Silver-water Nanofluid Research Articles

Darcian Natural Convection in an Inclined Trapezoidal Cavity Partly Filled with a Porous Layer and Partly with a Nanofluid Layer

The problem of Darcian natural convection in a trapezoidal cavity partly filled with porous layer and partly with nanofluid layer is studied numerically using finite difference method. The left slopping wall is maintained at a constant hot temperature and the right slopping wall is maintained at a constant cold temperature, while the horizontal walls are adiabatic. Water-based nanofluids with Ag or Cu or TiO2 nanoparticles are chosen for the investigation. The governing parameters of this study are the Rayleigh number (104 ≤ Ra ≤ 107), Darcy number (10–5 ≤ Da ≤ 10–3), nanoparticle volume fraction (0 ≤ φ ≤ 0.2), porous layer thickness (0.3 ≤ S ≤ 0,7), the side wall inclination angle (0° ≤ ϕ ≤ 21.8°) and the inclination angle of the cavity (0° ≤ ϖ ≤ 90°). Explanation for the influence of various above-mentioned parameters on streamlines, isotherms and overall heat transfer is provided on the basis of thermal conductivities of nanoparticles, water and porous medium. It is shown that convection increases remarkably by the addition of silver-water nanofluid and the heat transfer rate is affected by the inclination angle of the cavity variation. The results have possible applications in heat-removal and heat-storage fluid-saturated porous systems.

Biomechanically driven unsteady non-uniform flow of Copper water and Silver water nanofluids through finite length channel

Background and objectivesThis paper aims to investigate the unsteady flow of two types of nanofluids i.e Copper water nanofluids and Silver water nanofluids) through finite length non-uniform channel driven by peristaltic sinusoidal wave propagations. MethodsThe governing equations are reduced in linear form using dimensional analysis and considering the low Reynolds number and large wavelength approximations. The time dependent temperature field, axial velocity, transverse velocity and pressure difference are obtained analytically in closed form solution. Trapping phenomenon is also discussed with the help of contour plots of stream function. A comparative study of pure water (Newtonian fluid), Copper water nanofluids and Silver water nanofluids under the influence of relevant physical parameters is made in graphical form and also discussed. The effects of absorption parameter and Grashof number on velocity profiles, temperature profiles and pressure distribution along the length of channel are examined. Results conclusionsThe computational results reveal that the velocity profile is maximum for Silver water nanofluids however, it is least for Copper water nanofluids. It is also concluded the temperature profile is more for pure water in comparison to Silver water and Copper water nanofluids. This model is applicable to design, micro-peristaltic pumps which help in Nanoparticle-based targeted drug delivery and to transport the sensitive or corrosive fluids, sanitary fluids, slurries and noxious fluids in nuclear industry.

The preparation and thermal performance research of spherical Ag-H2O nanofluids & applied in heat pipe

Spherical silver-water (Ag-H2O) nanofluids with good suspension (more than 85days) have been obtained via one-step method in the water phase without any surfactants or additives in the present work. The size-control technique of spherical Ag nanoparticle has been obtained through adjusting the reaction rate and the mechanism of size effect has been studied in detail. It can be found that the faster the reaction rate, the smaller the nucleation density and the smaller the particle size. The thermal conductivity of spherical Ag-H2O nanofluids were higher than H2O even the few Ag nanoparticle incorporation. Based on the preparation of Ag-H2O nanofluids, the effects of particle size, solid content and temperature on the thermal conductivity of spherical Ag-H2O nanofluids were discussed and all the measure was performed in the same condition. The conclusion can be drawn that the thermal conductivity of Ag-H2O nanofluids increases with the content of Ag nanoparticles and temperature increasing and average size of Ag nanoparticles decreasing. The effect mechanism of particle size, temperature and content of Ag nanoparticles has been studied in detail. The Ag-H2O nanofluids were determined to be the Newtonian fluid whose viscosity is close to water and the viscosity increases with the increase of the mass fraction of Ag nanoparticles. The start-up and heat transfer performance of the heat pipe using the spherical Ag-H2O nanofluids have been improved compared to the heat pipe using DI water. It is expected that the spherical Ag-H2O nanofluids with a high thermal conductivity and low viscosity are expected to be new heat transfer fluid.

