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EN
Heat transfer study from the heated square cylinder at a different orientation angle to the stream of nanofluids has been investigated numerically. CuO-based nanofluids were used to elucidate the significant effect of parameters: Reynolds number (1–40), nanoparticle volume fraction (0.00–0.05), the diameter of the NPs (30–100 mn) and the orientation of square cylinder (0–90). The numerical results were expressed in terms of isotherm contours and average Nusselt number to explain the effect of relevant parameters. Over the range of conditions, the separation of the boundary layers of nanofluids increased with the size of the NPs as compared to pure water. NPs volume fraction and its size had a significant effect on heat transfer rate. The square cylinder of orientation angle (45) gained a more efficient heat transfer cylinder than other orientation angles. Finally, the correlations were developed for the average Nusselt number in terms of the relevant parameters for 45 orientation of the cylinder for new applications.
EN
In this paper, the effects of rotation on a Jeffery nanofluid flow in a porous medium which is heated from below is studied. Darcy model is employed for porous medium and the Jeffrey fluid model is used as a base fluid. The Navier-Stokes equations of motion of fluid are modified under the influence of the Jeffrey parameter, naoparticles and rotation. The basic perturbation technique based on normal modes is applied to derive the dispersion relation for a Rayleigh number. The effects of the Taylor number, Jeffrey parameter, Lewis number, modified diffusivity ratio, nanoparticles Rayleigh number and medium porosity on the stationary convection of the physical system have been analyzed analytically and graphically. It is observed that the rotation parameter has a stabilising influence for both bottom/top-heavy configurations.
EN
The current investigation deals with heat transfer of a non-newtonian fluid between two concentric cylinders. To describe the behavior of non-Newtonian fluid casson fluid model is used because of its various useful applications. The governing partial differential equations suchlike continuity, momentum, energy, solute concentration and nano-particle fraction equations are transubstantiated into non-linear ordinary differential equations with the assistance of resemblance alteration. Then those are numerically solved by the very efficient shooting method. Additionally, influences of distinct involved parameters are interpreted graphically. It is adhered that the velocity field shows inclined behavior due to the increment in the values of the casson parameter, so long as enhancing the temperature.
4
Content available remote Flow of a nanofluid in an inter blade canal of a centrifugal pump
EN
The use of centrifugal pumps in the hydraulic transport of nano-fluids poses major problems for the rational choice of the type of pump capable of working with a nanoparticle concentration difference in a base fluid . In this context, the objective of this work is to study the internal flow in an inter blading canal of a centrifugal pump for pumping fluid nano Al2O3/water to various concentrations. And this through the ANSYS - CFX software, based on the finite volume method. The turbulence of the flow in the inter-blade canal is taken into account using the k-ɛ model. The results obtained show that the addition of nanoparticles in the nano fluid has an appreciable effect on the flow velocity, pressure and shear stresses.
EN
This article reports the effects of CuO/water based coolant on specific fuel consumption and exhaust emissions of four stroke single cylinder diesel engine. The CuO nanoparticles of 27 nm were used to prepare the nanofluid-based engine coolant. Three different volume concentrations (i.e 0.05%, 0.1%, and 0.2%) of CuO/water nanofluids were prepared by using two-step method. The purpose of this study is to investigate the exhaust emissions (NOx), exhaust gas temperature and specific fuel consumption under different load conditions with CuO/water nanofluid. After a series of experiments, it was observed that the CuO/water nanofluids, even at low volume concentrations, have a significant influence on exhaust emissions. The experimental results revealed that, at full load condition, the specific fuel consumption was reduced by 8.6%, 15.1% and 21.1% for the addition of 0.05%, 0.1% and 0.2% CuO nanoparticles with water, respectively. Also, the emission tests were concluded that 881 ppm, 853 ppm and 833 ppm of NOx emissions were observed at high load with 0.05%, 0.1% and 0.2% volume concentrations of CuO/water nanofluids, respectively.
6
Content available Drag reduction in the flow of CuO based nanofluid
EN
Experimental studies on drag reduction (DR) of CuO based nanofluid with the additives of mixture of cationic surfactant CTAC (cetyltrimethylammonium chloride) and sodium salycilate - NaSal were performed. The obtained results were compared with those for water solution of CTAC/NaSal. Values of pressure drop were measured in specially designed laboratory setup equipped with measuring tubes of three different diameters - 4, 8 and 12 mm. It was found that the addition of surfactant and sodium salycilate mixture to nanofluid decreased its pressure drop during flow, however the drag reducing effect was greater for pure water. The DR effect obtained was in the range of 20 ÷ 70% for CuO based nanofluid. The diameter effect was also observed - the DR coefficient was greater for pipes of smaller inner diameters.
