Thermal Conductivity Of Nanofluids Research Articles

Thermal Conductivity of Ionic Liquid-Based Nanofluids Containing Magnesium Oxide and Aluminum Oxide Nanoparticles

A promising nanomaterial, magnesium oxide (MgO) and a commonly studied nanomaterial, aluminum oxide (Al2O3) were used to enhance the thermal conductivity of two ionic liquids, i.e., 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCa]) and 1-ethyl-3-methylimidazolium tricyanomethanide ([emim][TCM]) of potential as heat transfer medium. Effects of nanoparticle material, size, shape as well as mass concentration on thermal conductivity enhancement were investigated experimentally, along with stability analysis of the nanoparticle suspensions. The thermal conductivity of [emim][TCM] can be enhanced by up to 40% by adding 15 wt.% of polyhedral MgO nanoparticles. The thermal conductivity of Al2O3 ionanofluids does not vary much with nanoparticle size while that of MgO ionanofluids tends to increase as the nanoparticle size decreases. The Maxwell-Garnett model and the Hamilton–Crosser model could estimate the thermal conductivity of [emim][DCa]-based nanofluids containing Al2O3 and MgO nanoparticles, respectively, while under-prediction prevailed for [emim][TCM]-based nanofluids. Besides, challenges were encountered during zeta potential measurements created by the ionic liquids themselves. New methods need to be developed to correctly measure the zeta potential of ionic liquid-based nanofluids.

Modified Arrhenius and Thermal Radiation Effects on Three-Dimensional Magnetohydrodynamic Flow of Carbon Nanotubes Nanofluids Over Bi-Directional Stretchable Surface

In the current study, 3D hydro-magnetic flow of CNTs-EG/EO/H2O nanofluids over bi-directional stretchable surface along with linear thermal radiation, modified Arrhenius, thermophoresis and Brownian diffusion are studied. The three base fluids i.e., EG (Ethylene Glycol), EO (Engine Oil) and H2O are considered for the analysis. For computing the effective viscosity and thermal conductivity of nanofluid, Wang’s viscosity model and Hamilton-Crosser’s thermal conductivity model have been used. The system of transformed non-linear ODEs is solved by shooting scheme. The comparison of heat transfer rate in CNTs-EG, CNTs-EO and CNTs-H2O nanofluids is depicted by bar diagrams. The outcomes of the present work showed that MWCNTs based nanofluids have a higher temperature gradient compared to that of SWCNTs based nanofluids. Moreover, temperature distribution corresponding to the engine oil-based nanofluids declined at a very high rate followed by ethylene glycol and water-based nanofluids, respectively.

Review of Nanofluids and Their Biomedical Applications

Numerous researchers have reported significant improvements in nanofluid (NF) heat transfer (HT), suspension stability, thermal conductivity (TC), and rheological and mass transfer properties. As a result, nanofluids (NFs) play an important role in a variety of applications, including the health and biomedical engineering industries. The majority of the nanofluids (NFs) literature focuses on analyzing and comprehending the behavior of nanofluid models as heating or cooling mechanisms in various fields. This article represents a comprehensive study on nanofluids (NFs). It involves commonly used nanoparticles (NPs), magnetic nanofluids (MNFs), thermal conductivity (TC) enhancement, heat transfer (HT) enhancement, nanofluids (NFs) synthesis methods, stability evaluation methods, stability enhancement, nanofluids (NFs) applications in the biomedical field, and their impact on health and the environment. Nanofluids (NFs) play vital role in biomedical applications. It can be implemented in drug delivery systems, hyperthermia, sterilization processes, bioimaging, lubrication of orthopedic implants, and micro-pumping systems for drugs and hormones.

