Search results for: distribution temperature

Authors: C. F. Ocoleanu, A. I. Dolan, G. Cividjian, S. Teodorescu

Abstract:

In this paper we make a temperature investigations in two type of superposed crimped connections using experimental determinations. All the samples use 8 copper wire 7.1 x 3 mm2 crimped by two methods: the first method uses one crimp indents and the second is a proposed method with two crimp indents. The ferrule is a parallel one. We study the influence of number and position of crimp indents. The samples are heated in A.C. current at different current values until steady state heating regime. After obtaining of temperature values, we compare them and present the conclusion.

Keywords: crimped connections, experimental determinations, temperature, heat transfer

Procedia PDF Downloads 262

Authors: Seon Soon Choi

Abstract:

The fatigue crack growth is stochastic because of the fatigue behavior having an uncertainty and a randomness. Therefore, it is necessary to determine the probability distribution of a grown crack size at a specific fatigue crack propagation life for maintenance of structure as well as reliability estimation. The essential purpose of this study is to present the good probability distribution fit for the grown crack size at a specified fatigue life in a rolled magnesium alloy under different specimen thickness conditions. Fatigue crack propagation experiments are carried out in laboratory air under three conditions of specimen thickness using AZ31 to investigate a stochastic crack growth behavior. The goodness-of-fit test for probability distribution of a grown crack size under different specimen thickness conditions is performed by Anderson-Darling test. The effect of a specimen thickness on variability of a grown crack size is also investigated.

Keywords: crack size, fatigue crack propagation, magnesium alloys, probability distribution, specimen thickness

Procedia PDF Downloads 496

Authors: D. Gazdič, I. Hájková, M. Fridrichová

Abstract:

This paper involved the performance of a high-temperature X-Ray powder diffraction analysis (XRD) of a sample of chemical gypsum generated in the production of titanium white; this gypsum originates by neutralizing highly acidic water with limestone suspension. Specifically, it was gypsum formed in the first stage of neutralization when the resulting material contains, apart from gypsum, a number of waste products resulting from the decomposition of ilmenite by sulphuric acid. So it can be described as red titanogypsum. By conducting the experiment using XRD apparatus Bruker D8 Advance with a Cu anode (λkα=1.54184 Å) equipped with high-temperature chamber Anton Paar HTK 16, it was possible to identify clearly in the sample each phase transition in the system of CaSO4•xH2O.

Keywords: anhydrite, gypsum, bassanite, hematite, XRD, powder, high-temperature

Procedia PDF Downloads 338

Authors: Hadjadj Naima, K. Mahdi, D. Belhachat, F. S. Ait Chaouche, A. Ferradji

Abstract:

The Nigella Sativa oil yield extracted by hydraulic pressing is influenced by the pressure temperature and size particles. The optimization of oil extraction is investigated. The rate of extraction of the whole seeds is very weak, a crushing of seeds is necessary to facilitate the extraction. This rate augments with the rise of the temperature and the pressure, and decrease of size particles. The best output (66%) is obtained for a granulometry lower than 1mm, a temperature of 50°C and a pressure of 120 bars.

Keywords: oil, Nigella sativa, extraction, optimization, temperature, pressure

Procedia PDF Downloads 474

Authors: Tesfaye Sisay Dessalegn

Abstract:

The long-term performance of concrete structures is affected by the properties and behavior of concrete at an early age. However, the fundamental mechanisms affecting the early-age behavior of concrete have not yet been fully studied. The effect of water temperature on concrete is not sufficiently studied, and at the same time, the majority of studies focused on the effect of mixing water temperature on the workability and mechanical properties of concrete. However, to the best of the authors' knowledge, the effect of mixing water temperatures on plastic shrinkage cracking of concrete has not been studied yet.

Keywords: water temperature, early age concrete strength, mechanical properties of concrete, strength

Procedia PDF Downloads 50

Authors: Bouchemha Amel, Chachoui Takieddine, H. Maalem

Abstract:

Automatic detection of targets in a modern communication system RADAR is based primarily on the concept of adaptive CFAR detector. To have an effective detection, we must minimize the influence of disturbances due to the clutter. The detection algorithm adapts the CFAR detection threshold which is proportional to the average power of the clutter, maintaining a constant probability of false alarm. In this article, we analyze the performance of two variants of adaptive algorithms CA-CFAR and OS-CFAR and we compare the thresholds of these detectors in the marine environment (no-Gaussian) with a Weibull distribution.

