Loading...
Search for:
low-temperatures
0.017 seconds
Total 142 records
Performance and Rheological Characteristics of Modified Binders
, M.Sc. Thesis Sharif University of Technology ; Tabatabaee, Nader (Supervisor)
Abstract
The ever increasing usage of modified binders in road construction requires that the effect of different modifiers on the performance characteristics of the asphalt binder be determined through laboratory testing. The current Superpave protocol for performance grading asphalt binders has proven to be insufficient to properly characterize modified binders, thus researchers have searched for other testing methods to complement or possibly replace some of the Superpave tests. Most notable are the time sweep test for fatigue resistance, the multiple stress creep and recovery test (MSCR) for rutting resistance and the direct tension test (DTT) for low temperature cracking characteristics. In the...
Experimental and Numerical Investigations of Reactivity Controlled Compression Ignition (RCCI)Combustion Fueled by Diesel and Natural Gas
, Ph.D. Dissertation Sharif University of Technology ; Hosseini, Vahid (Supervisor) ; Shamloo, Amir (Supervisor)
Abstract
In this thesis, reactivity controlled compression ignition (RCCI) combustion fueled by diesel and natural gas is experimentally and numerically investigated. Natural gas as a fuel with low reactivity is injected into the intake manifold, and diesel as a fuel with high reactivity is injected directly into the combustion chamber. One of the main goals of this thesis is to experimentally examine the effect of important parameters on combustion phasing control, operational range extension, and pollutants. Natural gas is one of the important sources of energy in Iran and the world. Using natural gas in internal combustion engines can cause methane to slip into the atmosphere and intensify the...
CFD Modeling of PCCI Combustion for early Direct Injection of Diesel Fuel
, M.Sc. Thesis Sharif University of Technology ; Hosseini, Vahid (Supervisor) ; Taghizadeh Manzari, Mehrdad (Supervisor)
Abstract
At today’s crowded world, the importance of automobile transportation is obvious for all. Due to energy crisis and air pollution problems, designing and manufacturing high-performance and low emission engines is very important. Because of high efficiency and low fuel consumption, diesel engines have attracted more attention. In addition to the mentioned advantages, diesel engine’s nitrogen oxide and particulate matter emissions are very high. So to limit these pollutants, strict standards was legislated by different countries and nations. Recently in the field of diesel engines emission reduction, low temperature combustion concept is proposed that can reduce nitrogen oxide and particulate...
Design and Optimization of Helium Recovery Process from Natural Gas
, M.Sc. Thesis Sharif University of Technology ; 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...
Numerical and Experimental Analysis of Homogeneous Charge Compression Ignition with Normal Paraffins, Branched-chain Paraffins and Aromatics Combined Fuels
, Ph.D. Dissertation Sharif University of Technology ; Hosseini, Vahid (Supervisor) ; Mozafari, Ali Asghar (Supervisor)
Abstract
The purpose of this dissertation is to experimentally and numerically investigate the effect of molecular structure, composition, and physical and chemical properties of fuel on HCCI combustion. A well-equipped laboratory was set up to perform the required tests, capable of performing HCCI tests with different fuels. All tests used a single-cylinder diesel engine modified to operate in HCCI mode. Also, for numerical simulation, a chemical kinetic multi-zone model was developed to predict HCCI combustion behavior with appropriate accuracy. To investigate the effect of fuel chemical structure on HCCI combustion, three fuels, toluene, iso-octane and normal heptane, with entirely different...
SnO2 Layer Curing as a Low Temperature Electron Transporting Layer in Perovskite Solar Cell
, M.Sc. Thesis Sharif University of Technology ; Taghavinia, Nima (Supervisor)
Abstract
Perovskite solar cells have attracted much attention due to their high photovoltaic performance. The excellent performance of perovskite solar cells is attributed to the superior electrical properties of each layer, including the electron-transporting layer, the light-absorbing layer, and the hole-transporting layer. The electron transport layer plays a key role in influencing the photovoltaic parameters of perovskite solar cells. SnO2 is considered as an ideal electron transport layer for perovskite solar cells due to its high carrier mobility, deep conduction band, suitable band gap and low temperature processing. Surface modification of SnO2 has significantly improved device performance...
