• Energy Research

This paper investigates numerically the inherent irreversibility in unsteady generalized Couette flow between two parallel plates with variable viscosity. The nonlinear governing equations are derived from the Navier-Stokes equations and solved numerically using a semi-discretization finite difference method together with the Runge-Kutta-Fehlberg integration scheme. The profiles of velocity and the temperature obtained are used to compute the entropy generation number, Bejan number, skin friction and Nusselt number. The effects of embedded parameters on entire flow structure are presented graphically and discussed quantitatively.

AbstractThis work presents a theoretical numerical study of the bioconvection flow of Prandtl–Eyring nanofluid through a stretching cylinder with gyrotactic microorganisms. The mathematical model developed also incorporated the inclined magnetic field and heat generation effects. Further, stratification conditions are considered at the boundary of the stretched cylinder. The described flow problem conducting coupled high‐order partial differential equations (PDEs) is first reduced to the nonlinear system of ordinary differential equations (ODEs) by introducing suitable mathematical transformations. The resulting highly nonlinear flow equations are treated numerically by applying the shooting method. A comparison of the adapted method with previously reported data is also made to validate the presented results. The comparisons are in excellent agreement. The individual effect of controlling flow parameters/numbers on the flow profiles and physical quantities of engineering interest are represented graphically with physical descriptions. The significant results of the present analysis revealed that a rise in bioconvection Rayleigh number, thermal Grashof number, and angle of inclination boosts the velocity profile. The study shows that thermal stratification, mass stratification, and motile density stratification parameters diminish the temperature, concentration, and microorganism profiles, respectively. The nondimensional Sherwood number is decelerated significantly by thermophoresis and mass stratification parameters.

AbstractA second-law analysis of a pressure-driven variable viscosity fluid flow through a channel with asymmetric convective cooling at the walls is investigated. Flow is assumed to be steady, laminar and fully-developed. The effect of heat generation due to viscous dissipation is included. The resulting equations and boundary conditions are solved numerically, by using an efficient numerical shooting technique with a fourth order Runge–Kutta algorithm. The effect of variable viscosity parameter, the Brinkman number and the Biot numbers on the velocity, temperature and entropy generation profiles are provided and discussed with appropriate physical explanations.

This investigation includes a three-dimensional Darcy–Forchheimer flow model and the heat transfer phenomenon of H2O-CNTs nanofluid for a two-way stretchable surface. Xue’s proposed thermal conductivity model is employed. The numerical analysis scheme is applied to solve the transformed PDEs. The outline of velocities, temperature, surface drag forces and Nusselt number against relevant variables are portrayed. From this study, it has been noted that with an increase in Eckert numbers along both directions, two patterns were obtained for temperature curves, the initial temperature outlines increased and after that they decreased. Moreover, the width of the thermal boundary layer for H2O-MWCNT nanofluid was more compared to H2O-SWCNT nanofluid. To validate the existing code, numerical outcomes were compared to the earlier published data.

In this study, the hydromagnetic Blasius flow of power‐law nanofluids is investigated numerically. A convectively heated impermeable vertical plate is used and a constant transverse magnetic field is applied at the plate surface. The characteristics of water‐based non‐Newtonian nanofluids are explored using a non‐Newtonian power‐law model. A Buongiorno model is employed to include the effects of Brownian motion and thermophoresis in the study. The governing mass, momentum, thermal energy, and nanoparticle concentration equations are transformed into nonlinear ordinary differential equations which are solved using a spectral relaxation method. The effects of nanofluid parameters (), power index , generalized Prandtl (), and Schmidt () numbers on dimensionless velocity, temperature, concentration, skin friction, local Nusselt, and Sherwood numbers are explored. It is found that pseudoplastic nanofluids have higher skin friction and lower heat and mass transfer rates than dilatant nanofluids.

In this article, we investigate the combined effects of emission of CO2 and O2 depletion on thermal stability in a long cylindrical pipe of combustible reactive material. The cylindrical pipe loses heat by convection and radiation at the surface, and the nonlinear differential equations governing the heat and mass transfer problem are tackled numerically using Runge–Kutta–Fehlberg method coupled with shooting technique. The effects of various thermo-physical parameters on the temperature, CO2 and O2 fields, and thermal stability are presented graphically and discussed quantitatively.

The flow geometry plays a major role in heat and mass transfer processes of many engineering and industrial applications.In the present paper, we examined the combined effects of Cattaneo-Christov heat flux, external magnetic field, chemical reaction, heat source and buoyancy forces on the flow of an incompressible electrically conducting fluid with heat and mass transfer over three different geometries (cone, wedge and a plate). The nonlinear governing equations are obtained and tackled numerically using shooting technique with Runge-Kutta-Felhberg integration scheme. Numerical results are presented graphically and discussed quantitatively. It is found that the thermal boundary layer is highly effective on the flow over a wedge when compared with the other two geometries (plate and a cone).

The current study intended to discuss a comparative study on the three dimensional Casson nanofluid with nonlinear radiative MHD flow and heat transfer aspects between two parallel stretching/shrinking surfaces. The mathematical models for momentum and temperature are established by employing the boundary layer flow of fluids with spinel-type ferrite MnFe2O4 nanoparticles being distributed in Pure Water/ (H2O) as the base fluid. Remarkable models like Maxwell-Garnett and Patel models are inserted in view of thermal conductivity augmentation. The suitable similarity transformations are adopted for converting the governing non-linear partial differential equations into non-dimensional ODE's and obtaining the relevant parameters for discussion. The major outers of the present study are axial velocity {F′(η)} peters out with amplifying β subject to stretched and shrunk surfaces in relation to both Maxwell-Garnett and Patel models. Growing θw and n exhibits opposite effect on heat transfer rate.