Numerical Investigation of Slip Effects on Hydromagnetic Flow Due to a Rotating Porous Disk in a Nanofluid with Internal Heat Absorption

AbstractIn recent days, nanofluids have derived the attention of researchers, scientists and engineers due to their abundant applications in Engineering and technology and specific applications such as Electronics cooling, vehicle cooling, medical applications including cancer therapy and so on. Motivated by these applications of nanofluids, this work is mainly concerned with the convective heat transfer of nanofluids. MHD slip flow of nanofluids with heat absorption over a rotating disk subjected to suction has been analyzed. Two types of nanofluids such as copper-water nanofluid and silver-water nanofluid are considered for the present study. The system of axisymmetric nonlinear partial differential equations governing the hydromagnetic steady flow and heat transfer are reduced to nonlinear ordinary differential equations by introducing suitable similarity transformations. The resulting non-linear ordinary differential equations are solved numerically by most efficient Nachtsheim-Swigert shooting iteration technique for satisfaction of asymptotic boundary conditions along with Runge – Kutta Fehlberg Method. The flow field is affected by the presence of physical parameters, such as magnetic interaction parameter, suction parameter, slip parameter and solid volume fraction, whereas the temperature field is addionally affected by magnetic interaction parameter, suction parameter, internal heat absorption parameter and solid volume fraction. With the amplifying effect in magnetic interaction parameter, suction parameter, slip parameter and solid volume fraction, the radial and tangential velocities decline. Axial velocity gets decelerated for increasing magnetic interaction parameter and slip parameter whereas it gets accelerated for growing effect of suction parameter and solid volume fraction. The temperature of the fluid within the boundary layer enhances with the increasing effect of magnetic interaction parameter and solid volume fraction while it reduces for increasing values of the suction parameter and internal heat absorption parameter. Also the values of radial and tangential skin friction coefficients and Nusselt number are obtained numerically and are tabulated.

Thermal characteristics and performance of Ag-water nanofluid: Application to natural circulation loops

The goal of this study is to investigate the thermal conductivity, viscosity and thermal performance in a single-phase natural circulation mini loop of Ag-water nanofluid which can be a potential working fluid for natural convective flat-plate solar collectors. The silver-water nanofluid with 5wt% concentration, which contains also polyvinylpyrrolidone (PVP) with 1.25wt%, was purchased. Then, the sample was diluted with de-ionized water to four different concentrations of 0.25, 0.5, 0.75 and 1wt%. Thermal conductivity and viscosity were measured by 3ω method and Brookfield rheometer, respectively. An effectiveness factor was used to define the thermal performance of Ag-water nanofluids for different inclination angles and heating powers. The results showed that nanofluid samples are thermally less conductive than the literature, at ambient temperature (23°C). The viscosity of nanofluid decreases significantly with increasing temperature and increases with increasing concentration. Our measurements appear to be more compatible with PVP solution results available in the literature. Effectiveness is enhanced up to 11% with 1wt% concentrated nanofluid compared to de-ionized water and the effectiveness of the mini loop indicates an enhancement with increase in inclination angle and particle concentration at whole applied power. According to obtained results, it is concluded that Ag-water nanofluid has a promising potential to be used in natural convective flat-plate solar collector.

Magnetohydrodynamics flow of nanofluid with homogeneous-heterogeneous reactions and velocity slip

This article focuses on the steady magnetohydrodynamic flow of viscous nanofluid. The flow is caused by a stretching surface with homogeneous-heterogeneous reactions. An incompressible fluid fills the porous space. Copper-water and silver-water nanofluids are investigated in this study. Transformation method reduces the non-linear partial differential equations governing the flow into the ordinary differential equation by similarity transformations. The obtained equations are then solved for the development of series solutions. Convergence of the obtained series solutions is explicitly discussed. Effects of different parameters on the velocity, concentration and skin friction coefficient are shown and analyzed through graphs.

Dynamics of variable-viscosity nanofluid flow with heat transfer in a flexible vertical tube under propagating waves

Background and objectivesThe present investigation addresses nanofluid flow and heat transfer in a vertical tube with temperature-dependent viscosity. A Tiwari-Das type formulation is employed for the nanofluid with a viscosity modification. As geometry of the problem is flexible tube so flow equations are modeled considering cylindrical coordinates. Governing partial differential equations are simplified and converted into differential equations using non-dimensionless variables with low Reynolds number (Re≪0 i.e. inertial forces are small as compared to the viscous forces) and long wavelength (δ≪0 i.e. physiologically valid that length of tube is very large as compared to width of the tube) approximations. Methods results conclusionsMathematica software is employed to evaluate the exact solutions of velocity profile, temperature profile, axial velocity profile, pressure gradient and stream function. The influence of heat source/sink parameter (β), Grashof number (Gr) and the viscosity parameter (α) and nanoparticle volume fraction (ϕ) on velocity, temperature, pressure gradient, pressure rise and wall shear stress distributions is presented graphically. Three different nanofluid suspensions are investigated-Titanium oxide-water, Copper oxide-water and Silver-water. Streamline plots are also computed to illustrate bolus dynamics and trapping phenomena which characterize peristaltic propulsion. The computations show that wall shear stress is maximum for the Silver-water nanofluid case. Furthermore the pressure rise is reduced with increasing Grashof number, heat absorption parameter and viscosity parameter in the augmented pumping region whereas the contrary response is observed in the peristaltic pumping region. Significant modification in the quantity of trapped boluses is found with different nanofluids and the size of the trapped bolus decreased in the Titanium oxide-water nanofluid case with either greater heat source or sink parameter. The study is relevant to drug delivery systems exploiting nano-particles.