Keywords: CFAR, threshold, clutter, distribution, Weibull, detection

Procedia PDF Downloads 581

Authors: Mounir Soule, Hindatou Saidou, Razafimahefa, Mohamed Thani Ibouroi

Abstract:

High levels of habitat fragmentation and loss are the main drivers of plant species extinction. They reduce the habitat quality, which is a determining factor for the reproduction of plant species, and generate strong selective pressures for habitat selection, with impacts on the reproduction and survival of individuals. The Comorian’s yam (Dioscorea comorensis) is one of the most threatened plant species of the Comoros archipelago. The species faces one of the highest rates of habitat loss worldwide (9.3 % per year) and is classified as Endangered in the IUCN red list. Despite the nutritional potential of this tuber, the Comorian’s yam cultivation remains neglected by local populations due probably to lack of knowledge on its nutritional importance and the factors driving its spatial distribution and development. In this study, we assessed the nutritional characteristics of Dioscorea comorensis and the drivers of spatial distribution and abundance to propose conservation measures and improve crop yields. To determine the nutritional characteristics, the Kjeldahl method, the Soxhlet method, and Atwater's specific calorific coefficients methods were applied for analyzing proteins, lipids, and caloric energy respectively. In addition, atomic absorption spectrometry was used to measure mineral particles. By combining species occurrences with ecological (habitat types), climatic (temperature, rainfall, etc.), and physicochemical (soil types and quality) variables, we assessed habitat suitability and spatial distribution of the species and the factors explaining the origin, persistence, distribution and competitive capacity of a species using a Species Distribution Modeling (SDM) method. The results showed that the species contains 83.37% carbohydrates, 6.37% protein, and 0.45% lipids. In 100 grams, the quantities of Calcium, Sodium, Zinc, Iron, Copper, Potassium, Phosphorus, Magnesium, and Manganese are respectively 422.70, 599.41, 223.11, 252.32, 332.20, 780.41, 444.17, 287.71 and 220.73 mg. Its PRAL index is negative (- 9.80 mEq/100 g), and its Ca/P (0.95) and Na/K (0.77) ratios are less than 1. This species provides an energy value of 357.46 Kcal per 100 g, thanks to its carbohydrates and minerals and is distinguished from others by its high protein content, offering benefits for cardiovascular health. According to our SDM, the species has a very limited distribution, restricted to forests with higher biomass, humidity, and clay. Our findings highlight how distribution patterns are related to ecological and environmental factors. They also emphasize how the Comoros yam is beneficial in terms of nutritional quality. Our results represent a basic knowledge that will help scientists and decision-makers to develop conservation strategies and to improve crop yields.

Keywords: Dioscorea comorensis, nutritional characteristics, species distribution modeling, conservation strategies, crop yields improvement

Procedia PDF Downloads 22

Authors: S. Ramteke, K. S. Patel

Abstract:

Aerosols are complex mixture of particulate matters (PM) inclusive of carbons, silica, elements, various salts, etc. Aerosols get deep into the human lungs and cause a broad range of health effects, in particular, respiratory and cardiovascular illnesses. They are one of the major culprits for the climate change. They are emitted by the high thermal processes i.e. vehicles, steel, sponge, cement, thermal power plants, etc. Raipur (22˚33'N to 21˚14'N and 82˚6'E) to 81˚38'E) is a growing industrial city in central India with population of two million. In this work, the distribution of inorganics (i.e. Cl⁻, NO³⁻, SO₄²⁻, NH₄⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Al, Cr, Mn, Fe, Ni, Cu, Zn, and Pb) associated to the PM in the ambient air is described. The PM₁₀ in ambient air of Raipur city was collected for duration of one year (December 2014 - December 2015). The PM₁₀ was segregated into nine modes i.e. PM₁₀.₀₋₉.₀, PM₉.₀₋₅.₈, PM₅.₈₋₄.₇, PM₄.₇₋₃.₃, PM₃.₃₋₂.₁, PM₂.₁₋₁.₁, PM₁.₁₋₀.₇, PM₀.₇₋₀.₄ and PM₀.₄ to know their emission sources and health hazards. The analysis of ions and metals was carried out by techniques i.e. ion chromatography and TXRF. The PM₁₀ concentration (n=48) was ranged from 100-450 µg/m³ with mean value of 73.57±20.82 µg/m³. The highest concentration of PM₄.₇₋₃.₃, PM₂.₁₋₁.₁, PM₁.₁₋₀.₇ was observed in the commercial, residential and industrial area, respectively. The effect of meteorology i.e. temperature, humidity, wind speed and wind direction in the PM₁₀ and associated elemental concentration in the air is discussed.

