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In many engineering applications, it is important to consider the temperature dependence of a material's properties, such as its viscosity and thermal conductivity. Aiming the same, here, in the existing exploration, viscosity and thermal conductivity are taken as variables instead of constant. This study discusses the flow of a viscous fluid over a rotating disk with a surface catalyst. The homogeneous-heterogeneous reactions are supplemented by surface catalysis that boosts the chemical reaction rate in the minimum possible time. The novelty of the problem is enhanced by the incorporation of the variable diffusion coefficients of both chemical species. The Von Karman transformation is used and the system is scrutinized by the bvp4c function of the MATLAB software. The results are portrayed in the form of illustrations and tables. The outcomes divulged that the mass diffusion rate and wall concentration for the porosity and surface catalyzed parameter show a decreasing behavior. [ABSTRACT FROM AUTHOR]

A comparison of the hybrid and nanofluid flows performance amidst two spinning disks accompanying variable thermal conductivity and viscosity is appraised in this study. The hybrid nanofluid is comprised of single-wall-multiwall carbon nanotubes/water combination and a simple nanofluid consists of single-wall carbon nanotubes (multiwall carbon nanotubes)/water amalgamation. The selection of carbon nanotubes is based on their matchless characteristics including lightweight, extraordinary thermal conductivity attributes, and stability. The envisaged model is supported with catalysis on the surface to influence the homogeneous-heterogeneous reactions and trigger the process in a relatively lesser time. The cases of clockwise and anticlockwise rotation for both disks are undertaken. The numerical MATLAB-based bvp4c technique is betrothed. The graphical illustrations depicting the association of the prominent parameters with the allied profiles are given with logical arguments. The fallouts revealed that the hybrid nanofluids are more effective than the simple nanofluids as far as thermal efficiency is concerned. It is also heeded that the rate of mass transfer is proliferated for the surface catalyzed parameter. A comparison table in a limiting case is also supplemented to jazz up the justification of the presented model. [ABSTRACT FROM AUTHOR]

Lately, a new class of nanofluids, namely hybrid nanofluids, has been introduced that performs much better compared with the nanofluids when a healthier heat transfer rate is the objective of the study. Heading in the same direction, the present investigation accentuates the unsteady hybrid nanofluid flow involving CuO, Al2O3/C2H6O2 achieved by an oscillating disk immersed in the porous media. In a study of the homogeneous and heterogeneous reactions, the surface catalyzed reaction was also considered to minimize the reaction time. The shape factors of the nanoparticles were also taken into account, as these play a vital role in assessing the thermal conductivity and heat transfer rate of the system. The assumed model is presented mathematically in the form of partial differential equations. The system is transformed by invoking special similarity transformations. The Keller Box scheme was used to obtain numerical and graphical results. It is inferred that the blade-shaped nanoparticles have the best thermal conductivity that boosts the heat transfer efficiency. The oscillation and surface-catalyzed chemical reactions have opposite impacts on the concentration profile. This analysis also includes a comparison of the proposed model with a published result in a limiting case to check the authenticity of the presented model. [ABSTRACT FROM AUTHOR]

Here, we discuss three-dimensional dusty nanofluid thin film flow with nonlinear thermal radiation, where carbon nanotubes flow past an inclined rotating disk with a constant angular velocity of Ω. This novel mathematical model is unique and is discussed here for the first time. Downward draining flow and lateral flow arise due to inclination. The demonstrated geometry is characterized in terms of time-independent continuity, momentum, and energy balance. Similarity transformations convert the partial differential equation into a system of ordinary differential equations. The obtained equations are analyzed numerically using the bvp4c MATLAB function. The thermal field of the dust phase was smaller than that of the nanofluid phase, and this difference was exacerbated by increasing the thermal radiation. To validate the model presented here, it is compared to a previous model; the models showed high concordance. [ABSTRACT FROM AUTHOR]

In the present exploration, our objective is to investigate the importance of Hall current coatings in the establishment of Cattaneo–Christov (CC) heat flux model in an unsteady aqueous-based nanofluid flow comprising single (SWCNTs) and multi-walled (MWCNTs) carbon nanotubes (CNTs) amid two parallel rotating stretchable disks. The novelty of the presented model is strengthened with the presence of homogeneous-heterogeneous (HH) reactions and thermal stratification effects. The numerical solution of the system of coupled differential equations with high nonlinearity is obtained by applying the bvp4c function of MATLAB software. To corroborate the authenticity of the present envisioned mathematical model, a comparison table is added to this study in limiting case. An excellent harmony between the two results is obtained. Effects of numerous parameters on involved distributions are displayed graphically and are argued logically in the light of physical laws. Numerical values of coefficient of drag force and Nusselt number are also tabulated for different parameters. It is observed that tangential velocity (function of rotation parameter) is increasing for both CNTs. Further, the incremental values of thermal stratification parameter cause the decrease in fluid temperature parameter. [ABSTRACT FROM AUTHOR]