Influence of T-semi attached rib on turbulent flow and heat transfer parameters of a silver-water nanofluid with different volume fractions in a three-dimensional trapezoidal microchannel

This study aimed at exploring influence of T-semi attached rib on the turbulent flow and heat transfer parameters of a silver-water nanofluid with different volume fractions in a three-dimensional trapezoidal microchannel. For this purpose, convection heat transfer of the silver-water nanofluid in a ribbed microchannel was numerically studied under a constant heat flux on upper and lower walls as well as isolated side walls. Calculations were done for a range of Reynolds numbers between 10,000 and 16,000, and in four different sorts of serrations with proportion of rib width to hole of serration width (R/W). The results of this research are presented as the coefficient of friction, Nusselt number, heat transfer coefficient and thermal efficiency, four different R/W microchannels. The results of numerical modeling showed that the fluid's convection heat transfer coefficient is increased as the Reynolds number and volume fraction of solid nanoparticle are increased. For R/W=0.5, it was also maximum for all the volume fractions of nanoparticle and different Reynolds numbers in comparison to other similar R/W situations. That's while friction coefficient, pressure drop and pumping power is maximum for serration with R/W=0 compared to other serration ratios which lead to decreased fluid-heat transfer performance.

Studying peristaltic transport of shape nanosize silver–water nanomaterials in digestive system with heat generation effect

This communication addresses the peristaltic transport of silver–water nanofluid in the curved channel. Shape effects of nanosize particles are examined. Bricks, cylinder and platelets types nanoparticles are considered. Magnetic field is applied in the radial direction. Viscous dissipation and heat generation in the energy expression are included. Velocity and thermal slip conditions are invoked. Thermal conductivity model due to Hamilton-crosser is employed. A comparative study of velocity and the temperature for the considered nanoparticles is made. Outcome of sundry variables on velocity and temperature are graphically examined. It is noticed that both velocity and temperature are greater for brick type nanoparticles in comparison to cylinder and platelets. Moreover, the velocity is not symmetric about center of channel.

Thermal Performance of a Compact Loop Heat Pipe with Silver-Water Nanofluid

The thermal performance of a compact loop heat pipe is fabricated and tested for different heat inputs ranging from 30 W to 500 W using water and silver-water nanofluid with low volume concentrations of silver nanoparticles (0.03% and 0.09%) in vertical orientation. A flat square evaporator having a bottom area of 30 mm × 30 mm and a height of 15 mm is used in the present study. The effect of heat input on the thermal resistance, evaporation and condensation heat transfer coefficient is experimentally investigated. The results showed that a reduction in the evaporator thermal resistance of 26.45% is achieved with 0.09 volume percentage of silver nanoparticles when compared with that of water. Further an enhancement in the convective heat transfer coefficient of 25.23% has been observed with the same volume concentration of silver nanoparticles. Addition of small amount of nanoparticles enhanced the operating range of heat pipe beyond 500 W and without the occurrence of any dry out conditions. From the outcome of this study, it is concluded that the compact loop heat pipe with flat square evaporator can be used for thermal control of electronic equipments with limited space.

Different nano-particles volume fraction and Hartmann number effects on flow and heat transfer of water-silver nanofluid under the variable heat flux

Nanofluid flow and heat transfer composed of water-silver nanoparticles is investigated numerically inside a microchannel. Finite volume approach (FVM) is applied and the effects of gravity are ignored. The whole length of Microchannel is considered in three sections as l1=l3=0.151 and l2=0.71. The linear variable heat flux affects the microchannel wall in the length of l2 while a magnetic field with strength of B0 is considered over the whole domain of it. The influences of different values of Hartmann number (Ha=0, 10, 20), volume fraction of the nanoparticles (ɸ=0, 0.02, 0.04) and Reynolds number (Re=10, 50, 200) on the hydrodynamic and thermal properties of flow are reported. The investigation of slip velocity variations under the effects of a magnetic field are presented for the first time (to the best knowledge of author) while the non-dimensional slip coefficient are selected as B=0.01, 0.05, 0.1 at different states.

