Cordierite honeycomb monoliths coated with modified forms of ceria for the acid catalyzed synthesis of butylacetate via microwave irradiation

A series of solid acid catalysts like CeO2, CeO2-ZrO2 and SO4-2/CeO2-ZrO2 have been coated over monoliths by dip and dry process. Catalysts have been characterized by NH3-TPD for surface acidity, PXRD for crystallinity, FT-IR analysis for functionality, SEM and TEM for morphology. The catalytic activity of the synthesized materials is trialled by liquid-phase esterification of acetic acid with butanol. The catalytic activity is correlated with acid sites examined by NH3-TPD method. Optimization of reaction is carried out by altering the molar ratio, temperature, catalyst nature and time of the reaction. A detailed techno-economical analysis of the catalytic material and the procedure followed for the esterification reaction is also studied. In the techno-economical analysis, it is noticed that microwave assisted heating is more advantageous over conventional one. In case of microwave heating, the conversion of BA is 98% with a shorter reaction time of 12 min but in the case of conventional method of heating, it takes almost 6 h to get the above said conversion. It is further noticed that a comparative analysis of honeycomb over powder forms clearly states that, honeycomb forms shows almost 4 fold time increase in the conversion of BA compared to their powder analogs

Computational fluid dynamics analysis of moisture ingress in aircraft structural composite materials

Moisture in composite materials has been proven to be an important issue leading to significant deterioration of commercial aircraft wing structures. Lingering problems associated with this issue which is initiated with defects during manufacturing and finishing include delamination, de-bonding, potential fracture, debris etc. Despite extensive investigation and refinement in structural design, the water ingress problem persists as no general mitigation technique has yet been developed. Developing sustainable solutions to the water ingress problem can be very time-consuming and costly. The increasing use of composites in the aviation industry, in, for example, honeycomb sandwich components highlights the significant need to address the moisture ingress problem and develop deeper insights which can assist in combatting this problem. Experimental testing, although the most dependable approach, can take months, if not years. Numerical simulations provide a powerful and alternative approach to experimental studies for obtaining an insight into the mechanisms and impact of moisture ingress in aircraft composites. The principal advantage is that they can be conducted considerably faster, are less costly than laboratory testing, and furthermore can also utilize the results of laboratory studies to aid in visualizing practical problems. Therefore, the present study applies a computational fluid dynamics (CFD) methodology, specifically ANSYS finite volume software and the three fluid-based solvers, Fluent, CFX and ANSYS fluid structure interaction (FSI), to simulate water ingress in composite aerospace structures. It is demonstrated that ANSYS Fluent is a satisfactory computational solver for fundamental studies, providing reasonably accurate results relatively quickly, especially while simulating two-dimensional components. Three-dimensional components are ideally simulated on CFX, although the accuracy achievable is reduced. The structural-fluid based solver, ANSYS FSI (fluid structure interaction), unfortunately does not fully implement the material studied leading to reduced accuracy. The simulations reveal interesting features associated with different inlet velocities, inlet fastener hole numbers, void number and dimensions. Pressure, velocity, streamline, total deformation and normal stress plots are presented with extensive interpretation. Furthermore, some possible mitigation pathways for water ingress effects including hydrophobic coatings are outlined. KEY WORDS: Aircraft composites, Computational Fluid Dynamics, ANSYS, moisture ingress, Fluent, CFX, (fluid structure interaction) FSI, velocity, pressure, total deformation; elevator, mesh density

Adomain computation of radiative-convective bi-directional stretching flow of a magnetic non-Newtonian fluid in porous media with homogeneous-heterogeneous reactions

In the present communication, laminar, incompressible, hydromagnetic flow of an electrically conducting non-Newtonian (Sisko) fluid over a bi-directional stretching sheet in a porous medium is studied theoretically. Thermal radiation flux, homogeneous-heterogeneous chemical reactions and convective wall heating are included in the model. Darcy’s model is employed for the porous medium and Rosseland’s model for radiation heat transfer. The governing partial differential equations for mass, momentum, energy and concentration are reduced into ordinary differential equations via similarity transformations. The resultant nonlinear ordinary differential equations with transformed boundary conditions are then solved via the semi-analytical Adomain decomposition method (ADM). Validation with earlier studies is included for the non-radiative case. Extensive visualization of velocity, temperature and species concentration distributions for various emerging parameters is included. Increasing magnetic field and inverse permeability parameter are observed to decelerate both the primary and secondary velocity magnitudes whereas they increase temperatures in the regime. Increasing sheet stretching ratio weakly accelerates the primary flow throughout the boundary layer whereas it more dramatically accelerates the secondary flow near sheet surface. Temperature is consistently reduced with increasing stretching sheet ratio whereas it is strongly enhanced with greater radiative parameter. With greater Sisko non-Newtonian power-law index the primary velocity and temperature are decreased whereas the secondary velocity is increased. Increasing both homogenous and heterogenous chemical reaction parameters is found to weakly and more strongly, respectively, deplete concentration magnitudes whereas greater Schmidt number enhances them. Primary and secondary skin friction and Nusselt number profiles are also computed. The study is relevant to electro-conductive (magnetic polymer) materials processing operations

