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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... 

    Molecular dynamics simulation of nano channel as nanopumps

    , Article ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM 2011, 19 June 2011 through 22 June 2011, Edmonton, AB ; Volume 2 , 2011 , Pages 223-227 ; 9780791844649 (ISBN) Darbandi, M ; Abbasi, H. R ; Khaledi Alidusti, R ; Sabouri, M ; Schneider, G. E ; Sharif University of Technology
    Abstract
    We use three-dimensional molecular dynamics simulation to investigate the driven flow between two parallel plates separated by argon atoms. Our simulations show that fluids in such channels can be continuously driven. Difference in surface wettability can cause a difference in fluid density along the nano channel. To control the nanochannel temperature walls, we use the thermal wall idea, which models the walls using atoms connected to their original positions by enforcing linear spring forces. In this study, we propose a nanochannel system in which, half of the channel has a low surface wettability, while the other half has a higher surface wettability and that the middle part of channel... 

    Developing cross drag expressions for nanotube bundles using molecular dynamics

    , Article ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM 2011, 19 June 2011 through 22 June 2011 ; Volume 2 , June , 2011 , Pages 259-263 ; 9780791844649 (ISBN) Darbandi, M ; Khaledi Alidusti, R ; Abbaspour, M ; Abbasi, H. R ; Sabouri, M ; Schneider, G. E ; Sharif University of Technology
    2011
    Abstract
    The nonequilibrium molecular dynamics (NEMD) simulations are performed to calculation the cross drag over a nanotube located in a uniform liquid argon flow. As is known, the behavior of fluid flows in nano-scale sizes is very different from that in microscopic and macroscopic sizes. In this work, our concern is on the flow of argon molecules over a nanotube which occurs in nanoscale sizes. We calculate the cross drag enforced the nanotube at Re<10. In this regard, we use the molecular dynamics and simulate the flow of argon molecules over (6,0), (8,0) and (10,0) nanotubes. The simulations are performed at different velocities and the cross drag coefficient is computed at different Reynolds... 

    Simulation of methanol carbonylation reactor in acetic acid production plant: selection of an appropriate correlation for mass transfer coefficients

    , Article International Journal of Chemical Reactor Engineering ; Volume 17, Issue 4 , 2019 ; 15426580 (ISSN) Jafari, A. A ; Tourani, S ; Khorasheh, F ; Sharif University of Technology
    De Gruyter  2019
    Abstract
    This paper deals with mathematical modeling and simulation of methanol carbonylation reactor in acetic acid production plant that consisted of a continuous stirred tank reactor (CSTR), a flash drum, a Joule-Thomson valve, and a condenser. The model was based on material and energy balances that considered liquid-gas mass transfer, thermodynamics, and reactor hydrodynamics. The most important aspect of the model was the selection of an appropriate correlation for prediction of mass transfer coefficient. Several correlations were examined and comparison of the model results with plant data indicated that the correlation reported by Lemoine was most appropriate. The simulation results were... 

    Polymeric like carbon films prepared from liquid gas and the effect of nitrogen

    , Article Applied Surface Science ; Volume 254, Issue 20 , 15 August , 2008 , Pages 6441-6445 ; 01694332 (ISSN) Ghodselahi, T ; Vesaghi, M. A ; Sharif University of Technology
    Elsevier  2008
    Abstract
    Polymeric like carbon (PLC) films are grown by a capacitance coupled RF-PECVD on the grounded electrode at room temperature from liquid gas (40% propane and 60% butane) in two regimes with nitrogen and without nitrogen gas. Films are characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), Fourier transform infrared (FTIR) absorption and Raman spectroscopy. The result of FTIR analyses indicates that more than 90% of hydrogen atoms are bonded to carbon with sp 3 hybridization. The abundance of CH 3 is more than that of CH 2 and this one is more than that of CH for carbon with sp 3 hybridization in these films. The C 1s line of the XPS spectra is deconvoluted to... 

