Search results for: soil temperature

Authors: Elif Aykin Dincer, Mustafa Erbas

Abstract:

The vacuum drying behavior of beef slices (10 x 4 x 0.2 cm3) was experimentally investigated at the temperature of 60, 70, and 80°C under 25 mbar ultimate vacuum pressure and the mathematical models (Lewis, Page, Midilli, Two-term, Wangh and Singh and Modified Henderson and Pabis) were used to fit the vacuum drying of beef slices. The increase in drying air temperature resulted in a decrease in drying time. It took approximately 206, 180 and 157 min to dry beef slices from an initial moisture content to a final moisture content of 0.05 kg water/kg dry matter at 60, 70 and 80 °C of vacuum drying, respectively. It is also observed that the drying rate increased with increasing drying temperature. The coefficients (R2), the reduced chi-square (x²) and root mean square error (RMSE) values were obtained by application of six models to the experimental drying data. The best model with the highest R2 and, the lowest x² and RMSE values was selected to describe the drying characteristics of beef slices. The Page model has shown a better fit to the experimental drying data as compared to other models. In addition, the effective moisture diffusivities of beef slices in the vacuum drying at 60 - 80 °C varied in the range of 1.05 – 1.09 x 10-10 m2/s. Consequently, this results can be used to simulate vacuum drying process of beef slices and improve efficiency of the drying process.

Keywords: beef slice, drying models, effective diffusivity, vacuum

Procedia PDF Downloads 289

Authors: Tauhidur Rahman, Subhrajit Pathak

Abstract:

In this study, structural response of Bhairabi-Sairang Tunnel due to presence of seismic faults has been thoroughly examined. There may be several active faults located in and around the project. Faults are the key seismic sources from where earthquakes are originated. The magnitude of earthquake will depend on the length of the fault. A long fault more than 200 km can produce earthquake of magnitude (Mw ) more than 8.0 and smaller length less than 10 km will produce small magnitude earthquake. Now-a-days it is very much essential to identify the distance and length of a fault from the project site. Based on this, in the present paper, a case study of the Bhairabi Sairang Tunnel of 1.73 Km length located in the North Eastern Region of India has been selected to calculate the seismic hazard from the surrounding effect of faults. A comparative study of seismic hazard at the tunnel site has been made based on the location of faults with the seismic hazard obtained from the Indian Standards code of Practice. In this paper, a practical problem of a tunnel has been analysed based on the available faults around the project site accounting the soil factor.

Keywords: seismic hazard, effect of fault, soil factor, Bhairabi Sairang tunnel

Procedia PDF Downloads 566

Authors: Rachel Danielson, Brendan Bohannan, S.M. Tsai, Kyle Meyer, Jorge L.M. Rodrigues

Abstract:

The Amazon Rainforest is a global diversity hotspot and crucial carbon sink, but approximately 20% of its total extent has been deforested- primarily for the establishment of cattle pasture. Understanding the impact of this large-scale disturbance on soil microbial community composition and activity is crucial in understanding potentially consequential shifts in nutrient or greenhouse gas cycling, as well as adding to the body of knowledge concerning how these complex communities respond to human disturbance. In this study, surface soils (0-10cm) were collected from three forests and three 45-year-old pastures in Rondonia, Brazil (the Amazon state with the greatest rate of forest destruction) in order to determine the impact of forest conversion on microbial communities involved in nitrogen fixation. Soil chemical and physical parameters were paired with measurements of microbial activity and genetic profiles to determine how community composition and process rates relate to environmental conditions. Measuring both the natural abundance of 15N in total soil N, as well as incorporation of enriched 15N2 under incubation has revealed that conversion of primary forest to cattle pasture results in a significant increase in the rate of nitrogen fixation by free-living diazotrophs. Quantification of nifH gene copy numbers (an essential subunit encoding the nitrogenase enzyme) correspondingly reveals a significant increase of genes in pasture compared to forest soils. Additionally, genetic sequencing of both nifH genes and transcripts shows a significant increase in the diversity of the present and metabolically active diazotrophs within the soil community. Levels of both organic and inorganic nitrogen tend to be lower in pastures compared to forests, with ammonium rather than nitrate as the dominant inorganic form. However, no significant or consistent differences in total, extractable, permanganate-oxidizable, or loss-on-ignition carbon are present between the two land-use types. Forest conversion is associated with a 0.5- 1.0 unit pH increase, but concentrations of many biologically relevant nutrients such as phosphorus do not increase consistently. Increases in free-living diazotrophic community abundance and activity appear to be related to shifts in carbon to nitrogen pool ratios. Furthermore, there may be an important impact of transient, low molecular weight plant-root-derived organic carbon on free-living diazotroph communities not captured in this study. Preliminary analysis of nitrogenase gene variant composition using NovoSeq metagenomic sequencing indicates that conversion of forest to pasture may significantly enrich vanadium-based nitrogenases. This indication is complemented by a significant decrease in available soil molybdenum. Very little is known about the ecology of diazotrophs utilizing vanadium-based nitrogenases, so further analysis may reveal important environmental conditions favoring their abundance and diversity in soil systems. Taken together, the results of this study indicate a significant change in nitrogen cycling and diazotroph community composition with the conversion of the Amazon Rainforest. This may have important implications for the sustainability of cattle pastures once established since nitrogen is a crucial nutrient for forage grass productivity.