Unsteady reactive magnetic radiative micropolar flow, heat and mass transfer from an inclined plate with joule heating: a model for magnetic polymer processing

Magnetic polymer materials processing involves many multi-physical and chemical effects. Motivated by such applications, in the present work a theoretical analysis is conducted of combined heat and mass transfer in unsteady mixed convection flow of micropolar fluid over an oscillatory inclined porous plate in a homogenous porous medium with heat source, radiation absorption and Joule dissipation. A first order homogenous chemical reaction model is used. The transformed non-dimensional boundary value problem is solved using a perturbation method and Runge-Kutta fourth order numerical quadrature (shooting technique). The emerging parameters dictating the transport phenomena are shown to be the gyro-viscosity micropolar material parameter, magnetic field parameter, permeability of the porous medium, Prandtl number, Schmidt number, thermal Grashof number, species Grashof number, thermal radiation-conduction parameter, heat absorption parameter, radiation absorption parameter, Eckert number, chemical reaction parameter and Eringen coupling number (vortex viscosity ratio parameter). The impact of these parameters on linear velocity, microrotation (angular velocity), temperature and concentration are evaluated in detail. Results for skin friction coefficient, couple stress coefficient, Nusselt number and Sherwood number are also included. Couple stress is observed to be reduced with stronger magnetic field. Verification of solutions is achieved with earlier published analytical results

Facile synthesis of bis(indolyl)methanes over cordierite honeycomb coated with modified forms of zirconia under microwave irradiation condition

Zirconia (ZrO2), Mo(VI)/ZrO2, W(VI)/ZrO2 and SO42-/ZrO2 have been coated on honeycomb monoliths and used as catalytic material in the microwave-assisted synthesis of various bis(indolyl)methane derivatives via condensation. These catalytic materials have been characterized for their properties such as surface acidity, crystallinity, morphology and elemental analysis by suitable techniques. A correlation between the acidity, crystallinity and the catalytic activity of these catalytic materials is observed. The effect of conventional heating and microwave heating on the synthesis of these derivatives has been studied. Microwave-assisted synthesis of bis(indolyl)methane derivatives over zirconia and its modified forms is found to be a fast and facile catalytic route. Up to 98% yield of bis(indolyl)methanes is obtained in a very short reaction time of 4 min under microwave irradiation, whereas it requires 20 min to obtain 98% yield under conventional heating. The honeycomb monoliths coated with modified forms of zirconia as catalytic materials are efficient, easily reactivable and reusable for at least six reaction cycles.

The occurrence and potential ecological risk assessment of bauxite mine-impacted water and sediments in Kuantan, Pahang, Malaysia

Recent bauxite mining activities in the vicinity of Kuantan, Pahang, have been associated with apparent environmental quality degradation and have raised environmental concerns among the public. This study was carried out to evaluate the overall ecological impacts on water and sediment quality from the bauxite mining activities. Water and sediment samples were collected at seven sampling locations within the bauxite mining areas between June and December 2015. The water samples were analyzed for water quality index (WQI) and distribution of major and trace element geochemistry. Sediment samples were evaluated based on geochemical indices, i.e., the enrichment factor (EF) and geoaccumulation index (Igeo). Potential ecological risk index was estimated to assess the degree to which sediments of the mine-impacted areas have been contaminated with heavy metals. The results showed that WQIs of some locations were classified as slightly polluted and contained metal contents exceeding the recommended guideline values. The EFs indicated minimal to moderate enrichment of metals (Pb, Cu, Zn, Mn, As, Cd, Cr, Ni, Co, and Sr) in the sediments. Igeo showed slightly to partially polluted sediments with respect to As at some locations. The potential ecological risk index (RI) showed that As posed the highest potential ecological risk with RI of 52.35–60.92 at two locations, while other locations indicated low risk. The findings from this study have demonstrated the impact of recent bauxite mining activities, which might be of importance to the local communities and relevant authorities to initiate immediate rehabilitation phase of the impacted area

