The method of industrial extraction of helium from natural gas is cryogenic. Due to the low temperature of this process, relatively high power consumption is used to extract helium from natural gas. Therefore, the optimization of this process is of great... 

    Design and Optimization of Helium Extraction and Liquefaction Cycle from Natural Gas by Direct Method

    , Ph.D. Dissertation Sharif University of Technology Ardeshir Larijani, Morteza (Author) ; Afshin, Hossein (Supervisor)
    Abstract
    Helium is known as a strategic material due to its unique properties and applications in the development of advanced industries. Currently, natural gas is the only source from which helium can be produced economically. The United States, Qatar, Algeria, and Russia have the largest share of helium production, respectively. In this research, the process of helium extraction from natural gas and its liquefaction, independent of LNG production based on helium in South Pars gas of Iran, which is the largest helium reservoir in the world, were designed and simulated.In the helium liquefaction section, the speed and accuracy of the process simulation were improved by developing a home code based on... 

    Study of Effective Parameters on Helium Liquefaction Cycle using Exergy Analysis

    , M.Sc. Thesis Sharif University of Technology Eslami, Mahdi (Author) ; Afshin, Hosein (Supervisor)
    Abstract
    Liquefaction of gases is one of the applications of cryogenic science. Among the gases, Helium has the lowest boiling point, which at a pressure of 1atm is approximately 4.2K. Liquid helium can be used to cool superconductors in transportation equipment, military radars, and medical imaging equipment. For helium liquefaction, various cycles are used; these cycles have different parameters in their structure such as of input mass fraction to expanders, heat exchanger effectiveness, expander arrangement and ... which their analysis for improving the performance of the cycle is important. In this research, the aim is to study 2, 3 and 4 expander cycle with various parameters and structure. For... 

    Synthesis of Graphene Oxide and Graphene Oxide Membrane for Separation of Gas Mixtures

    , M.Sc. Thesis Sharif University of Technology Abbasi, Fateme (Author) ; Ghotbi, Sirus (Supervisor) ; Karimi Sabet, Javad (Supervisor) ; Mousavi, Abbas (Co-Advisor)
    Abstract
    Thin film graphene oxide(GO) membranes have been promising potential for gas purification due to thin lamellar microstructure, stable a few atom thick layers and very short intersheet distances. In this research, the nanoporous graphene oxide membranes have been prepared by vacuum and pressurized ultrafiltration on the modified polyacrylonitryle(mPAN) sublayer for helium separation from Nitrogen and carbon dioxide gas mixture. The separation performance of synthesized GO membrane was controlled by varying parameters such as concentration of stabilized aqueous GO solution, pores size range of support and its surface properties, centrifuge time, applied pressure after synthesis, humidity,... 

    Three Dimensional Simulation and Experimental Modeling of Two Stage GM Type Pulse Tube Refrigeration with Double-Inlet

    , M.Sc. Thesis Sharif University of Technology Ashouri, Mahyar (Author) ; Saidi, Mohammad Hassan (Supervisor)
    Abstract
    There are numerous ways available to achieve low temperatures that cryocoolers might be among the most important of them. In the meantime, the pulse tube refrigerator has a special place due to its simple geometry and not be using any moving parts. This simple property make the pulse tube refrigerator one of the most popular methods to achieve low temperatures. Nowadays, a pulse tube refrigerator is used for cooling in the range of 4 to 123 Kelvin in two form of one-stage and two-stage and up to an approximate power of 1 KW. Today, due to the temperature and the amount of power required for cooling, as well as the time it takes to reach that temperature, this chiller is used in medical,... 