Keywords: free-living diazotrophs, land use change, metagenomic sequencing, nitrogen fixation

Procedia PDF Downloads 194

Authors: Pulcherie Matsodoum Nguemte, Adrien Wanko Ngnien, Guy Valerie Djumyom Wafo, Ives Magloire Kengne Noumsi, Pierre Francois Djocgoue

Abstract:

The identification of plant species with the capacity to grow on hydrocarbon-polluted soils is an essential step for phytoremediation. In view of developing phytoremediation in Cameroon, floristic surveys have been conducted in 4 cities (Douala, Yaounde, Limbe, and Kribi). In each city, 13 hydrocarbon-polluted, as well as unpolluted sites (control), have been investigated using quadrat method. 106 species belonging to 76 genera and 30 families have been identified on hydrocarbon-polluted sites, unlike the control sites where floristic diversity was much higher (166 species contained in 125 genera and 50 families). Poaceae, Cyperaceae, Asteraceae and Amaranthaceae have higher taxonomic richness on polluted sites (16, 15,10 and 8 taxa, respectively). Shannon diversity index of the hydrocarbon-polluted sites (1.6 to 2.7 bits/ind.) were significantly lower than the control sites (2.7 to 3.2 bits/ind.). Based on a relative frequency > 10% and abundance > 7%, this study highlights more than ten plants predisposed to be effective in the cleaning-up attempts of soils contaminated by hydrocarbons. Based on the floristic indicators, 6 species (Eleusine indica (L.) Gaertn., Cynodon dactylon (L.) Pers., Alternanthera sessilis (L.) R. Br. ex DC †, Commelinpa benghalensis L., Cleome ciliata Schum. & Thonn. and Asystasia gangetica (L.) T. Anderson) were selected for a study to determine their capacity to remediate a soil contaminated with fuel oil (82.5 ml/ kg of soil). The experiments lasting 150 days takes into account three modalities - Tn: uncontaminated soils planted (6) To contaminated soils unplanted (3) and Tp: contaminated soil planted (18) – randomized arranged. 3 on 6 species (Eleusine indica, Cynodon dactylon, and Alternanthera sessilis) survived the climatic and soil conditions. E. indica presents a significantly higher growth rate for density and leaf area while C. dactylon had a significantly higher growth rate for stem size and leaf numbers. A. sessilis showed stunted growth and development throughout the experimental period. The species Eleusine indica (L.) Gaertn. and Cynodon dactylon (L.) Pers. can be qualified as polluo-tolerant plant species; polluo-tolerance being the ability of a species to survive and develop in the midst subject to extreme physical and chemical disturbances.

Keywords: Cameroon, cleaning-up, floristic surveys, phytoremediation

Procedia PDF Downloads 243

Authors: Flur R. Ismagilov, Irek Kh. Khayrullin, Vyacheslav E. Vavilov, Ruslan D. Karimov, Anton S. Gorbunov, Danis R. Farrakhov

Abstract:

The paper presents another structural scheme of high-temperature starter-generator with external rotor to be installed on High Pressure Shaft (HPS) of aircraft engines (AE) to implement More Electrical Engine concept. The basic materials to make this starter-generator (SG) were selected and justified. Multi-criteria optimization of the developed structural scheme was performed using a genetic algorithm and Pareto method. The optimum (in Pareto terms) active length and thickness of permanent magnets of SG were selected as a result of the optimization. Using the dimensions obtained, allowed to reduce the weight of the designed SG by 10 kg relative to a base option at constant thermal loads. Multidisciplinary computer simulation was performed on the basis of the optimum geometric dimensions, which proved performance efficiency of the design. We further plan to make a full-scale sample of SG of HPS and publish the results of its experimental research.

Keywords: high-temperature starter-generator, more electrical engine, multi-criteria optimization, permanent magnet

Procedia PDF Downloads 368

Authors: Sadegh Sadeghi, Negar Shabani

Abstract:

From a thermal point of view, zeotropic mixtures are likely to be more efficient than azeotropic fluids in low-temperature thermodynamic cycles due to their suitable boiling characteristics. In this study, performance of a low-temperature Kalina cycle with R717/water working fluid used in different existing power plants is mathematically investigated. To analyze the behavior of the cycle, mass conservation, energy conservation, and exergy balance equations are presented. With regard to the similarity in molar mass of R717 (17.03 gr/mol) and water (18.01 gr/mol), there is no need to alter the size of Kalina system components such as turbine and pump. To optimize the cycle energy and exergy efficiencies simultaneously, a constrained multi-objective optimization is carried out applying an Artificial Bee Colony algorithm. The main motivation behind using this algorithm lies on its robustness, reliability, remarkable precision and high–speed convergence rate in dealing with complicated constrained multi-objective problems. Convergence rates of the algorithm for calculating the optimal energy and exergy efficiencies are presented. Subsequently, due to the importance of exergy concept in Kalina cycles, exergy destructions occurring in the components are computed. Finally, the impacts of pressure, temperature, mass fraction and mass flow rate on the energy and exergy efficiencies are elaborately studied.