Keywords: ambient aerosol, ions, metals, segregation

Procedia PDF Downloads 197

Authors: Majid Zargar, Frank Bullen, Ron Ayers

Abstract:

One of the important factors in the design of asphalt concrete mixes is the accurate measurement of air voids and their variable distribution. Both can have significant impact on long and short term fatigue and creep behaviour under traffic. While some simple methods exist for overall evaluation of air voids, measuring air void distribution in asphalt concrete is very complex, involving expensive techniques such as X-ray methodologies. The research reported in the paper investigated the use of non-destructive ultrasonic techniques as an alternative to estimate the amount of air voids and their distribution within asphalt samples. Seventy-four Standard AC–14 asphalt samples made with three types of bitumen; Multigrade, PMB and C320 were analysed using ultrasonic techniques. The results have illustrated that ultrasonic testing has the potential of being a rapid, accurate and cost-effective method of estimating air void distribution in asphalt.

Keywords: asphalt concrete, air voids, ultrasonic, mechanical behaviour

Procedia PDF Downloads 342

Authors: Karine Pimenta Teixeira, Jessica Flores, Isadora PerdigãO Rocha, Leticia De Sá Carneiro, Mahsa Kamali, Ali Ghahremaninezhad

Abstract:

The advent of nanotechnology has enabled innovative solutions towards improving the behavior of infrastructure materials. Nanomaterials have the potential to revolutionize the construction industry by improving the performance and durability of construction materials, as well as imparting new functionalities to these materials. Due to variability in the environmental temperature during mixing and curing of cementitious materials in practice, it is important to understand how curing temperature influences the behavior of cementitious materials. In addition, high temperature curing is relevant in applications such as oil well cement and precast industry. Knowledge of the influence of temperature on the performance of cementitious materials modified with nanoparticles is important in the nanoengineering of cementitious materials in applications such as oil well cement and precast industry. This presentation aims to investigate the influence of temperature on the hydration, mechanical properties and durability of cementitious materials modified with TiO2 nanoparticles. It was found that temperature improved the early hydration. The cement pastes cured at high temperatures showed an increase in the compressive strength at early age but the strength gain decreased at late ages. The electrical resistivity of the cement pastes cured at high temperatures was shown to decrease more noticeably at late ages compared to that of the room temperature cured cement paste. SEM examination indicated that hydration product was more uniformly distributed in the microstructure of the cement paste cured at room temperature compared to the cement pastes cured at high temperature.

Keywords: cement paste, nanoparticles, temperature, hydration

Procedia PDF Downloads 315

Authors: Nitu Chhikaraa, S. B. Tyagia, Kiran Jainb, Mamta Kharkwala

Abstract:

The I–III–VI2 semiconductor Nanocrystals such as AgInS2 have great interest for various applications such as optical devices (solar cell and LED), cellular Imaging and bio tagging etc. we synthesized the phase and shape controlled chalcopyrite AgInS2 (AIS) colloidal nanoparticles by thermal decomposition of metal xanthate at low temperature in an organic solvent’s containing surfactant molecules. Here we are focusing on enhancements of photoluminescence of AgInS2 Nps by coating of ZnS at low temperature for application of optical devices. The size of core shell Nps was less than 50nm.by increasing the time and temperature the emission of the wavelength of the Zn coated AgInS2 Nps could be adjusted from visible region to IR the QY of the AgInS2 Nps could be increased by coating of ZnS from 20 to 80% which was reasonably good as compared to those of the previously reported. The synthesized NPs were characterized by PL, UV, XRD and TEM.

Keywords: PL, UV, XRD, TEM

Procedia PDF Downloads 369

Authors: María del Carmen Recio-Ruiz, Ramiro Ruiz-Rosas, Juana María Rosas, José Rodríguez-Mirasol, Tomás Cordero

Abstract:

At the present time, conventional fossil fuels show environmental and sustainability disadvantages with regard to renewables energies. Producing energy and chemicals from biomass is an interesting alternative for substitution of conventional fossil sources with a renewable feedstock while enabling zero net greenhouse gases emissions. Pyrolysis is a well-known process to produce fuels and chemicals from biomass. In this work, conventional and fast pyrolysis of different agro-industrial residues (almond shells, hemp hurds, olive stones, and Kraft lignin) was studied. Both processes were carried out in a fixed bed reactor under nitrogen flow and using different operating conditions to analyze the influence of temperature (400-800 ºC) and heating rate (10 and 20 ºC/minfor conventional pyrolysis and 50 ºC/s for fast pyrolysis)on the yields, products distribution, and composition of the different fractions. The results showed that for both conventional and fast pyrolysis, the solid fraction yield decreased with temperature, while the liquid and gas fractions increased. In the case of the fast pyrolysis, a higher content of liquid fraction than that obtained in conventional pyrolysis could be observed due to cracking reactions occur at a lesser extent. With respect to the composition of de non-condensable fraction, the main gases obtained were CO, CO₂ (mainly at low temperatures), CH₄, and H₂ (mainly at high temperatures).

