Geometry: shape, size, aspect ratio and orientation Flow Type: forced, natural, laminar, turbulent, internal, external Boundary: isothermal (Tw = constant) or isoflux (q̇w = constant) Fluid Type: viscous oil, water, gases or liquid metals Properties: all properties determined at film temperature Tf = (Tw + T∞)/2 Note: ρ and ν ∝ 1/Patm ⇒ see Q12-40 density: ρ ((kg/m) specific heat: Cp (J/kg ·K) dynamic viscosity: μ, (N · s/m) kinematic viscosity: ν ≡ μ/ρ (m/s) thermal conductivity: k, (W/m ·K) thermal diffusivity: α, ≡ k/(ρ · Cp) (m/s) Prandtl number: Pr, ≡ ν/α (−−) volumetric compressibility: β, (1/K)

Convection Heat Transfer

Hydrodynamic and hydromagnetic stability

In recent years, the study of rheological behavior and heat transfer of nanofluids in the industrial equipment has become widespread among the researchers and their results have led to great advancements in this field. In present study, the laminar flow and heat transfer of water/functional multi-walled carbon nanotube nanofluid have been numerically investigated in weight percentages of 0.00, 0.12 and 0.25 and Reynolds numbers of 1–150 by using finite volume method (FVM). The analyzed geometry is a two-dimensional backward-facing contracting channel and the effects of various weight percentages and Reynolds numbers have been studied in the supposed geometry. The results have been interpreted as the figures of Nusselt number, friction coefficient, pressure drop, velocity contours and static temperature. The results of this research indicate that, the enhancement of Reynolds number or weight percentage of nanoparticles causes the reduction of surface temperature and the enhancement of heat transfer coefficient. By increasing Reynolds number, the axial velocity enhances, causing the enhancement of momentum. By increasing fluid momentum at the beginning of channel, especially in areas close to the upper wall, the axial velocity reduces and the possibility of vortex generation increases. The mentioned behavior causes a great enhancement in velocity gradients and pressure drop at the inlet of channel. Also, in these areas, Nusselt number and local friction coefficient figures have a relative decline, which is due to the sudden reduction of velocity. In general, by increasing the mass fraction of solid nanoparticles, the average Nusselt number increases and in Reynolds number of 150, the enhancement of pumping power and pressure drop does not cause any significant changes. This behavior is an important advantage of choosing nanofluid which causes the enhancement of thermal efficiency.

The numerical modeling of water/FMWCNT nanofluid flow and heat transfer in a backward-facing contracting channel

Fully-developed free-convective flow of micropolar and viscous fluids in a vertical channel

The problem of unsteady oscillatory flow and heat transfer of two viscous immiscible fluids through a horizontal channel with isothermal permeable walls has been considered. The partial differential equations governing the flow and heat transfer are solved analytically using two-term harmonic and non-harmonic functions in both fluid regions of the channel. Effects of physical parameters such as viscosity ratio, conductivity ratio, Prandtl number and frequency parameter on the velocity and temperature fields are shown graphically. It is observed that the velocity and temperature decrease as the viscosity ratio increases, while they increase with increases in frequency parameter. The effect of increasing the thermal conductivity ratio also suppresses the temperature in both fluid regions. The effect of periodic frequency on the flow is depicted in tabular form. It is predicted that both the velocity and temperature profiles decrease as the periodic frequency increases.

Unsteady two-fluid flow and heat transfer in a horizontal channel

The problem of fully developed free convection two fluid magnetohydrodynamic flow in an inclined channel is investigated. The governing momentum and energy equations are coupled and highly nonlinear due to dissipation terms, solutions are found employing perturbation technique for small values of Pr · Ec (=ɛ) the product of Prandtl number and Eckert number. Effects of Grashof number, Hartmann number, inclination angle, the ratios of electrical conductivities, viscosities and heights of two fluids on the flow are explored. It is observed that the flow can be controlled effectively by suitable adjustment of the values for the ratios of heights, electrical conductivities and viscosities of the two fluids.

Convective magnetohydrodynamic two fluid flow and heat transfer in an inclined channel

Convective flow and heat transfer in an inclined channel bounded by two rigid plates held at constant different temperatures with one region filled with porous matrix saturated with a viscous fluid and another region with a clear viscous fluid different from the fluid in first region is studied analytically. The coupled nonlinear governing equations are solved using regular perturbation method. It is found that the presence of porous matrix in one of the region reduces the velocity and temperature. Results have been presented for a wide range of governing parameters such as Grashof number, porous parameter, angle of inclination, ratio of heights of the two layers and also the ratio of viscosities.

Two fluid flow and heat transfer in an inclined channel containing porous and fluid layer

Two-fluid magnetoconvection in a vertical enclosure consisting of two regions, one electrically conducting and another electrically non-conducting is investigated analytically. The transport properties of both fluids are assumed constant. The resulting coupled non-linear equations are solved using regular perturbation method. It is found that the effect of negative electric load parameter E is to aid the flow while the effect of positive E is to oppose the flow as compared to the case when E=0. The effects of various physical parameters such as Grashof number, viscosity ratio and width ratio are presented for heat absorption and heat generation case.

Magnetoconvection of two-immiscible fluids in vertical enclosure

An analysis of fully developed combined free and forced convective flow in a fluid saturated porous medium channel bounded by two vertical parallel plates is presented. The flow is modeled using Brinkman equation model. The viscous and Darcy dissipation terms are also included in the energy equation. Three types of thermal boundary conditions such as isothermal–isothermal, isoflux–isothermal, and isothermal–isoflux for the left–right walls of the channel are considered. Analytical solutions for the governing ordinary differential equations are obtained by perturbation series method. In addition, closed form expressions for the Nusselt number at both the left and right channel walls are derived. Results have been presented for a wide range of governing parameters such as porous parameter, ratio of Grashof number and Reynolds number, viscosity ratio, width ratio, and conductivity ratio on velocity, and temperature fields. It is found that the presence of porous matrix in one of the region reduces the velocity and temperature.

J. Prathap Kumar

Papers

Fully-developed free-convective flow of micropolar and viscous fluids in a vertical channel

Convective magnetohydrodynamic two fluid flow and heat transfer in an inclined channel

Two fluid flow and heat transfer in an inclined channel containing porous and fluid layer

Magnetoconvection of two-immiscible fluids in vertical enclosure

Fully Developed Mixed Convection Flow in a Vertical Channel Containing Porous and Fluid Layer with Isothermal or Isoflux Boundaries