An experimental study on thermophysical properties and heat transfer characteristics of low volume concentrations of Ag-water nanofluid

An experimental research has been conducted on low concentration of silver-water nanofluids through a straight tube for turbulent flow condition. This study aims at showing the impact of nanoparticle existence and volume concentration on thermal conductivity, dynamic viscosity, convective heat transfer characteristics, and pressure drop in turbulent flows regime. The findings showed that adding nanoparticles in the fluid and increasing Reynolds number bring about an increase in the Nusselt number in turbulent flow. When Reynolds number is approximately 22,000 the Nusselt number increases by 11.8% at volume concentration of 1%. This value is 10.35% when Reynolds number is about 5100. Also, at 1% volume concentration, there is 15.75% (average) increase in pressure drop.

Cautions required for the boiling test of a silver–water nanofluid

Various experimental works have been reported on boiling of nanofluids, and some contradictory data are reported in this case in the literature. Systematic errors in experiments may be one of the factors causing a significant gap in the data. In this paper, boiling of Ag–water nanofluid is studied empirically. A NiCr wire is used for the experiments. According to UV–Vis absorption spectra data, Ag–water nanofluid changes during the tests. Since the electrical resistance–temperature relationship for the NiCr test section changes during the experiments, the wire temperature cannot be determined by this method. This can be accounted for by the presence of a porous nanoparticle layer created through particle deposition during nucleate boiling.

Hydromagnetic mixed convection flow of copper and silver water nanofluids due to a curved stretching sheet

Main objective of present analysis is to study the MHD mixed convection flow of nanofluid due to a curved stretching sheet. Water based nanofluid comprising copper and silver as nanoparticles is used. Heat transfer analysis is carried out in the presence of Joule heating and nonlinear thermal radiation. Similarity transformations are used to obtain the system of nonlinear ordinary differential equations. Convergent series solutions are obtained. Effects of different variables on velocity and temperature are examined. Skin friction coefficient and Nusselt number are examined and analyzed for the influence of different involved parameters.

Numerical study for transport of water based nanofluids through an asymmetric channel with wavy walls

Purpose – The purpose of this paper is to develop a model for the peristaltic transport of water-based nanofluids and to analyze the impact of nanoparticles on the heat transfer characteristics. Design/methodology/approach – Numerical solutions are obtained using the shooting method. Findings – Pressure gradient decreases whereas the peristaltic pumping region increases with an increase in nanoparticle volume fraction. Silver-water nanofluid experiences greater frictional force at the wall. Temperature of the nanofluid decreases with an increase in nanoparticle volume fraction. Nanoparticles largely increase the heat transfer rate at the boundary. Such increase is maximum when is varied between zero and 0.1. Originality/value – This paper first time develops a model to examine the peristaltic flow of water-based nanofluids. Enhancement of heat transfer in the peristaltic flows due to addition of nanoparticles is investigated.

Experimental and numerical investigation of nanofluid heat transfer in helically coiled tubes at constant wall heat flux

The current study focuses on numerical and experimental investigation of the laminar, steady state flow in helical tubes with constant wall heat flux boundary condition. Pressure drop and convection heat transfer behavior of water–silver nanofluid in helical coils were evaluated and compared to the pure water. In the numerical part of the study, incompressible Navier–Stokes equations, derived from an orthogonal helical coordinate system were solved by finite difference method with projection algorithm using FORTRAN programming language. Homogeneous model with constant effective properties was used for nanofluid. The Local Nusselt number in the entrance region of the helical tubes and the effects of curvature and torsion ratios and Reynolds number have been discussed. In the experimental part, six helical heat exchangers with different curvature and torsion ratios were designed, capable of providing a constant wall heat flux. Pressure drop measurement and fully developed heat transfer coefficient and Nusselt number calculations were carried out and compared with the numerical results.The results show that for laminar flow with constant wall heat-flux boundary condition, the helical tubes with larger curvature ratio lead to higher heat transfer enhancement and higher pressure drop increase, when employing the nanofluid instead of the base fluid. Moreover, compared to using metal Ag nanofluid in straight tubes, utilization of base fluid in helical coils with greater curvature increases heat transfer more effectively. Finally, we conclude that since using Ag nanofluid increases the heat transfer of helical heat exchangers about 3.5–3.8%, utilizing this nanofluid could enhance the thermal performance of heat exchangers, which can benefit the industry.