Keywords: artificial bee colony algorithm, binary zeotropic mixture, constrained multi-objective optimization, energy efficiency, exergy efficiency, Kalina cycle

Procedia PDF Downloads 153

Authors: Anna Drzewicz, Marzena Tykarska

Abstract:

The chiral liquid crystal phases form the helicoidal structure, which is characterized by the helical pitch and the helical twist sense. In anticlinic smectic phase with antiferroelectric properties three types of helix temperature dependence have been obtained: increased helical pitch with temperature and right-handed helix, decreased helical pitch with temperature and left-handed helix and the inversion of both. The change of helical twist sense may be observed during the transition from one liquid crystal phase to another or within one phase for the same substance. According to Gray and McDonnell theory, the helical handedness depends on the absolute configuration of the assymetric carbon atom and its position related to the rigid core of the molecule. However, this theory does not explain the inversion of helical twist sense phenomenon. It is supposed, that it may be caused by the presence of different conformers with opposite handendess, which concentration may change with temperature. In this work, the inversion of helical twist sense in the chiral liquid crystals differing in the length of alkyl chain, in the substitution the benzene ring by fluorine atoms and in the type of helix handedness was tested by vibrational spectroscopy (infrared and raman spectroscopy) and by nuclear magnetic resonance spectroscopy. The results obtained from the vibrational spectroscopy confirm the presence of different conformers. Moreover, the analysis of nuclear magnetic resonance spectra is very useful to check, on which structural fragments the change of conformations are important for the change of helical twist sense.

Keywords: helical twist sense, liquid crystals, nuclear magnetic resonance spectroscopy, vibrational spectroscopy

Procedia PDF Downloads 282

Authors: B. Vinod, L. Jsudev

Abstract:

Natural fibers as reinforcement in polymer matrix material is gaining lot of attention in recent years, as they are light in weight, less in cost, and ecologically advanced surrogate material to glass and carbon fibers in composites. Natural fibers like jute, sisal, coir, hemp, banana etc. have attracted substantial importance as a potential structural material because of its attractive features along with its good mechanical properties. Cryogenic applications of natural fiber reinforced polymer composites like cryogenic wind tunnels, cryogenic transport vessels, support structures in space shuttles and rockets are gaining importance. In these unique cryogenic applications, the requirements of polymer composites are extremely severe and complicated. These materials need to possess good mechanical and physical properties at cryogenic temperatures such as liquid helium (4.2 K), liquid hydrogen (20 K), liquid nitrogen (77 K), and liquid oxygen (90 K) temperatures, etc., to meet the high requirements by the cryogenic engineering applications. The objective of this work is to investigate the mechanical behavior of hybrid hemp/jute fibers reinforced epoxy composite material at liquid nitrogen temperature. Hemp and Jute fibers are used as reinforcement material as they have high specific strength, stiffness and good adhering property and has the potential to replace the synthetic fibers. Hybrid hemp/jute fibers reinforced polymer composite is prepared by hand lay-up method and test specimens are cut according to ASTM standards. These test specimens are dipped in liquid nitrogen for different time durations. The tensile properties, flexural properties and impact strength of the specimen are tested immediately after the specimens are removed from liquid nitrogen container. The experimental results indicate that the cryogenic treatment of the polymer composite has a significant effect on the mechanical properties of this material. The tensile properties and flexural properties of the hybrid hemp/jute fibers epoxy composite at liquid nitrogen temperature is higher than at room temperature. The impact strength of the material decreased after subjecting it to liquid nitrogen temperature.

Keywords: liquid nitrogen temperature, polymer composite, tensile properties, flexural properties

Procedia PDF Downloads 338

Authors: J. Ramirez, A. Maldonado, M. de la L. Olvera

Abstract:

The effect of both the molar concentration of the starting solution and the substrate temperature on the electrical, morphological, structural and optical properties of chemically sprayed fluorine-doped zinc oxide (ZnO:F) thin films deposited on glass substrates, is analyzed in this work. All the starting solutions employed were aged for ten days before the deposition. The results show that as the molar concentration increases, a decrease in the electrical resistivity values is obtained, reaching the minimum in films deposited from a 0.4 M solution at 500°C. A further increase in the molar concentration leads to a very slight increase in the resistivity. On the other hand, as the substrate temperature is increased, the resistivity decreases and a tendency towards to minimum value is evidenced; taking the molar concentration as parameter, minimum values are reached at 500°C. The attain of ZnO:F thin films, with a resistivity as low as 7.8×10-3 Ώcm (sheet resistance of 130 Ώ/☐ and film thickness of 600 nm) measured in as-deposited films is reported here for the first time. The concurrent effect of the high molar concentration of the starting solution, the substrate temperature values used, and the ageing of the starting solution, which might cause polymerization of the zinc ions with the fluorine species, enhance the electrical properties. The structure of the films is polycrystalline, with a (002) preferential growth. Molar concentration rules the surface morphology as at low concentration an hexagonal and porous structure is developed changing to a uniform compact and small grain size surface in the films deposited with the high molar concentrations.

Keywords: zinc oxide, chemical spray, thin films, TCO

Procedia PDF Downloads 503

Authors: Si Abdallah Mayouf

Abstract:

In this work, the effects of the wavy surface on free convection heat transfer boundary layer flow between two parallel wavy plates have been studied numerically. The two plates are considered at a constant temperature. The equations and the boundary conditions are discretized by the finite difference scheme and solved numerically using the Gauss-Seidel algorithm. The important parameters in this problem are the amplitude of the wavy surfaces and the distance between the two wavy plates. Results are presented as velocity profiles, temperature profiles and local Nusselt number according to the important parameters.