Investigation and Accomplishment of CO2 Capturing with Solid Sorbent
, M.Sc. Thesis Sharif University of Technology ; Safekordi, Ali Akbar (Supervisor)
Abstract
Carbon dioxide emissions account for 80% of current greenhouse gas emissions that contribute to global warming; this majority stake held by carbon dioxide indicates that reduction in its release to the atmosphere and capturing emissions accomplished is imperative in conservation of human life in earth. The aim of this project is CO2 capturing from ambient air to decrease air pollution with uses building surface that is wide available surface, as basis of adsorbent. In this research, we select CaO as absorbent that it is proven good absorbent in high temperature for CO2. We studied this absorbent in low temperature and pressure. We experimented different weight amount of sorbent 2,3,4,5,6.5...
Experimental and Numerical Study on Reactivity Controlled Compression Combustion Ignition Natural Gas-diesel
, M.Sc. Thesis Sharif University of Technology ; Hosseini, Vahid (Supervisor)
Abstract
According to limitation of fossil fuel consumption and cost, reduction of fuel consumption is very important in internal combustion engine. This requirement becomes twofold in light of the greenhouse effect of CO2 on global warming. Therefore, the use of engines with less fuel consumption is a global success. Diesel engines are among the most productive internal combustion engines. They have a lower fuel economy and carbon monoxide. But unfortunately, these engines respectively in rich and dilute blend have highly soot and nitrogen oxides. One of the methods in the development of the combustion process is the low temperature combustion method, which reduces the production of Knox due to low...
On the Microstructure and Mechanical Properties of Aluminum after Low-temperature Multi-directional Forging
, M.Sc. Thesis Sharif University of Technology ; Kazeminezhad, Mohsen (Supervisor)
Abstract
Severe Plastic Deformation (SPD) has been used as an effective approach to access fine grain (FG) and ultra-fine grain (UFG) materials.the Temperature of SPD is a dominant parameter to controlling ultimate properties. SPD at room-temperature and the high temperature was used widely in literature but the low-temperature process (sub-zero and cryogenic temperatures) was not used comparably. In this study, Low-temperature Multi-Directional Forging (LMDF) was applied on commercially pure aluminum and room-temperature MDF (RMDF) was attained for contrast temperature effects, and resulting in more fine grains. The grain refinement was attributed to the fragmentation process with a limitation in...
Microstructure Investigation of Low Temperature Carburized Precipitation Hardenable 17-4 And 13-8 Mo Stainless Steels
, M.Sc. Thesis Sharif University of Technology ; Asgari, Sirous (Supervisor)
Abstract
Recently, low temperature carburizing of stainless steels, especially austenitic stainless steels, have been considered by so many researchers. The improvement of tribological properties of which is so impressive so much so that such properties like hardness and wear resistance increase to manifold. In this research, low temperature carburizing was done on two kinds of precipitation hardenable stainless steels 17-4 and 13-8 Mo. After that, microstructural investigations were done on the carburized surfaces and in 5, 10, 20, 80, and 150 micrometer depths. Moreover, in each depth, in order to phase structure and tribological properties investigation, XRD and microhardness tests were done,...
Experimental Study of the Conversion of Heat to Electricity Using Movement of a Magnet Inside an Oscillating Heat Pipe
, M.Sc. Thesis Sharif University of Technology ; Shafii, Mohammad Behshad (Supervisor)
Abstract
Heat sources with temperatures less than 100 °C are available in various processes in the form of waste heat and from renewable sources such as solar energy. One of the methods of gaining benefit from these ubiquitous and abundant heat sources is using thermal harvesters that convert low-temperature heat into electrical energy without the need for the power grid. Portable harvesters can be a reliable and low-cost option for providing stable energy for low-power electronic devices such as wireless sensors. Many studies have been conducted at the global level to design and develop efficient low-temperature heat harvesting mechanisms. However, each of them is associated with fundamental...
