FORCED CONVECTION HEAT TRANSFER OF TURBULENT PULSATING FLOW THROUGH AN AXISYMMETRIC SUDDEN EXPANSION PIPE WITH DIFFERENT DIAMETER RATIOS

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.

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