Keywords: free convection, wavy surface, parallel plates, fluid dynamics

Procedia PDF Downloads 307

Authors: Anas Cherqui, Audrey Pecourt, Manuella Catterou, Candice Mazoyon, Hervé Demailly, Vivien Sarazin, Frédéric Dubois, Jérôme Duclercq

Abstract:

Aphids are pests that can cause severe yield losses in field crops. Chemical control is currently widely used to control aphids, but this method is increasingly controversial. The pea is able to recruit bacteria that are beneficial to its development, growth and health. However, the effects of this microbial recruitment on plant-insect interactions have generally been underestimated. This study investigated the interactions between Pisum sativum, key bacteria of pea rhizosphere (Rhizobium and Sphingomonas species) and the pea aphid, Acyrthosiphon pisum. We assessed the bottom-up effects of single and combined bacterial inoculations on pea plant health and subsequent aphid performance, as well as the top-down effects of aphid infestation on soil functionality. The presence of S. sediminicola or S. daechungensis limited the fecundity of the pea aphid without strongly affecting its feeding behaviour. Nevertheless, these bacteria limited the effect of A. pisum on the plant phenotype. In addition, the aphid infestation decreased the soil functionality, suggesting a potential strategy to hinder the recruitment of beneficial microorganisms.

Keywords: Acyrthosiphon pisum, Pisum sativum, Sphingomonas, rhizobium, EPG, productivity

Procedia PDF Downloads 22

Authors: Abdelghani Boucheham, Djoudi Bouhafs, Nabil Khelifati, Baya Palahouane

Abstract:

The main aim of this study is to investigate the low temperature internal gettering of manganese and chromium transition metals content in p-type multicrystalline silicon grown by Heat Exchanger Method (HEM). The minority carrier lifetime variation, the transition metal elements behavior, the sheet resistivity and the interstitial oxygen concentration after different temperatures annealing under N2 ambient were investigated using quasi-steady state photoconductance technique (QSSPC), secondary ion mass spectroscopy (SIMS), four-probe measurement and Fourier transform infrared spectrometer (FTIR), respectively. The obtained results indicate in the temperature range of 300°C to 700°C that the effective lifetime increases and reaches its maximum values of 28 μs at 500 °C and decreasing to 6 μs at 700 °C. This amelioration is due probably to metallic impurities internal gettering in the extended defects and in the oxygen precipitates as observed on SIMS profiles and the FTIR spectra. From 300 °C to 500 °C the sheet resistivity values rest unchanged at 30 Ohm/sq and rises significantly to reach 45 Ohm/sq for T> 500 °C.

Keywords: mc-Si, low temperature annealing, internal gettering, minority carrier lifetime, interstitial oxygen, resistivity

Procedia PDF Downloads 308

Authors: Riffat Kalsoom, Qurat-Ul-Ain Javed

Abstract:

Optical and dielectric properties of lithium niobates have made them the fascinating materials to be used in optical industry for device formation such as Q and optical switching. Synthesis of lithium niobates was carried out by solvothermal process with and without temperature fluctuation at 200°C for 4 hrs, and behavior of properties for different durations was also examined. Prepared samples of LiNbO₃ were examined in a way as crystallographic phases by using XRD diffractometer, morphology by scanning electron microscope (SEM), absorption by UV-Visible Spectroscopy and dielectric measurement by impedance analyzer. A structural change from trigonal to spherical shape was observed by changing the time of reaction. Crystallite size decreases by the temperature fluctuation and increasing reaction time. Band gap decreases whereas dielectric constant and dielectric loss was increased with increasing time of reaction. Trend of AC conductivity is explained by Joschner’s power law. Due to these significant properties, it finds its applications in devices, such as cells, Q switching and optical switching for laser and gigahertz frequencies, respectively and these applications depend on the industrial demands.

Keywords: lithium niobates, renewable energy devices, controlled structure, temperature fluctuations

Procedia PDF Downloads 131

Authors: Weber A. R. Souza, Andre A. N. Dantas, Marcio A. Medeiros, Rafaella F. Costa

Abstract:

The erosive processes are natural phenomena that cause changes in the soil continuously due to the actions of natural erosive agents and their speed can be intensified or retarded by factors such as climate, inclination, type of matrix rock, vegetation and anthropic activities, the latter being very relevant in occupied areas without planning and urban infrastructure. Inadequate housing sites associated with an inefficient urban drainage network and lack of vegetation cover potentiate the erosive processes that, over time, are gaining alarming proportions, as is the case of the erosion in Planaltina in Federal district, a Brazilian state in the central west. Thus, the aim of this work was to compare the use of Vetiver grass and Alfalfa as vegetation cover to slope protection. For that, a study was carried out in the scientific literature about the improvement of the soil properties provided by them and verification of the safety factor through the simulation of slopes with different heights and inclination using SLOPE / W software. The Vetiver grass presented little more satisfactory results than the Alfalfa, but these obtained results slightly closer to that of the vetiver grass in less time of planting.

Keywords: erosive processes, planting, slope protection, vegetation cover

Procedia PDF Downloads 180

Authors: Tsung-Yen Tsai, Naveen Bunekar, Ming Hsuan Chang, Wen-Kuang Wang, Satoshi Onda

Abstract:

The structure-property relationship and initiator effect on bulk polymerized poly(methyl methacrylate) (PMMA)–oragnomodified layered silicate nanocomposites was investigated. In this study, we used 2, 2'-azobis (4-methoxy-2,4-dimethyl valeronitrile and benzoyl peroxide initiators for bulk polymerization. The bulk polymerized nanocomposites’ morphology was investigated by X-ray diffraction and transmission electron microscopy. The type of initiator strongly influences the physiochemical properties of the polymer nanocomposite. The thermal degradation of PMMA in the presence of nanofiller was studied. 5 wt% weight loss temperature (T5d) increased as compared to pure PMMA. The peak degradation temperature increased for the nanocomposites. Differential scanning calorimetry and dynamic mechanical analysis were performed to investigate the glass transition temperature and the nature of the constrained region as the reinforcement mechanism respectively. Furthermore, the optical properties such as UV-Vis and Total Luminous Transmission of nanocomposites are examined.