MHD 3D Crossflow in the Streamwise Direction Induced by Nanofluid Using Koo–Kleinstreuer and Li (KLL) Correlation

Aluminum nanoparticles are suitable for wiring power grids, such as local power distribution and overhead power transmission lines, because they exhibit high conductivity. These nanoparticles are also among the most utilized materials in electrical field applications. Thus, the present study investigated the impact of magnetic field on 3D crossflow in the streamwise direction with the impacts of Dufour and Soret. In addition, the effects of activation energy and chemical reaction were incorporated. The viscosity and thermal conductivity of nanofluids were premeditated by KKL correlation. Prominent PDEs (Partial Differential Equations) were converted into highly nonlinear ODEs (Ordinary Differential Equations) using the proper similarity technique and then analyzed numerically with the aid of the built-in bvp4c solver in MATLAB. The impact of diverse important variables on temperature and velocity was graphically examined. Additionally, the influences of pertaining parameters on the drag force coefficient, Nusselt number, and Sherwood number were investigated. Inspections revealed that the mass transfer rate decreases, while the heat transport increases with increasing values of the Soret factor. However, the Nusselt and Sherwood numbers validate the differing trend for rising quantities of the Dufour factor.

Investigation of Thermal Conductivity and Convective Heat Transfer Coefficient of Water-based ZnO Nanofluids

Nanofluids are stable suspensions of nanoparticles in a conventional fluid. They have shown superior potential in heat transfer enhancement. In this research, ZnO/water nanofluids were prepared at various concentrations from 0.2 to 1.5vol%, and their thermal conductivity was measured. The results showed that the thermal conductivity of ZnO/water nanofluids depends on particle concentration and increases non-linearly with the volume fraction of nanoparticles. The effects of particles size and temperature on the thermal conductivity were also investigated at 1.5vol%. The results indicated that thermal conductivity enhanced with decreasing particles size and increasing with temperature. For nanofluids containing 10-15 nm and 45-50 nm particle sizes, the enhancements were 26.3 and 22.8% at 40oC, respectively. In this research, the convective heat transfer coefficient of ZnO/water nanofluids with the above particle sizes was also measured under laminar flow in a horizontal tube heat exchanger. It was observed that both nanofluids showed higher heat transfer coefficients compared to the base fluid at a constant concentration (1.5 vol%). For nanofluids with 10-15 nm and 45-50 nm particle sizes, the average heat transfer coefficient enhancement was 18.1 and 14.9% at Re=1115, respectively.

Development of a mathematical model for prediction of heat transfer coefficient in micro-channel heat sink

The advancement of miniaturization and high-density manufacturing of electronic devices necessitates lightweight and high-performance heat dissipation components. As a result, traditional coolants and cooling technologies are rapidly unable to satisfy the ever conditioning problems and requirements of specific high temperature generated electronic devices. A microchannel heat sink (MCHS) has been extensively researched and commonly used in electronics cooling as a novel system that is highly suitable for applications with high power and small heat dissipation space. This research presents a mathematical model focused on dimension analysis to determine the heat transfer coefficient of a microchannel heat sink in electronics cooling. Buckingham Pi (π)theorem with dimensional analysis was used to determine a functional correlation between the heat transfer coefficient and independent variables. Independent variables comprise; thermal conductivity (copper MCHS), hydraulic diameter (MCHS), length (MCHS), a mass flow rate of nanofluid, the density of nanofluid, inlet temperature of nanofluid, heat flux, % by volume concentration of nanoparticle and thermal conductivity of nanofluid. The established relationship between dependent and independent variables concerning various operating conditions is helpful for analyzing behaviour.

Effects of variable thermal conductivity and electrical conductivity on flow of Williamson nanofluid between two parallel disks

The variable nature of the thermal conductivity of nanofluid with respect to temperature plays an important role in many engineering and industrial applications including solar collectors and thermoelectricity. Thus, the foremost motivation of this article is to investigate the effects of thermal conductivity and electric conductivity due to variable temperature on the flow of Williamson nanofluid. The flow is considered between two stretchable rotating disks. The mathematical modeling and analysis have been made in the presence of magnetohydrodynamic and thermal radiation. The governing differential equations of the problem are transformed into non-dimensional differential equations by using similarity transformations. The transformed differential equations are thus solved by a finite difference method. The behaviors of velocity, temperature and concentration profiles due to various parameters are discussed. For magnetic parameter, the radial and tangential velocities have showed decreasing behavior, while converse behavior is observed for axial velocity. The temperature profile shows increasing behavior due to an increase in the Weissenberg number, heat generation parameter and Eckert number, while it declines by increasing electric conductivity parameter. The nanoparticle concentration profile declines due to an increase in the Lewis number and Reynolds number.