    Design and Simulation of Cryogenic Spiral Heat-exchanger for Gas Liquefaction Plant

    , M.Sc. Thesis Sharif University of Technology Rajabi, Vahid (Author) ; Afshin, Hossein (Supervisor)
    Abstract
    Heat exchangers are one of the most important components used in liquefaction cycles and overall efficiency of the cycle mainly depends on the heat exchangers effectiveness. It has been shown that the effectiveness of these equipments should be high enough to be able to liquefy a gas. Spiral heat exchangers are used frequently in cryogenic industry and specially in Helium liquefaction industry due to their specific characteristics, however according to literature review it turns out that little study is done in the field of simulation and geometrical parameter investigation of these kind of heat exchangers, so in this study the design and simulation of these cryogenics heat exchangers are... 

    One Dimensional Numerical Solution of Pulsating Flow in a Pulse Tube Cycle Considering Real Gas Behavior

    , M.Sc. Thesis Sharif University of Technology Roshanghalb, Farid (Author) ; Saidi, Mohammad Hassan (Supervisor) ; Kazemzade Hannani, Siamak (Co-Advisor)
    Abstract
    Helium gas is the working fluid in common Pulse Tube Refrigerators (PTRs) due to its brilliant properties in reaching cryogenics temperature as low as 4 K. Generally ideal gas equation of state has been used to evaluate thermodynamic performance of He. However using ideal gas equation of state for He in 10 bar and 5 K causes considerable error on estimation of density. The objective is to use real gas equation of state for temperatures near zero Kelvin. This approach makes an accurate prediction of PT cooling capacity and COP. In this thesis the objective is to realize the most relevant equations of state describing the proper behavior of He in the regions of operating point of PTR. Later on... 

    An Economic Approach To Study & Optimization of Helium liquefier

    , M.Sc. Thesis Sharif University of Technology Mahmoudabad Bozchelou, Mohammad Amin (Author) ; Afshin, Hossein (Supervisor)
    Abstract
    Gas liquefaction is one of the main applications of Cryogenics science. Due to the unique properties of Helium, it is a strategic product in the world. Therefore, appropriate and applicable analysis should be used to investigate and optimize the Helium liquefaction cycles. In the current study, the goal is to find the optimal point with the help of energy and exergy analysis based on economic criterion, for the various parameters of Collins’ cycle. In order to simulate the cycle, a computer code is developed. First, sensitivity analysis of different parameters affecting the exergy efficiency and liquid fraction of the cycle has been done. Then, Artificial Neural Network and Genetic Algorithm... 

    Numerical study of species separation in rarefied gas mixture flow through micronozzles using DSMC

    , Article Physics of Fluids ; Volume 31, Issue 4 , 2019 ; 10706631 (ISSN) Sabouri, M ; Darbandi, M ; Sharif University of Technology
    American Institute of Physics Inc  2019
    Abstract
    This work investigates the species separation in the rarefied flow of the argon-helium mixture through convergent-divergent micronozzles. Imposing a molecular mass ratio in the order of 10, the flow of this mixture can lead to the formation of serious nonhomogeneous phenomena such as the species separation. This study is performed in the ranges of 2.0-4.0 for the geometrical expansion ratio, 200-400 K for the wall temperature, and 0.003-1.454 for the inlet Knudsen number. The effects of these parameters are examined on the separative performances of micronozzle. The direct simulation Monte Carlo method is selected as the solution method because it can provide reliable solutions in the... 

    Modeling and analysis of power conversion system for high temperature gas cooled reactor with cogeneration

    , Article 2008 ASME Turbo Expo, Berlin, 9 June 2008 through 13 June 2008 ; Volume 2 , August , 2008 , Pages 649-655 ; 9780791843123 (ISBN) Afrazeh, A ; Khaledi, H ; Ghofrani, M. B ; International Gas Turbine Institute ; Sharif University of Technology
    2008
    Abstract
    A gas turbine in combination with a nuclear heat source has been subject of study for some years. This paper describes the advantages of a gas turbine combined with an inherently safe and well-proven nuclear heat source. The design of the power conversion system is based on a regenerative, non-intercooled, closed, direct Brayton cycle with high temperature gas-cooled reactor (HTGR), as heat source and helium gas as the working fluid. The plant produces electricity and hot water for district heating (DH). Variation of specific heat, enthalpy and entropy of working fluid with pressure and temperature are included in this model. Advanced blade cooling technology is used in order to allow for a... 

