Hydrothermal behavior of nanofluid fluid between two parallel plates is studied. One of the plates is externally heated, and the other plate, through which coolant fluid is injected, expands or contracts with time. The effective thermal conductivity and viscosity of nanofluid are calculated by KKL correlation. The effects of the nanoparticle volume fraction, Reynolds number, Expansion ratio and power law index on Hydrothermal behavior are investigated. Results show that heat transfer enhancement has direct relationship with Reynolds number when power law index is equals to zero but opposite trend is observed for other values of power law index.
No abstract is provided for this article.
Machining of hard materials has always experienced challenges in their production process owing to several elements such as surface roughness, dimensional and geometrical tolerances, machining forces, longevity of the tools, and the generated heat during the operation. In order to tackle these technical problems, cutting tools, cutting fluids, and chipping strategies have undergone precise evaluation to facilitate the machining challenges. The current study is fixated on the assessment of cutting fluids and their significant efficacy on turning process. The desirable quality of a production part in machining processes is contingent upon the effectiveness of lubrication and cooling process during the turning operation. Hence, the tests have been done under various conditions regarding the cutting fluid for the cooling purpose. This study evaluates the efficacy of dispersion in the base fluid with volume fractions of 1.5 % and 3 % on temperature of the cutting tool in Mo40 steel turning operation, compared to the conditions utilizing coolant oil and conventional dry condition. Nanofluid minimum quantity lubrication (NMQL) strategy, as the main hindrance for immoderate use of cutting fluid, has been applied within the machining phenomena of Mo40 steel. Cutting speed and feed rates have been selected as the variable input parameters, for which the tests were performed and compared. The obtained results of this work revealed that employing nanofluid in machining operation led the cutting tool to experience an average reduction of about 60 % in the temperature range. Notable to mention, the growth in concnetration of the nanofluid intensifies temperature decrement of the cutting tool. In detail, the cutting zone temperature for 3 % volume concentration found to be 2 °C less than that of 1.5 %. Furthermore, using nanoparticles improved the roughness quality of the workpiece, and tool wear. Tool geometry, tool coating, along with various nanofluids are other factors, for which the experiment can be implemented as the future study.
In this study the lattice Boltzmann method is applied to investigate the effect of magnetic field on natural convection heat transfer of Al2O3–water nanofluid in a two-dimensional horizontal annulus. In this model, the effect of Brownian motion on the effective thermal conductivity is also considered. The effective thermal conductivity and the effective viscosity of nanofluid are calculated by KKL (Koo–Kleinstreuer–Li) correlation. The effect of nanoparticle volume fraction for the enhancement of heat transfer was examined for several sets of values of Rayleigh and Hartmann numbers. Also, a correlation of the Nusselt number with physical parameters is presented. The obtained results indicate that the value of the maximum stream function decreases with increasing Hartmann number. Furthermore, we notice that the Nusselt number has a direct relationship with the Rayleigh number; but quite the opposite is true with the Hartmann number. The obtained results indicate that the Lattice Boltzmann method with double-population is a powerful approach for the simulation of natural convection heat transfer in nanofluids in regions with curved boundaries.
Influence of a spatially varying magnetic field on Fe 3 O 4 -plasma nanofluid flow in a vessel as a targeted drug delivery system is investigated. Combined effects of ferrohydrodynamic (FHD) and magnetohydrodynamic (MHD) are considered in mathematic models. The lattice Boltzmann method is applied to solve the governing equations. Effects of active parameters, such as the Reynolds number and magnetic number on the flow characteristics, have been examined. Results indicate that the presence of the magnetic field affects considerably the flow field. Back flow occurs near the region where the magnetic source is located. Also, it can be found that the skin friction coefficient is a decreasing function of the Reynolds number and magnetic number.
