الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 276 |  |  |
| | | from | 276 | | |
Abstract
It is well known that the flow over segmental baffles is relevant to my engineering applications such as heat exchanges, corrugated channels and cooling of gas turbine blade . The presence of baffles causes the flow to separate , reattach and thus creates regions of reverse flow and high shearing rate , thus which means an augmenting of heat transfer.
The object of the present work show the behavior of the flow scross the segmental baffles. The research is directed also to study the effect of baffle height inside a rectangular duct on the flow pattern, heat transfer and pressure DROP for fixed baffle space. The baffles are located alternatively at top and bottom walls of the main duct . The duct has a rectangular cross-section areas (300 mm x 60 mm) with an aspect ratio equal to 5.
The tested air stream was heated by means electric coils which wound on the upper and the down surface of the main duct where the two other sides were kept adiabatic .
The total heat librated from the heaters was directed to the air stream while the different losses were eliminated.
The experiment 3 were carried out for different baffle materials of different thermal conductivities. Window cut ratios of 0.7 0.5 and 0 .3 were performed for constant spacing baffle ratio of 1.0. The investigated Reynolds numbers were ranged from 7000 to 22000.
For the periodic cell, the distribution of the mean velocity temperature and the local Nusselt number of both the top and bottom walls were illustrated. The distribution of walls temperature and local heat transfer coefficient on middle centre of each cell along the duct length were also obtained. The overall Nusselt number and the pressure DROP were presented for periodic cell and the influence of Reynolds number window cut and thermal conductivity of the baffle materials on these values were also studied. The heat transfer coefficients were related in terms of the ratio of Nusselt number value in the actual baffle duct to the value of smooth duct for laminar flow.
The given experimental results showed that, after a finite entry length the flow periodic fully developed for thermal boundary layer. It was found that, the flow became periodic after only after only 2-5 cells from the entrance section . The baffles were found to cause the flow to deflect significanctly . However, the associated increase in pressure DROP was an order of magnitude higher than the increase in heat transfer . In addition , conduction in the baffle materials was found to play a highly beneficial role in enhancing heat transfer .
General relations for the effect of window cut and thermal conductivity of the baffle materials on heat transfer coefficient were obtained.