للكاتبين :
M. Moawed1and E. Ibrahim2
1Faculty of Engineering Shoubra, Benha University, Cairo, , Egypt
2Faculty of Engineering, Zagazig University, Zagazig, 44519, Egypt
ABSTRACT
Free convection heat transfer from the inside surface of the horizontal elliptic tube of different
axis ratios and different orientation angles with a uniformly heated surface are investigated
experimentally. The axis ratio is changed from 1.5 to 3.5 and the orientation angle is changed
from 0o to 90o with step 15o. The experiments covered a range of Rayleigh number, Ra from6.5*105 to 1.13*108. The local and average heat transfer coefficients and Nusselt number are
estimated for different axis ratios and different orientation angles at different Rayleigh
numbers. The results showed that, the surface temperature increases with the increase of axial
distance from both ends until a maximum value at the middle of the elliptic tube at a constant
heat flux. The surface temperature decreases with the increase of the axis ratio or the
orientation angle, consequently the local Nu increase with the increase of the axis ratio or the
orientation angle at the same axial distance and Ra. The average Nu increases with the
increase of the axis ratio or the orientation angle at the same Ra. The results obtained are
correlated by dimensionless groups and with the available data of the horizontal elliptic tube.