Keywords: bio-oil, biomass, conventional pyrolysis, fast pyrolysis

Procedia PDF Downloads 183

Authors: Ali Moarrefzadeh

Abstract:

In metalworking, rolling is a metal forming process in which metal stock is passed through a pair of rolls. Rolling is classified according to the temperature of the metal rolled. If the temperature of the metal is above its recrystallization temperature, then the process is termed as hot rolling. If the temperature of the metal is below its recrystallization temperature, the process is termed as cold rolling. In terms of usage, hot rolling processes more tonnage than any other manufacturing process, and cold rolling processes the most tonnage out of all cold working processes. This article describes the use of advanced tubing inspection NDT methods for boiler and heat exchanger equipment in the petrochemical industry to supplement major turnaround inspections. The methods presented include remote field eddy current, magnetic flux leakage, internal rotary inspection system and eddy current.

Keywords: hot forming, cold forming, metal, rolling, simulation

Procedia PDF Downloads 525

Authors: Anton S. Perin, Vladimir M. Shandarov

Abstract:

Compensation for the nonlinear diffraction of narrow laser beams with wavelength of 532 and the formation of photonic waveguides and waveguide circuits due to the contribution of pyroelectric effect to the nonlinear response of lithium niobate crystal have been experimentally demonstrated. Complete compensation for the linear and nonlinear diffraction broadening of light beams is obtained upon uniform heating of an undoped sample from room temperature to 55 degrees Celsius. An analysis of the light-field distribution patterns and the corresponding intensity distribution profiles allowed us to estimate the spacing for the channel waveguides. The observed behavior of bright soliton beams may be caused by their coherent interaction, which manifests itself in repulsion for anti-phase light fields and in attraction for in-phase light fields. The experimental results of this study showed a fundamental possibility of forming optically complex waveguide structures in lithium niobate crystals with pyroelectric mechanism of nonlinear response. The topology of these structures is determined by the light field distribution on the input face of crystalline sample. The optical induction of channel waveguide elements by interacting spatial solitons makes it possible to design optical systems with a more complex topology and a possibility of their dynamic reconfiguration.

Keywords: self-action, soliton, lithium niobate, piroliton, photorefractive effect, pyroelectric effect

Procedia PDF Downloads 165

Authors: Yahya A. Sadiq, Grace F. Balogun, Olufemi J. Anjorin

Abstract:

This study analyzed the spatial distribution of socio-economic factors in Kogi state with a view to examining its implications on the development of the state. Consequently, questionnaires were administered on both the selected individual respondents (784) in the state and on the administrative offices (local council offices, 21) to solicit relevant information on the spatial distribution of socio-economic factors in their areas. The collected data were tabulated and analyzed using percentages. The study revealed commerce/trade, education, and health care, etc. as the major socio-economic factors in the state but with marked variation/imbalance in their spatial distribution across the study area. The rural-based local government areas have far less of such important facilities. Conclusively, it was recommended that there is need for socio-economic transformation of living conditions of people in the study area especially by positively redistributing local political power and the resources that are abound in the state will be felt by everybody including the commoners.

Keywords: development, local government areas (LGAs), spatial distribution, socio-economic factors

Procedia PDF Downloads 399

Authors: Meryem Kanzari, Rabah Boukhanouf, Hatem G. Ibrahim

Abstract:

Indirect Evaporative Cooling process has the advantage of supplying cool air at constant moisture content. However, such system can only supply air at temperatures above wet bulb temperature. This paper presents a mathematical model for a sub-wet bulb temperature indirect evaporative cooling arrangement that can overcome this limitation and supply cool air at temperatures approaching dew point and without increasing its moisture content. In addition, the use of porous ceramics as wet media materials offers the advantage of integration into building elements. Results of the computer show that the proposed design is capable of cooling air to temperatures lower than the ambient wet bulb temperature and achieving wet bulb effectiveness of about 1.17.

