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A Review on Exergy Analysis of Solar Refrigeration Technologies
Paiguy Armand Ngouateu Wouagfack,
Maurice Tenkeng,
Daniel Lissouck,
Réné Tchinda
Issue:
Volume 4, Issue 2, December 2020
Pages:
14-32
Received:
11 March 2020
Accepted:
24 April 2020
Published:
27 August 2020
Abstract: Solar energy is becoming more and more useful in the modern day life in industrial, domestic and commercial sectors, because of his cleanliness from an environmental point of view and also contributes to the reduction of greenhouse effect gases such as CO2. Exergy analysis is a thermodynamic analysis technique based on the Second Law of Thermodynamics, which provides an alternative and illuminating means of assessing and comparing processes and systems rationally and meaningfully. Exergy analysis can assist in improving and optimizing designs. In this paper, the exergy analysis of solar thermal refrigeration cyles is reviewed. A review of the research state of art of the solar absorption and adsorption refrigeration technologies is also carried out. The cycles involved in these technologies are: open, closed, continuous and intermittent cycles. An overview of mesures of merit with regard to exergy (exergetic efficiency, exergy losses, exergy improvement and exergetic coefficient of performance) is presented. Besides, an historical and chronological view is done on the development scenario of exergy analysis in the world from 1824 until 2014. The main mathematical relations for the simulation of those cycles are presented.
Abstract: Solar energy is becoming more and more useful in the modern day life in industrial, domestic and commercial sectors, because of his cleanliness from an environmental point of view and also contributes to the reduction of greenhouse effect gases such as CO2. Exergy analysis is a thermodynamic analysis technique based on the Second Law of Thermodynam...
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Effect of Irrigation Methods and Irrigation Levels on Yield and Water Productivity of Onion at Awash Melkasa, Ethiopia
Anbese Ambomsa,
Teshome Seyoum,
Tilahun Hordofa
Issue:
Volume 4, Issue 2, December 2020
Pages:
33-42
Received:
26 March 2020
Accepted:
16 April 2020
Published:
27 August 2020
Abstract: Water is scarce resource in Central Rift Valley of Ethiopia and is major limiting factor for crop production. The field experiment was conducted in 2018 at Melkasa Agricultural Research Center during the off-season to identify irrigation method and irrigation application level that maximizes productivity of onion per unit of water consumed and enhanced onion crop production. The experiment was carried out using split plot design in RCBD having three replications. The experiment consisted of two irrigation methods viz., furrow and drip irrigation as main plot and three levels of manageable allowable depletion viz., 120%, 100% and 80% as sub-plot. The ANOVA revealed that their interaction had a significant (p<0.01) effect on bulb diameter, total bulb yield, marketable bulb yield and water productivity. The maximum total bulb yield (41.76 t/ha), marketable bulb yield (38.39 t/ha), bulb diameter (6.02 cm) and water productivity (13.05 kg/m3) were observed from drip irrigation method at 80% management allowed depletion application, while significantly lower of 34.48 t/kg, 31.6 t/ha, 5.11 cm, and 6.84 kg/m3 respectively were recorded from furrow irrigation method at 120% management allowed depletion application. Among all tested treatments drip irrigation method with 80% MAD was the best practice because of its high yield, water productivity.
Abstract: Water is scarce resource in Central Rift Valley of Ethiopia and is major limiting factor for crop production. The field experiment was conducted in 2018 at Melkasa Agricultural Research Center during the off-season to identify irrigation method and irrigation application level that maximizes productivity of onion per unit of water consumed and enha...
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Experimental Research of the Influence of Bedload Sediment Heterogeneity on Length, Height and Shifting Velocity of Growing Bed Configuration
Nazir Ikramov,
Takhir Majidov
Issue:
Volume 4, Issue 2, December 2020
Pages:
43-49
Received:
9 October 2019
Accepted:
26 October 2019
Published:
3 September 2020
Abstract: In the natural current of water, the growing bed movement leads to a reduction of reservoir volume and canal cross-section area, filling by forebay of pump station and hydroelectric station pressure basins with sediment. This leads to abrasive wear of pumps, water turbines, and pressure pipelines, as well as other negative consequences. In many countries, rivers come laden with a large amount of sediment and enormous costs. At determining of sediment discharge it is important values of height and movement velocity of bed ridges. The determination of these values is based on experimental studies was not taken into account the heterogeneity of sediment with different fractions. For this reason, the calculated values according to obtained formulas have large discrepancies with field data. To eliminate these discrepancies, experimental studies were conducted using six types of fractions with the same weighted average diameter. Based on of laboratory data diagrams and interrelation were obtained for ridge length, height and movement velocity from sediment hydraulic and geometric sizes.