PL
Przeprowadzono badania eksperymentalne dotyczące obniżenia oporów przepływu (DR) w nanopłynie z cząstkami CuO oraz dodatkiem mieszaniny kationowego surfaktantu CTAC (chlorek cetylotrimetyloamoniowy) i salicylanu sodu - NaSal. Otrzymane wyniki porównano z otrzymanymi dla wodnego roztworu CTAC/NaSal. Wartości oporów przepływu mierzono w specjalnie w tym celu zaprojektowanej instalacji laboratoryjnej wyposażonej w rurki pomiarowe o trzech różnych średnicach - 4, 8 i 12 mm. Stwierdzono, że dodatek mieszaniny surfaktantu i salicylanu sodu do nanopłynu zmniejsza jego opory przepływu w rurze, lecz w mniejszym stopniu niż dla czystej wody. Uzyskano współczynnik DR dla nanopłynu zawierającego cząstki CuO w zakresie 20 ÷70%. Zaobserwowano także wpływ średnicy rurki - współczynnik DR był większy dla rurek o mniejszej średnicy.
7
Content available Unsteady natural convection in micropolar nanofluids
EN
This paper presents the analysis of momentum, angular momentum and heat transfer during unsteady natural convection in micropolar nanofluids. Selected nanofluids treated as single phase fluids contain small particles with diameter size 10-38.4 nm. In particular three water-based nanofluids were analyzed. Volume fraction of these solutions was 6%. The first of the analyzed nanofluids contained TiO2 nanoparticles, the second one contained Al2O3 nanoparticles, and the third one the Cu nanoparticles.
EN
Nanofluids, i.e. suspensions of nanoparticles in base fluid, may be prepared either by the one- or two-step method. In the one-step method nanoparticles are synthesized directly in base fluid. In the two-step method nanoparticles prepared as a powder are suspended in base fluid. Influence of sonication time, stabilizer and pH on stability, particle size distribution and zeta potential of CuO- and Al2O3-water nanofluids prepared by the two-step method is presented in the paper.
PL
Nanopłyny, czyli zawiesiny nanocząstek w płynie bazowym, mogą być otrzymywane metodą jedno- i dwustopniową. W metodzie jednostopniowej nanocząstki otrzymuje się bezpośrednio w płynie bazowym. W metodzie dwustopniowej nanocząstki otrzymane w postaci proszku zawieszane są w płynie bazowym. Przedstawiono wpływ czasu nadźwiękawiania, rodzaju stabilizatora i pH na stabilność oraz rozkłady ziarnowe i potencjał zeta nanopłynów CuO i Al2O3 w wodzie otrzymanych metodą dwustopniową.
9
Content available remote Przybliżona formuła analityczna określająca przewodnictwo cieplne nanopłynów
PL
W pracy przedstawiono nową formułę analityczną pozwalającą określić przewodnictwo cieplne nanopłynów w zależności od objętościowej zawartości nanocząstek i temperatury. Formuła ta ma szerszy zakres zastosowania od proponowanych w literaturze prostych zależności liniowych.
EN
A new analytical formula for determination of heat conduction in nanofluids as a function of temperature and volumetric concentration of nanoparticles is shown in the paper. The formula represents a broader application range in comparison with proposed in literature simple linear dependencies.
EN
Purpose: In this study we report measurements of effective thermal conductivity by using 3ω method and effective viscosity by vibro-viscometer for SiO2-water and Al2O3-water nanofluids at different particle concentrations and temperatures. Design/methodology/approach : The effective thermal conductivity of nanofluids is measured by a technique based on a hot wire thermal probe with ac excitation and 3ω lock-in detection. There is presented an experimental study of thermal conductivity and viscosity of nanofluids. It was investigated Alumina and Silica nanoparticles in water with different particle concentrations. Findings: Measured results showed that the effective thermal conductivity of nanofluids increase as the concentration of the particles increase but not anomalously as indicated in the majority of the literature and this enhancement is very close to Hamilton-Crosser model, also this increase is independent of the temperature. The effective viscosities of these nanofluids increased by the increasing particle concentration and decrease by the increase in temperature, and can not be predicted by Einstein model. Practical implications: The results show that for our samples, thermal conductivity values are inside the limits of (moderately lower than) Hamilton-Crosser model. Originality/value: Experiments at different temperatures show that relative thermal conductivity of nanofluids is not related with the temperature of the fluid.
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