In this study, we propose a reliable algorithm to develop an analytical solution for the problem of laminar steady magnetohydrodymanics (MHD) nanofluid flow in a semi-permeable channel using the differential transformation method (DTM). The working fluid is water with copper nanoparticles. The effects of Hartmann number and Reynolds number on velocity profiles have been also considered for various numerical cases. The effective thermal conductivity and viscosity of nanofluid are calculated by the Maxwell and Brinkman models, respectively. A close agreement between the obtained solution and some well-known results has been established.
Nowadays, the rise in the human population and consequently increasing demand for energy in different fields, have caused serious trouble for societies. Increasing energy demand necessitates the need to produce more energy, thus, the consumption of fossil fuels that are a form of non-renewable energy will be increased. Phase change materials as environments for storing heat have wide applications in storing solar energy. This energy source is clean, inexhaustible, and accessible. Its usage by humans varies based on circumstances such as geographical conditions, terrain, time variations, and cloud cover. Current article reports a comprehensive overview of TES technologies using PCM throughout discharging and charging. The purpose of current research is to scrutinize the used techniques for augmenting performance of TES for non-power plants and PCM applications. In addition, heat transfer enhancement using extended surfaces, encapsulation, different ways of augmenting the thermal features, and applying of multiple PCMs were scrutinized. Furthermore, a brief discussion on the recent articles on various fluids and nanoparticles has been presented. The results show that the paraffin was the most used PCM in the studies, and the most common unit was shell and tube heat exchanger. Results also indicate that addition of longitudinal fin is the most popular technique in TES units.
Acid copper chromate fixation reactions on oak (Quercus castaneifolia C. A. Mey) sapwood were characterized by at least two distinguished reaction periods which differ in their kinetic behavior, particularly reaction rate. In this research, chemical rate equation parameters were studied in detail as a function of chromium fixation time. Theoretically, the kinetic data were distinguished between the adsorption and reduction reactions and consequently, the rate parameters were determined for each stage distinctly. The obtained results showed that at the investigated thermal range (25–33°C), almost for every 3°C increase in temperature the reaction duration has decreased 20.4 min for the first reaction period and 78 min for the second reaction period. Besides that, in all sample replications, up to 58.3% of hydrogen ions function at the reduction reactions of the initial period, demonstrating that acidity (H+ ions) has a major effect on reaction rate constant. Accordingly, adsorption reactions of the hexavalent chromium at the starting point follow a pseudo-first-order kinetic reaction. Different to the adsorption reaction the CrVI reduction reaction is exothermic with a measured exothermal energy of 48.2 kJ/mol.
This communication examines the entropy generation on the interaction of nanoparticles over a stretching porous sheet with nonlinear thermal radiation. The water-based Nanofluid having Nimonic 80a metal nanoparticles of Bricks shape. Similarity transformations are used for the simplification of governing flow equations. Numerical results for temperature, velocity, Bejan number, and entropy profiles are obtained and investigated by Successive linearization technique and Chebyshev spectral collocation scheme. Simultaneous effects of the porous medium, Radiation parameter, nanoparticle volume fraction, Prandtl number, Brinkman number, and Reynolds number are demonstrated through graphs. Additionally, the outcomes taken from the prevailing scheme ratifies magnificent conformity with the predecessors while comparing among investigations to the existing literature. The formulation for skin friction coefficient and Nusselt number are interpreted and displayed through graphs.
In this research, by studying the thermodynamics' laws, the thermal efficiency of microchannel was investigated employing the entropy analysis. Water is used as a base fluid with Al2O3 nanoparticles. Forchheimer -Brinkman model has been applied to include porous zone effect in momentum equations. The two-energy-equation model, which consists of two coupled equations, one for fluid and one for solid phase was employed. The analytical approach is applied to solve energy and momentum equations. The goal for using this method is the existence of nonlinear terms in equations. The effects of magnetic field, Reynolds number, α and ε on the parameters affecting irreversibility were studied. Then, it was concluded that by augmenting the Reynolds number to Reop, Ns decreases. Beyond Reop, the rise in Re enhance the Sgen and declines efficiency of the system. However, applying the magnetic field is beneficial between Re = 1.1 and Recr, and reduces the generated entropy. It was also observed that with the increase of α, Ns takes an upward trend. Increasing the ε value from 0.25 to 0.5 results in the downward trend of Ns, however, in high ε (0.75), Ns rises noticeably with augment of frictional irreversibility.