Hydromagnetic peristaltic transport of water-based nanofluids with slip effects through an asymmetric channel

This paper addresses the effects of applied magnetic field and partial slip effects in peristalsis of water-based nanofluids in an asymmetric flow configuration. Analysis is carried out using silver and copper nanoparticles. Viscous dissipation, mixed convection, Ohmic heating and heat generation/absorption are considered. Mathematical modeling is done employing lubrication approximations. Resulting coupled system is solved numerically. Physical quantities like axial velocity, pressure gradient, temperature and heat transfer rate are graphically analyzed. Comparison between the silver–water and copper–water nanofluids is presented and analyzed. Results show that the maximum velocity, temperature and heat transfer rate at the wall in silver–water nanofluid are comparatively greater than that of copper–water nanofluid. It is also observed that addition of nanoparticles results in a decrease in the velocity and temperature of fluid. However, the heat transfer rate at the wall is enhanced through addition of nanoparticles.

Studying the Effect of Indentation on Flow Parameters and Slow Heat Transfer of Water-Silver Nano-Fluid with Varying Volume Fraction in a Rectangular Two-Dimensional Micro Channel

The purpose of this study is to investigate the influence of indentations on the parameters of fluid flow and heat of water-silver nanofluid in a rectangular two-dimensional micro channel. It includes heat transfer water silver nano fluid in an indented micro channel under the constant temperature. The system is numerically modeled, by Finite Volume Method. After solving the governing equations for U, V and θ, other useful quantities such as Nusselt number and friction factor can be determined. The hot fluid inlet exits after cooling by the cold walls of the micro channel. Calculations are done for the two ranges of Reynolds number (Re). It was observed that at times the fluid has more indentations; it has a greater temperature drop that is at the output cross section of the micro channel. With increasing Reynolds number (Re), number of the indentations and the increasing volume fraction of the nanoparticles, greater temperature drop occurs. The presence of indentation in the micro channel increases the speed and the dimensionless temperature at the center line. Finally, the results are provided in the form of the contour of flow and isothermal lines, the coefficient of friction, Nusselt number, temperature and velocity profiles in different micro channel sections. The results of the numerical simulation indicate that the heat transfer rate is significantly affected by the solid volume fraction and Reynolds number.

MHD Thermosolutal Marangoni Convection Boundary Layer Nanofluid Flow Past a Flat Plate with Radiation and Chemical Reaction

Objectives: To investigate the effects of Magneto Hydro Dynamic marangoni convection in nanofluids subject to radiation along with first order chemical reaction. Method: The analysis is taken over Copper-Water and Silver-Water nanofluids. Water with Prandtl number 6.2 is taken as base fluid. Flow equations are formed by a suitable similarity transformation. Using MATLAB, numerical solutions are obtained for Velocity, Temperature and Concentration of the nanofluid particles for different parameters. Also it is observed the heat and mass transfer effects. Results: The effect of magnetic parameter on fluid motion and temperature is appreciable. Further at low magnetic number ( ), velocity of Cu nanofluid particles move faster than that of Ag nanofluid particles. It is observed that increase in Soret number results in decrease of mass transfer rate and this rate is more in Ag-water nanofluid. Conclusion: Copper nanofluid particles possess higher heat and mass transfer rates. It is also noticed that Sherwood number decreases with increase of Soret number.

Heatline visualization of natural convection in a trapezoidal cavity partly filled with nanofluid porous layer and partly with non-Newtonian fluid layer

The problem of natural convection in a trapezoidal cavity partly filled with nanofluid porous layer and partly with non-Newtonian fluid layer is visualized by heatline. Water-based nanofluids with silver or copper or alumina or titania nanoparticles are chosen for investigation. The governing equations are solved numerically using the Finite Volume Method (FVM) over a wide range of Rayleigh number (Ra=105 and 106), Darcy number (10-5⩽Da⩽10-1), nanoparticle volume fraction (0⩽ϕ⩽0.2), power-law index (0.6⩽n⩽1.4), porous layer thickness (0.3⩽S⩽0.7), the side wall inclination angle (0°⩽φ⩽21.8°) and the inclination angle of the cavity (0°⩽ω⩽90°). Explanation for the influence of various above mentioned parameters on streamlines, isotherms and overall heat transfer is provided on the basis of thermal conductivities of nanoparticles, water and porous medium. It is shown that convection increases remarkably by the addition of silver–water nanofluid and the heat transfer rate is affected by the inclination angle of the cavity variation. The results have possible applications in heat-removal and heat-storage fluid-saturated porous systems.