Keywords: indirect evaporative cooling, porous ceramic, sub-wet bulb temperature, mathematical modeling

Procedia PDF Downloads 290

Authors: Talal Al-Bazali, S. Mohammad

Abstract:

The threshold capillary pressure of shale caprocks is an important parameter in CO₂ storage modeling. A correct estimation of the threshold capillary pressure is not only essential for CO₂ storage modeling but also important to assess the overall economical and environmental impact of the design process. A standard step by step approach has to be used to measure the threshold capillary pressure of shale and non-wetting fluids at different temperatures. The objective of this work is to assess the impact of high temperature on the threshold capillary pressure of four different shales as they interacted with four different oil based muds, air, CO₂, N₂, and methane. This study shows that the threshold capillary pressure of shale and non-wetting fluid is highly impacted by temperature. An empirical correlation for the dependence of threshold capillary pressure on temperature when different shales interacted with oil based muds and gasses has been developed. This correlation shows that the threshold capillary pressure decreases exponentially as the temperature increases. In this correlation, an experimental constant (α) appears, and this constant may depend on the properties of shale and non-wetting fluid. The value for α factor was found to be higher for gasses than for oil based muds. This is consistent with our intuition since the interfacial tension for gasses is higher than those for oil based muds. The author believes that measured threshold capillary pressure at ambient temperature is misleading and could yield higher values than those encountered at in situ conditions. Therefore one must correct for the impact of temperature when measuring threshold capillary pressure of shale at ambient temperature.

Keywords: capillary pressure, shale, temperature, thresshold

Procedia PDF Downloads 366

Authors: M. Akif Ceviz, Alirıza Kaleli, Erdoğan Güner

Abstract:

LPG pressure regulator is a device which is used to change the phase of LPG from liquid to gas by decreasing the pressure. During the phase change, it is necessary to supply the latent heat of LPG to prevent excessive low temperature. Engine coolant is circulated in the pressure regulator for this purpose. Therefore, pressure regulator is a type of heat exchanger that should be designed for different engine operating conditions. The design of the regulator should ensure that the flow of LPG is in gaseous phase to the injectors during the engine steady state and transient operating conditions. The pressure regulators in the LPG gaseous injection systems currently used can easily change the phase of LPG, however, there is no any control on the LPG temperature in conventional LPG injection systems. It is possible to increase temperature excessively. In this study, a control unit has been tested to keep the LPG temperature in a band. Result of the study showed that the engine performance characteristics can be increased by using the system.

Keywords: temperature, pressure regulator, LPG, PID

Procedia PDF Downloads 512

Authors: Nur Farah Ain Zainee, Ahmad Ismail, Nazlina Ibrahim, Asmida Ismail

Abstract:

The study of genus Halimeda in Malaysia is in the early stage due to less specific study on its taxonomy. Most of the previous research tend to choose other genus such as Caulerpa and Gracilaria because of the potential of being utilized. The identification of Halimeda is complex by the high morphological variation within individual species due to different types of habitat and the changes in composition of seawater. The study was completed to study the diversity and distribution of Halimeda in Malaysia and to identify the morphological and anatomical differences between Halimeda species. The methods which have been used for this study are collection of Halimeda and seawater, preservation of specimen, identification of the specimen including the preparation of the temporary slide and decalcification of the calcium layer by using diluted hydrochloric acid. The specimen were processed in laboratory and kept as herbarium specimen in Algae Herbarium, Universiti Kebangsaan Malaysia. Environmental parameters were tested by using YSI multiparameter probe and the recorded data were temperature, salinity, pH and dissolved oxygen. The nutrient content of seawater such as nitrate and phosphate were analysed by using Hach kit model DR 2000. In the present study, out of 330 herbarium specimen, ten species were identified as Halimeda cuneata, H. discoidea, H. macroloba, H. macrophysa, H. opuntia, H. simulans, H. stuposa, H. taenicola, H. tuna and H. velasquezii. Of these, five species were new record to Malaysia. They are Halimeda cuneata, H. macrophysa, H. stuposa, H. taenicola and H. velasquezii. H. opuntia was found as the most abundance species with wide distribution in Malaysia coastal area. Meanwhile, from the study of their distribution, two localities in which Pulau Balak Balak, Kudat and Pulau Langkawi, Kedah, were noted having high number of Halimeda species. As a conclusion, this study has successfully identified ten species of Halimeda of Malaysia with full description of morphological characteristics that may assist further researcher to differentiate and identify Halimeda.

