Theoretical and experimental investigations have been carried out on developing laminar
combined free and forced convection heat transfer in a vertical concentric annulus with uniformly
heated outer cylinder (constant heat flux) and adiabatic inner cylinder for both aiding and opposing
flows. The theoretical investigation involved a mathematical modeling and numerical solution for
two dimensional, symmetric, simultaneously developing laminar air flows was achieved. The
governing equations of motion (continuity, momentum and energy) are solved by using implicit
finite difference method and the Gauss elimination technique. The theoretical work covers heat flux
range from (200 to 1500) W/m2, Re range from 400 to 2000 and (1.36×105 ≤ Ra ≤ 1.1×107) with
radius ratio of 0.555 which is the same radius ratio used in the experimental part of this study and
Pr=0.7. The experimental work includes construct a rig consists essentially of an annulus with
uniformly heated outer cylinder and adiabatic inner cylinder to give clear insight into heat transfer
process and compare its results with that obtained in theoretical part, the range of the study are
(Re= 383, 724, 1000, 1500) and heat flux equal to (q =370, 422, 588, 980) W/m2. Numerical results
were represented by the temperature profile, axial velocity profile, outer surface temperature and
the distribution of local Nusselt number along the dimensionless axial distance. The velocity and
temperature profile results have revealed that the secondary flow created by natural convection have
significant effects on the heat transfer process. Results reveal also that the experimental local
Nusselt number along the annulus follows the same trend as present theoretical results with mean
difference 10.23 %.
The current research aims to examine the effect of the rapid learning method in developing creative thinking among second-grade female students in the subject of history. Thus, the researcher has adopted an experimental design of two groups to suit the nature of the research. The sample of the study consists of (36) randomly selected students from Al-Shafaq Secondary School for Women, which are divided randomly into two groups. The first group represents the experimental; it includes (31) students who studied the subject of history using the quick learning method. The second group, on the other hand, is the control group, which consists of (32) students, who studied the same subject using the traditional way. Before starting with the exp
... Show MoreThe problem of present study is determined by answering the following questions:
1) What is the effect of using the oral open- ended questions on Students' achievement in the third-stage of Arabic department in the college of Education? 2) What is the effect of the oral open-ended questions on developing the creative thinking of students in
... Show MoreThe study aims to develop the awareness of the criteria for judging electronic educational materials among students of educational qualification at Dhofar University over spreading the Corona pandemic through a program based on mini-educational units. The study was applied to (18) students studying Teaching diploma at Dhofar University for the academic year 2020-2021, and their number. They were chosen intentionally. The study resulted in reaching a list of criteria for judging electronic educational materials, roughly (18) criteria in the selection themes and (15) criteria in the use theme. The level of awareness of the sample members with the criteria for selecting and using electronic educational materials and the effectiveness of the
... Show MoreThe event of crossing the barriers is one of the Power Games activities that have received great attention in the field of researches. Which led to ma..
The main focus of research is on how to achieve the internal and external dimensions of corporate social responsibility through human resources management strategies, which is a major of research aimed. The main problem of this research was confirmed, which confirms that there is an unclear role for social responsibility, lack of human resources management strategies, and ambiguity of roles in the municipality under study. The diagnose of the problem and determining the gap between the internal and external dimensions of social responsibility and human resources management was identified, which attacked the researcher's attention to navigate in this subject, look for the reasons for the gaps and try to reduce them. The case study
... Show MoreAdvertisement on smart phone shopping apps are a new way of driving users to satisfy their needs and influence their purchasing decisions, In this way, the research could be aimed to know The role of the relationship between the motivations for audience exposure to shopping apps advertisement and purchasing decisions, In order to achieve the objectives of the research, the researcher adopted the survey method and used the questionnaire and the scale to collect data and information, The researcher chose the "random sample multi stages", The sample size was (475) respondents from Baghdad city center (18 years and above) women and men.
This work is based on the synthesis of Cobalt(II) and Cadmium(II) mixed-ligands compounds obtained from the reaction of N'-(4-methylsulfanyl-benzoyl)-hydrazine carbodithioic acid methyl ester as a ligand and using ethylendiamine (en), 2,2'-bipyridine (bipy) or 1,10-phenanthroline (phen) as a co-ligand. The synthesis of ligand (HL) was based on multi-steps synthetic procedure. The reaction of 4-methylsulfanyl-benzoyl chloride with hydrazine gave 4-methylsulfanyl-benzoic acid hydrazide. This compound was reacted with carbon disulfide and potassium hydroxide in methanol to yield N'-(4-methylsulfanylbenzoyl)-hydrazine potassium thiocarbamate, which upon reaction with methyl iodide resulted in the formation of the ligand. A range of physico-chem
... Show MoreStaphylococcus aureus and Pseudomonas aeruginosa are the major globally distributed pathogens, which causes chronic and recalcitrant infections due to their capacity to produce biofilms in large part. Biofilm production represents a survival strategy in these species, allowing them to endure environmental stress by altering their gene expression to match their own survival needs. In this study, we co-cultured different clinical isolates of S. aureus and P. aeruginosa as mono- and mixed-species biofilms in a full-strength Brain Heart Infusion Broth (BHI) and in a 1000-fold diluted Brain Heart Infusion Broth (BHI/1000) using Microtiter plate assay and determination of colony-forming units. Furthermore, the effect of starvation stress on the e
... Show MoreMixed ligand of Co and Ni (II) complexes were prepared from [5-(p-nitrophenyl)-4/-phenyl-1,2,4-triazole-3-dithiocarbamato hydrazide](TRZ.DTC) as primary ligand and 2,2'-bipyridyl (bipy) as a co-ligand with metal salts. These complexes were analytically and spectroscopically characterized in solid state by elemental analyses, flame atomic absorption, magnetic susceptibility and molar conductance measurements, as well as by UV–Vis and FTIR spectroscopy. Infrared, ultra violet spectra reveal a bidentate coordination of the two ligands with metal ions 1:1:1 mole ratio. Room temperature magnetic moments and solid reflectance spectra data indicate paramagnetic complexes with five-coordinate square pyramidal geometry for nickel (II) comple
... Show MoreThe effect of solution heat treatment on the mechanical properties of Aluminum-Copper alloy. (2024-T3) by the rolling process is investigated. The solution heat treatment was implemented by heating the sheets to 480 C° and quenching them by water; then forming by rolling for many passes. And then natural aging is done for one month. Mechanical properties (tensile strength and hardness) are evaluated and the results are compared with the metal without treatment during the rolling process. ANSYS analysis is used to show the stresses distribution in the sheet during the rolling process. It has been seen that good mechanical properties are evident in the alloy without heat treatment due to the strain hardening and also the mechanical
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