Transient three-dimensional natural convection heat transfer due to the influences of heating from one side of an enclosure filled with a saturated porous media, whereas the opposite side is maintained at a constant cold temperature, and the other four sides are adiabatic, were investigated in the present work experimentally. Silica sand was used as a porous media saturated with distilled water filled in a cubic enclosure heated from the side,using six electrical controlled heaters, at constant temperatures of (60, 70, 80, 90, and 100oC). The inverse side cooled at a constant temperature of (24oC) using an aluminum heat exchanger, consisted of 15 channels feeded with constant temperature water. Eighty thermocouples were used to control the heated and cooled sides, and to measure the temperature in the entire enclosure. Experimental results showed that the heat transfer regime was mainly conduction for all Rayleigh numbers with small influence of convection for Ra=42 and greater for Ra=55. This effect increased with the angle of inclination of the enclosure. Numerical and experimental results showed a good agreement. There was a rapid increase in the temperature at the entire media at the early time, reduced gradually until the steady state condition reached. This temperature and heat transfer to and from the porous media, were increased as the Rayleigh number and/or inclination angle increased. The Nusselt number increased directly with the angle of inclination up to o θ = 45 and then decreased. Correlation equations are obtained from the experimental investigation, showed the change of the average and local Nusselt number with time, distance, Rayleigh number, and the inclination angle.
In this work gold nanoparticles (AuNPs), were prepared. Chemical method (Seed-Growth) was used to prepare it, then doping AuNPs with porous silicon (PS), used silicon wafer p-type to produce (PS) the processes doping achieved by electrochemical etching, the solution etching consist of HF, ethanol and AuNPs suspension, the result UV-visible absorption for AuNPs suspension showed the single peak located at ~(530 – 521) nm that related to SPR, the single peak is confirmed that the NPs present in the suspension is spherical shape and non-aggregated. X-ray diffraction analysis indicated growth AuNPs with PS. compare the PS layer without AuNPs and with AuNPs doped for electrical properties and sensitivity properties we found AuNPs:PS is more
... Show MoreThe simulation have been made for 3D flow structure and heat transfer with and without
longitudinal riblet upstream of leading edge vane endwall junction of first stage nozzle guide vane .The research explores concept of weakening the secondary flows and reducing their harmful effects.Numerical investigation involved examination of the secondary flows ,velocity and heat transfer rates by solving the governing equations (continuity, Navier -stokes and energy equations ) using the known package FLUENT version (12.1).The governing equations were solved for three dimentional, turbulent flowe, incompressible with an appropriate turbulent model (k-ω,SST) .The numerical solution was carried out for 25 mode
... Show MoreRecent developments in two main phases of cumulus cloud studies are discussed; first the relations between the clouds and their energy sources in the subcloud layer and second, the interaction between the clouds and their environment in the cloud layer. Under the first heading, the various originating impulses for cumulus formation are mentionitd. and how the character of this impulse affects the spacing, scale and temperature structure of the clouds. The possible origins of trade cumuli are considered.
The fresh water green alga Chlorella vulgaris was selected to study its ability to degrade one of polycyclic aromatic hydrocarbon (PAHs)known is anthracene (ANT). ANT is widely used in artificial products such as wood preservatives; insecticides; dye and coating materials. This algae was cultivated in CH-10 medium under constant laboratory conditions and exposed to different concentrations (1, 3, and 5 mg/l) of anthracene for 3, 5, 7, 9 and 15 days, with the concentration of ANT measured by high performance liquid chromatographic analysis (HPLC). The results showed that C.vulgaris has high ability to reduce anthracene to 80% at 1mg/Lcon centration after 3 days and 100% after 5 days, while at 3 and 5 mg / L concent
... Show MoreThe experimental study showed the use of closed cavity wall (the thickness of the cavity 5cm) made a percentage reduction in the cooling load caused by heat gain from the wall by (21.5 %) compared with the conventional wall. also the thermal resistance of the closed cavity was an average (0.2 m2.oC/W).
The experimental results of the study showed that the use of closed cavity wall reduced the average temperature of the inner surface of the wall during the day, and that the reduction was an average (0.45 oC) when compared with the conventional wall , as well as the use of closed cavity wall reduced the temperature difference range of the inner surface of the wall during the day, and that the
... Show MoreBackground: With the increasing demand on esthetic orthodontic appliances, discoloration of clear elastomeric chains and modules remains an issue which concerns both orthodontics and patients. This in vitro study was conducted to evaluate the effect of exposing stretched clear elastomeric chains from six different companies (Ortho Technology, Ormco, Ortho Organizer, American Orthodontics, Opal and G&H companies) to three types of dietary media (tea, coffee and turmeric). Materials and methods: A total of 960 lengths of six modules were cut from short type elastomeric chain; 160 pieces from each brand. The specimens were stretched 50%, placed on plastic boards, and incubated in water at 37°C for 1 day, 7 days, 14 days and 28 days. Once a
... Show MoreJournalistic discourse is a fertile through which most of the segments of the society interact in all their platforms: intellectual, cultural, social, and various settings between the vital structures of the state; which makes it the link between the groups and segments of the society.
The role of discourse, moreover, engages in a vital way by establishing a culture of debate on controversial issues that provided a space in the different visions and differing perceptions on how to formulate the discourse and the magnitude of vocabulary for the diagnosis of these issues. Since there is no system of any community empty of the emergence of issues reflecting the public interest which is necessary is reflected in the context discourse
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