Keywords: Distribution, diversity, Halimeda, morphological, taxonomy

Procedia PDF Downloads 342

Authors: Ziqu Ouyang, Kun Su

Abstract:

A novel efficient and clean coal combustion system, namely the purification-combustion system, was designed by the Institute of Engineering Thermal Physics, Chinese Academy of Science, in 2022. Among them, the purification system was composed of a mesothermal activating unit and a hyperthermal reductive unit, and the combustion system was composed of a mild combustion system. In the purification-combustion system, the deep in-situ removal of coal-N could be realized by matching the temperature and atmosphere in each unit, and thus the NOx emission was controlled effectively. To acquire the methods for realizing the efficient and clean coal combustion, this study investigated the effect of the activating temperature (including 822 °C, 858 °C, 933 °C, 991 °C), which was the key factor affecting the system operation, on combustion and NOx emission characteristics of pulverized coal in a 30 kW purification-combustion test bench. The research result turned out that the activating temperature affected the combustion and NOx emission characteristics significantly. As the activating temperature increased, the temperature increased first and then decreased in the mild combustion unit, and the temperature change in the lower part was much higher than that in the upper part. Moreover, the main combustion region was always located at the top of the unit under different activating temperatures, and the combustion intensity along the unit was weakened gradually. Increasing the activating temperature excessively could destroy the reductive atmosphere early in the upper part of the unit, which wasn’t conducive to the full removal of coal-N in the reductive coal char. As the activating temperature increased, the combustion efficiency increased first and then decreased, while the NOx emission decreased first and then increased, illustrating that increasing the activating temperature properly promoted the efficient and clean coal combustion, but there was a limit to its growth. In this study, the optimal activating temperature was 858 °C. Hence, this research illustrated that increasing the activating temperature properly could realize the mutual matching of improving the combustion efficiency and reducing the NOx emission, and thus guaranteed the clean and efficient coal combustion well.

Keywords: activating temperature, combustion characteristics, nox emission, purification-combustion system

Procedia PDF Downloads 84

Authors: Merve Nur Güven Biçer

Abstract:

Conductive inks are used extensively in electronic devices like sensors, batteries, photovoltaic devices, antennae, and organic light-emitting diodes. These inks are typically made from silver. Wearable technology is another industry that requires inks to be flexible. The aim of this study is the fabrication of low-temperature silver paste by synthesis long silver nanowires.

Keywords: silver ink, conductive ink, low temperature conductive ink, silver nanowire

Procedia PDF Downloads 182

Authors: Wenjing Ding, Weiwei Shan, Zijuan, Wang, Chao He

Abstract:

Liquid spray heat exchanger is the critical equipment of temperature regulating system by gaseous nitrogen which realizes the environment temperature in the range of -180 ℃~+180 ℃. Liquid nitrogen is atomized into smaller liquid drops through liquid nitrogen sprayer and then contacts with gaseous nitrogen to be cooled. By adjusting the pressure of liquid nitrogen and gaseous nitrogen, the flowrate of liquid nitrogen is changed to realize the required outlet temperature of heat exchanger. The temperature accuracy of shrouds is ±1 ℃. Liquid nitrogen spray heat exchanger is simulated by CATIA, and the numerical simulation is performed by FLUENT. The comparison between the tests and numerical simulation is conducted. Moreover, the results help to improve the design of liquid nitrogen spray heat exchanger.

Keywords: liquid nitrogen spray, temperature regulating system, heat exchanger, numerical simulation

Procedia PDF Downloads 323

Authors: Solomon Weldegebriel Gebrelibanos

Abstract:

Water is one of the most important substances in human life that can give a human liberality with its cost and availability. Water comes from rainfall and runoff and reaches the ground as runoff that is stored in a river, ponds, and big water bodies, including sea and ocean and the remaining water portion is infiltrated into the ground to store in the aquifer. Water can serve human beings in various ways, including irrigation, water supply, hydropower and soon. Water supply is the main pillar of the water service to the human being. Water supply distribution in Addis Ababa arises from Legedadi, Akakai, and Gefersa. The objective of the study is to measure the performance of the water supply distribution in Addis Ababa city. The water supply distribution model is developed by computer-aided design software. The model can analyze the operational change, loss of water, and performance of the network. The two design criteria that have been employed to analyze the network system are velocity and pressure. The result shows that the customers are using the water at high pressure with low demand. The water distribution system is older than the expected service life with more leakage. Hence the study recommended that fixing Pressure valves and new distribution facilities can resolve the performance of the water supply system

Keywords: distribution, model, pressure, velocity

Procedia PDF Downloads 130

Authors: Rong Li, Brian D. Wirth, Bing Liu

Abstract:

