Double diffusive flow of a hydromagnetic nanofluid in a rotating channel with Hall effect and viscous dissipation: Active and passive control of nanoparticles

The investigation of simultaneous effects of Hall current and viscous dissipation on three-dimensional magnetohydrodynamic nanofluid flow in a horizontal rotating channel with active and passive control of nanoparticles, is carried out. The lower sheet is considered stretching while the upper sheet is kept fixed. Mathematical model is developed using boundary layer and scale analysis approach. Similarity transformation technique is employed to translate the governing partial differential equations into ordinary differential equations. The bvp4c solver of MATLAB is employed to solve transformed equations. Computations for nanofluid velocity, nanofluid temperature distribution and distribution of nanoparticles along with skin friction co-efficient and Nusselt number, are carried out for a range of values of pertinent flow parameters. A comparative analysis of effect of $\text{CuO}$ and ${\text{Al}}_2{\text{O}}_3$ nanoparticles on velocity, temperature, nanoparticle distribution, skin friction coefficient and Nusselt number is carried out. Rate of heat transfer at the lower sheet is observed to be a decreasing function of magnetic field whereas this physical quantity is getting enhanced as the volume fraction of nanoparticles are increased.     

Numerical analysis of conjugate natural and mixed convection heat transfer of nanofluids in a square cavity using the two-phase method

In the present study, the problem of conjugate natural and mixed convection of nanofluid in a square cavity containing several pairs of hot and cold cylinders is visualized using non-homogenous two-phase Buongiorno's model. Such configuration is considered as a model of heat exchangers in order to prevent the fluids contained in the pipelines from freezing or condensing. Water-based nanofluids with Cu, Al₂O₃, and TiO₂ nanoparticles at different diameters ($25\text{nm}?d_p?145\text{nm}$) are chosen for investigation. The governing equations together with the specified boundary conditions are solved numerically using the finite volume method based on the SIMPLE algorithm over a wide range of Rayleigh number (${10}^4?\mathit{Ra}?{10}^7$), Richardson number (${10}^{-2}?\mathit{Ri}?{10}^2$) and nanoparticle volume fractions ($0?\phi ?5\%$). Furthermore, the effects of three types of influential factors such as: orientation of conductive wall, thermal conductivity ratio ($0.2?K_r?25$) and conductive obstacles on the fluid flow and heat transfer rate are also investigated. It is found that the heat transfer rate is significantly enhanced by incrementing Rayleigh number and thermal conductivity ratio. It is also observed that at all Rayleigh numbers, the total Nusselt number rises and then reduces with increasing the nanoparticle volume fractions so that there is an optimal volume fraction of the nanoparticles where the heat transfer rate within the enclosure has a maximum value. Finally, the results reveal that by increasing the thermal conductivity of the nanoparticles and Rayleigh number, distribution of solid particles becomes uniform.     

Chloride penetration into concrete structures in the marine atmosphere zone – Relationship between deposition of chlorides on the wet candle and chlorides accumulated into concrete

The relationship between chlorides from marine aerosol and chlorides accumulated into concrete is discussed in this paper. The experimental programme comprised an environmental characterisation, with climatic and chloride deposition data, and a study of chloride penetration into concrete based on natural exposure of specimens in a marine atmosphere zone. Results show that salt concentration in marine aerosol strongly decreases in the first meters from the sea. Chlorides present in the atmosphere can be studied using the wet candle method and correlated with chlorides accumulated into concrete. This relationship can be represented by the equation $C_{\text{tot}}=C_0+k_{\text{d}}·\sqrt{D_{\text{ac}}}$, where k_d is a coefficient which depends on concrete and environmental characteristics, C_tot is the average total amount of chlorides accumulated into concrete, C₀ is the chloride content in concrete before exposure and D_ac is the accumulated dry deposition of chlorides.     

Framing the performance of induced magnetic field and entropy generation on Cu and TiO2 nanoparticles by using Keller box scheme

Aim of present communication is to inspect the impact of induced magnetic field and entropy generation on water based nanofluid. The thermal characteristic of nanofluids are explored using copper and titanium nanoparticles. The governing physical problem is modelled and by using scaling group of transformations. Obtained system of coupled nonlinear partial differential equations is converted into set of ordinary differential equations. These equations are solved numerically using implicit finite difference scheme. Entropy generation analysis is carried out to measure the disorder within the thermodynamical system. Effect of nanoparticles volume fraction on magnetic field components, skinfriction and local heat flux are computed and discussed in a physical manner. It is examined that magnetic field parameter reduces wall stress while it increases rate of heat transfer at surface. Local heat flux accelerate with increasing nanoparticles volume fraction. ${\text{TiO}}_2$ water based nanofluid showed better results for heat transfer than $\text{Cu}$ water based nanofluid.