The evacuated tube solar collector ETC is studied intensively and extensively by experimental and
theoretical works, in order to investigate its performance and enhancement of heat transfer, for Baghdad climate
from April 2011 till the end of March 2012. Experimental work is carried out on a well instrumented collector
consists of 16 evacuated tubes of aspect ratio 38.6 and thermally insulated tank of volume 112L. The relation
between convective heat transfer and natural circulation inside the tube is estimated, collector efficiency, effect of
tube tilt angles, incidence angle modifier, The solar heating system is investigated under different loads pattern (i.e
closed and open flow) to evaluate the heat loss coefficient from tank and tubes, test the collector with various
aspect ratios (32.9 and 27.2). The enhancement in collector performance is studied by using two reflectors (Flat
Plate and Curved Plate) and nanofluid (Water-AL2O3).Theoretical work is run by software (Fluent 6.3), to compute
the velocity and temperature profiles within the tube, for different tube diameters, effect of tube junction angle and
stagnant region in the bottom of the evacuated tube. The experimental results shows that the heat loss coefficient
for tube is W/m2.K and for tank is W/m2.K, the maximum collector temperature is 79°C in winter and
99°C in summer, while that belong to nanofluid collector is 99°C in winter. The best tilted angle (optimum) of
evacuated tube is 41° annually. The collector efficiency increased when using nanofluid of (1, 0.6, 0.3)% volume
fraction as(28.4, 6.8, 0.6)% respectively. The efficiency decreases as (33, 62)% when decreasing tube aspect ratio
from 38.6% to 32.9% and 27.2% respectively. An increase of (16.9 and 7.08)% in collector efficiency is obtained
when using curved and flat plate reflectors respectively. From simulation the best junction angle of the tank is
22.5°. The stagnant region is influenced with changing heat flux, tilted angle and aspect ratio.
Background: Saliva plays an important role in oral health. Several salivary proteins are involved in the antimicrobial defence mechanism and are able to eliminate or inhibit bacterial growth in the oral cavity. Secretory IgA (SIgA) is one of the principal antibodies present in saliva, could help oral immunity by preventing microbial adherence, neutralizing enzymes and toxins. The aim of this study was to investigate the relationship between salivary Streptococcus Mutans (SM) count and S IgA in stimulated whole saliva in children with primary dentition compared to those with permanent teeth in relation to some oral hygiene parameters. Material and methods: Stimulated whole saliva was collected from 50 children (25 with primary dentation and
... Show MoreResearching performance audits according to the dimensions of financial sustainability in light of the scarcity of resources and economic and social transformations in the business environment is of utmost importance in the non-profit non-governmental organizations in achieving the goals and correct the path and address deviations, and help them in improving the outputs of processes and associated procedures and capacity The research was based on the hypothesis that the existence of a performance audit program in accordance with the dimensions of financial sustainability leads to the measurement of the commitment of the Olympic Committee. National Iraqi indicators of financial sustainability of the dimension of revenue in order to improv
... Show MoreThe problem of the research lies in special motor abilities training programs like the balance that positively affect coordination between the nervous system and muscles. These training programs did not get enough attention from athletes especially young athletes; their training was restricted to physical abilities like strength, speed, and endurance instead. The research aimed at designing an apparatus for developing athletes’ balance in national centers for gifted/ ministry of youth and sport so as to provide a measurement for coached in this field. The results showed that the designed apparatus have a positive effect on developing the subjects’ balance in boxing and basketball athletes.
The research aims to study the effect of knowledge upgrade on business continuity in private colleges and universities in Baghdad. The research problem is summarized in the main question (were the academic leaders able to employ knowledge upgrading to enhance business continuity). The most important of this sector were the universities and the private college in the city of Baghdad as a field for this research, the researchers conducted a field visit to (10) universities or private colleges, the research sample consisted of (177) individuals from the deans of colleges and their assistants, as well as heads of scientific and administrative departments. The data was analyzed and the hypotheses were tested using the appropriate statistical
... Show MoreTwo main grand bus national stations in Baghdad ( Alawi-alhila and Bab-almudam) were chosen as examples to determine lead effect on its drivers. This lead came from ethyl tetra lead or ethyl tri lead which used to improve gasoline quality ,so these two stations could be consider as two of the most polluted places due to gasoline burned by hundreds cars located in these stations .The determination of environmental lead pollution was measured in blood and urines drivers. Drivers were divided in two main groups due to their ages ( 30 persons in each group). The first group for men of 22-30 years old. The second group for men of 40-60 years old. Those men were carefully chosen in order to be non-fumiers or non-alcoholics persons because of
... Show MoreThis study aims to establish an empirical correlation between biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) of the sewage flowing in Al-Diwaniyah wastewater treatment plant. The strength of the wastewater entering the plant varied from medium to high. High concentrations of BOD5 and COD in the effluent were obtained due to the poor performance of the plant. This was observed from the BOD5 /COD ratios that did not confirm with the typical ratios for the treated sewage. To improve the performance of this plant, regression equations for BOD5 and COD removal percentages were suggested which can be used to facilitate rapid effluent assessment or optimal process control. The equations relating the percentage removal of
... Show More