Graphite is the matrix, and structural material in the high temperature gas-cooled reactor exhibits an irradiation response. It is of significant importance to analyze the defect production and evaluate the role of graphite under irradiation. A vast experimental literature exists for graphite on the dimensional change, mechanical properties, and thermal behavior. However, simulations have not been applied to the atomistic perspective. Remarkably few molecular dynamics simulations have been performed to study the irradiation response in graphite. In this paper, irradiation-induced damage cascades in graphite were investigated with molecular dynamics simulation. Statistical results of the graphite defects were obtained by sampling a wide energy range (1–30 KeV) and 10 different runs for every cascade simulation with different random number generator seeds to the velocity scaling thermostat function. The chemical bonding in carbon was described using the adaptive intermolecular reactive empirical bond-order potential (AIREBO) potential coupled with the standard Ziegler–Biersack–Littmack (ZBL) potential to describe close-range pair interactions. This study focused on analyzing the number of defects, the final cascade morphology and the distribution of defect clusters in space, the length-scale cascade properties such as the cascade length and the range of primary knock-on atom (PKA), and graphite mechanical properties’ variation. It can be concluded that the number of surviving Frenkel pairs increased remarkably with the increasing initial PKA energy but did not exhibit a thermal spike at slightly lower energies in this paper. The PKA range and cascade length approximately linearly with energy which indicated that increasing the PKA initial energy will come at expensive computation cost such as 30KeV in this study. The cascade morphology and the distribution of defect clusters in space mainly related to the PKA energy meanwhile the temperature effect was relatively negligible. The simulations are in agreement with known experimental results and the Kinchin-Pease model, which can help to understand the graphite damage cascades and lifetime span under irradiation and provide a direction to the designs of these kinds of structural materials in the future reactors.

Keywords: graphite damage cascade, molecular dynamics, cascade morphology, cascade distribution

Procedia PDF Downloads 151

Authors: Thomas Okechukwu Onah, Onyekachi Marcel Egwuagu

Abstract:

Zero-surface temperature, which controlled the cooling profile, was modeled and used to investigate the effect of process parameters on the hot-rolled steel plates. The parameters include impingement gaps of 40mm to 70mm; pipe diameters of 20mm to 45mm feeding jet nozzle with 30 holes of 8mm diameters each; and flow rates within 2.896x10-⁶m³/s and 3.13x10-⁵m³/s. The developed simulation model of the Zero-Surface Temperature, upon validation, showed 99% prediction accuracy with dimensional homogeneity established. The evaluated Zero-Surface temperature of Controlled Water Jet Impingement Steel plates showed a high cooling rate of 36.31 Celsius degree/sec at an optimal cooling nozzle diameter of 20mm, impingement gap of 70mm and a flow rate of 1.77x10-⁵m³/s resulting in Reynold's number 2758.586, in the turbulent regime was obtained. It was also deduced that as the nozzle diameter was increasing, the impingement gap was reducing. This achieved a faster rate of cooling to an optimum temperature of 300oC irrespective of the starting surface cooling temperature. The results additionally showed that with a tested-plate initial temperature of 550oC, a controlled cooling temperature of about 160oC produced a film and nucleated boiling heat extraction that was particularly beneficial at the end of controlled cooling and influenced the microstructural properties of the test plates.

Keywords: temperature, mechanistic-model, plates, impingements, dimensionless-numbers

Procedia PDF Downloads 35

Authors: Emmanuel Iyamuremye

Abstract:

Extreme rainfall events have caused significant damage to agriculture, ecology, and infrastructure, disruption of human activities, injury, and loss of life. They also have significant social, economic, and environmental consequences because they considerably damage urban as well as rural areas. Early detection of extreme maximum rainfall helps to implement strategies and measures, before they occur, hence mitigating the consequences. Extreme value theory has been used widely in modeling extreme rainfall and in various disciplines, such as financial markets, the insurance industry, failure cases. Climatic extremes have been analyzed by using either generalized extreme value (GEV) or generalized Pareto (GP) distributions, which provides evidence of the importance of modeling extreme rainfall from different regions of the world. In this paper, we focused on Peak Over Thresholds approach, where the Poisson-generalized Pareto distribution is considered as the proper distribution for the study of the exceedances. This research also considers the use of the generalized Pareto (GP) distribution with a Poisson model for arrivals to describe peaks over a threshold. The research used statistical techniques to fit models that used to predict extreme rainfall in Kigali. The results indicate that the proposed Poisson-GP distribution provides a better fit to maximum monthly rainfall data. Further, the Poisson-GP models are able to estimate various return levels. The research also found a slow increase in return levels for maximum monthly rainfall for higher return periods, and further, the intervals are increasingly wider as the return period is increasing.

