الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Impingement cooling has been widely used to cool elements exposed to high imperatures and/or high heat flux environments because of its advantages in the effective moval of locally concentrated heat and easy adjustment to the location where cooling is ceded .
It has been widely used for the heat transfer augmentation in a variety of engineering applications such as cooling of hot steel plates. Tempering of glass, during of stiles and paper. High-density electronic component and eliminate the excessive thermal near the leading edge of gas turbine blades inner surface.
By reviewing the literature. A few papers have been published to investigate the heat transfer characteristics with a swirling impinging jet. Moreover, a few papers have studied the impingement heat transfer from a curved surface. As a result, the intent of the present study is to provide a quantitative measurement data to investigate the effects of swirling flow intensity on the jet impingement cooling flow and the heat transfer processes over a concave in order to make distinctions between favorable and undesirable effects of swirl.
In the experiments a single air jet issuing from different size round nozzles continuously impinges normally on the concave side of a heated semi cylindrical surface under constant heat flux conditions. The values of jet Reynolds number of
Re = 11, 000, 23,000 and 50,000 the nozzle-to-surface distance
of d/D = 2,4,6,8 and 10, the relative surface curvature of d/D = 0,022,0,031 and 0,043, and the studied swirl numbers were S = 0,0.21,0.44 and 0.77.
The temperature distributions over the concave surface have been measured using the iR imaging Radiometer and the recorder images are analyzed using thermal image processing software.
The results showed that the effect of swirling flow is mainly represented near the stagnation region and the recommended zone of using the swirl flow in the impinging jet heat transfer is low to medium Re value
(11,000 and 23,000) high curvature ratio (d/D ≥0.043), and low and moderate swirl intensity (S < 0.44), otherwise, the swirl flow will result in undesirable effects. For all eases the local Nusselt number along the concave surface decrease monotonically from its maximum value at the stagnation point up to r/d ≈ 7.5 at surface curvature of d/D = 0.043, r/d ≈ 14 at d/D = 0.031 and r/d ≈ 16 at d/D = 0.022 over 2 ≤ l/d ≤ 10. Then a gradual reduction in the local Nusselt number continues beyond the previous values of r/d as the thermal boundary layer thickness grows with r/d.