The present work presents design and implementation of an automated two-axis solar tracking system using local materials with minimum cost, light weight and reliable structure. The tracking system consists of two parts, mechanical units (fixed and moving parts) and control units (four LDR sensors and Arduino UNO microcontroller to control two DC servomotors). The tracking system was fitted and assembled together with a parabolic trough solar concentrator (PTSC) system to move it according to information come from the sensors so as to keep the PTSC always perpendicular to sun rays. The experimental tests have been done on the PTSC system to investigate its thermal performance in two cases, with tracking system (case 1) and without tracking system (case 2). The experimental results showed that the average solar radiation falling on the PTSC prototype in the two cases during the same time was 854 and 701 watt/m2, respectively, which means an increase in the solar radiation about 21.8 % when using tracking system. It was found that the average useful heat gain output of solar collector was equal to (376.2, 252.6 watt) for the two cases, respectively, so there was an increase of about 48.9 % when using the tracking system. Also, the average thermal efficiency of the PTSC was found to be (20.7, 26.5 %) for the two cases, respectively, which means an increase in the average efficiency by 28% with use of tracking system compared to the fixed case.
In this study, chemical oxidation was employed for the synthesis of polypyrrole (PPy) nanofiber. Furthermore, PPy has been subjected to treatment using nanoparticles of neodymium oxide (Nd2O3), which were produced and added in a certain ratio. The inquiry centered on the structural characteristics of the blend of polypyrrole and neodymium oxide after their combination. The investigation utilises X-ray diffraction (XRD), FTIR, and Field Emission Scanning Electron Microscopy (FE-SEM) for PPy, 10%, 30%, and 50% by volume of Nd2O3. According to the electrochemical tests, it has been noted that the nanocomposites exhibit a substantial amount of pseudocapacitive activity.
We conducted a theoretical study on the potential use of amorphous hydrogenated silicon (a-Si:H) as the high-index material in quarter-wave-stack Bragg mirrors for cavity quantum electrodynamics applications. Compared to conventionally employed
This work was conducted to study the coefficient of performance for solar absorption refrigeration by using direct solar energy using aqueous ammonia 0.45 mass fraction (ammonia – water).The experiments were carried out in solar absorption system .The system consisted of solar collector generator (0.25 m × 0.25 m × 0.04m) and condenser cooled by a water bath followed by liquid receiver and evaporator. The results showed that the maximum generator temperature was (92° - 97°) during June 2009, and the minimum evaporator temperature was (5°C - 10°C) for aqua ammonia system.. It was, also, found that the coefficient of performance, cooling ratio and amount of cooling obtainable increased with increasing maximum generator temperature
... Show MoreThe 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
Influence of combined square nozzle with helical tape inserted in a constant heat flux tube on heat transfer enhancement for turbulent airflow for Reynolds number ranging from 7000 to 14500 were investigated experimentally. Three different pitch ratios for square nozzle (PR = 5.8, 7.7 and 11.6) according to three different numbers of square nozzle (N = 3, 4 and 5) and constant pitch ratios for helical tape were used. The results observed that the Nusselt number and friction factor for combination with winglets were found to be up to 33.8 % and 21.4 %, respectively higher than nozzle alone for pitch ratio PR=5.8. The maximum value of thermal performance for using combination with winglets was about 1.351 for pitch ratio= 5.8. Nusselt numb
... Show MoreAbstract
The economic and financial crises in the world economy series led to increased awareness of the importance of the internal control system, because it is one of the main pillars of any economic unit, as it works to verify the application of policies, regulations and laws and verification of asset protection from theft and embezzlement procedures, it is also working on trust accounting information imparted through the validation of accounting information, analyze and detect the misleading.
The existence the internal control system a factor in many of the accounting practices that limit the ability of the administration to produce misleading financial reporting
The
... Show More