Heat Transfer Enhancement of Water Based Al<sub>2</sub>O<sub>3</sub>- Cu Hybrid Nanofluid Trough Square Cavity

The present numerical work, based on the finite volume method, deals with the characterization of natural convective flow and thermal fields inside differentially vertical heated square cavities filled with a nanofluid as well as the quantification of the convective exchanges. The investigation is devoted to study the influence of the hybrid nanofluid (Al2O3-Cu / water) on the flow’s general structure with a particular attention to the Nusselt number. An exhaustive parametric study is conducted considering different combinations of Al2O3 and Cu nanoparticles (NPs) dispersed in water for a range of Rayleigh numbers (Ra) and total volume fractions An appropriate agreement with experimental data was observed for the estimation of the hybrid nanofluid thermal conductivity. From the results, it is observed that the heat transfer intensifies by increasing the Ra number and the nanoparticles volume fraction. The hybrid nanofluid seems to be the most efficient nanofluid in comparison with a base fluid and a single nanofluid. This heat transfer enhancement becomes more convincing with the increase of the Cu NPs content (% in volume).

Influence of Radiative Heat Energy on the MHD Flow of Cu-kerosene Nanofluid Over a Vertical Plate: Laplace Transform Technique

The present study reveals the heat transfer phenomena of magnetohydrodynamic (MHD) nanofluid over a moving vertical plate due to the interaction of thermal radiation. Due to enhancing thermal properties, instead of water, kerosene is treated as the base fluid with the inclusion of Cu (Copper) nanoparticles. In addition to that, for the nanofluid viscosity and thermal conductivity the Einstein’s model and Mintsa’s model, respectively. The transformed models for the governing equations proposed here are handled analytically employing Laplace Transform Technique. However, the variations of various parameters are obtained because the constructed flow phenomena are presented via graph. In the particular case, the consequence obtained is compared with the earlier study to get the validation which provides a road map for further investigation.

Analysis of parallel flow heat exchanger using SiO2 nanofluids in the laminar flow region

Convective and overall heat transfer coefficients of SiO2 nanofluid flowing in a concentric DTHE are determined experimentally. The tests are carried out in the 800<Re<1900 range using SiO2/22nm nanofluids prepared in 0.2, 0.6 and 1.0% volume concentrations in 30:70 ratio glycerol-water mixture base liquid. The thermal and physical properties of silica nanofluids are determined in the range of 20-80°C. Viscosity, thermal conductivity, and density of nanofluids increased with particle concentration whereas specific heat decreased. Thermal conductivity and specific heat of nanofluids increased with temperature while viscosity and density decreased. Heat transfer experiments are conducted using nanofluids at a bulk temperature of 35°C in a laminar developing flow region. Overall heat transfer coefficient and convective HTC of 1.0% silica nanofluids are increased by 21.2 and 36.3% compared to base liquid.

Concentration and Temperature Dependent Effects on Acoustical Parameters and Thermal Conductivity in Cobalt Oxide Nanofluids

Concentration and Temperature Dependent Effects on Acoustical Parameters and Thermal Conductivity in Cobalt Oxide Nanofluids

Thermal conductivity and heat capacity of nanofluid based on water modified by hybrid material of composition detonation nanodiamonds-carbon nanotubes

For the first time, the rheological and thermophysical properties of stable nanofluids based on water and ethylene glycol modified by the DND-CNT hybrid material and obtained without surfactants have been investigated. It was found that at the maximum concentration of the DND-CNT hybrid material 0.5 wt. % for water and 0.3 wt. % for ethylene glycol was increased in thermal conductivity at 50 to 84% and 44%, respectively, without changing the dynamic viscosity. It is shown that the use of a hybrid material can reduce the freezing point by 11 in the case of water and by 7 in the case of ethylene glycol.

