للكاتبين :
A. R. EL-SHAMY*, R. Y. SAKR*, N. S. BERBISH*, AND M. H. MESSRA**
*Mech. Eng. Dept., Shoubra Faculty of Eng., Benha Univ., Egypt
**M.Sc. Student, Mech. Eng. Dept., Shoubra Faculty of Eng., Benha Univ., Egypt
ABSTRACT
The aim of the present work is an experimental and numerical study of forced convection heat
transfer from an inclined heated plate placed beneath a porous medium. The experiments were
carried out on an aluminum flat plate of 320 mm length, 140 mm width, and 6 mm thickness
and the plate was electrically heated with a uniform heat flux condition. The tested heated
plate was inclined on the flow direction with different angles of attack (α) varied from 0o
(horizontal position) to 30o, within a range of Reynolds number (based on the test plate
length) from 52000 to 171000. The porous media used in the experiments were made of PVC,
glass, and stainless steel materials, covering a wide range of solid thermal conductivities. The
nominal sphere diameter of all used materials was nearly about 12 mm, and the porosity of
the porous media was about 0.52. Also, the present problem was solved numerically using a
commercial CFD code. Two cases have been investigated; flat plate without porous media
and with porous media. Both cases were solved in two dimensions. The case of smooth plate
without porous media utilized the standard k-ε model to model the flow of air over the plate,
but the laminar model was used to predict the case of plate with porous media. For plate with
or without porous medium and the same inclination angle, the experimental results showed
that the heat transfer coefficient was increased with increasing the Reynolds number. Also, it
was found that the heat transfer coefficient was increased with increasing the inclination
angle, and was reached the maximum enhancement ratio at inclination angle of 20o and with
further inclination of the heating plate (20o < ≤ 30o), the heat transfer coefficient was
slightly decreased. Moreover, it was observed that the existence of the packed bed increases
the heat transfer coefficient. In addition, for a constant particle size, higher heat transfer
coefficients were obtained with higher particle thermal conductivity (steel spheres). For
smooth inclined plate without porous medium, the maximum average Nusselt number
enhancement ratio (average Nusselt number of the inclined smooth plate/average Nusselt
number of the horizontal smooth plate without porous media), Nusm / Nuo , was about 1.239
and was obtained at = 20o and Re = 71927. Also, for the inclined plate with porous medium,
the maximum enhancement ratio of the average Nusselt number ( Nup / Nuo ) was about 3.10.
This value was obtained at = 20o, Re=71927, and using stainless steel spheres porous
medium. Good agreement was observed between the experimental data and the numerical
results that obtained from the models in the range of (0o ≤ ≤ 20o) and for the all range of
Reynolds number used in this study. Finally, empirical correlation for the average Nusselt
number was obtained utilizing the present experimental data as a function of the Reynolds
number, the inclination angle (angle of attack), and the thermal conductivity of the packing
material.