Low Temperature Performance Evaluation of Modified Asphalt Binders
, M.Sc. Thesis Sharif University of Technology ; Tabatabaei, Nader (Supervisor)
Abstract
Low temperature cracking is the most important type of asphalt pavement distress that occurs in cold climates. Up until the development of performance grading (PG) based binder specification, there was no irect indication of low temperature suitability of asphalt binders. PG specification was mainly developed for and validated by neat binders.
With increased use of modified asphalt binders in recent years, some of the limitations and shortcomings of the original PG specifications have surfaced.Considering that low temperature cracking is a fracture failure, it was hypothesized that tests based on the fracture mechanics and fracture energy parameter can lead to better classification of...
With increased use of modified asphalt binders in recent years, some of the limitations and shortcomings of the original PG specifications have surfaced.Considering that low temperature cracking is a fracture failure, it was hypothesized that tests based on the fracture mechanics and fracture energy parameter can lead to better classification of...
Evaluation of Warm Mix Asphalt containing Sasobit
, M.Sc. Thesis Sharif University of Technology ; Tabatabaee, Nader (Supervisor)
Abstract
Warm mix asphalt has received considerable attention over the past decade particularly due to its potential environmental benefit such as lower energy consumption and emission, its ability to be placed at lower ambient temperatures making it a suitable material for areas with short construction season. There are three warm mix asphalt (WMA) techniques are available; organic additive, foaming, and chemical additive. This study examined Sasobit, a micro crystalline wax which is an organic additive. The concentrations tested were 1.5, 2.5 and 3.5 percent of the base binder. A PG 64-22 asphalt binder from an Iranian refinery (Tehran refinery) was used as the base binder. Superpave binder...
Water-energy nexus approach for optimal design of hybrid cooling system in direct reduction of iron plant
, Article Journal of Cleaner Production ; Volume 287 , 2021 ; 09596526 (ISSN) ; Morad Bazofti, M ; Akbari Mohammadi, A ; Mokhtari, H ; Saboohi, Y ; Golkar, B ; Ghandi, A. H ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Direct reduction of iron process in steel industry has special production conditions. Low quality cooling water, low cold and high hot cooling water temperature, space limitation for new equipment installation, high value-added of product and severe effect of cooling water temperature on production rate are of these conditions. Considering technical and economic constraints and limitations, this situation makes this process an attractive case study for converting the existing wet cooling tower to hybrid cooling system. In this paper, based on integration of process, dry and wet cooling system and ambient conditions profiles, a new method for designing hybrid cooling system has been proposed....
Water-based sol-gel nanocrystalline barium titanate: Controlling the crystal structure and phase transformation by Ba:Ti atomic ratio
, Article Journal of Materials Science ; Volume 44, Issue 18 , 2009 , Pages 4959-4968 ; 00222461 (ISSN) ; Esmaeili Rad, A ; Fray, D. J ; Sharif University of Technology
2009
Abstract
Highly stable, water-based barium titanate (BaTiO3) sols were developed by a low cost and straightforward sol-gel process. Nanocrystalline barium titanate thin films and powders with various Ba:Ti atomic ratios were produced from the aqueous sols. The prepared sols had a narrow particle size distribution in the range 21-23 nm and they were stable over 5 months. X-ray diffraction pattern revealed that powders contained mixture of hexagonal- or perovskite-BaTiO3 as well as a trace of Ba2Ti 13O22 and Ba4Ti2O27 phases, depending on annealing temperature and Ba:Ti atomic ratio. Highly pure barium titanate with cubic perovskite structure achieved with Ba:Ti = 50:50 atomic ratio at the high...
