MHD natural convection in inclined wavy annulus utilizing hybrid nanofluid with discrete wavy coolers

Journal of Thermal Analysis and Calorimetry - In the present framework, the combined effect of magnetic field (Hartmann number, Ha), angle of inclination $$(\alpha )$$ , nanoparticle volume...     

Neuro-computing intelligent networks for entropy optimized MHD fully developed nanofluid flow with activation energy and slip effects

In this paper, the main focus of this research is to represent an intelligent computing model through an artificial backpropagated Levenberg-Marquardt neural network (ABP-LMNN) for entropy optimized magnetohydrodynamic fully developed nanofluid flow with slip and activation energy effects. In mathematical modeling, dimensionless non-linear ODEs represent the magnetohydrodynamic nanofluid flow model (MHD-NFM). A reference dataset of ABP-LMNN is constructed for diverse situations of MHD-NFM by discrepancy of parameters. The attained reference dataset (RD) is randomly utilized for validation, testing and training processes for ABP-LMNN are employed to examine the approximate solution of MHD-NFM is demonstrated by comparison of outcomes. The authentic performance of the ABP-LMNN is validated through accuracy in the phrase of error histogram, mean square error and regression learning. The thermal and solutal parameters upsurge both the thermal and the concentration gradients. Moreover, the velocity profiles are declined owing to an increase in the second-order slip parameter in the tangential direction of the flow.     

Ion transport in materials with a developed surface

The experimental data on surface charge and mass transfer in ionic solids (ceramics, composites, nanostructures, and heterostructures) are generalized. Interphase and intergrain boundaries are shown to play an important role in transfer processes. The influence of the wetting phase transition on the transport properties of solids is considered.     

Mechanism and stereospecificity of a fully saturating polyketide synthase module: nanchangmycin synthase module 2 and its dehydratase domain

Recombinant nanchangmycin synthase module 2 (NANS module 2), with the thioesterase domain from the 6-deoxyerythronolide B synthase (DEBS TE) appended to the C-terminus, was cloned and expressed in Escherichia coli. Incubation of NANS module 2+TE with (±)-2-methyl-3-keto-butyryl-N-acetylcysteamine thioester (1), the SNAC analog of the natural ACP-bound substrate, with methylmalonyl-CoA (MM-CoA) in the absence of NADPH gave 3,5,6-trimethyl-4-hydroxypyrone (2), identified by direct comparison with synthetic 2 by radio-TLC-phosphorimaging and LC-ESI(+)-MS-MS. The reaction showed k(cat) 0.5 ± 0.1 min(-1) and K(m)(1) 19 ± 5 mM at 0.5 mM MM-CoA and k(cat)(app) 0.26 ± 0.02 min(-1) and K(m)(MM-CoA) 0.11 ± 0.02 mM at 8 mM 1. Incubation in the presence of NADPH generated the fully saturated triketide chain elongation product as a 5:3 mixture of (2S,4R)-2,4-dimethyl-5-ketohexanoic acid (3a) and the diastereomeric (2S,4S)-3b. The structure and stereochemistry of each product was established by comparison with synthetic 3a and 3b by a combination of radio-TLC-phosphorimaging and LC-ESI(-)-MS-MS, as well as chiral capillary GC-MS analysis of the corresponding methyl esters 3a-Me and 3b-Me. The recombinant dehydratase domain from NANS module 2, NANS DH2, was shown to catalyze the formation of an (E)-double bond by syn-dehydration of the ACP-bound substrate anti-(2R,3R,4S,5R)-2,4-dimethyl-3,5-dihydroxyheptanoyl-ACP6 (4), generated in situ by incubation of (2S,3R)-2-methyl-3-hydroxypentanoyl-SNAC (5), methylmalonyl-CoA, and NADPH with the recombinant [KS6][AT6] didomain and ACP6 from DEBS module 6 along with the ketoreductase from the tylactone synthase module 1 (TYLS KR1). These results also indirectly establish the stereochemistry of the reactions catalyzed by the KR and enoylreductase (ER) domains of NANS module 2.     