    Shielding factor enhancement method for Bi-stage active shield in SQUID-based magnetocardiography system

    , Article 29th Iranian Conference on Electrical Engineering, ICEE 2021, 18 May 2021 through 20 May 2021 ; 2021 , Pages 129-133 ; 9781665433655 (ISBN) Alipour, Z ; Esmaeili, F ; Shanehsazzadeh, F ; Fardmanesh, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Abstract
    We proposed a simple method to enhance shielding factor of our previously proposed bi-stage active shield system employed in a SQUID-based magnetocardiography system. The additional proposed design is optimized for canceling the power-line magnetic interference field to provide a calmer magnetic environment for the bi-stage active shield. A 50 Hz cancellation coil is placed around the bi-stage shielding system which includes inner and outer coils designed for compensating low-frequency (0-0.1Hz) and high-frequency (0.1-100Hz) environmental magnetic noise, respectively. In this configuration, a SQUID magnetometer is located at the center of these coils. Considering that the power-line... 

    Shielding factor enhancement method for bi-stage active shield in SQUID-based magnetocardiography system

    , Article 29th Iranian Conference on Electrical Engineering, ICEE 2021, 18 May 2021 through 20 May 2021 ; 2021 , Pages 129-133 ; 9781665433655 (ISBN) Alipour, Z ; Esmaeili, F ; Shanehsazzadeh, F ; Fardmanesh, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Abstract
    We proposed a simple method to enhance shielding factor of our previously proposed bi-stage active shield system employed in a SQUID-based magnetocardiography system. The additional proposed design is optimized for canceling the power-line magnetic interference field to provide a calmer magnetic environment for the bi-stage active shield. A 50 Hz cancellation coil is placed around the bi-stage shielding system which includes inner and outer coils designed for compensating low-frequency (0-0.1Hz) and high-frequency (0.1-100Hz) environmental magnetic noise, respectively. In this configuration, a SQUID magnetometer is located at the center of these coils. Considering that the power-line... 

    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... 

    A molecular dynamics study of fluid flows through slit-like nanochannels using two different driving systems

    , 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 ; Issue PARTS A AND B , 2010 , Pages 1029-1033 Darbandi, M ; Khaledi Alidusti, R ; Sabouri, M ; Abbasi, H. R ; Sharif University of Technology
    Abstract
    The Poiseuille flow through slit-like nanochannels is investigated using the nonequilibrium molecular dynamics simulations. To drive a dense flow through the channel, we use two self-adjusting vertical plates strategy. These plates force the liquid to flow through the nanochannel under adjustable inlet and outlet boundary conditions. Comparing with the dual-control-volume grand-canonical molecular dynamics method, the current strategy provides many advantages. The current strategy does not need particle insertion and deletion, therefore, the system dynamics would not be affected at all. Moreover, the number of particles in the simulation system is fixed due to inserting the two... 

    Numerical investigation of gaseous hydrogen and liquid oxygen combustion under subcritical condition

    , Article Energy and Fuels ; Volume 33, Issue 9 , 2019 , Pages 9249-9271 ; 08870624 (ISSN) Mardani, A ; Ghasempour Farsani, A ; Farshchi, M ; Sharif University of Technology
    American Chemical Society  2019
    Abstract
    This study is on combustion modeling of gaseous hydrogen and cryogenic liquid oxygen at the subcritical condition for the well-known Mascotte laboratory combustor. The proposed strategy relies on the hybrid Eulerian-Lagrangian framework in which the continuous phase is evaluated by Reynolds Average Navier-Stokes (RANS) equations and the quick discretization method. The dispersed phase of the combustion field is evaluated by the Discrete Phase Method (DPM). The Eddy Dissipation Concept (EDC) has been performed for combustion-turbulence interaction modeling. Effects of the turbulence model, chemical kinetic mechanism, equation of state, and inlet momentum jet flux are investigated in terms of... 

    HTS transformer’s partial discharges raised by floating particles and nitrogen bubbles

    , Article Journal of Superconductivity and Novel Magnetism ; Volume 33, Issue 10 , 6 July , 2020 , Pages 3027-3034 Moradnouri, A ; Vakilian, M ; Hekmati, A ; Fardmanesh, M ; Sharif University of Technology
    Springer  2020
    Abstract
    Presence of defects, conducting particles, nonconducting particles, and nitrogen gas bubbles in the insulation system of high-temperature superconducting (HTS) transformers, mainly inside the liquid nitrogen as its major insulation, can create local field enhancement and consequently partial discharges which eventually lead to the catastrophic failure of the transformer. In this paper, two-dimensional (2D) axisymmetric finite element method (FEM) modeling via COMSOL Multiphysics software has been utilized for the investigation of the impact of size and shape of conducting particles and nitrogen gas bubbles on partial discharge (PD) activities in liquid nitrogen. Conducting particles of... 

