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Owing to enhanced performance, the hybrid nanofluids are finding increasingly varied applications in areas such as energy systems, extrusion operations, industrial activities, and chemical processes. The aim of current model is to explore thermal behavior of Casson hybrid nanofluid flow when subjected to a magnetic force. Two types of carbon nanotubes, the single‐walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs), dispersed in blood were investigated. The study addressed the problem based on time‐dependent thermal conductivity and considering an external heat source. It is important to understand how heat transfer occurs in nanofluids with variable thermal conductivity because it is a significant feature in many thermodynamic systems where nanofluids play important roles. To formulate the set of dimensionless governing equations, similarity variables are employed. The numerical shooting method, known for its high precision, is applied to solve these equations. The accuracy of the solutions is verified by comparison with results from previous studies, and the impact of various parameters is examined. It is noticed that velocity profile declined due to unsteady parameter for both types of CNTs (SWCNTs‐MWCNTs). An increase in the nanoparticles' volume fraction results in elevated temperatures. [ABSTRACT FROM AUTHOR]

The current study presents a time dependent couple stress nanofluid flow across a bidirectional periodically stretched surface under magnetic effects. The effects of nonuniform heat source and variable thermal conductivity on the convective heat transfer are analyzed. The effect of the chemical reaction, nonlinear mixed convection, and activation energy are also considered. Adequate dimensional quantities are utilized to entertained the problem in simplified from. Then, a series of solutions are obtained via homotopic analysis method. Tables and graphs are organized to evaluates the physical dynamic of problem. The archived observations convey that the nonlinear convective parameters cause a rise in horizontal velocity component. It is determined that flow intensity and skin friction have an increasing behavior with most of the governing parameters. Current investigation emphasized that the temperature increases by imposing variable thermal conductivity. The concentration values become higher by increasing the activation energy but decrease with the reaction rate. [ABSTRACT FROM AUTHOR]

The nanofluids became much of interest due to their superior heat mechanism over the conventional fluids. The addition of nanoparticles in the host solvent enhances the internal ability of the liquid to store and transmit heat. Therefore, these fluids are widely used in biomedical engineering, detergents, medication, applied thermal engineering, mechanical, and chemical engineering and so forth. Keeping in mind the significance of nanofluids, this study is conducted to investigate the comparative heat transmission in γAl2O3−H2O${\mathrm{\gamma Al}}_2{{\mathrm{O}}}_3 - {{\mathrm{H}}}_2{\mathrm{O}}$ and γAl2O3−C2H6O2${\mathrm{\gamma Al}}_2{{\mathrm{O}}}_3 - {{\mathrm{C}}}_2{{\mathrm{H}}}_6{{\mathrm{O}}}_2$ under the Effective Prandtl Number Model (EPNM) effects over a vertical permeable cylinder. Formulation of the model is carried out over a vertical cylinder about the stagnation point and the heat transport model is achieved after the successful implementation of the cylindrical stream function, nanofluids effective characteristics, and cylindrical similarity equations. The mathematical treatment was done via RK technique and furnished the results. The nanofluids have the capacity to control the fluid motion more effectively than ordinary fluid and combined convection is better where rapid fluid movement is desired. In the existence of EPNM, higher heat transmission is achieved and is prominent for γAl2O3−C2H6O2${\mathrm{\gamma Al}}_2{{\mathrm{O}}}_3 - {{\mathrm{C}}}_2{{\mathrm{H}}}_6{{\mathrm{O}}}_2$ based on their thermophysical values. Further, the skin friction and Nusselt number are optimum for γAl2O3−C2H6O2${\mathrm{\gamma Al}}_2{{\mathrm{O}}}_3 - {{\mathrm{C}}}_2{{\mathrm{H}}}_6{{\mathrm{O}}}_2$ against α1${\alpha }_1$. [ABSTRACT FROM AUTHOR]

The research on hybrid nanofluid has been focused by researchers widely in the current decade. Being the combination of two distinct nanoparticles, the researchers have predicted the thermal efficiencies of hybrid nanofluid model in view of distinct nanoparticles. However, the no attention is devoted by researchers towards the thermal mechanism of hybrid nanofluid with boron nitride nanotubes (BNNTs) and multiwall carbon nanotubes (MWCNTs) with distinct impressive characteristics. This communication aims explore the thermal flow of BNNTs and MWCNTs confining the axisymmetric rotational stagnation point flow executing by a bi‐axial stretching surface. The numerical computations are performed the implementation of Keller Box numerical technique. The results verification is done via making the comparative analysis. The thermal aspect of hybrid nanofluid model is entertained. The physical inspection of the formulated problem with flow parameters is done in terms of distinct graphs. It is observed that increase in the solid volume fraction of BNNTs enhanced the velocity profile. The temperature profile declined with stretching parameter for MWCNTs and hybrid nanofluid. The Nusselt number increases for thermal Biot number and increasing change is more progressive for hybrid nanomaterials as compared to MWCNTs. [ABSTRACT FROM AUTHOR]