First and second laws of thermodynamics analysis of nanofluid flow inside a heat exchanger duct with wavy walls and a porous insert

This paper investigates the combined effects of using nanofluid, a porous insert and corrugated walls on heat transfer, pressure drop and entropy generation inside a heat exchanger duct. A series of numerical simulations are conducted for a number of pertinent parameters. It is shown that the waviness of the wall destructively affects the heat transfer process at low wave amplitudes and that it can improve heat convection only after exceeding a certain amplitude. Further, the pressure drop in the duct is found to be strongly influenced by the wave amplitude in a highly non-uniform way. The results, also, show that the second law and heat transfer performances of the system improve considerably by thickening the porous insert and decreasing its permeability. Yet, this is associated with higher pressure drops. It is argued that the hydraulic, thermal and entropic behaviours of the system are closely related to the interactions between a vortex formation near the wavy walls and nanofluid flow through the porous insert. Viscous irreversibilities are shown to be dominant in the core region of duct where the porous insert is placed. However, in the regions closer to the wavy walls, thermal entropy generation is the main source of irreversibility. A number of design recommendations are made on the basis of the findings of this study.

     

Energy and mass transport of Casson nanofluid flow over a slanted permeable inclined surface

In this problem, examination of Casson nanofluid flow over nonlinear slanted extending sheet with chemical reaction and heat generation/absorption influences are under thought. Nanofluid exhibits in this examination is established on Buongiorno model. The governing nonlinear PDE’s are reduced to nonlinear ODE’s by employing suitable transformations. The Keller-box numerical technique is considered for simulation of this research. The influence of chemical reaction and nonlinear parameter on concentration and velocity distribution is analyzed. The recovered results exhibit that the impact of inclination and Casson factor reduced liquid velocity. While energy and mass transport rates are increased against inclination factor. Numerical and graphical outcomes are additionally exhibited in tables and graphs.

     

Nanoparticles phenomenon for the thermal management of wavy flow of a Carreau fluid through a three-dimensional channel

Journal of Thermal Analysis and Calorimetry - A hybrid nanofluid phenomenon is considered involving nanoparticles since such particles are potential medication transportation devices in biomedical...     

Total mass transport through a nonhomogeneous membrane

A recent analysis of total mass transport through a homogeneous membrane is generalized to the case of membrane nonuniformity as well as the presence of irreversible, firstorder degradation or hydrolysis. The results show that for initial conditions where none of the transported mass is present in the membrane, the total mass transported is just the ratio of the time integral of the mass concentration on the donor side of the membrane to the effective steady-state resistance of the membrane. Four specific cases are considered which can be applied to the transport analysis of biological membranes such as the skin and the cornea.     

Exact solutions in MHD natural convection of a Bingham fluid: fully developed flow in a vertical channel

Journal of Thermal Analysis and Calorimetry - In nature, many fluid-like materials exhibit a yield stress below which they behave like a solid. The Bingham model aims to describe such materials....     

Analysis of fully developed mixed convection in open-ended annuli with viscous dissipation

Journal of Thermal Analysis and Calorimetry - The vertical, open-ended double-passage annular space between three vertical concentric co-axial cylinders is an important geometry representing...     

Effects of recycle type on solvent extraction through a parallel-plate membrane module

The effects of recycle type on membrane extraction through a parallel-plate module has been studied. Theoretical predictions are in fairly good agreement with the experimental results. Considerable improvement in mass-transfer is obtainable if membrane extraction is operated with recycle which provides the effects of pre-extraction and increasing fluid velocity. The influences of recycle type on the performance of membrane extraction, as well as on the fixed and operating costs, have been also discussed.     

Spin-dependent transport through a magnetic carbon nanotube-molecule junction

The electronic structure and spin-dependent conductance of a magnetic junction consisting of two Fe-doped carbon nanotubes and a C60 molecule are investigated using a first-principles approach that combines the density functional theory with the nonequilibrium Greens function technique. The tunneling magnetoresistance ratio is found to be 11%. The density of states and transmission coefficient through the molecular junction are analyzed and compared to layered magnetic tunneling junctions. Our findings suggest new possibilities for experiments and for future technology.     

Nitrate and chloride transport through a smart membrane

To develop membranes having ionic selective properties under control of external stimuli is a challenge of the membrane and material scientific community. Conducting polymers swell and shrink under electrochemical control, so they are good candidates to prepare such smart membranes. The ionic transport through a new free-standing polypyrrole film working as a membrane in a diffusion cell was studied. The driving forces were transversal electric fields or concentration gradients across the film. The obtained ionic conductivity was dependent on both the electrolyte nature and concentration, as well as on the oxidation degree of the film, which was controlled by the applied external electric potential. Reverse and continuous changes of up to one order of magnitude on the transversal ionic conductivity are obtained when the membrane is in stationary oxidation states attained by polarisations at a constant potential in the range between −0.6 V and +0.4 V, respectively. A prevalent conductivity of anions (t₋ = 0.94) was obtained from Donnan potential measurements. The experimental results indicate that the oxidised film behaves as a nanoporous membrane highly permeable to nitrate ions, while the rejection of these ions is very high in the reduced film. The free-standing polypyrrole film works then as a smart membrane selective to nitrate ions under concentration gradient.     