    The end part of cryogenic H. V. bushing insulation design in a 230/20 kV HTS transformer

    , Article Cryogenics ; Volume 108 , June , 2020 Moradnouri, A ; Vakilian, M ; Hekmati, A ; Fardmanesh, M ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    Appealing advantages of high-temperature superconducting (HTS) transformers are very promising for the contemporary and future power delivery systems. Cryogenic insulation technology is one of the key technologies for their commercialization. In this paper insulation design of the end part of cryogenic high voltage (H. V.) bushing of a 230/20 kV HTS transformer is developed. Analytical relations and finite element method (FEM) modelling, through application of COMSOL Multiphysics software, are employed for determination of electric field distribution in this design process. Weibull 0.1% dielectric breakdown strength has been considered as criterion for insulation design. Different shape and... 

    Numerical study of the pseudo-boiling phenomenon in the transcritical liquid oxygen/gaseous hydrogen flame

    , Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; 2020 Zeinivand, H ; Farshchi, M ; Sharif University of Technology
    SAGE Publications Ltd  2020
    Abstract
    The interactions and effects of turbulent mixing, pseudo-boiling phenomena, and chemical reaction heat release on the combustion of cryogenic liquid oxygen and gaseous hydrogen under supercritical pressure conditions are investigated using RANS simulations. Comparisons of the present numerical simulation results with available experimental data reveal a reasonably good prediction of a supercritical axial shear hydrogen-oxygen flame using the standard k-ε turbulence model and the eddy dissipation concept combustion model with a 23 reaction steps kinetics for H2-O2 reaction. The present simulation qualitatively reproduced oxygen injection and its reaction with the co-flowing hydrogen, which is... 

    Simulation of wetting tendency of fluids with high density ratios using RK Lattice Boltzmann method

    , Article 16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019, 14 October 2019 through 18 October 2019 ; 2020 Sadeghi, M ; Pak, A ; Sadeghi, H ; Sharif University of Technology
    Asian Regional Conference on Soil Mechanics and Geotechnical Engineering  2020
    Abstract
    Several lattice Boltzmann models for multi-phase flow have been developed, but few of them are capable of modeling fluid flows with high density ratio in the order of 1000. Therefore, an advanced chromodynamics, Rothmann-Keller (RK) type model is employed in current study, which can handle liquid-gas density ratio in the order of 1000 and viscosity ratio in the order of 100. Other distinctive characteristics of the proposed model are high stability, and capability of setting parameters such as surface tension independently. In spite of these benefits, the original RK model fails to model wetting tendency of the fluids. As a result, it is impossible to correctly simulate two-fluid phase flow... 

    Simulation of heat transfer in nanoscale flow using molecular dynamics

    , 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 1563-1568 ; 9780791854501 (ISBN) Darbandi, M ; Abbasi, H. R ; Sabouri, M ; Khaledi Alidusti, R ; Sharif University of Technology
    2010
    Abstract
    We investigate heat transfer between parallel plates separated by liquid argon using two-dimensional molecular dynamics (MD) simulations incorporating with 6-12 Lennard-Jones potential between molecule pairs. In molecular dynamics simulation of nanoscale flows through nanochannels, it is customary to fix the wall molecules. However, this approach cannot suitably model the heat transfer between the fluid molecules and wall molecules. Alternatively, we use thermal walls constructed from the oscillating molecules, which are connected to their original positions using linear spring forces. This approach is much more effective than the one which uses a fixed lattice wall modeling to simulate the... 

    Energy, exergy, and economic analyses of an innovative energy storage system; liquid air energy storage (LAES) combined with high-temperature thermal energy storage (HTES)

    , Article Energy Conversion and Management ; Volume 226 , 15 December , 2020 Nabat, M. H ; Zeynalian, M ; Razmi, A. R ; Arabkoohsar, A ; Soltani, M ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    Liquid air energy storage is one of the most recent technologies introduced for grid-scale energy storage. As the title implies, this technology offers energy storage through an air liquefaction process. High energy storage density, no geographical limitation, and applicability for large-scale uses are some of the advantages of this technology. To improve the performance and environmental friendliness of the conventional design of this technology, a novel liquid air energy system combined with high-temperature thermal energy storage, thermoelectric generator, and organic Rankine cycle is proposed in the present article. The thermal energy storage unit removes the need for the conventional...