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 %.
Emotional competence, is relatively a new concept, stands for the ability of people to perceive their feelings and emotions, and sharing them with others. It also refers to capability in optimizing these feeling and emotions, and managing them over various situations. Thus, this study aims to examine the efficiency of counseling program in developing an emotional competence among intermediate school students in Baghdad city. The sample included group of female students at intermediate stage. The findings revealed none of experimental and control groups have statistically significant differences in pre-posttests of emotional competence efficiency.
Collaborative learning is a way that prepares students practically for real-world applications. Working together as teamwork to execute various writing skills is essential in most professions since it increases the level of experience. Thus, the current study aims to identify the role collaborative writing in developing students' level of performance in writing. It is qualitative in nature since the researcher depended on the extant literature in achieving the objective of the study. The researcher touched upon related theories that addressed Collaborative learning, categories, and problems .It concluded that collaborative writing increases the students’ self-confidence, self-esteem, creativity, and motivation through the interact
... Show MoreDespite the principle of separation of powers brought by the French Revolution, which entrusted the task of drafting legislation and its amendment to the legislative authority and the task of settling disputes and settling them in the judiciary. However, since that date, the French judiciary has played a major role in the development of French civil law (In spite of all the economic and social developments that have taken place in French society throughout these years) since its promulgation until February of 2016, the date of the Legislative Decree No. 131 of the year 2016 A modification is the largest in the history of the French Civil Code (which was the judicial precedents in which a significant impact), was assisted by the French judic
... Show MoreAbstract
The research aims to stand on the practice of operations management of solid waste in the city of Hilla, carried out by the mayor of Hilla Directorate - solid and the environment Waste Division, through field visits and personal interview to officials of the municipal departments and units of its data collection and information related to solid waste, and assess the current status of the processes of collection and transport waste through the questionnaire that had been prepared for citizens and employees, the search reach a set of conclusions was the most important, operations carried out by the municipality of Hilla Directorate only limited to two (collection, transportation and disposal of wa
... Show MoreThis research aims at highlighting the strategic role of human resource development in developing competitive advantage in light of the great challenges and rapid changes witnessed in recent years in the business world. The human element is the main engine of the organization's resources, especially when it possesses the skill quality and cognitive abilities commensurate with the nature of work. Therefore, this research focuses on the importance of human resources development strategy in contemporary organizations and reviews the summary of literature and theoretical foundations related to human resources development, as well as various philosophical concepts related to the competitive advantage and to indicate the important role
... Show MoreBackground: The most widely used material for fabrication of denture base is poly methyl methacrylate, despite its popularity, the main problems associated with it as a denture base material are poor strength particularly under fatigue failure inside the patient mouth, impact failure outside the patient mouth, which are the main causes for fracture of denture, several studies was done to increase mechanical properties of denture base. The present study was conducted to evaluate and compare the effect of addition single walled carbon nanotubes in different concentrations to polymethyl methacrylate on some mechanical properties (surface hardness, surface roughness, impact strength and transverse strength). Materials and methods: Forty eight
... Show More An experimental and computational study is conducted to analyze the thermal performance of heat sinks and to pick up more profound information in this imperative field in the electronic cooling. One important approach to improve the heat transfer on the air-side of the heat exchanger is to adjust the fin geometry. Experiments are conducted to explore the impact of the changing of diverse operational and geometrical parameters on the heat sink thermal
performance. The working fluid used is air. Operational parameters includes: air Reynolds number (from 23597 to 3848.9) and heat flux (from 3954 to 38357 W/m
2 ). Conformational parameters includes: change the direction of air flow and the area of conduct
The research objective focuses on spraying the leaves of the plant from the top and bottom through a spraying machine designed and made of aluminum with a movable arm equipped with a nozzle holder divided into three parts and each piece contains a nozzle of the type (Flat Fan 120-C3) as the machine was tried in a greenhouse with a study of the effect of changing the positions of the upper and lower piece of the tube carrying the nozzles to four levels (A1, A2, A3, A4) and the effect of pressure change on two levels (2,4) bar and studying the effect of the previous factors on some of the characteristics of the study, Spray quality on adaxial of leaf, Spray quality on the abaxial surfac
PC-based controller is an approach to control systems with Real-Time parameters by controlling selected manipulating variable to accomplish the objectives. Shell and tube heat exchanger have been identified as process models that are inherently nonlinear and hard to control due to unavailability of the exact models’ descriptions. PC and analogue input output card will be used as the controller that controls the heat exchanger hot stream to the desired temperature.
The control methodology by using four speed pump as manipulating variable to control the temperature of the hot stream to cool to the desired temperature.
In this work, the dynamics of cross flow shell and tube heat exchanger is modeled from step changes in cold water f