An experimental and numerical study has been carried out to investigate the heat transfer by natural convection in a three dimensional annulus enclosure filled with porous media (silica sand) between two inclined concentric cylinders with (and without) annular fins attached to the inner cylinder under steady state condition; The experiments were carried out for a range of modified Rayleigh number (0.2 ≤Ra*≤ 11) and extended to Ra* =500 for numerical study, annulus inclination angle of (δ = 0˚, 30˚, 60˚ and 90˚). The numerical study was to write the governing equation under an assumptions used Darcy law and Boussinesq’s approximation and then solved numerically using finite difference approximation. It was found that the average Nusselt number depends on (Ra*, Hf, δ and Rr) and the maximum value of the local Nusselt number for vertical cylinder is about two times as large as that of the horizontal case. The results showed that, increasing of fin length increases the heat transfer rate for any fins pitch unless the area of the inner cylinder exceeds that of the outer one, then the heat will be stored in the porous media. A correlation for Nu in terms of Ra, Rr and δ, has been developed for inner cylinder. A comparison was made between the results of the present work and with other researches for the case without fins and excellent agreement was obtained and reveals deviation less than 5 % for average Nusselt number.
AN Salih, LO Hamza, Ann. For. Res, 2022 - Cited by 2
The present study dealt with taxonomic characters of species Zygophyllum fabago L. in Iraq . this study included the exo-morphological characters which indicated that the species was sub-shrub with solid stem and swallow nodes ,with compound bifoliate and stipulate leaves, the flower is complete and perfect with clawed petals . stamen colored with scaly appendage , fruit capsule with ribs . Anatomical study of vegetative parts indicate that the sclerenchymal tissue was very diffuse in stem such as fibers and sclerides ( stone cells ) , the leaves were bifacial . The geographical distiribution of the species plants was studied . The results supported with photographs
In recent years, the linguo-philosophical studies of metaphor have tended to define metaphor as an interaction of the object, that is the referent of conceptualization and some features that are associated with sensual manner realities, whose name is used when resolving the conceptual problem-nominative situation, namely the situation of the formation of a new concept and its verbalization. The objective of this term paper lies in the phenomenon of metaphors used in modern political discourse. In our understanding a metaphor is not only of a linguistic nature, but also political. This paper approaches the subject of conceptual metaphor and political argumentation through the prism of synergies of the political topic, affirmative or negative
... Show MoreThe current study aimed to examine the histomorphological features of the oral salivary ducts and the peacock tongue (Pavo cristatus) of this species. In this study, eight healthy adult peacocks were used after collecting them from a commercial market in Baghdad to investigate and describe the tongue in these bird species. After being euthanized, they were killed by cutting off the major neck blood vessels and bleeding until death; the tongue was identified. The tongue was the sharp end, elongated, somewhat triangular, and measured 8.2 mm. The apex, trunk, and base are its three sections. There are 4 to 5 layers of big conical papillae on the area where the root and body converge. Without gustatory papillae, the dense keratinized ep
... Show MoreBackground: Many types of instruments and techniques are used in the instrumentation of the root canal system. These instruments and techniques may extrude debris beyond the apical foramen and may cause post-instrumentation complications. The aim of this study was to evaluate the amount of apically extruded debris resulted by using 4 types of nickel-titanium instruments (WaveOne, TRUShape 3D conforming files, Hyflex CM, and One Shape files) during endodontic instrumentation. Materials and methods: Forty freshly extracted human mandibular second premolar with straight canals and a single apex were collected for this study. All teeth were cut to similar lengths. Pre-weighted glass vials were used as collecting containers. Samples were randoml
... Show MoreThe study aims to identify the mechanical and electrical activities of the heart according to the energy systems of advanced players and to detect the differences between the energy systems in terms of the mechanical and electrical activities of the heart for advanced players. It was clear from the results of the significance of the differences between the three groups according to the energy systems of the advanced players in all research variables that (the non-oxygenic system "Lactic"), which represents the advanced players in the arches (800 m, 1500 m) was the first in most tests of mechanical and electrical activities of the heart, which is (Margaria-Kalamen, Wingate, systolic muscle strength of the heart FC, Stroke Volume SV
... Show MoreDBN Rashid, Journal of Education College Wasit University 1(1):412-423, 2007