Engineering and Technology Journal

This work concerns with experimental and numerical study for the cooling characteristics of a target plate under the effect of air impingement from orifice of different sizes D of (5,10,15 and 20 mm). A centrifugal blower was used for air impinging with jet velocity in the range (18-40 m/s). Tested Reynolds number Re is in the range of (7100-44400) with orifice to plate spacing ratio H/D of (2,4,6,8). Numerical analysis using CFD commercial code Fluent version 14.5 with K-ε RNG turbulence model has been used to simulate the flow and heat transfer in impingement jet. Both numerical and experimental results are analyzed to determine the effect of using different orifice sizes on heat transfer rates and flow structure on the target plate. A correlation is obtained for the stagnation Nusselt number as a function of Re and H/D. Optimum heat removal rate are found to occur at H/D=6. According to the experimental results which indicates that orifice diameter and jet velocity are the most effective variables which characterize the heat removal rate, a control system is designed and constructed to vary the orifice diameter in order to control the air flow rate and the plate temperature. Fixing the optimum H/D and for the used blower characteristics the control system is tested and the results show a good response for the control system for different operation conditions so that the cooling rates are increased for the heated plate.

On the wise of structural advantages of flat plate slab systems, the
researches still deal with punching shear hazards and solution techniques for
adopting a rational design comes from experimental investigations. Beside that
there is a rapid development in production the high performance concretes using
chemical additives and wide spectrum of different features fibers which avail
additional options for the structural designers.
The present work is an experimental study adopts the comparison between
uniform concrete sections with specific strength and hybrid sections (consists of
two different layers with different strength in the top half and the bottom one) to
provide reinforced concrete flat plate slabs and conclude the more advantage
option for improving their behaviors against eventual punching shear failure.
Normal strength, high strength and fibrous concrete with (34, 48 and 21) MPa
compressive strength respectively are used to produce the slabs in this study.
The results revealed the preference of the high strength uniform section in
improving the slab behavior besides increasing its ultimate load twice in
comparison with a hybrid section contains high strength concrete at the top half
only and there is no advantage from increasing the tension zone strength on the
hybrid section slab behavior except the ductility.