Perturbation analysis of radiative effect on free convection flows in porous medium in the presence of pressure work and viscous dissipation

The effect of thermal radiation with a regular three-parameter perturbation analysis has been studied for the effects in some free convection flows of Newtonian fluid-saturated porous medium. The effects of the thermal radiation, permeability of the porous medium, pressure stress work and viscous dissipation on the flows and temperature fields have been included in the analysis. Four different vertical flows have been analyzed, those adjacent to an isothermal surface, uniform heat flux surface, a plane plume and flow generated from a horizontal line energy source, and, a vertical adiabatic surface. Rosseland approximation is used to describe the radiative heat flux in the energy equation. The numerical results of the perturbation analysis for four conditions are solved numerically by the fourth-order Runge–Kutta integration scheme. Numerical values of the main physical quantities are the skin friction and a heat transfer and total heat and mass convected downstream are presented in a tabular form with the parameters characterizing the radiation, permeability of the porous medium, pressure stress work and viscous dissipation. The obtained results are compared and a representative set is displayed graphically to illustrate the influences of the radiation, permeability of the porous medium, pressure stress work and viscous dissipation on the velocity and the temperature profiles.     

Induction heating studies of magnetite nanospheres synthesized at room temperature for magnetic hyperthermia

An investigation of the synthesis of Fe₃O₄ nanopowders by the co-precipitation method is reported from aqueous and ethanol mediums. X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer are utilized to study the effect of variation of synthesis conditions on the crystal structure, crystallite size, microstructure and magnetic properties of the formed powders. The XRD analysis showed that the crystalline Fe₃O₄ phase was formed at Fe³⁺/Fe²⁺ molar ratio 2.0 prepared at room temperature for 1 h at pH 10. The crystallite size was in the range between 8 and 11 nm. TEM micrographs showed that the particles appeared as nanospheres. Superparamagnetic nanoparticles with low coercivity and remanence magnetization were achieved. Heating properties of the nanosphere samples in an alternating magnetic field at 160 KHz were evaluated. An excellent heating efficiency for the sample prepared in ethanol medium is a result of more relaxation losses occurring due to its small particle size.     

Synthesis of novel 2‐alkoxy(aralkoxy)‐4H‐[1,2,4]triazolo[1,5‐a]quinazolin‐5‐ones starting with dialkyl‐N‐cyanoimidocarbonates

A novel series of 2‐alkoxy(aralkoxy)‐4H‐[1,2,4]triazolo[1,5‐a]quinazolines were synthesized employing N‐cyanoimidocarbonates and 2‐hydrazinobenzoic acid as building blocks. Chemical transformation of the inherent lactam moiety in the targeted 2‐alkoxy(aralkoxy)[1,2,4]triazolo[1,5‐a]quinazolines was offered access to a variety of derivatives. J. Heterocyclic Chem., (2011).     

Studies on the Reactivity of Amino‐1‐(6‐phenyl‐pyridazin‐3‐yl)‐1H‐pyrazole‐4‐carboxylic Acid Hydrazide Towards Some Reagents for Biological Evaluation

Novel 5‐amino‐1‐(6‐phenyl‐pyridazin‐3‐yl)‐1H‐pyrazole‐4‐carboxylic acid ethyl ester ( 2 ) was formed using (6‐phenyl‐pyridazin‐3‐yl)‐hydrazine ( 1 ) and ethyl(ethoxymethylene)cyanoacetate. The β‐enaminoester derivative 2 was in turn used as precursor for the preparation of 1‐(6‐phenyl‐pyridazin‐3‐yl)‐pyrazoles ( 3 , 4 , 7 , 8 , 9 , 10 , 11 , 12 , 15 , 16 ), 1‐(6‐phenyl‐pyridazin‐3‐yl)‐pyrazolo[3,4‐d]pyrimidines ( 5 , 6 , 14 ) and 1‐(6‐phenyl‐pyridazin‐3‐yl)‐pyrazolo[3,4‐d][1,2,3]triazine ( 13 ). The in vitro antimicrobial activity of the synthesized compounds was evaluated by measuring the inhibition zone diameters where some of them showed potent antimicrobial activity in compared with well‐known drugs (standards).     

