In this study, free convection heat transfer in a concentric annulus between a cold square and heated elliptic cylinders in presence of magnetic field is investigated. The square and elliptic ...cylinders are maintained at uniform temperatures and it is assumed that the walls are insulating magnetic field. Lattice Boltzmann method is applied to solve the governing equations. The effective thermal conductivity and viscosity of nanofluid are calculated by KKL (Koo–Kleinstreuer–Li) correlation. In this model effect of Brownian motion on the effective thermal conductivity is considered. The numerical investigation is carried out for different governing parameters namely; the Hartmann number, Rayleigh number and nanoparticle volume fraction. Also a correlation of Nusselt number corresponding to active parameters is presented. The results reveal that average Nusselt number is an increasing function of nanoparticle volume fraction and Rayleigh number, while it is a decreasing function of Hartmann number. Moreover it can be found that the enhancement in heat transfer increases as Hartmann number increases but it decreases with increase of Rayleigh number.
•MHD free convection of nanofluid in a semi annulus enclosure is studied.•LBM is applied to solve this problem.•KKL correlation is used to simulate knf and μnf.•Nuave is an increasing function of ϕ and Ra, while it is a decreasing function of Ha.
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42.
Effects of Different Polypropylene Momeni, Vahid; Shahroodi, Zahra; Gonzalez-Gutierrez, Joamin ...
Polymers,
07/2023, Volume:
15, Issue:
14
Journal Article
Peer reviewed
The current study presents the effect of the backbone as an important binder component on the mechanical, rheological, and thermal properties of Aluminium (Al) alloy feedstocks. A thermoplastic ...elastomer (TPE) main binder component was blended with either polypropylene (PP), grafted-maleic anhydride-PP (PPMA), or grafted-maleic anhydride-PPwax (PPMAwax) plus PP, as the backbone. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) tests were performed to investigate the thermal properties of binder systems and feedstocks. Fourier-transform infrared (FTIR) spectroscopy was used to study the chemical interaction between the binder and the Al alloy. After making feedstock filaments, tensile tests, scanning electron microscopy (SEM), and fused filament fabrication (FFF) printing were done. The results showed that although the PP printability was acceptable, the best mechanical properties and printed quality can be achieved by PPMA. TGA test showed that all binder systems in the feedstocks could be removed completely around 500 °C. From FTIR, the possibility of chemical reactions between Al alloy particles and maleic anhydride groups on the grafted PP backbone could explain the better dispersion of the mixture and higher mechanical properties. Tensile strength in PP samples was 3.4 MPa which was improved 1.8 times using PPMA as the backbone.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The peak dimensionless thermoelectric figure-of-merit (ZT) of Bi2Te3-based n-type single crystals is about 0.85 in the ab plane at room temperature, which has not been improved over the last 50 years ...due to the high thermal conductivity of 1.65 W m−1 K−1 even though the power factor is 47 × 10−4 W m−1 K−2. In samples with random grain orientations, we found that the thermal conductivity can be decreased by making grain size smaller through ball milling and hot pressing, but the power factor decreased with a similar percentage, resulting in no gain in ZT. Reorienting the ab planes of the small crystals by repressing the as-pressed samples enhanced the peak ZT from 0.85 to 1.04 at about 125 °C, a 22% improvement, mainly due to the more increase on power factor than on thermal conductivity. Further improvement is expected when the ab plane of most of the small crystals is reoriented to the direction perpendicular to the press direction and grains are made even smaller.
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► Synthesis and characterization of alumina–copper hybrid particles using a thermo-chemical method. ► Preparation of alumina–copper/water hybrid nanofluids by dispersion of synthesized hybrid ...particles in deionised water. ► Heat transfer and pressure drop studies of prepared hybrid nanofluid with volume concentration 0.1%. ► Significant enhancement in convective heat transfer due to the addition of synthesised hybrid particles compared to water. ► Empirical correlations proposed for Nusselt number and friction factor agree well with the experimental results.