Oscillatory dissipative conjugate heat and mass transfer in chemically-reacting micropolar flow with wall couple stress : a finite element numerical study

High temperature non-Newtonian materials processing provides a stimulating area for process engineering simulation. Motivated by emerging applications in this area, the present article investigates the time-dependent free convective flow of a chemically-reacting micropolar fluid from a vertical plate oscillating in its own plane adjacent to a porous medium. Thermal radiative, viscous dissipation and wall couple stress effects are included. The Rosseland diffusion approximation is used to model uni-directional radiative heat flux in the energy equation. Darcy’s model is adopted to mimic porous medium drag force effects. The governing two-dimensional conservation equations are normalized with appropriate variables and transformed into a dimensionless, coupled, nonlinear system of partial differential equations under the assumption of low Reynolds number. The governing boundary value problem is then solved under physically viable boundary conditions numerically with a finite element method based on the weighted residual approach. Graphical illustrations for velocity, micro-rotation (angular velocity), temperature and concentration are obtained as functions of the emerging physical parameters i.e. thermal radiation, viscous dissipation, first order chemical reaction parameter etc. Furthermore, friction factor (skin friction), surface heat transfer and mass transfer rates have been tabulated quantitatively for selected thermo-physical parameters. A comparison with previously published paper is made to check the validity and accuracy of the present finite element solutions under some limiting cases and excellent agreement is attained. Additionally, a mesh independence study is conducted. The model is relevant to reactive polymeric materials processing simulation

Finite element computation of multi-physical micropolar transport phenomena from an inclined moving plate in porous media

Non-Newtonian flows arise in numerous industrial transport processes including materials fabrication systems. Micropolar theory offers an excellent mechanism for exploring the fluid dynamics of new non-Newtonian materials which possess internal microstructure. Magnetic fields may also be used for controlling electrically-conducting polymeric flows. To explore numerical simulation of transport in rheological materials processing, in the current paper, a finite element computational solution is presented for magnetohydrodynamic (MHD), incompressible, dissipative, radiative and chemically-reacting micropolar fluid flow, heat and mass transfer adjacent to an inclined porous plate embedded in a saturated homogenous porous medium. Heat generation/absorption effects are included. Rosseland’s diffusion approximation is used to describe the radiative heat flux in the energy equation. A Darcy model is employed to simulate drag effects in the porous medium. The governing transport equations are rendered into non-dimensional form under the assumption of low Reynolds number and also low magnetic Reynolds number. Using a Galerkin formulation with a weighted residual scheme, finite element solutions are presented to the boundary value problem. The influence of plate inclination, Eringen coupling number, radiation-conduction number, heat absorption/generation parameter, chemical reaction parameter, plate moving velocity parameter, magnetic parameter, thermal Grashof number, species (solutal) Grashof number, permeability parameter, Eckert number on linear velocity, micro-rotation, temperature and concentration profiles. Furthermore, the influence of selected thermo-physical parameters on friction factor, surface heat transfer and mass transfer rate is also tabulated. The finite element solutions are verified with solutions from several limiting cases in the literature. Interesting features in the flow are identified and interpreted

Numerical study of a dissipative micropolar fluid flow past an inclined porous plate with heat source/sink

Micropolar theories present an excellent mechanism for exploring new non-Newtonian materials processing provides a stimulating area for process engineering simulation. Motivated by area for process engineering applications, the present article presents the scope of finite element method in solving a mathematical model for magnetohydrodynamic, incompressible, dissipative and chemically reacting micropolar fluid flow and heat and mass transfer through a porous medium from an inclined plate with heat source/sink has been investigated. For this purpose, the set of governing equations have been reframed and put into a dimensionless form under the assumption of low Reynolds number with appropriate dimensionless quantities that can fit into the finite element formulation. In addition to highlighting the operational aspects of weighted residual scheme, a detailed investigation has been carried out on the associated flow structure, heat and mass transfer. The evolution of many multi-physical parameters in these variables is illustrated graphically. Finite element code is benchmarked with the results reported in the literature to check the validity and accuracy under some limiting cases and excellent agreement is seen with published solutions and results of skin friction coefficient, couple stress coefficient, Nusselt number and Sherwood number for invoked parameter are tabulated which shows that increasing heat source/sink parameter elevates temperature. Chemical reaction parameter reduces velocity and concentration gradients. Sherwood number enhances as chemical reaction parameter increases but reverse phenomena is observed in case of inclination of angle. Furthermore, a grid independency test has been carried out for different grid sizes which has proven this method is adequate. Keywords: Heat source/sink, Chemical reaction, Inclined porous plate, Micropolar fluid, Finite element method (FEM