Sharif Digital Repository

Nanofluids viscosity is one of the most important thermophysical properties in nanofluids usage especially in chemical and petroleum engineering applications. So it is highly desirable to predict the viscosity of nanofluids accurately. Experimental measurements are impossible in most situations and present models are not comprehensive and efficient especially for high temperature, high volume concentration and high viscosity values. In this study, a new correlation has been developed based on the comprehensive database of water based Al2O3, TiO2, SiO2 and CuO nanofluids viscosity data found in literature. The proposed correlation uses temperature, nanoparticle size, nanoparticle volumetric... 

In this paper, an experimental evaluation on the viscosity of water-based manganese ferrite nanofluid with and without magnetic field with 100, 200, 300, and 400 G intensities has been conducted. The Brookfield DV-I PRIME viscometer is implemented to measure the MnFe2O4/water nanofluid viscosity and to evaluate the influence of different volume concentrations (from 0.25% to 3%) and various temperatures (from 20 to 60 °C) on the viscosity. According to the measurements, viscosity incrementally increases with the augmentation of nanoparticles concentration while it remarkably decreases at higher temperatures under absence and attendance of magnetic field. The maximum viscosity ratio of 1.14 is... 

Erosive wear is one of the efficiency reduction causes in centrifugal compressors. The presence of suspended solid particles in the fluid causes deformations in different parts of the compressor, especially blades of the impeller. Therefore, erosion not only decreases the part lifetime by destruction of blades form, but also increases energy losses. For this reason, specifying the erosion locations and choosing a suitable material have an important effect on optimum functionality of the machine. In this paper, erosion locations of a compressor impeller by using computational fluid dynamics (CFD) in high temperature and pressure are attained and compared with experimental model. The... 

In this study, the influence of temperature on serrated flow behavior, strain rate sensitivity (SRS) and effective activation volume in a Ti-based bulk metallic glass (BMG) bent at different strain rates has been investigated. Results reveal that the fundamental origin of shear deformation is related to the time-dependent structural relaxations, which occur during deformation at special temperatures and strain rates. Furthermore, the localized structural relaxation processes at intermediate temperatures cause an inelastic shuffling within cages and mitigate the activation of STZs. The main reason of negative SRS at intermediate temperatures is due to the insufficient time for structural... 

In this study, the flow of a fiber filled viscoelastic matrix through planar contractions is investigated. It was found that by adding fiber to the matrix vortex, the intensity increases. Fiber orientation along "x" and "y" axes was studied too. It was found that fiber orientation could be used for determining the flow regime through the contraction geometry. The rigidity condition of fibers, which needs the trace of the orientation tensor to be unity everywhere in the domain, is correct except near walls and the reentrant corner, which is slightly less than one. In these regions, the stress magnitude is higher, which results in more numerical errors, and which further leads to some error in... 

The aim of this paper is to investigate the thermal conductivity and viscosity of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe3O4 nanoparticles and gum arabic (GA) coated carbon nanotubes (CNTs), experimentally. The magnetic nanoparticles and CNTs are physically attached as the result of interaction between the TMAH and GA molecules. The morphology and structure of the samples are characterized with X-ray diffraction (XRD) and transmission electron microscopy (TEM). The experiments are carried out in the magnetic nanoparticles volume concentration range of 0.1–0.9 %, CNT volume concentration range of 0.05–1.35 % and the temperature range of 25–55 °C. The... 

In this paper, the thermal conductivity of water-based hematite Fe2O3 and magnetite Fe3O4 nanofluids have been investigated in the absence and presence of a uniform magnetic field. The experiments have been performed in the volume concentration range of 0 % to 4.8 % and the temperature range of 20∘C to 60∘C. The effects of the particle volume fraction, temperature, and magnetic field strength on the thermal conductivity have been analyzed. Results show that the thermal conductivity of iron oxide nanofluids has a direct relation with the particle volume fraction and temperature, without the presence of a magnetic field. But surprisingly, when the magnetic field is applied, it is observed that... 