Investigation on the aggregation structure of nanoparticle on the thermal conductivity of nanofluids by molecular dynamic simulations

In this paper, equilibrium molecular dynamic simulations were used to calculate the thermal conductivity of Cu-Ar nanofluid with various initial aggregation structures at different volume fractions. The microscopic mechanism of the effect of nanoparticle agglomerate aggregation mode on the thermal conductivity of nanofluids was analyzed. Results showed that the particle size is the key factor to determine the aggregation structure of nanoparticles. The enhancement efficiency of diffusion-limited aggregation on the thermal conductivity of nanofluids was found to be greater than that of reaction-limited aggregation, and the effect of different aggregation structures on the diffusion coefficient of nanofluidic systems may be one of the potential mechanisms affecting the thermal conductivity of nanofluids.

The effect of radiation on entropy and heat transfer of MHD nanofluids inside a quarter circular enclosure with a changing L-shaped source: lattice Boltzmann methods

Simulations of free convective heat transfer (HT) and entropy generation (S Gen) in a closed enclosure are carried out in this research. Tc is the temperature of the enclosure's top circular wall. A piece of the enclosure's left wall (L) and a section of the enclosure's right wall (H) are both at Th . The remainder of the walls are insulated. A constant volumetric radiation (Rd ) is produced within the cavity. In relation to the horizon, the enclosure is at 45° angle. The equations are solved using the lattice Boltzmann method (LBM). The thermal conductivity of nanofluids (NFs) was also calculated using a model based on empirical data. The following findings are obtained by varying the Ha, the length of the heated walls, and the angle of the magnetic field (MaF). An increase in Ha lowers the quantity of Nu on both heated walls and weakens the fluid flow in the enclosure. The HT rate is increased by increasing the length of heated walls. The quantity of HT from hot walls varies depending on the angle of the MaF. The quantity of HT from one of the hot walls may be larger depending on the angle of the MaF. An increment in the angle of the magnetic field from 0 to 60° enhances the Nusselt number by 10.3%.

Tuning the thermal properties of aqueous nanofluids by taking advantage of size-customized clusters of iron oxide nanoparticles

In this study, the thermal conductivity of aqueous nanofluids containing clusters of iron oxide (Fe3O4/γ-Fe2O3) nanoparticles has been investigated experimentally for the first time, with the aim of assessing the role of a controlled aggregation of nanoparticles in these final nanofluids. For that, clusters of iron oxide nanoparticles of different cluster size (46–240 nm diameter range) were synthesized by a solvothermal method and fully characterized by transmission electron microscopy, X-ray diffraction and Raman spectroscopy. The rheological behavior of the optimal nanofluids was also studied by rotational rheometry. The nanofluids were obtained by dispersing the clusters of iron oxide nanoparticles in water taking into account different solid volume fractions (from 0.50 to 1.5 wt%) and the experiments were conducted in the temperature range from 293.15 K to 313.15 K. The study reveals and quantifies enhancements in the thermal conductivity of nanofluid with increase of cluster size and temperature. Furthermore, a 0.50 wt% concentration of clusters of iron oxide nanoparticles within the whole range of proposed nanofluids offers great stability and improved thermal conductivity for heat transfer applications with an small dynamic viscosity increase. In addition, the larger the size of the clusters of iron oxide nanoparticles, the greater the increase in thermal conductivity for the designed Fe3O4/γ-Fe2O3 cluster-based nanofluids, with thermal conductivity values following a constant upward trend and reaching a maximum increase of 4.4% for the largest synthesized clusters (average size of 240 nm). These results open the door for the development of iron oxide-based nanofluids on which taking advantage of an optimized aggregation of nanoparticles by using size-customized clusters.

A review of the characters of nanofluids used in the cooling of a photovoltaic -thermal collector

A nanofluid is a basic fluid that incorporates nanoparticles that improve the fluid's thermal performance in this study. A colloidal dispersion of a biphasic system including nanoparticles in the solid phase and the main fluid in the liquid phase is referred to as a nanofluid. The physical characterization of nanofluid (NFs), (Al2O3, CuO, MgO, SiO2, TiO2 and ZnO) nanofluid is done in the areas of pharmacological physics, cooling capacity, and economic performance. To make nanofluids, nanoparticles are removed into water. Nanofluid thermal conductivity and viscosity the influence of concentration and temperature on the thermal conductivity and viscosity of Nanofluids has been thoroughly studied. The thermal conductivity of nanofluids increases dramatically as concentration and temperature change. However, only a change in concentration impacted the viscosity enhancement in nanofluids.