Electrokinetic transport through nanochannels

This article presents a numerical study of the electrokinetic transport phenomena (electroosmosis and electrophoresis) in a three-dimensional nanochannel with a circular cross-section. Due to the nanometer dimensions, the Boltzmann distribution of the ions is not valid in the nanochannels. Therefore, the conventional theories of electrokinetic flow through the microchannels such as Poisson-Boltzmann equation and Helmholtz-Smoluchowski slip velocity approach are no longer applicable. In the current study, a set of coupled partial differential equations including Poisson-Nernst-Plank equation, Navier-Stokes, and continuity equations is solved to find the electric potential field, ionic concentration field, and the velocity field in the three-dimensional nanochannel. The effects of surface electric charge and the radius of nanochannel on the electric potential, liquid flow, and ionic transport are investigated. Unlike the microchannels, the electric potential field, ionic concentration field, and velocity field are strongly size-dependent in nanochannels. The electric potential gradient along the nanochannel also depends on the surface electric charge of the nanochannel. More counter ions than the coions are transported through the nanochannel. The ionic concentration enrichment at the entrance and the exit of the nanochannel is completely evident from the simulation results. The study also shows that the flow velocity in the nanochannel is higher when the surface electric charge is stronger or the radius of the nanochannel is larger.     

Thermal conductivity of a hybrid nanofluid

Journal of Thermal Analysis and Calorimetry - Hybrid nanofluid can be considered as a new generation of nanofluids. Despite the success of the researchers in the field of hybrid nanofluids, no...     

Influence of channel-width ratio on solvent extraction through a double-pass parallel-plate membrane module

The effect of the location of an impermeable barrier, which is placed for double pass in the raffinate phase, on solvent extraction through a parallel-plate membrane module, has been investigated. Theoretical predictions are in fairly good agreement with the experimental results. Considerable improvement in performance is obtainable if the subchannel width, as well as the mass-transfer area, of concurrent flow is as large as possible than that of concurrent flow, especially for low flow rate operation. It has been also checked that the hydraulic dissipated power due to the friction loss of fluid flow is very small and generally, the operating cost in all devices may be ignored.     

Single molecule measurements of DNA transport through a nanopore

We examined the voltage-driven movement of single-stranded DNA molecules in a membrane channel or "nanopore". Using single channel recording methods and a statistical analysis of many single molecule events, we determined how voltage influences capture and translocation in the nanopore. We verified that the mean time between capture events follows a simple exponential distribution, whereas the translocation times follow a unique distribution that is partly Gaussian and partly exponential. Measurements of polymer sequence effects demonstrated that translocation duration is heavily influenced by specific or nonspecific purine-channel interactions. The single molecule approach we used revealed molecular interactions that can influence both capture rates and translocation velocities in a manner that enriches naive barrier crossing models.     

Numerical simulation of forced convective power law nanofluid through circular annulus sector

Journal of Thermal Analysis and Calorimetry - In this article, we have studied effect of two types of solid nanoparticles (i.e., TiO $$_{2}$$ and Cu) on the forced convective power law fluid flow...     

Mechanistic interpretation of solute permeation through a fully aromatic polyamide reverse osmosis membrane

The objective of this study was to assess the contribution of various mass transfer steps (concentration polarization, partitioning, and diffusive and convective transport) toward overall permeation of major solute sodium chloride (NaCl), and trace component nitrobenzene across the fully aromatic polyamide FT-30^® membrane. Experiments were performed with a closed-loop flat-leaf reverse osmosis apparatus. Feed solutions tested contained 2000, 4000 or 6000 mg/l NaCl, and 10 mg/l nitrobenzene at pH 6 and 25°C. Solute rejection ranged from 95 to 99.2% for NaCl and from 20 to 60% for nitrobenzene. The overall permeation of both NaCl and nitrobenzene appeared to be primarily by partitioning at water/membrane interfaces and diffusion across the membrane phase. Convection accounting for less than 25 and 0.4% of the overall NaCl and nitrobenzene permeation, respectively, appeared to be the result of a small leakage of feed solution through membrane imperfections estimated at 0.14% of the overall product water flux. Solute permeation was affected by concentration polarization taking place primarily within a fouling film of corrosion products. Concentration polarization levels corresponded to solute concentrations next to the feed water/membrane interface ranging from 5 to 70% (NaCl), and from 8 to 140% (nitrobenzene) higher than bulk feed concentrations.