No abstract is provided for this article.
In this paper, Least Square and Galerkin methods are used to solve the problem of laminar nanofluid flow in a semi-porous channel in the presence of transverse magnetic field. Obtained results are compared with fourth order Runge–Kutta numerical method. The difference in the velocity profiles is almost negligible when the two methods (LSM and GM) are compared. The results obtained by GM are slightly more accurate than LSM in this problem. The influence of the three dimensionless numbers: the nanofluid volume fraction, Hartmann number and Reynolds number on non-dimensional velocity profile are considered. The results show that velocity boundary layer thickness decrease with increase of Reynolds number and it increases as Hartmann number increases.
Nanofluids are produced by dispersing the nanometer-scale solid particles into base liquids with low thermal conductivity such as water, ethylene glycol, oils, etc. The presence of the nanoparticles in the fluids noticeably increases the effective thermal conductivity of the fluid and consequently enhances the heat transfer characteristics. Therefore, numerous methods have been taken to improve the thermal conductivity of these fluids by suspending nano/micro-sized particle materials in liquids. Also nanostructures such as nanobeam, nanotube, etc., have many applications in mechanical engineering. This chapter focuses on the solving problems in this field and contains the following sections: 5.1 Introduction 5.2 Nanofluid in Divergent/Convergent Channels 5.3 Magneto-hydrodynamic Couette Nanofluid Flow 5.4 Nanofluid Between Parallel Plates 5.5 Vibrational of Nanobeams 5.6 Buckling Analysis of a Single-Walled Carbon Nanotube
Forced convective turbulent hydrothermal analysis in a double pipe heat exchanger is presented experimentally. Perforated turbulators have been utilized in annulus region. Hot water makes the cold air in outer tube warmer. Various amounts of pitch ratio, open area ratio and Reynolds number are considered. Correlations for Nusselt number, thermal performance and Darcy friction factor are examined. NSGA II is utilized to optimize the design. Physical phenomena are shown by means of FVM. Results reveal that thermal performance enhances with augment of open area ratio. Temperature gradient reduces with augment of pitch ratio. The maximum value of thermal performance obtained at η =1.59 which is occurred for Re = 6000 , λ = 0.07 , PR = 1.06 .
Transportation of Al2O3 nanoparticles due to magnetic forces through a permeable cubic domain with cubic hot obstacle is presented in this research. Roles of permeability and Lorentz and buoyancy forces on nanoparticles transportation are described via LBM. Brownian motion effect impact is included in properties of Al2O3- H 2 O nanofluid. Outputs prove that increasing Ha leads to stronger conduction mode. As Darcy number enhances, thermal boundary layer becomes thinner. Augmenting permeability makes N u a v e to augment.
In this study, heat transfer and pressure loss in an air to water double pipe heat exchanger are experimentally investigated. Typical circular-ring (TCR) and perforated circular-ring (PCR) turbulators are placed in annular pipe. The working fluids are air, flowing in the annular pipe, and water through the inner circular tube. The experiments are conducted for different governing parameters namely; air flow Reynolds number (6000–12,000), pitch ratio (1.83, 2.92 and 5.83) and number of perforated hole (0, 2, 4 and 8). Correlations for friction factor, Nusselt number and thermal performance are presented according to experimental data. Results indicated that using PCRs leads to obtain lower heat transfer enhancement than the CRs because of reduction of intersection angle between the velocity and the temperature field. Thermal performance increases with increase of N but it decreases with increase of Reynolds number and pitch ratio.