The effect of magnetic field inclination and double lid‐driven on the mixed convection in a square cavity is investigated based on the local thermal non‐equilibrium model. The cavity was filled with a copper–water micropolar nanofluid saturated with a porous medium. The top and bottom walls are considered moving to the left or right directions at a constant velocity. In the current work, the ranges of parameters are as follow: Hartmann number (0 ≤ Ha ≤ 50), length of the heat source (0.2 ≤ B ≤ 0.8), Richardson number (0 ≤ Ri ≤ 10), Reynolds number (0 ≤ Re ≤ 100), location of the heat source (0.3 ≤ D ≤ 0.7), vortex to molecular viscosity ratio (0 ≤ Δ ≤ 2), Nield number (1 ≤ Q ≤ 100) and solid volume fraction (0 ≤ φ ≤ 0.1). It was found that the heat transfer decreases as the dimensionless heat source location and the Nield number increase. Also, the growing in the Nield number enhances the rate of the heat transfer for the porous phase and increases the thermal equilibrium state of the system. [ABSTRACT FROM AUTHOR]

The heat transfer phenomena inside a horizontal channel with an open trapezoidal enclosure subjected to a heat source of different lengths was investigated numerically in the present work. The heat source is considered as a local heating element of varying length, which is embedded at the bottom wall of the enclosure and maintained at a constant temperature. The air flow enters the channel horizontally at a constant cold temperature and a fixed velocity. The other walls of the enclosure and the channel are kept thermally insulated. The flow is assumed laminar, incompressible, and two‐dimensional, whereas the fluid is considered Newtonian. The results are presented in the form of the contours of velocity, isotherms, and Nusselt numbers profiles for various values of the dimensionless heat source lengths (0.16 ≤ ε ≤ 1). while, both Prandtl and Reynolds numbers are kept constant at (Pr = 0.71) and (Re = 100), respectively. The results indicated that the distribution of the isotherms depends significantly on the length of the heat source. Also, it was noted that both the local and the average Nusselt numbers increase as the local heat source length increases. Moreover, the maximum temperature is located near the heat source location. [ABSTRACT FROM AUTHOR]

This paper presents results of a numerical investigation involving bifurcation sequence leading to chaos in natural convection inside a vertically tall rectangular cavity having an aspect ratio equal to 15 and a Prandtl number equal to 125, corresponding to water‐glycerin mixture. The flow is characterized by a vertical stratification of the temperature field for Grashof numbers greater than or equal to 200 that is outside the conduction regime and it is stationary monocellular up to a critical value Grc = 2800 where a periodic oscillatory regime appears. As Grashof number is increased, a transition from a steady periodic bicellular flow to an oscillatory multicellular flow, with 2 main central cells and 2 secondary cells, occurs. The regime remains periodic until Gr = 3100 where there is a first appearance of the chaotic regime which extends over a narrow interval of the Grashof number delimited by Gr = 3200. [ABSTRACT FROM AUTHOR]

Three-dimensional natural convection in an inclined solar collector equipped with partitions has been investigated numerically. The presence of partitions improves the performances of the collector by increasing the heat transfer near the absorber. A parametric study was done for various partitions length and Rayleigh numbers, while Prandtl number and inclination angle were fixed at 0.71 and 45°, respectively. Results are reported in terms of isosurfaces of temperature, isotherms, particles trajectories, velocity vector projection, average Nusselt number along the absorber plate and entropies generation contours. [ABSTRACT FROM AUTHOR]

A steady laminar two-dimensional magneto-hydrodynamic natural convection flow in an inclined trapezoidal enclosure filled with a fluid-saturated porous medium is investigated numerically using a finite difference method. The left and right vertical sidewalls of the trapezoidal enclosure are maintained at a cold temperature. The horizontal top wall is considered adiabatic while the bottom wall is subjected to isoflux heating. A volumetric internal heat generation or absorption is embedded inside the trapezoidal enclosure while an external magnetic field is applied on the left sidewall of the enclosure. In the current work, the following parametric ranges of the non-dimensional groups are used: Hartmann number is varied as $0 \le Ha \le 50$, Darcy number is taken as $Da = 10^{-3}$, 10−4, and 8 × 10−5, Rayleigh number is varied as $10^3 \le Ra \le 10^5$, Prandtl number is considered constant at Pr = 0.7, the dimensionless internal heat generation or absorption parameter is varied as Δ = −0.2, 0, 1, and 2.0, while the trapezoidal enclosure inclination angle is varied as $0^\circ \le \psi \le 90^\circ$. The results indicated a strong flow circulation occurs when the Darcy and the Rayleigh numbers are high. In addition, it is found that the Hartmann number, internal heat generation or absorption parameter and inclination angle have an important role on the flow and thermal characteristics. It is also found that when the enclosure inclination angle and Hartmann number increase the average Nusselt number along the hot bottom wall decreases. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21013 [ABSTRACT FROM AUTHOR]