The investigation of natural convection in an annular space between two concentric cylinders partially filled with metal foam is introduced numerically. The metal foam is inserted with a new suggested design that includes the distribution of metal foam in the annular space, not only in the redial direction, but also with the angular direction. Temperatures of inner and outer cylinders are maintained at constant value in which inner cylinder temperature is higher than the outer one. Naiver Stokes equation with Boussinesq approximation is used for fluid regime while Brinkman-Forchheimer Darcy model used for metal foam. In addition, the local thermal equilibrium condition in the energy equation of the porous media is presumed to be applicable for the present investigation. CFD ANSYS FLUENT software package (version 18.2) is used as a solver to this problem. Various parameters are examined; Rayleigh number, Darcy number, and thermal conductivity ratio to study the effect of them on fluid flow and heat transfer inside the annuli space in the suggested design of metal foam layer. current model is compared with the available published results and good agreement is noticed. Results showed that as Rayleigh number increases the dominated of convection mode increases and Nusselt increases. Also, Nusselt is larger at the higher Darcy and thermal conductivity ratio. It was found that at Rayleigh of 106 and thermal conductivity ratio of 104 Nusselt reach its higher value which is 6.69 for Darcy of 0.1 and 6.77 for Darcy of 0.001. A comparison between this design and the traditional design was established for Darcy 0.001 and thermal conductivity ratio 102, and its showed a good enhancement in Nusselt number and the greatest enhancement percentage was 44% at Rayleigh equal 5*104 while the lowest percentage is 6% for Rayleigh equal106.
The objective of present study was to compare of several methods for estimating the degree of heritability and calculating the number of genes using generation mean analysis of maize (
The present paper focuses on studying a rhetorical form often used in Spanish linguistic discourse .It also examines the study two sides (theoretical and practical), the concept of metaphor, the most important modern school that deals with this issue, the development of this technique and its relationship with other intellectual ideologies, and the role metaphor plays in interpreting the meaning of the linguistic discourse especially in conveying political message. The study allows the formulation and the creation of a conceptual picture for the purposes of metaphor in the linguistic discourse used in Spanish press. It investigates discursive models from the Spanish press,
... Show MoreThis paper aims to identify how the United Nations works through its website in prioritizing audiences towards international issues، by identifying the digital PR mechanisms used in digital PR contents in prioritizing audiences towards the international issues they deal with. To achieve the objectives of this paper, the researcher used the survey method and content analysis tool with a view to identifying the ranking of international issues on the website of health، peace and security، humanitarian assistance، human rights، women، migrants، refugees and displaced persons، economic development، United Nations affairs، culture and education، environment and climate، sustainable development, and law and crime prevention. One of
... Show MoreBackground: Enterococcus faecalis is emerging as an important endodontic pathogen, which can persist in the environment for extended periods after treatment and may cause endodontic failure. It is known to produce biofilms, a community of bacteria enclosed within a protective polymeric matrix. This study aimed to establish whether the biofilm formation by Enterococcus faecalis can be inhibited with steralium, co+steralium, and 5% sodium hypochlorite in the root surface environment. Materials and Methods: Extracted human teeth were biomechanically prepared, vertically sectioned, placed in the tissue culture wells exposing the root canal surface to E. faecalis to form a biofilm. At the end of the 3rd and 6th weeks, all groups were treated fo
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