Keywords: initiator, bulk polymerization, layered silicates, methyl methacrylate

Procedia PDF Downloads 292

Authors: Jingjing Lan, Jun Yu, Muthukumaraswamy Annamalai Arasu

Abstract:

This paper presents a digital non-linear pulse-width modulation (PWM) controller in a high-voltage (HV) buck-boost DC-DC converter for the piezoelectric transducer of the down-hole acoustic telemetry system. The proposed design controls the generation of output signal with voltage higher than the supply voltage and is targeted to work under high temperature. To minimize the power consumption and silicon area, a simple and efficient design scheme is employed to develop the PWM controller. The proposed PWM controller consists of serial to parallel (S2P) converter, data assign block, a mode and duty cycle controller (MDC), linearly PWM (LPWM) and noise shaper, pulse generator and clock generator. To improve the reliability of circuit operation at higher temperature, this design is fabricated with the 1.0-μm silicon-on-insulator (SOI) CMOS process. The implementation results validated that the proposed design has the advantages of smaller size, lower power consumption and robust thermal stability.

Keywords: DC-DC power conversion, digital control, high temperatures, pulse-width modulation

Procedia PDF Downloads 395

Authors: Abdelkader Nouri, M’hamed Bouslama, Faouzi Saidi, Hassan Maaref, Michel Gendry

Abstract:

Self-organized InAs quantum dots (QDs) have been grown on 3,1% InP (110) lattice mismatched substrate by Solid Source Molecular Beam Epitaxy (SSMBE). Stranski-Krastanov mode growth has been used to create self-assembled 3D islands on InAs wetting layer (WL). The optical quality depending on the temperature and power is evaluated. In addition, Atomic Force Microscopy (AFM) images shows inhomogeneous island dots size distribution due to temperature coalescence. The quantum size effect was clearly observed through the spectra photoluminescence (PL) shape.

Keywords: AFM, InAs QDs, PL, SSMBE

Procedia PDF Downloads 687

Authors: Jelvin Tom Sebastian, Vinod Yeldho Baby

Abstract:

In space, electronic devices are constantly attacked with radiation, which causes certain parts to fail or behave in unpredictable ways. To advance the thermal controllability for microsatellites, we need a new approach and thermal control system that is smaller than that on conventional satellites and that demand no electric power. Heat exchange inside the microsatellites is not that easy as conventional satellites due to the smaller size. With slight mass gain and no electric power, accommodating heat using phase change materials (PCMs) is a strong candidate for solving micro satellites' thermal difficulty. In other words, PCMs can absorb or produce heat in the form of latent heat, changing their phase and minimalizing the temperature fluctuation around the phase change point. The main restriction for these systems is thermal conductivity weakness of common PCMs. As PCM is having low thermal conductivity, it increases the melting and solidification time, which is not suitable for specific application like electronic cooling. In order to increase the thermal conductivity nanoparticles are introduced. Adding the nanoparticles in base PCM increases the thermal conductivity. Increase in weight concentration increases the thermal conductivity. This paper numerically investigates the thermal energy storage panel with nanoparticle enhanced phase change material. Silver nanostructure have increased the thermal properties of the base PCM, eicosane. Different weight concentration (1, 2, 3.5, 5, 6.5, 8, 10%) of silver enhanced phase change material was considered. Both steady state and transient analysis was performed to compare the characteristics of nanoparticle enhanced phase material at different heat loads. Results showed that in steady state, the temperature near the front panel reduced and temperature on NePCM panel increased as the weight concentration increased. With the increase in thermal conductivity more heat was absorbed into the NePCM panel. In transient analysis, it was found that the effect of nanoparticle concentration on maximum temperature of the system was reduced as the melting point of the material reduced with increase in weight concentration. But for the heat load of maximum 20W, the model with NePCM did not attain the melting point temperature. Therefore it showed that the model with NePCM is capable of holding more heat load. In order to study the heat load capacity double the load is given, maximum of 40W was given as first half of the cycle and the other is given constant OW. Higher temperature was obtained comparing the other heat load. The panel maintained a constant temperature for a long duration according to the NePCM melting point. In both the analysis, the uniformity of temperature of the TESP was shown. Using Ag-NePCM it allows maintaining a constant peak temperature near the melting point. Therefore, by altering the weight concentration of the Ag-NePCM it is possible to create an optimum operating temperature required for the effective working of the electronics components.

Keywords: carbon-fiber-reinforced polymer, micro/nano-satellite, nanoparticle phase change material, thermal energy storage

Procedia PDF Downloads 204

Authors: Eyuphan Manay

Abstract:

In this study, it was aimed to determine the convective heat transfer characteristics of water-based silicon dioxide nanofluids (SiO₂) with particle volume fractions of 0.2 and 0.4% vol. Nanofluids were tested in a plate type heat exchanger with six plates. Plate type heat exchanger was manufactured from stainless steel. Water was driven in the hot flow side, and nanofluids were driven in the cold flow side. The thermal energy of the hot water was taken by nanofluids. Effect of the inlet temperature of the hot water was investigated on heat transfer performance of the nanofluids while the inlet temperature of the nanofluids was fixed. In addition, the effects of the particle volume fraction and the cold flow rate on the performance of the system were tested. Results showed that increasing inlet temperature of the hot flow caused heat transfer to enhance. The suspended solid particles into the carrier fluid also remarkably enhanced heat transfer, and, an increase in the particle volume fraction resulted in an increase in heat transfer.