    The Modeling of Hydrogen Purification and Carbon Dioxide Capture by two Dimensional Porous Membranes Using Molecular Dynamicssimulations

    , M.Sc. Thesis Sharif University of Technology Rezaee, Parham (Author) ; Tafazzoli, Mohsen (Supervisor)
    Abstract
    Carbon dioxide is one of the most significant greenhouse gases in biocycle. This gas makes the equilibrium temperature by absorbing IR radiations on the earth. It is the reason that prevent the earth from freezing. Increasing CO2 emissions in atmosphere, makes problems such as global warming. According to the Kyoto Protocol, all the countries attended to this protocol, must decrease greenhouse gases emissions. Although H2 fuel is one of the best alternative fuel against fossil fuels, the most important industrial process (steam-methane reforming) produce CO2 as by-product. Thus, gas separation has a prominent role in industrial processes such as CO2 capture and H2 purification.Today, gas... 

    A Numerical Model Development for Cryogenic Spiral Wound Heat Exchanger Design Considering Temperature dependent thermo-physical properties, Heat Leakage, and Longitudinal Heat Conduction

    , M.Sc. Thesis Sharif University of Technology Beheshtikhoo, Amir (Author) ; Afshin, Hossein (Supervisor)
    Abstract
    Cryogenic temperature is below than 123 Kelvin and any physical study that occurs below this temperature is Cryogenic science. Cryogenic has varaiety of application in medical, industry, food, oil and gas etc. Based on this paper and its relavant source spiral wound HE is one of the most optimum HE for cryogenic application specially for helium liquification cycle. In order to liquefy helium in helium cycle efficiency of spiral wound HE shall be over than 85 percent. For this reason and special fluid behavour in low temperature considering property variation, heat in leak and axial conduction is vital for calculating efficiency in cryogenic temperature of helium liquification cycle. In this... 

    The study of microfilter performance in different environments using DSMC

    , Article ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM 2011, 19 June 2011 through 22 June 2011 ; Volume 1 , June , 2011 , Pages 289-294 ; 9780791844632 (ISBN) Darbandi, M ; Karchani, A ; Khaledi Alidusti, R ; Schneider, G. E ; Sharif University of Technology
    2011
    Abstract
    Microfilters are commonly used to block undesirable particles in the fluid flows and to control the flow patterns in MEMS. The main purpose of this study is to understand the effect of gas type on density, pressure, Mach number, and velocity distributions of fluid flows through a microfilter. The Knudsen number is the slip flow regime passing through the microfilter. We use direct simulation Monte Carlo (DSMC) method to simulate the flow of nitrogen, helium, oxygen, air and methane passing through a specific microfilter. The geometry of microfilter is unique in all cases. Our results confirm that every gas performs a different performance passing through a specific microfilter, and that the... 

    Observation of quasi mono-energetic electron bunches in the new ellipsoid cavity model

    , Article Laser and Particle Beams ; Volume 27, Issue 2 , 2009 , Pages 223-231 ; 02630346 (ISSN) Sadighi Bonabi, R ; Navid, H. A ; Zobdeh, P ; Sharif University of Technology
    2009
    Abstract
    In this work, we introduce a new ellipsoid model to describe bubble acceleration of electrons and discuss the required conditions of forming it. We have found that the electron trajectory is strongly related to background electron energy and cavity potential ratio. In the ellipsoid cavity regime, the quality of the electron beam is improved in contrast to other methods, such as that using periodic plasma wakefield, spherical cavity regime, and plasma channel guided acceleration. The trajectory of the electron motion can be described as hyperbola, parabola, or ellipsoid path. It is influenced by the position and energy of the electrons and the electrostatic potential of the cavity. In the... 