Keywords: exceedances, extreme value theory, generalized Pareto distribution, Poisson generalized Pareto distribution

Procedia PDF Downloads 134

Authors: Ashna Babu, Deepshikha Jaiswal Nagar

Abstract:

Cuprate high-temperature superconductors (HTSCs) have been immensely studied during the past few decades because of their structure which is described as a superlattice of superconducting CuO₂ layers. In particular, YBa₂Cu₃O₆₊δ (YBCO), with its critical temperature of 93 K, has received the most attention due to its well-defined metal stoichiometry and variable oxygen content that determines the carrier doping level. Substitution of metal ions at the Cu site is known to increase the critical current density without destroying superconductivity in YBCO. The construction of vortex phase diagrams is very important for such doped YBCO materials both from a fundamental perspective as well as from a technological perspective. By measuring field-dependent magnetization on annealed single crystals of Al-doped YBCO, YBa₂Cu₃₋ₓAlₓO₆₊δ (Al-YBCO), we were able to observe a second magnetization peak anomaly (SMP) in a very large part of the phase diagram. We were also able to observe the SMP anomaly in temperature-dependent magnetization measurements, the first observation to our knowledge. Critical current densities were calculated using Bean’s critical state model, flux jumps associated with symmetry reorientation of vortex lattice were studied, the oxygen cluster distribution was also analysed, and by incorporating all observations, we made a vortex phase diagram for oxygenated Al-YBCO single crystal.

Keywords: oxygen deficient clusters, second magnetization peak anomaly, flux jumps, vortex phase diagram

Procedia PDF Downloads 63

Authors: Rajinder Kaur, Atul Khanna

Abstract:

Transparent glass-ceramic and crystalline samples of the system: xSrO-(100-x)TeO2; x = 7.5 and 8.5 mol% were prepared by quenching the melts in the temperature range of 700 to 950oC. A very interesting effect of the temperature on the glass-forming ability (GFA) of strontium tellurite melts is observed,and it is found that the melts produce transparent glass-ceramics when it is solidified from lower temperatures in the range of 700-750oC, however, when the melts are cooled from higher temperatures in the range of 850-950oC, the GFA is significantly reduced andanti-glass and/or crystalline phases are produced on solidification.The effect of temperature on GFA of strontium tellurite melts is attributed to short-range structural transformations: TeO₄TeO₃ which procceds towards the right side with an increrase in temperature. This isomerization reaction lowers the melt viscosity and enhances the crystallization tedendency. It is concluded that the high-temperature strontium tellurite meltsfreeze faster into crystalline phases as compared to the melts at a lower temperature; the latter supercooland solidify into glassy phases.

Keywords: anti-glasss, ceramic, supercool liquid, raman spectroscopy

Procedia PDF Downloads 76

Authors: Han Joo Choe, Soon-Ho Kwon, Jung-Joong Lee

Abstract:

Tin particles of various size and distribution were self-assembled by plasma treating tin film deposited on silicon oxide substrates. Plasma treatment was conducted using an inductively coupled plasma (ICP) source. A range of ICP power and topographic templated substrates were evaluated to observe changes in particle size and particle distribution. Scanning electron microscopy images of the particles were analyzed using computer software. The evolution of tin film dewetting into particles initiated from the hole nucleation in grain boundaries. Increasing ICP power during plasma treatment produced larger number of particles per area and smaller particle size and particle-size distribution. Topographic templates were also effective in positioning and controlling the size of the particles. By combining the effects of ICP power and topographic templates, particles of similar size and well-ordered distribution were obtained.

Keywords: dewetting, particles, plasma, tin

Procedia PDF Downloads 252

Authors: K. AlJimaz, A. Abdullah, A. Abdulsalam, K. Ebdah, A. Abdalrasheed

Abstract:

Understanding flow distribution and head losses is essential to design and calculate Thermo fluid parameters in order to reduce the pressure to a certain required pressure. This paper discusses the ways acquired in design and simulation to create and design an impedance box that reduces pressure. It's controlled by specific scientific principles such as Bernoulli’s principle and conservation of mass. In this paper, the design is made using SOLIDWORKS, and the simulation is done using ANSYS software to solve differential equations and study the parameters in the 3D model, also to understand how the design of this box reduced the pressure. The design was made so that fluid enters at a certain pressure of 3000 Pa in a single inlet; then, it exits from six outlets at a pressure of 300 Pa with respect to the conservation of mass principle. The effect of the distribution of flow and the head losses has been noticed that it has an impact on reducing the pressure since other factors, such as friction, were neglected and also the temperature, which was constant. The design showed that the increase in length and diameter of the pipe helped to reduce the pressure, and the head losses contributed significantly to reduce the pressure to 10% of the original pressure (from 3000 Pa to 300 Pa) at the outlets.

Keywords: box, pressure, thermodynamics, 3D

Procedia PDF Downloads 81