Keywords: heat transfer enhancement, SiO₂-water, nanofluid, plate heat exchanger

Procedia PDF Downloads 203

Authors: Agung Sugeng Widodo

Abstract:

Water boiling system (WBS) using conventional gas stove (CGS) is relatively inefficient unless its mechanism being considered. In this study, an addition of ceramic stove cover (CSC) to a CGS and the gap between CSC and pan have been assessed. Parameters as energy produced by fuel, CSC temperature and water temperature were used to analyze the performance of a CGS. The gaps were varied by 1 – 7 mm in a step of 1 mm. The results showed that a CSC able to increase the performance of a CGS significantly. In certain fuel rate of 0.75 l/m, the efficiency of a CGS obtained in a gap of 4 mm. The best efficiency obtained in this study was 46.4 % due to the optimum condition that achieved simultaneously in convection and radiation heat transfer processes of the heating system. CSC also indicated a good characteristic for covering heat release at the initially of WBS.

Keywords: WBS, CSC, CGS, efficiency, gap

Procedia PDF Downloads 268

Authors: L.L. Costa, A. M. G. Brito, S. Khan, L. Schaeffer

Abstract:

Microstructure resulting from the forging process is studied as a function of variables such as temperature, deformation, austenite grain size and cooling rate. The purpose of this work is to study the thermomechanical behavior of DIN 42CrMo4 (AISI 4140) steel maintained at the temperatures of 900°, 1000°, 1100° and 1200°C for the austenization times of 22, 66 and 200 minutes each and subsequently forged. These samples were quenched in water in order to study the austenite grain and to investigate the microstructure instead of quenching the annealed samples after forging they were cooled down naturally in the air. The morphologies and properties of the materials such as hardness; prepared by these two different routes have been compared. In addition to the forging experiments, the numerical simulation using the finite element model (FEM), microhardness profiles and metallography images have been presented. Forging force vs position curves has been compared with metallographic results for each annealing condition. The microstructural phenomena resulting from the hot conformation proved that longer austenization time and higher temperature decrease the forging force in the curves. The complete recrystallization phenomenon (static, dynamic and meta dynamic) was observed at the highest temperature and longest time i.e., the samples austenized for 200 minutes at 1200ºC. However, higher hardness of the quenched samples was obtained when the temperature was 900ºC for 66 minutes. The phases observed in naturally cooled samples were exclusively ferrite and perlite, but the continuous cooling diagram indicates the presence of austenite and bainite. The morphology of the phases of naturally cooled samples has shown that the phase arrangement and the previous austenitic grain size are the reasons to high hardness in obtained samples when temperature were 900ºC and 1100ºC austenization times of 22 and 66 minutes, respectively.

Keywords: austenization time, thermomechanical effects, forging process, steel AISI 4140

Procedia PDF Downloads 145

Authors: T. Nishido, S. Fukumoto

Abstract:

The functions of movable bearings decline due to corrosion and sediments. As the result, they cannot move or rotate according to the behaviors of girders. Because of the constraints, the bending moments are generated by the horizontal reaction forces and the heights of girders. Under these conditions, the authors obtained the following results by analysis and experiment. Tensile stresses due to the moments occurred at temperature fluctuations. The large tensile stresses on concrete slabs around the bearings caused cracks. Even if concrete slabs are newly replaced, cracks will come out again with function declined bearings. The functional declines of bearings are generally found by using displacement gauges. However the method is not suitable for long-term measurements. We focused on the change in the strains at the bearings and the lower flanges near them at temperature fluctuations. It was found that their strains were particularly large when the movements of the bearings were constrained. Therefore, we developed a long-term health monitoring wireless system with FBG (Fiber Bragg Grating) sensors which were attached to bearings and lower flanges. The FBG sensors have the characteristics such as non-electrical influence, resistance to weather, and high strain sensitivity. Such characteristics are suitable for long-term measurements. The monitoring system was inexpensive because it was limited to the purpose of measuring strains and temperature. Engineers can monitor the behaviors of bearings in real time with the wireless system. If an office is away from bridge sites, the system will save traveling time and cost.

Keywords: bridge bearing, concrete slab, 　FBG sensor, health monitoring

Procedia PDF Downloads 221

Authors: Ismail Rahama Adam Hamid

Abstract:

This paper presents the development of a thermal model for a flat, double-sided linear generator designed for use in free-piston engines. The study conducted in this paper examines the influence of temperature on the performance of the permeant magnet linear generator, an integral and pivotal component within the system. This research places particular emphasis on the Neodymium Iron Boron (NdFeB) permanent magnet, which serves as a source of magnetic field for the linear generator. In this study, an internal combustion engine that tends to produce heat is connected to a generator. Considering the temperatures rise from both the combustion process and the thermal contributions of current-carrying conductors and frictional forces. Utilizing Computational Fluid Dynamics (CFD) method, a thermal model of the (NdFeB) magnet within the linear generator is constructed and analyzed. Furthermore, the temperature field is examined to ensure that the linear generator operates under stable conditions without the risk of demagnetization.