Viscoelastic-based approach to evaluate low temperature performance of asphalt binders
, Article Construction and Building Materials ; Volume 128 , 2016 , Pages 384-398 ; 09500618 (ISSN) ; Karimi, M. M ; Moghadas Nejad, F ; Jahangiri, B ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
Through the strategic highway research program (SHRP) project, time-temperature superposition (TTS) was used to reduce the loading time of bending beam rheometer (BBR) test. Based on TTS, stiffness of the asphalt binder after a two-hour loading time is similar to that after 60 s at 10 °C above. This study attempted to evaluate the TTS validity using finite element (FE) method by developing master curves in a broad range of low temperatures. The results indicated that TTS was neither valid for modified asphalt binders nor for neat binder. Also, in addition to the loading time dependency of m-value, limiting values of stiffness and m-value find no rheological acceptance. As a remedy, thermally...
Ultra-high voltage SnO2 based varistors prepared at low temperature by two-step sintering
, Article Journal of Alloys and Compounds ; Volume 805 , 2019 , Pages 794-801 ; 09258388 (ISSN) ; Delshad Chermahini, M ; Alipour, S ; Mahmoudi, P ; Safaee, I ; Abdollahi, M ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
In this research, full density, single phase microstructure (in the XRD and SEM detection limits), and fine-grained SnO2 varistors with an average grain size of 0.65 μm was acquired at low temperature by the two-step sintering technique. The sintering temperature was successfully decreased from 1300 °C in the normal sintering to 1150 °C and 1100 °C of respectively the first and the second stage in the two-step sintering. The mechanism of grain growth suppression of the two-step sintered samples was discussed and it was suggested that in addition to triple point junction, solute drag and/or nano-secondary phases contribute to cease the grain growth. These SnO2 varistors exhibited ultra-high...
Thermodynamic behavior of the XXZ Heisenberg s = 1/2 chain around the factorizing magnetic field
, Article Journal of Physics Condensed Matter ; Volume 22, Issue 21 , May , 2010 ; 09538984 (ISSN) ; Langari, A ; Siahatgar, M ; Sharif University of Technology
2010
Abstract
We have investigated the zero-and finite-temperature behaviors of the anisotropic antiferromagnetic Heisenberg XXZ spin-1/2 chain in the presence of a transverse magnetic field (h). The attention is concentrated on an interval of magnetic field between the factorizing field (hf) and the critical one (hc). The model presents a spin-flop phase for 0 < h < hf with an energy scale which is defined by the long range antiferromagnetic order while it undergoes an entanglement phase transition at h = hf. The entanglement estimators clearly show that the entanglement is lost exactly at h = hf, which justifies different quantum correlations on both sides of the factorizing field. As a consequence of...
Thermodynamic analysis of application of organic Rankine cycle for heat recovery from an integrated DIR-MCFC with pre-reformer
, Article Energy Conversion and Management ; Volume 67 , 2013 , Pages 197-207 ; 01968904 (ISSN) ; Khazaeli, A ; Roshandel, R ; Panjeshahi, M. H ; Sharif University of Technology
2013
Abstract
This work deals with waste heat recovery from a proposed direct internal reforming molten carbonate fuel cell (DIR-MCFC), including an integrated pre-reformer. In this regard, some advantages are attainable over exhaust gas recycling. For instance, due to low temperature in the pre-reformer, carbon deposition and coke formation resulting from higher hydrocarbons can be eliminated. In this study, the cathode outlet provides the heat requirement for the pre-reforming process. After partial heat recovery from the cathode outlet, the stream still has a considerable energy and exergy (352.55 °C and 83.687 kW respectively). This study investigates waste heat recovery from the proposed DIR-MCFC,...
Thermal stability investigation of expanded martensite
, Article Surface and Coatings Technology ; Volume 300 , 2016 , Pages 87-94 ; 02578972 (ISSN) ; Bahmannezhad, B ; Nikpoor, N ; Asgari, S ; Sharif University of Technology
Elsevier
2016
Abstract
The aim of this work is to investigate thermal stability of expanded martensite. For this purpose, two martensitic stainless steels, PH 17-4 and 13-8Mo, were low temperature gas carburized. After heat treatment, it was found out that thermal stability of expanded layer of PH 17-4 is higher than that of PH 13-8Mo. Auger Electron Spectroscopy and microhardness machines were used to investigate carbon concentration and hardness of samples, respectively. X-ray diffraction was done to study crystal structures of samples before and after heat treatment