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Nanofluids are suspensions of nanoparticles in base fluids, a new challenge for thermal sciences provided by nanotechnology. The tested fluids are prepared by dispersing the Al2O3 into water at three different concentrations such as 1 %, 2 %, and 4 %. Thermophysical properties of nanofluids are measured by KD2 Pro, Ostwald viscometer and specific g...
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GHAFOURI Link to the corrected article 10.2298/TSCI130309048P
Citations
... A researcher found that this liquid's thermal properties and heat capacity will improve by immersing nanoparticles into the water. This solution has received lots of attention from researchers [3][4][5][6][7]. Consequently, several parameters have had an impact on the performance of nanofluids, such as their stability, agglomeration, viscosity, interfacial nanomaterial layering, Brownian motion and nano-material size [8]. ...
Recently, nanofluid application as a heat transfer fluid for a closed-loop solar heat collector is receiving great attention among the scientific community due to better performance. The performance of solar systems can be assessed effectively with the exergy method. The present study deals with the thermodynamic performance of the second law analysis using graphene nanoplatelets nanofluids. Second law analysis is the main tool for explaining the exergy output of thermodynamic and energy systems. The performance of the closed-loop system in terms of energy and exergy was determined by analyzing the outcome of field tests in tropical weather conditions. Moreover, three parameters of entropy generation, pumping power and Bejan number were also determined. The flowrates of 0.5, 1 and 1.5 L/min and GNP mass percentage of 0.025, 0.5, 0.075 and 0.1 wt% were used for these tests. The results showed that in a flow rate of 1.5 L/min and a concentration of 0.1 wt%, exergy and thermal efficiencies were increased to about 85.5 and 90.7%, respectively. It also found that entropy generation reduced when increasing the nanofluid concentration. The Bejan number surges up when increasing the concentration, while this number decreases with the enhancement of the volumetric flow rate. The pumping power of the nanofluid-operated system for a 0.1 wt% particle concentration at 0.5 L/min indicated 5.8% more than when pure water was used as the heat transfer fluid. Finally, this investigation reveals the perfect conditions that operate closest to the reversible limit and helps the system make the best improvement.
... The interaction between DNA polymerase and AuNPs produced the decreased PCR amplification induced by excess AuNPs, and raising the polymerase concentration in the system may overcome the amplification limiting effect. [21] Nano drug delivery ...
... The single-step method simultaneously makes and disperses nanoparticles directly into base fluids while the two-step method first makes nanoparticles and then disperses them into base fluid. In either case, a well-mixed and uniformly dispersed nanofluid is needed for successful production or reproduction of enhanced properties and interpretation of experimental data [58]. ...
This chapter describes recent progress on the development of suspensions of
nanometer-sized solid particles in base liquids [nanofluids (NFs)] for thermal
energy storage (TES) application. Among the various methods of energy storage,
latent heat TES systems using phase change materials (PCMs) have been gaining
importance in many fields due to their high energy storage density and their
ability to provide heat at a constant temperature with an overall reduction of
costs. The chapter starts with a description of TES and continues with some
useful definitions of the NFs and their material components (base fluid and
nanoparticles). A brief presentation of different types of NFs is reported along
with the principal methods of NF preparation. NFs based on salts as PCMs with
the addition of different nanoparticles are considered. This chapter focuses on the
heat capacity enhancement of NFs with a comparison of both theoretical models
and experimental results since it can lead to a reduction in the amount of storage
material. Other fundamental thermal properties are reported in the chapter (heat
of fusion, melting temperatures, and thermal storage capability and thermal
conductivity). Finally, the challenges of using NFs in solar energy devices are
discussed.
... On the other hand, certain contradicting reports revealed that nanofluid specific heat is unaffected by the change in temperature but would decrease with the increase concentration [56,57]. For a more detailed information pertaining to specific heat of nanofluids, one may alternatively seek for the comprehensive review [34]. ...
The limitation of the conventional fluids to facilitate cooling/heating rates remains the primary basis for exploring alternative heat transfer nanofluids. Research efforts on nanofluids have evolved over the past two decades in establishing extensive literature. Several models for thermophysical properties were made available to characterize the behaviors of diverse individual nanofluids. However, lack of reasonable agreement between theory and experimental results has been a limiting factor for the development of a unified nanofluid model for thermal conductivity. Existing models for thermo-physical properties of nanofluids such as density, specific heat, thermal conductivity, and viscosity are critically surveyed and appropriate equations are extended for composite nanofluids. Consequently, based on reliable models identified predictions for thermal conductivity and viscosity for composite nanofluids are presented. Overall results show that existing thermophysical models for density and specific heat are valid for all water based oxide nanofluids for both single material and composites whereas models for thermal conductivity and viscosity show selective response but have the versatility for predicting the behavior of single and composite nanofluids within acceptable deviation
... Syam Sunder et al. [209] estimated density of nanofluids in different temperatures and reported that density decreases as temperature increases. Similarly, using specific weight at 30°C-90°C and different concentrations 1%-4%, Harkirat [210] measured density of aqueous suspension of Al 2 O 3 . He found that as concentration of nanoparticles increases compared to base fluid, the density of nanofluids increases. ...
