International Journal of Numerical Methods for Heat and Fluid Flow

Maged A.I. El‐Shaarawi; Esmail M. A. Mokheimer

1998 International Journal of Numerical Methods for Heat and Fluid Flow

doi: 10.1108/09615539810220243

The paper utilizes a boundary‐layer model in bipolar coordinates to study the developing laminar free convection in vertical open‐ended eccentric annuli with one of the boundaries uniformly heated while the other boundary is cooled and kept isothermal at the ambient temperature. This model has been solved numerically using finite‐difference techniques. Results not available in the literature are presented for a fluid of Prandtl number 0.7 in an annulus of radius ratio 0.5 for three values of the dimensionless eccentricity, namely, 0.1, 0.5 and 0.7. These results include the developing velocity profiles and the pressure along the annulus, the channel heights required to naturally induce different flow rates and the variation of the total heat absorbed by the fluid with the channel height.

Rama Subba Reddy Gorla; A. Slaouti; H.S. Takhar

1998 International Journal of Numerical Methods for Heat and Fluid Flow

doi: 10.1108/09615539810220261

A boundary layer solution is presented to the steady free convection from a vertical plate with uniform surface heat flux conditions and immersed in a micropolar fluid. Numerical solutions for governing nonsimilar boundary layer equations are presented for a range of values of the material properties and Prandtl number of the fluid. An asymptotic solution is developed for large distances away from the leading edge.

J.J. Hwang; T.Y. Lia; S.H. Chen

1998 International Journal of Numerical Methods for Heat and Fluid Flow

doi: 10.1108/09615539810220270

Turbulent fluid flow and heat transfer characteristics are analyzed numerically for fluids flowing through a rotating periodical two‐pass square channel. The smooth walls of this two‐pass channel are subject to a constant heat flux. A two‐equation k ‐ ॉ turbulence model with modified terms for Coriolis and rotational buoyancy is employed to resolve this elliptic problem. The duct through‐flow rate and rotating speed are fixed constantly; while the wall heat flux into the fluid is varied to examine the rotating buoyancy effect on the heat transfer and fluid flow characteristics. It is disclosed that the changes in local heat transfer due to the rotational buoyancy in the radially outward flow are more significant than those in the radially inward flow. However, the channel averaged heat transfer is altered slightly due to the rotational buoyancy in the both ducts. Whenever the buoyancy effects are sufficiently strong, the flow reversal appears over the leading face of the radially outward‐flow channel, and the radial distance for initiation of flow separation decreases with increasing the buoyancy parameter. A comparison of the present numerical results with the available experimental data by taking buoyancy into consideration is also presented.

Ahmed Hamza H. Ali; Koki Kishinami; Yutaka Hanaoka; Jun Suzuki

1998 International Journal of Numerical Methods for Heat and Fluid Flow

doi: 10.1108/09615539810220289

A two‐dimensional numerical study was carried out to investigate laminar forced‐convection heat transfer characteristics of air flow in a two parallel plate channel with offset plates and heated by a radiation heat flux. The SIMPLE method was used for the numerical prediction of the flow and thermal fields. The flow field temperature boundary conditions were obtained by applying the energy balance equation to boundary elements. The ray tracing technique was used to obtain the net absorbed radiation fractions in the boundary elements. The numerical results were validated with measured temperature values and experimentally calculated values of local Nusselt number (Nu x ), and a reasonable agreement was shown. Then the numerical simulation was used to study effects of design parameters on the convective heat transfer coefficient. It was found that in Re numbers from 650 to 2,550, the optimum spacing of offset plates relative to the nearest channel wall was around one third of the channel height. Also, the optimum offset plates’ numbers can be calculated based on one offset plate length being equal to one and a half times the channel hydraulic diameter. A correlation of average Nusselt number between the flowing air and the offset plates was obtained as follows; —Nu = 1.81 Re 0.352 Pr 1/3 (D h /l) 1/2 .

Ò. À. Bèg; H.S. Takhar; V.M. Soundalgekar

1998 International Journal of Numerical Methods for Heat and Fluid Flow

doi: 10.1108/09615539810220298

Numerical results generated by a highly efficient finite‐difference method (originated by Keller for aerodynamical flows at the California Institute of Technology in 1970), and a robust double shooting Runge‐Kutta‐Merson scheme are presented for the boundary layer equations representing the convection flow of a viscous incompressible fluid past a hot vertical flat plate embedded in a non‐Darcy porous medium. Viscous dissipation due to mechanical work is included in the temperature field equation. The computations for both solution techniques are compared at the leading edge ( क़ = 0.0) and found to be in excellent agreement. The effects of the viscous heating parameter (Ec), thermal conductivity ratio ( ॕ ) and a Darcy porous parameter (Re/GrDa) on the fluid velocities, temperatures, local shear stress and wall heat transfer rate are discussed with applications to geothermal and industrial flows.