Keywords: free piston engine, permanent magnet, linear generator, demagnetization, simulation

Procedia PDF Downloads 57

Authors: Chih Yuan Chen, Chien Chon Chen, Jin-Shyong Lin

Abstract:

The microstructure characterization of tempered nanocrystalline bainitic steel is investigated in the present study. It is found that two types of plastic relaxation, dislocation debris and nanotwin, occurs in the displacive transformation due to relatively low transformation temperature and high carbon content. Because most carbon atoms trap in the dislocation, high dislocation density can be sustained during the tempering process. More carbides only can be found in the high tempered temperature due to intense recovery progression.

Keywords: nanostructure bainitic steel, tempered, TEM, nano-twin, dislocation debris, accommodation

Procedia PDF Downloads 536

Authors: M. Hadji, N. Chiker, Y. Hadji, A. Haddad

Abstract:

In this paper, we report for the first time on the synthesis and characterization of novel MAX phases (Ti3SiC2, Ti2AlC) reinforced Ni-matrix and Ti2AlC reinforced Al-matrix. The stability of MAX phases in Al-matrix and Ni-matrix at a temperature of 985°C has been investigated. All the composites were cold pressed and sintered at a temperature of 985°C for 20min in H2 environment, except (Ni/Ti3SiC2) who was sintered at 1100°C for 1h.Microstructure analysis by scanning electron microscopy and phase analysis by X-Ray diffraction confirmed that there was minimal interfacial reaction between MAX particles and Ni, thus Al/MAX samples shown that MAX phases was totally decomposed at 985°C.The Addition of MAX enhanced the Al-matrix and Ni-matrix.

Keywords: MAX phase, microstructures, composites, hardness, SEM

Procedia PDF Downloads 347

Authors: Athina Puype, Lorenzo Malerba, Nico De Wispelaere, Roumen Petrov, Jilt Sietsma

Abstract:

Reduced Activation Ferritic/Martensitic (FM) steels like EUROFER are of interest for first wall application in the future demonstration (DEMO) fusion reactor. Depending on the final design codes for the DEMO reactor, the first wall material will have to function in low-temperature mode or high-temperature mode, i.e. around 250-300°C of above 550°C respectively. However, the use of RAFM steels is limited up to a temperature of about 550°C. For the low-temperature application, the material suffers from irradiation embrittlement, due to a shift of ductile-to-brittle transition temperature (DBTT) towards higher temperatures upon irradiation. The high-temperature response of the material is equally insufficient for long-term use in fusion reactors, due to the instability of the matrix phase and coarsening of the precipitates at prolonged high-temperature exposure. The objective of this study is to investigate the influence of thermal ageing for 1000 hrs and 4000 hrs on microstructural features and mechanical properties of lab-cast EUROFER. Additionally, the ageing behavior of the lab-cast EUROFER is compared with the ageing behavior of standard EUROFER97-2 and T91. The microstructural features were investigated with light optical microscopy (LOM), electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). Additionally, hardness measurements, tensile tests at elevated temperatures and Charpy V-notch impact testing of KLST-type MCVN specimens were performed to study the microstructural features and mechanical properties of four different F/M grades, i.e. T91, EUROFER97-2 and two lab-casted EUROFER grades. After ageing for 1000 hrs, the microstructures exhibit similar martensitic block sizes independent on the grain size before ageing. With respect to the initial coarser microstructures, the aged microstructures displayed a dislocation structure which is partially fragmented by polygonization. On the other hand, the initial finer microstructures tend to be more stable up to 1000hrs resulting in similar grain sizes for the four different steels. Increasing the ageing time to 4000 hrs, resulted in an increase of lath thickness and coarsening of M23C6 precipitates leading to a deterioration of tensile properties.

Keywords: ageing experiments, EUROFER, ferritic/martensitic steels, mechanical properties, microstructure, T91

Procedia PDF Downloads 261

Authors: Sandra K. Enriquez, Claudia Camargo, Jesús E. Olguín, Juan A. López, German Galindo

Abstract:

Currently companies have increased the number of disorders of cumulative trauma (CTDs), these are increasing significantly due to the Highly Repetitive Movements (HRM) performed in workstations, which causes economic losses to businesses, due to temporary and permanent disabilities of workers. This analysis focuses on the prevention of disorders caused by: repeatability, duration and effort; And focuses on reducing cumulative trauma disorders such as occupational diseases using sensory thermography as a noninvasive method, the above is to evaluate the injuries could have workers to perform repetitive motions. Objectives: The aim is to define rest periods or job rotation before they generate a CTD, this sensory thermography by analyzing changes in temperature patterns on wrists and elbows when the worker is performing HRM over a period of time 2 hours and 30 minutes. Information on non-work variables such as wrist and elbow injuries, weight, gender, age, among others, and work variables such as temperature workspace, repetitiveness and duration also met. Methodology: The analysis to 4 industrial designers, 2 men and 2 women to be specific was conducted in a business in normal health for a period of 12 days, using the following time ranges: the first day for every 90 minutes continuous work were asked to rest 5 minutes, the second day for every 90 minutes of continuous work were asked to rest 10 minutes, the same to work 60 and 30 minutes straight. Each worker was tested with 6 different ranges at least twice. This analysis was performed in a controlled room temperature between 20 and 25 ° C, and a time to stabilize the temperature of the wrists and elbows than 20 minutes at the beginning and end of the analysis. Results: The range time of 90 minutes working continuous and a rest of 5 minutes of activity is where the maximum temperature (Tmax) was registered in the wrists and elbows in the office, we found the Tmax was 35.79 ° C with a difference of 2.79 ° C between the initial and final temperature of the left elbow presented at the individual 4 during the 86 minutes, in of range in 90 minutes continuously working and rested for 5 minutes of your activity. Conclusions: It is possible with this alternative technology is sensory thermography predict ranges of rotation or rest for the prevention of CTD to perform HRM work activities, obtaining with this reduce occupational disease, quotas by health agencies and increasing the quality of life of workers, taking this technology a cost-benefit acceptable in the future.