Experimental investigations are performed in order to determine the thermal conductivity of NiFe2O4 nanoparticles dispersed in deionized water. The magnetic nanoparticles are synthesized using a microemulsion method. The X-ray diffraction (XRD), transmission electronic microscopy (TEM), and vibration sample magnetometer (VSM) are used to characterize the structure, the size and the magnetic properties of the nanoparticles. The VSM results disclose that the NiFe2O4 nanoparticles are ferromagnetic at room temperature. Experimental measurements on thermal conductivity of the prepared nanofluids are conducted at different volume concentrations between 0% and 2% and in the temperature range of... 

Increasing cuttings bed height is a serious concern during extended-reach well drilling. In order to predict and prevent cuttings bed height increase, it is essential to study how the critical parameters influence the cuttings transport, especially the drill pipe rotation effects on the cuttings transport process. In conventional models for cuttings transport, the dynamic behavior of particles due to drill pipe rotation is neglected or empirically simplified. This paper presents a coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) approach to simulate the cuttings transport considering the dynamic collision process. The fluid phase is treated as an Eulerian continuum... 

The aim of this paper is to investigate the thermal conductivity and viscosity of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe3O4 nanoparticles and gum arabic (GA) coated carbon nanotubes (CNTs), experimentally. The magnetic nanoparticles and CNTs are physically attached as the result of interaction between the TMAH and GA molecules. The morphology and structure of the samples are characterized with X-ray diffraction (XRD) and transmission electron microscopy (TEM). The experiments are carried out in the magnetic nanoparticles volume concentration range of 0.1–0.9 %, CNT volume concentration range of 0.05–1.35 % and the temperature range of 25–55 °C. The... 

In this paper, the effects of both constant and alternating magnetic fields on the laminar forced convective heat transfer of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe3O4 nanoparticles and gum arabic (GA) coated carbon nanotubes (CNTs) flowing through a heated tube were investigated experimentally. The experiments were carried out over wide range of parameters such as Reynolds number (548-2190), volume concentrations of Fe3O4 (0.5-0.9%) and carbon nanotube (0.25-1.35%) nanoparticles, magnetic field strength (300-700 Gauss) and alternating magnetic field frequency (10-50 Hz). In present study, the experimental observations in the case without magnetic field... 

In this study, the influence of temperature on serrated flow behavior, strain rate sensitivity (SRS) and effective activation volume in a Ti-based bulk metallic glass (BMG) bent at different strain rates has been investigated. Results reveal that the fundamental origin of shear deformation is related to the time-dependent structural relaxations, which occur during deformation at special temperatures and strain rates. Furthermore, the localized structural relaxation processes at intermediate temperatures cause an inelastic shuffling within cages and mitigate the activation of STZs. The main reason of negative SRS at intermediate temperatures is due to the insufficient time for structural... 

Power consumption of wellbore drilling in oil and gas exploitations count for 40% of total costs, hence power saving of WBM (water-based mud) by adding different concentrations of Al2O3, TiO2 and SiO2 nanoparticles is investigated here. A high-speed Taylor–Couette system (TCS) was devised to operate at speeds 0–1600 RPM to simulate power consumption of wellbore drilling using nanofluids in laminar to turbulent flow conditions. The TCS control unit uses several sensors to record current, voltage and rotational speed and Arduino microprocessors to process outputs including rheological properties and power consumption. Total power consumption of the TCS was correlated with a second-order... 

A body insonified by a sound field is known to experience a steady force that is called the acoustic radiation force. In this paper, the method of wave function expansion is adopted to study the scattering and the radiation force function caused by a plane normal harmonic acoustic wave incident upon an arbitrarily thick-walled functionally graded cylindrical shell submerged in and filled with compressible ideal fluids. A laminate approximate model and the so-called state space formulation in conjunction with the classical transfer matrix (T-matrix) approach are employed to present an analytical solution based on the two-dimensional exact equations of elasticity. Two typical models,...