    Synthesis and characterization of pure metallic titanium nanoparticles by an electromagnetic levitation melting gas condensation method

    , Article RSC Advances ; Vol. 4, issue. 14 , 2014 , pp. 7104-7108 ; ISSN: 20462069 Mohammadi, A. V ; Halali, M ; Sharif University of Technology
    Abstract
    Pure titanium nanoparticles were synthesized by utilizing an Electromagnetic Levitation Melting Gas Condensation (ELM-GC) method. Pure bulk titanium samples were melted and evaporated by electromagnetic levitation technique in an inert gas atmosphere in a silica tube. Titanium nanoparticles were formed from ascending vapor by employing high purity argon and helium as carrier gases and cooling agents. Particle size and morphology of the produced nanoparticles were studied by Field-Emission Scanning Electron Microscopy (FE-SEM) and Dynamic Light Scattering (DLS) analysis. Results showed almost spherical nanoparticles with a narrow size distribution under both cooling atmospheres. The purity of... 

    Superconducting compact coplanar waveguide filters based on quarter-wavelength spiral resonators with suppressed slot-line mode

    , Article Electromagnetics ; Volume 34, Issue 1 , 2 January , 2014 , Pages 12-18 ; ISSN: 02726343 Javadzadeh, S. M. H ; Bruno, A ; Farzaneh, F ; Fardmanesh, M ; Sharif University of Technology
    Abstract
    Quarter-wavelength superconducting spiral resonators have been used to realize a coplanar waveguide bandpass filter and bandstop filter around the center frequency of 6 GHz. These compact coplanar waveguide filters have been made from 300-nm-thick NbTiN thin film on a 525-μm-thick silicon substrate. The bandpass filter is a six-pole Chebyshev filter with two zero transmissions due to nonadjacent coupling in its structure. Accurately microfabricated air-bridges have been used to suppress the undesired slot-line mode in this filter. The bandstop filter is a very simple two-pole structure that used wire bonding to suppress the slot-line mode. Measurements have been done at a temperature of 4.2... 

    Adsorption and diffusion of Xenon in a granulated nano-NaY zeolite

    , Article Adsorption ; Volume 18, Issue 2 , 2012 , Pages 75-86 ; 09295607 (ISSN) Charkhi, A ; Kazemeini, M ; Ahmadi, S. J ; Allahyar, S. A ; Sharif University of Technology
    Springer  2012
    Abstract
    Henry's law constant and crystal diffusivity of xenon in the granulated nano-NaY zeolite were measured by the pulse gas chromatography method. For this purpose the moments of response peaks of xenon were analyzed. The effect of extra column parts of the utilized chromatographic system was also considered by analyzing the moments of the response peak which was obtained by pulse injection of inert gas of helium into the carrier gas of nitrogen. In addition, the measurement of average velocity of the carrier gas regarding the pressure drop in the extra column parts of the system attributed to precise results. By carrying out the experiments at various temperatures in the range of 30-110 °C the... 

    Gas properties effects in microchannel studies using direct simulation Monte Carlo

    , Article ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels Collocated with 3rd Joint US-European Fluids Engineering Summer Meeting, ICNMM2010, 1 August 2010 through 5 August 2010, Montreal, QC ; Issue PARTS A AND B , 2010 , Pages 1021-1027 ; 9780791854501 (ISBN) Darbandi, M ; Karchani, A ; Akhlaghi, H ; Schneider, G ; Sharif University of Technology
    2010
    Abstract
    This paper concern is to study the gas properties effect in flow and heat transfer behaviors through microchannels using the direct simulation Monte Carlo method. The flow is rarefied and supersonic. The channels are investigated at two different inlet boundary conditions. The collision process is modeled using the NTC (no-time-counter) scheme. The VHS model is chosen to simulate collision between particle pairs. The study is provided for many different gases including nitrogen, helium, and oxygen. The Knudsen number is chosen in a manner to provide slip flow through the channel. The results show that the heat transfer from the wall is lower for heavier gases. A comparative study among the...