Experimental investigation of dispersion stability and thermophysical properties of ZnO/DIW nanofluids for heat transfer applications

Metal-oxide based nanofluids have grabbed many researchers' attention because of their better dispersion stability and enhanced thermophysical properties for potential heat transfer applications. This work presents an experimental investigation of well-dispersed ZnO nanoparticles' dispersion stability and thermophysical properties in deionized water. Aqueous ZnO nanofluids with different mass concentrations (0.012, 0.024, 0.036, and 0.048%) of nanoparticles were synthesized using a typical two-step method with and without using surfactants. Sodium hexametaphosphate and acetylacetone were used as stabilizing agents in this study. Under optimal operating conditions and surfactants' concentration, acetylacetone-based nanofluids were found stable for more than 60 days. Viscosity and thermal conductivity of nanofluids have been investigated in the 20–60 °C temperature range. Both viscosity and thermal conductivity of nanofluids increased with increasing nanoparticle loading, while with an increase in temperature, viscosity decreased, in contrast to an increase in nanofluids' thermal conductivity. At a fixed temperature and concentration of nanoparticles, maximum enhancement in viscosity and thermal conductivity was recorded as 16.75% and 23.70%, respectively, for sodium hexametaphosphate stabilized nanofluids. The existing well-known theoretical models failed to predict the nanofluids' viscosity and thermal conductivity; however, the proposed new correlations well projected the experimental findings.

Geometrical Analysis of the Thermal Conductivity of Nanofluids Using Different Models

Geometrical Analysis of the Thermal Conductivity of Nanofluids Using Different Models

Experimental investigations of stability, density, thermal conductivity, and electrical conductivity of solar glycol-amine-functionalized graphene and MWCNT-based hybrid nanofluids.

This research article discusses properties such as density, thermal conductivity, and electrical conductivity of solar glycol with amine-functionalized graphene and multi-walled carbon nanotubes (MWCNTs). The hybrid nanofluid is prepared by dispersing the amine-functionalized graphene (AFG) and MWCNTs (50:50 in % by weight ratio) in pure solar glycol. The AFG and MWCNTs are dispersed in different volume concentrations of 0.05%, 0.1%, and 0.15% through the classical two-step homogenizing technique. Good colloidal stability nanofluid are prepared with Gum Arabic (non-covalent) as the surfactant. The stability of nanofluids is ensured through scanning electron microscopy, UV-Vis spectrometer, and zeta potential analyzer. The nanofluid thermal conductivity is measured with varying the nanomaterial loading from 0.05 to 0.15 vol% using a KD2 pro thermal analyzer. The thermal conductivity and electrical conductivity of nanofluid augmentations are considerably with an increasing volume concentration of AFG and MWCNT loading. The thermal conductivity of the AFG-MWCNT-based hybrid nanofluid is augmented by 8.59% for the maximum concentration of 0.15 vol% at 50 °C. The electrical conductivity of the solar glycol-based nanofluids is enhanced linearly with increased operating temperatures. The maximum electrical conductivity enhancement attained is ~28.85% at a nanoparticle loading of 0.15 vol% and 70 °C.

Experimental Measurements on the Thermal Conductivity of Glycerol-Based Nanofluids with Different Thermal Contrasts

We report, in this work, our study of the thermal conductivity of high-viscosity nanofluids based on glycerol. Three nanofluids have been prepared with different thermal contrasts, by suspending graphene flakes, copper oxides, or silica nanoparticles in pure glycerol. The nanofluids were thermally characterized at room temperature with the 3ω technique, with low amplitudes of the temperature oscillations. A significant enhancement of the thermal conductivity is found in both the glycerol/copper oxide and the glycerol/graphene flake nanofluids. Our results question the role played by the Brownian motion in the microscopic mechanisms of the thermal conductivity of high-viscosity glycerol-based nanofluids. A similar behavior of the thermal conductivity as a function of the nanoparticle volume fraction was found for all three glycerol-based nanofluids presently investigated. These results could be explained on the basis of fractal aggregation in the nanofluids.