شبكة التخطيط العمراني بسم الله الرحمن الرحيم
للكاتبين :
A. A. Abdel Aziz1, A. E. Zohir2 , and N. S. Berbish3
1 Mech. Eng. Dept., Faculty of Eng. At Shoubra, Benha University, Cairo, Egypt
2 Mech. Eng. Dept., Tabbin Institute for Metallurgical Studies, Cairo, Egypt
ABSTRACT
Heat transfer characteristics of turbulent pulsating flow through a sudden expansion pipe with
different diameter ratios were investigated experimentally. The pulsation system was located
downstream of an axisymmetric sudden expansion pipe. The effects of the diameter ratio of
wide range, Reynolds number, and pulsating frequency on the heat transfer were examined.
The tested pipe was heated with a uniform heat flux condition and using air as the working
fluid within Reynolds number range from 7700 to 40000. Experiments were carried out for
different diameter ratios of 0.31, 0.40, 0.46, 0.61, 0.67, 0.83, and 1.0 and pulsation frequency
range of 1.0 to 6.2 Hz. It was found that the average Nusselt number of the tested pipe was
increased with decreasing the diameter ratio for unpulsated flow. For pulsated flow, the
results showed that heat transfer was slightly affected by pulsation frequency while it was
strongly affected by Reynolds number for the tested diameter ratios. Moreover, the
enhancement obtained by the diameter ratio of 0.40, up to 20% due to pulsation only, was
greater than that obtained by the other higher values of the diameter ratio. Empirical
correlations of the average Nusselt number enhancement ratio of the pulsated flow through
the sudden expansion pipe were obtained in terms of the Reynolds number, dimensionless
frequency, and diameter ratio.