One of the most important scientific challenges in industrial centers is coolants, which involve many different products. Technological developments such as high-speed operational microelectronic systems and high-power motors, leading to increased thermal load, recall the necessity to develop coolants. In order to increase heat transfer, common methods may envisage with increased area for more heat transfer. This results in abnormal increase in size of heat management systems. So it seems that some new coolant is necessary, which improves total performance of heat transfer systems. The term nanofluid is introduced by researchers as the suspension of nanosized particles
(>100 nm) including metals, metallic oxide, and nanostructure in heat transfer base fluids such as water and ethylene glycol. The main property of nanofluids is enhanced thermal conductive and convective heat transfer compared to the base fluid. Numerous efforts have been performed on
nanofluids with potential applications in industries such as microelectronic, defense, nuclear, aerospace, and industry.
... Syam Sunder et al. [32] estimated nanofluids densities in different temperatures and reported that as temperature increased, the density decreased. Similarly, using specific weight in the temperature range 30-90°C and different concentrations of 1-4 %, Harkirat [33] measured the density of the aqueous suspension of Al 2 O 3 . He observed that nanofluid density increased as nanoparticles concentration increased relative to the base fluid. ...
Since carbon nanotubes (CNTs) are unstable in different polar solvents such as water, using surfactants can open a new gateway for solving the challenge by attaching non-covalent hydrophilic bonds. Here, the influence of different surfactants including gum arabic (GA), cetyl trimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) on stability and thermophysical properties of multi-walled carbon nanotubes (MWCNTs) in aqueous media is experimentally investigated. To reach this purpose, aqueous suspension of surfactant-MWCNT was synthesized in the ratios 0.5-1, 1-1 and 2-1. Zeta potential was used to determine stability of above-mentioned suspensions as a common method. Dynamic light scattering analysis was also employed to determine particles size distribution. The results indicated relative stability of suspensions in all ratios. It was also found that the minimum particle size was obtained in the presence of the ratio 1-1 of SDS and CTAB. Thermophysical properties of above-mentioned suspensions including viscosity, shear stress, electrical conductivity, surface tension and density were also studied at the range of 20-80 °C. The results indicated an increase in the electrical conductivity, density, viscosity, shear stress and a decrease in the surface tension (except in GA) of suspensions in all concentrations relative to pure water in constant temperature. As temperature increases, the electrical conductivity increases significantly, while the viscosity, shear stress, density and surface tension decreases more or less for all concentrations.
... The reduced PCR amplification caused by excess AuNPs was due to the interaction between DNA polymerase and AuNPs, and increasing the polymerase concentration in the system could avoid the amplification-restraining effect. [33] Nanodrug delivery Over the last few decades, colloidal drug delivery systems have been developed in order to improve the efficiency and the specificity of drug action. The small size, customized surface, improved solubility and multi-functionality of nanoparticles open many doors and create new biomedical applications. ...
Pharmaceutical nanotechnology is evolved as a powerful tool for pharmaceutical chemist and formulation scientists. It has given a new direction to pharmaceutical and drug discovery research. Nanofluid technology which deals with nanofluids has provided an ultimate engineering solution for heat transfer application and automotive application in different industries. Nanofluids are engineered colloidal suspensions of nanoparticles in a base fluid. The nanoparticles used in nanofluids are typically made up of metals, oxides, carbides or carbon nanotubes. Common base fluids include water, ethylene glycol and oil. Preparation of nanofluids may be done by one step, two step method, chemical approach or laser ablation. The stability of nanofluids can be enhanced by different means such as addition surfactants, surface modification technique, pH control and ultrasonic agitation. Nanofluids are well known for their applications in engineering field, many researchers have also reported their use for different biological, medical and biomedical applications. Considering the tremendous growth of pharmaceutical nanotechnology with respect to drug discovery, formulation and development of nanoparticulate novel drug delivery systems, it is expected in coming years that high performance drug nanoparticle fluid suspensions (nanofluids) will begin a new era of formulation research. This review article summarises method of preparation, characterization, stability, recent research and applications of nanofluids. It also identifies future scope of nanofluid technology for applications in pharmaceutical field.