Abstract: In the natural current of water, the growing bed movement leads to a reduction of reservoir volume and canal cross-section area, filling by forebay of pump station and hydroelectric station pressure basins with sediment. This leads to abrasive wear of pumps, water turbines, and pressure pipelines, as well as other negative consequences. In many cou...
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Effect of SBF on Cyclic Compression Behaviour of Porous Titanium Component for Implant Application
Munshi Muhammad Raihan,
Afrina Khan Piya,
Mohammad Alamgir Hossain
Issue:
Volume 4, Issue 2, December 2020
Pages:
50-54
Received:
25 June 2020
Accepted:
24 August 2020
Published:
3 September 2020
Abstract: In the recent years, porous structure is being drawn attention to the researcher for implant application for superior characteristics over bulk materials. The aim of this study is to evaluate the cyclic compression behaviour of porous titanium components in simulated body fluid (SBF). Porous titanium component developed by replica impregnation method was taken for study. Compression tests in air revealed that the yield strength of the porous body is 8MPa on average and elastic modulus is around 180MPa which is compatible to cancellous bone application. After 10% strain porous structure deformed plastically producing a long plateau region. Compressive fatigue tests revealed that at higher stress level porous titanium failed earlier in SBF than in air. In contrast, fatigue limit of porous substrate is 2 MPa which was not affected by SBF medium. After 10 million cycles in SBF, Calcium Phosphate layer was partially formed on the surface of porous titanium by re-precipitation from SBF. EDS analysis showed that the Ca/P atomic ratio was 1.44 which is near to beta TCP and HA phase and these phases are beneficial for bone tissue ingrowth.
Abstract: In the recent years, porous structure is being drawn attention to the researcher for implant application for superior characteristics over bulk materials. The aim of this study is to evaluate the cyclic compression behaviour of porous titanium components in simulated body fluid (SBF). Porous titanium component developed by replica impregnation meth...
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Effects of Strong Government in Attaining Outstanding Performance on Construction Projects: Stakeholder’s Opinions in Tanzania
Ramadhani Said Tekka,
Saidi Mustapha Msangi
Issue:
Volume 4, Issue 2, December 2020
Pages:
55-60
Received:
24 December 2019
Accepted:
10 February 2020
Published:
10 September 2020
Abstract: Attaining an outstanding performance in a construction project has for decades being a problem in Tanzania. Contractors have too many projects failed to conquer the project’s value for money as a result of time extension, increase in cost with unsatisfactory quality. This study aims to identify the Tanzanian opinion on the effects of strong government in attaining outstanding performance on construction projects. The questionnaire and an-in-depth interview survey method were opted to collect the data from one hundred fifty-four (154) respondents obtained through purposely sampling technique. Microsoft Excel was used to analyze the quantitative descriptive data. The finding of the study has identified twelve (12) effects of a stable government on performance in construction industry in Tanzania: attainment value for money, fight against malpractices (corruption), timely project completion, timely project completion, society satisfaction with projects, society satisfaction with projects, community participation/local fundi, reduced of construction cost, abide to construction specification, increased quality social services, suspending of ghost engineer, de-register incompetent contractors, reasonable operational cost, timely payment grouped into four variables namely: an increased construction quality, fighting against malpractices, society satisfaction, and timely payment. However, the study has eventually proposed the measure to be considered for local firms to attain a sustainable, outstanding performance and growth.
Abstract: Attaining an outstanding performance in a construction project has for decades being a problem in Tanzania. Contractors have too many projects failed to conquer the project’s value for money as a result of time extension, increase in cost with unsatisfactory quality. This study aims to identify the Tanzanian opinion on the effects of strong governm...
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