Magneto-thermo analysis of oscillatory flow around a non-conducting horizontal circular cylinder

Journal of Thermal Analysis and Calorimetry - The present study is based on oscillatory mixed-convection flow of electrically conducting fluid around a non-conducting horizontal circular cylinder....     

Sweet Corrosion Inhibition on API 5L-B Pipeline Steel

Corrosion inhibition and adsorption behavior of two triazole derivatives on API 5L-B carbon steel in CO₂-saturated 3.5% NaCl solutions was investigated using potentiodynamic polarization, EIS and EFM techniques. Specimen surfaces were characterized using SEM, EDX and XRD. Results show that the two compounds are mixed-type inhibitors and inhibition efficiency increases with increasing concentrations. Adsorption of the two compounds is a mixed between chemisorptions and physisorption and obeys Langmuir adsorption isotherm. Activation energy and thermodynamic parameters were calculated. Surface analyses confirm the formation of iron nitrides on the metal surface, which supports results obtained from previous techniques.     

Synthesis of Novel 2-Methylsulfanyl-4H-[1,2,4]triazolo[1,5-a]quinazolin-5-one and Derivatives

A novel 2-methylsulfanyl-4H-[1,2,4]triazolo[1,5-a]quinazolin-5-one was synthesized using dimethyl-n-cyanoimidodithiocarbonate and 2-hydrazinobenzoic acid as building blocks. Chemical transformation of the inherent lactam moiety in the targeted 2-methylsulfanyl-[1,2,4]triazolo[1,5-a]quinazolin-5-one offered access to a variety of derivatives.     

Influence of radiation on MHD free convection from a vertical flat plate embedded in porous media with thermophoretic deposition of particles

Magneto-hydrodynamics and thermal radiation effects on heat and mass transfer in steady laminar boundary layer flow of a Newtonian, viscous fluid over a vertical flat plate embedded in a fluid saturated porous media in the presence of the thermophoresis particle deposition effect is studied in this paper. The governing equations are transformed by special transformations. Brownian motion of particles and thermophoretic transport are considered in the flow equations. The magnetic field is considered to be applied. Rosseland approximation is used to describe the radiative heat flux in the energy equation. The resulting similarity equations are solved numerically by the fourth-order Runge–Kutta method with shooting technique. Many results are obtained and representative set is displayed graphically to illustrate the influence of the various parameters on the wall thermophoretic deposition velocity, concentration, temperature and velocity profiles.     

Entropy generation and MHD natural convection of a nanofluid in an inclined square porous cavity: Effects of a heat sink and source size and location

The effects of a heat sink and the source size and location on the entropy generation, MHD natural convection flow and heat transfer in an inclined porous enclosure filled with a Cu-water nanofluid are investigated numerically. A uniform heat source is located in a part of the bottom wall, and a part of the upper wall of the enclosure is maintained at a cooled temperature, while the remaining parts of these two walls are thermally insulated. Both the left and right walls of the enclosure are considered to be adiabatic. The thermal conductivity and the dynamic viscosity of the nanofluid are represented by different verified experimental correlations that are suitable for each type of nanoparticle. The finite difference methodology is used to solve the dimensionless partial differential equations governing the problem. A comparison with previously published works is performed, and the results show a very good agreement. The results indicate that the Nusselt number decreases via increasing the nanofluid volume fraction as well as the Hartmann number. The best location and size of the heat sink and the heat source considering the thermal performance criteria and magnetic effects are found to be D?=?0.7 and B?=?0.2. The entropy generation, thermal performance criteria and the natural heat transfer of the nanofluid for different sizes and locations of the heat sink and source and for various volume fractions of nanoparticles are also investigated and discussed.