Outer Surface Of Inner Cylinder Research Articles

Role of magnetic field on mixed convective flow between two concentric microtubes with heat generation/absorption: An exact solution

This study examines the role of magnetic field on fully developed mixed convection flow of heat generating/absorbing fluid in a vertical micro-concentric annulus with velocity slip and temperature jump at the surfaces of the cylinders. Exact solution of momentum and energy equations are obtained separately in terms of Bessel’s function and modified Bessel’s function of first and second kind. The solutions obtained are graphically represented and the effects of pertinent parameters on flow formation and skin-friction are investigated in details. Results show that the role of magnetic field is to decrease fluid velocity as well as skin-friction at the outer surface of inner cylinder. In addition, reverse flow formation can be controlled by increasing magnetic field strength.

Role of radial magnetic field on heat transfer in MHD Couette flow in an annulus with viscous and Joule dissipation

This paper presents an analytical investigation of steady, fully developed MHD Couette flow of viscous, incompressible, electrically conducting fluid in the presence of radial magnetic field. Exact solutions are derived for the governing energy and momentum equations by taking into account the effects of viscous and Joule dissipations under relevant boundary conditions. The solutions obtained are graphically represented and the effects of various controlling parameters such as Hartmann number and Brinkman number on the temperature profile and consequently the Nusselt numbers are discussed. The significant result from the study is that increase in Hartmann number leads to enhancement on the Nusselt number at outer surface of inner cylinder while the role of Hartmann number is just reverse on Nusselt number at inner surface of outer cylinder. In addition, the Brinkman number has an insignificant effect on the Nusselt numbers when both surfaces are kept at equal temperature.

Transient natural convection flow between vertical concentric cylinders heated/cooled asymmetrically

This paper investigates the impact of asymmetric heating or cooling of cylinder surfaces on transient natural convection flow in between vertical concentric cylinders. The outer surface of inner cylinder is assumed to be heated with temperature greater than the cooled inner surface of the outer cylinder. Closed form expressions are obtained by using the well-known Laplace transform technique to solve the governing partial differential equations in Laplace domain, whereas the Riemann-sum approximation is used to invert to time domain. Results show that the role of buoyancy force distribution parameter is to increase temperature, velocity, skin-friction and volume flow rate for both air and water. Further, reverse flow formation can be controlled by using suitable buoyancy force distribution parameter.

Transient Natural Convection in an Annulus with Thermal Radiation

The interaction of transient fully developed natural convection flow with thermal radiation inside a vertical annulus is analyzed both analytically and numerically. The Rosseland approximation is used to describe the radiative heat flux in the energy equation. The mathematical model capturing the present physical situation is highly non-linear due to the presence of radiation effect. The solution of transient model is obtained by implicit finite difference method. To check accuracy of the numerical solution, steady state solution for energy and momentum equations are derived analytically using perturbation series method. Skin-friction and Nusselt number at the outer surface of inner cylinder as well as inner surface of the outer cylinder are obtained. Selected sets of graphical results illustrating the effects of various controlling parameters involved in the problem on flow formation are discussed.

Transient free convective flow in an annular porous medium: A semi-analytical approach

The transient fully developed free-convective flow of viscous incompressible fluid between two concentric vertical cylinders filled with porous material and saturated with the same fluid have been analysed due to isothermal or isoflux heating of the outer surface of inner cylinder. The governing partial differential equations of motion and energy are transformed into ordinary differential equations using Laplace transform technique. The ordinary differential equations are then solved analytically in Laplace domain. The Riemann-sum approximation method is used to invert the Laplace domain into time domain. The solution obtained is validated by comparison with closed form solution obtained for steady states which has been obtained separately. An excellent agreement was found for transient and steady state solution at large value of time. The governing partial differential equations are also solved by implicit finite difference method to verify the present proposed method. The variation of temperature, velocity, skin-frictions and mass flow rate with dimensionless parameter controlling the present physical situation are illustrated graphically and discussed. It is observed that velocity and temperature increases with time and finally attains its steady state status. Furthermore, both velocity as well as temperature of the fluid is higher in case of isothermal heating of the outer surface of the inner cylinder compared with the isoflux heating case when the gap between the cylinder is less or equal to the radius of inner cylinder while reversed trend is observed when the gap between the cylinders is greater than the radius of inner cylinder for all considered values of time.

Steady fully developed mixed convection flow in a vertical micro-concentric-annulus with heat generating/absorbing fluid: An exact solution

Abstract This study investigates the influence of heat generating/absorbing fluid on fully developed mixed convection flow in a vertical micro-concentric-annulus (MCA) taking into account the velocity slip and temperature jump at the outer surface of inner cylinder and inner surface of outer cylinder. Exact solution of momentum and energy equations is derived separately in terms of Bessel’s function of first and second kind for heat generating fluid and modified Bessel’s function of first and second kind for heat absorbing fluid. The solutions obtained are graphically represented and the effects of governing parameters on flow formation and heat transfer aspects are investigated in detail. During the course of numerical computations, it is found that increase in heat generation parameter enhanced the temperature and velocity of the fluid but reduced the rate of heat transfer at the outer surface of the inner cylinder while the reverse trend is observed for heat absorbing fluid.

Magnetohydrodynamic mixed convection flow in vertical concentric annuli with time periodic boundary condition: Steady periodic regime

This work reports an analytical solution for fully developed mixed convection flow of viscous, incompressible, electrically conducting fluid in vertical concentric annuli under the influence of a transverse magnetic field, where the outer surface of inner cylinder is heated sinusoidally and the inner surface of outer cylinder is kept at a constant temperature. The analysis is carried out for fully developed parallel flow and steady-periodic regime. The governing dimensionless momentum and energy equations are separated into steady and periodic parts and solved analytically. Closed form solutions are expressed in terms of modified Bessel function of first and second kind. The influence of each governing parameters such as magnetic field parameter, Prandtl number and the dimensionless frequency of heating on flow formation and thermal behaviour are discussed with the aid of graphs. During the course of investigation, it is found that the oscillation amplitude of the friction factor is maximized at a resonance frequency near the surface of the concentric annuli where there is periodic heating. Furthermore, increasing transverse magnetic field decreases the oscillation amplitude of the friction factor.