In this experimental work, a fully developed laminar convective heat transfer and pressure drop characteristics through a uniformly heated circular tube using Al2O3–Cu/water hybrid nanofluid is presented. For this we synthesized Al2O3–Cu nanocomposite powder in a thermo chemical route that involves a hydrogen reduction technique and then dispersed the prepared hybrid nano powder in deionised water to form a stable hybrid nanofluid of 0.1% volume concentration. The prepared powder was characterized by X-ray diffraction and Scanning Electron Microscope to confirm the chemical composition, to determine the particle size and to study the surface morphology. The convective heat transfer experimental results showed a maximum enhancement of 13.56% in Nusselt number at a Reynolds number of 1730 when compared to Nusselt number of water. The experimental results also show that 0.1% Al2O3–Cu/water hybrid nanofluids have slightly higher friction factor when compared to 0.1% Al2O3/water nanofluid. The empirical correlations proposed for Nusselt number and friction factor are in good agreement with the experimental data.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We have measured the pressure drop and convective heat transfer coefficient of water-based Al2O3 nanofluids flowing through a uniformly heated circular tube in the fully developed laminar flow ...regime. The experimental results show that the data for nanofluid friction factor show a good agreement with analytical predictions from the Darcy's equation for single-phase flow. However, the convective heat transfer coefficient of the nanofluids increases by up to 8% at a concentration of 0.3 vol% compared with that of pure water and this enhancement cannot be predicted by the Shah equation. Furthermore, the experimental results show that the convective heat transfer coefficient enhancement exceeds, by a large margin, the thermal conductivity enhancement. Therefore, we have discussed the various effects of thermal conductivities under static and dynamic conditions, energy transfer by nanoparticle dispersion, nanoparticle migration due to viscosity gradient, non-uniform shear rate, Brownian diffusion and thermophoresis on the remarkable enhancement of the convective heat transfer coefficient of nanofluids. Based on scale analysis and numerical solutions, we have shown, for the first time, the flattening of velocity profile, induced from large gradients in bulk properties such as nanoparticle concentration, thermal conductivity and viscosity. We propose that this flattening of velocity profile is a possible mechanism for the convective heat transfer coefficient enhancement exceeding the thermal conductivity enhancement.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We study the structural phase transition, elastic and thermodynamic properties of HfCr.sub.2 from first-principles calculations. The simulated results are very close to those of previous studies. The ...phase transition from C.sub.15 to C.sub.36 occurs at about 202.7 GPa, while the phase transition pressure from C.sub.36 to C.sub.14 is about 283.9 GPa. It can be seen from the phonon spectra and elastic constants that HfCr.sub.2 is mechanically stable at C.sub.15 phase. It can be concluded that C.sub.15 phase HfCr.sub.2 is ductile from 0 to 200 GPa, and the bigger the pressure, the greater the ductility from G/B value and Poisson's ratio. Then, through the analysis of density of states, the mechanism of metal properties is discussed. Finally, the relation of thermal expansion coefficient, Debye temperature and thermal capacity to pressure and temperature is discussed.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The relationship between linear elasticity theory of solids and their equations of state (EoS) is reviewed, along with the commonly-used types of isothermal EoS, thermal expansion models, and P-V-T ...EoS. A new console program, EosFit7c, is presented. It performs EoS calculations and fitting for both volume and linear isothermal data, isobaric data and P-T data. Linear data is handled by cubing the quantities and treating them as volumes in all EoS formulations. Least-squares fitting of EoS to data incorporates the option to weight the fit with the measurement uncertainties in P, V and T simultaneously. The EosFit7c program is built with a new library of subroutines for EoS calculations and manipulation, written in Fortran. The library has been incorporated as a module, cfml_eos, in the publicly-available CrysFML library. The module handles Murnaghan, Tait, Birch-Murnaghan, Vinet, and Natural Strain EoS. For P-V-T calculations any of these isothermal EoS can be combined with a variety of published thermal expansion models, including a model of thermal pressure. The entire library has been revalidated against other software and against an ab-initio re-derivation of the EoS, which identified a number of small errors in published formulae for some EoS.
The electronic structure and elastic and thermodynamic properties of the AgMO.sub.3 (M = Nb, Ta) were investigated using first-principles calculations. The lattice parameters and volumes are in ...reasonable agreement with the experimental results. The calculated Cauchy's pressure, Poisson's ratio, and B/G ratio confirm the ductile nature of both the compounds. The variation in entropy (S), thermal expansion coefficient (alpha), constant volume heat capacity (C.sub.v), and the constant pressure heat capacity C.sub.p with temperature have been studied.
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DOBA, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Modulation-doping was theoretically proposed and experimentally proved to be effective in increasing the power factor of nanocomposites (Si80Ge20)70(Si100B5)30 by increasing the carrier mobility but ...not the figure-of-merit (ZT) due to the increased thermal conductivity. Here we report an alternative materials design, using alloy Si70Ge30 instead of Si as the nanoparticles and Si95Ge5 as the matrix, to increase the power factor but not the thermal conductivity, leading to a ZT of 1.3 ± 0.1 at 900 °C.
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