Search results for: effeciency

Authors: Fekadu Melak, Tsegaye Girma Asere

Abstract:

Trace element ions, such as Cr(VI) and F−, are of particular interest due to their environmental impact. Both ions exhibit an anionic nature in water that can show similar removal tendencies except for their significant differences in ionic radius. Accordingly, partial freezing was performed to examine freeze separation efficiencies of Cr(VI) and F– from aqueous solutions. Real groundwater and simulated wastewater were included to test effeciency of F– and Cr(VI), respectively. Parameters such as initial ion concentration, salt addition, and freeze duration were explored. Under optimal operating conditions, freeze separation efficiencies of 90 ± 0.12 to 97 ± 0.54% and 58 ± 0.23% to 60 ± 0.34% from 5 mg/L of Cr(VI) and F–, respectively, were demonstrated. The F– ion intercalation into the ice, initiating the decrement of freeze separation efficiency was observed in the salt addition processes. The influences of structuring-destructuring (kosmotropicity-chaotropicity) and the size-exclusion nature of ice crystals were used to explain the plausible mechanism in freeze separation efficiency trace elemental ions.

Keywords: Cr(VI), F-, partial freezing, size exclusion

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Authors: Chadel Meriem, Bensmaine Souhila, Chadel Asma, Bouchikhi Chaima

Abstract:

The Methylammonium Lead Iodide CH3NH3PbI3 is used in solar cell as an absorber layer since 2009. The efficiencies of these technologies have increased from 3.8% in 2009 to 29.15% in 2019. So, these technologies Methylammonium Lead Iodide is promising for the development of high-performance photovoltaic applications. Due to the high cost of the experimental of the solar cells, researchers have turned to other methods like numerical simulation. In this work, we evaluate and simulate the performance of a CH₃NH₃PbI₃ lead-based perovskite solar cell when the amount of materials of absorber layer is reduced. We show that the reducing of thickness the absorber layer influent on performance of the solar cell. For this study, the one-dimensional simulation program, SCAPS-1D, is used to investigate and analyze the performance of the perovskite solar cell. After optimization, maximum conversion efficiency was achieved with 300 nm in absorber layer.

Keywords: methylammonium lead Iodide, perovskite solar cell, caracteristic J-V, effeciency

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Authors: Taher M. Abou-deif, Esmail M. El-Bialy, Essam E. Khalil

Abstract:

The paper is devoted to numerically investigating the influence of the air supply outlets geometry on human comfort inside living looms. A computational fluid dynamics model is developed to examine the air flow characteristics of a room with different supply air diffusers. The work focuses on air flow patterns, thermal behavior in the room with few number of occupants. As an input to the full-scale 3-D room model, a 2-D air supply diffuser model that supplies direction and magnitude of air flow into the room is developed. Air distribution effect on thermal comfort parameters was investigated depending on changing the air supply diffusers type, angles and velocity. Air supply diffusers locations and numbers were also investigated. The pre-processor Gambit is used to create the geometric model with parametric features. Commercially available simulation software “Fluent 6.3” is incorporated to solve the differential equations governing the conservation of mass, three momentum and energy in the processing of air flow distribution. Turbulence effects of the flow are represented by the well-developed two equation turbulence model. In this work, the so-called standard k-ε turbulence model, one of the most widespread turbulence models for industrial applications, was utilized. Basic parameters included in this work are air dry bulb temperature, air velocity, relative humidity and turbulence parameters are used for numerical predictions of indoor air distribution and thermal comfort. The thermal comfort predictions through this work were based on ADPI (Air Diffusion Performance Index),the PMV (Predicted Mean Vote) model and the PPD (Percentage People Dissatisfied) model, the PMV and PPD were estimated using Fanger’s model.

Keywords: thermal comfort, Fanger's model, ADPI, energy effeciency

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Authors: Sumaya Adina

Abstract:

The productivity of the construction industry has faced numerous challenges, rising costs, and scarce resources over the past forty years; therefore, one approach for improving and enhancing the framework is the use of lean techniques. Lean method outcomes from the use of a brand-form of manufacturing control in production. At a time when sustainability and efficiency are essential, lean offers a clear path to make the construction industry fit for the future. An excessive number of construction professionals and experts have efficiently optimised development initiatives using lean construction (LC) techniques to reduce waste, maximise value creation, and focus on the process that creates real added value and continuous improvement, strengthening flexibility and adaptability. The present research has been undertaken to study the improvement in the performance of construction projects using lean principles. The study work is divided into three stages. Initially, a questionnaire survey was conducted on visual management techniques to improve the performance of the construction projects. The questionnaire was distributed to civil engineers, architects, site managers, project managers, and full-time executives, with nearly 100 questionnaires shared with respondents. A total of 83 responses were received to determine the reliability of the data, and analysis was done using SPSS software. In the second stage, the impact of value stream mapping on the real-time project is determined and its performance in the form of time and cost reduction is evaluated. The case study examines a bunker-building project located in Kabul Afghanistan; the project was planned conventionally without considering the lean concepts. To reduce overall kinds of waste in the project, a plan was developed using the Vico Control software to visualize the value stream of the project. Finally, the impact of value stream mapping on the project's total cash flow is evaluated and compared by plotting the total cash flow curve using Vico software. As a result, labour costs were reduced by 33%. The duration of the project was reduced by 17% reducing the duration of the project also improved the cash flow of the entire project by 14% and increased the cash flow from negative 67% to negative 44%.

Keywords: lean construction, cost and time overrun, value stream mapping, construction effeciency

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