... This consequently raises the heat losses to the environment resulting in low thermal efficiency of such collectors. Therefore, to improve the thermal efficiency of such collectors, new heat transfer fluids known as nanofluids have been applied by many researchers as found in the literatures [8][9][10][11][12][13][14][15][16][17] nanoparticles volume fraction, % density, kg/m 3 overall entropy production, J/kg·sK k thermal conductivity, W/m K Nanofluids are one of these new types of fluids that have been studied extensively in the last 20 years [8]. Hoffmann et al. [9] described this as an innovative class of nanotechnology-based heat transfer fluid having superior thermal properties compared to conventional water based fluids. ...
... Many researchers have found that the addition of a moderately small amount (<1% by volume) of nanoparticles in a base fluid can boost the thermal properties (i.e. thermal conductivity, mass diffusivity and heat transfer coefficient) [10][11][12][13][14]. ...
... This consequently raises the heat losses to the environment resulting in low thermal efficiency of such collectors. Therefore, to improve the thermal efficiency of such collectors, new heat transfer fluids known as nanofluids have been applied by many researchers as found in the literatures [8][9][10][11][12][13][14][15][16][17] nanoparticles volume fraction, % density, kg/m 3 overall entropy production, J/kg·sK k thermal conductivity, W/m K Nanofluids are one of these new types of fluids that have been studied extensively in the last 20 years [8]. Hoffmann et al. [9] described this as an innovative class of nanotechnology-based heat transfer fluid having superior thermal properties compared to conventional water based fluids. ...
... Many researchers have found that the addition of a moderately small amount (<1% by volume) of nanoparticles in a base fluid can boost the thermal properties (i.e. thermal conductivity, mass diffusivity and heat transfer coefficient) [10][11][12][13][14]. ...
This paper theoretically analyses entropy generation, heat transfer enhancement capabilities and pressure drop for a flat-plate solar collector operated with single wall carbon nanotubes (SWCNTs) based nanofluids as an absorbing medium. Specific heat (Cp) of the nanofluid was measured using a PerkinElmer DSC 4000, and a density meter was used to measure the density of the nanofluid. Second law based exergy analysis was carried out to evaluate the efficiency of the flat plate collector. It is observed that the SWCNTs nanofluid reduced the entropy generation by 4.34% and enhance the heat transfer coefficient by 15.33% theoretically compared to water as an absorbing fluid. Pumping power penalty of nanofluid operated solar collector found to be 1.20% higher than the water as a working fluid.
... Nanofluid is defined as a modern engineering material that consists of solid nanoparticles with sizes typically ranging from 1 to 100 nm suspended in a base fluid [2]. Hoffmann et al. [3] described this new class of nanotechnology-based heat transfer fluids that exhibit thermal properties, which are much better than those of their host fluids or conventional particle fluid suspensions [4], researchers have found that nanofluids can be used to enhance a wide range of fluid properties. This is a new challenge in thermal sciences provided by nanotechnology. ...
Compared to thermal conductivity and convection studies with nanofluids; the optical and radiative properties of nanofluids have received much less interest. However, very recently, the number of studies on radiative heat transfer in nanofluids has been increasing. This is due to the fact that, in general, a composite nanofluid has different properties than those found in either the base fluid or the particles. At high temperatures, knowledge of the resultant radiative properties becomes increasingly significant. The concept of using direct absorbing nanofluid (suspension formed by mixing nanoparticles and a liquid) recently been shown numerically and experimentally to be an efficient method for harvesting solar thermal energy. Nanofluid is a product of emerging field of nanotechnology, where nanoparticles (1–100 nm in size) are mixed with conventional base fluids (water, oils, glycols, etc.). Nanofluids as an innovative class of heat transfer fluids represent a rapidly emerging research field where nano-science and thermal engineering coexist. Nanofluids are considered to be a two-phase system, comprised of a solid and a liquid phase. Compared to the base fluids like water or oil, nanofluids feature enhanced thermo-physical properties such as thermal diffusivity, viscosity, thermal conductivity, convective heat transfer coefficients, and optical properties. They offer unprecedented potential in many applications. Recent development in solar thermal collectors is the use of nanofluids to absorb the light directly. There is much current work going on the use of nanoparticles in several applications. With thousands of papers published every year, a comprehensive literature survey is impossible, and only selected representative publications are cited in this paper, particularly as they concern fundamental scientific insights on the fundamental optical properties of nanofluids.