Keywords: sensory thermography, temperature, cumulative trauma disorder (CTD), highly repetitive movement (HRM)

Procedia PDF Downloads 429

Authors: Yen-Hui Chen, Terry Walker

Abstract:

As the world experiences an energy crisis, investing in sustainable energy resources is a pressing mission for many countries. Microalgae-derived biodiesel has attracted intensive attention as an important biofuel, and microalgae Chlorella protothecoides lipid is recognized as a renewable source for microalgae-derived biodiesel production. Supercritical carbon dioxide (SC-CO₂) is a promising green solvent that may potentially substitute the use of organic solvents for lipid extraction; however, the efficiency of SC-CO₂ extraction may be affected by many variables, including temperature, pressure and extraction time individually or in combination. In this study, response surface methodology (RSM) was used to optimize the process parameters, including temperature, pressure and extraction time, on C. protothecoides lipid yield by SC-CO₂ extraction. A second order polynomial model provided a good fit (R-square value of 0.94) for the C. protothecoides lipid yield. The linear and quadratic terms of temperature, pressure and extraction time—as well as the interaction between temperature and pressure—showed significant effects on lipid yield during extraction. The optimal lipid yield from the model was predicted as the temperature of 59 °C, the pressure of 350.7 bar and the extraction time 2.8 hours. Under these conditions, the experimental lipid yield (25%) was close to the predicted value. The principal fatty acid methyl esters (FAME) of C. protothecoides lipid-derived biodiesel were oleic acid methyl ester (60.1%), linoleic acid methyl ester (18.6%) and palmitic acid methyl ester (11.4%), which made up more than 90% of the total FAMEs. In summary, this study indicated that RSM was useful to characterize the optimization the SC-CO₂ extraction process of C. protothecoides lipid yield, and the second-order polynomial model could be used for predicting and describing the lipid yield very well. In addition, C. protothecoides lipid, extracted by SC-CO₂, was suggested as a potential candidate for microalgae-derived biodiesel production.

Keywords: Chlorella protothecoides, microalgal lipids, response surface methodology, supercritical carbon dioxide extraction

Procedia PDF Downloads 444

Authors: Tadesse Menjetta, Daniel Dana, Serkadis Debalke

Abstract:

Schistosomiasis/Bilharziasis is one of the neglected tropical parasitic diseases caused by different species of genus Schistosoma. Among the species, S. mansoni (causative agents of intestinal schistosomiasis) is one of the causes of severe intestinal parasitic infections with high public and medical importance in Ethiopia. There is a scarcity of information about the status of S. mansoni infection among the fisherman in our study area and in the country at large. Therefore, this study was designed to determine the prevalence and risk factors of S.mansoni infection among fishermen at Lake Hawassa, southern Ethiopia. A cross-sectional study was conducted among the fishermen from April to June 2013 in Hawassa, Southern Ethiopia. A total of 243 fishermen were included by systematic sampling from the lists of the fishermen members in the registration book of fishermen associations in the Hawassa Town. Data on socio-demographic features and risk factors were collected by using semi-structured questionnaires. Stool samples were collected and processed using Kato-Katz thick smear techniques and examined between 30- 40 minute for hookworm and after 24 hours for S. mansoni and other soil-transmitted helminths (STHs). The overall prevalence of S.mansoni among the fishermen was 29.21% (71/243), and the mean intensity of infection was 158.88 egg per gram (EPG). The prevalence of intestinal helminths including S. mansoni was 69.54% (169/243). Moreover, the prevalence of soil-transmitted helminths (STHs) was 40.74% (99/243), 35.80% (87/243) and 5.76% (14/243) for A. lumbricoides, T. trichiura and hookworm species, respectively. Almost similar prevalence of S.mansoni, 31.82%, 31.75%, 31.94% were recorded in age groups of 15-19, 20-24 and 25-29 years, respectively. Fishermen who are swimming always were 2.92 times [95% CI: 1.554, 5.502] more likely to acquire S. mansoni infection than other water contacting habit of the study participants. The results of the current investigation indicated the moderate endemicity of S. mansoni among the fishermen at Lake Hawassa, southern Ethiopia. Fishermen could be the potential risk group for S. mansoni infection and might be responsible for the transmission of S. mansoni to other segments of the communities. Since the high prevalence of STH was recorded among the fishermen, integrated prevention and control strategies from different sectors might be important to tackle the problem.

Keywords: S. mansoni, soil transmitted helminths, fishermen, Lake Hawassa, Ethiopia

Procedia PDF Downloads 154

Authors: Anurita Selvarajoo, Svenja Hanson

Abstract:

Growing energy needs and increasing environmental issues are creating awareness for alternative energy which substitutes the non-renewable and polluting fossil fuels. Agricultural wastes are a good feedstock for biochar production through the pyrolysis process. There is potential to generate solid fuel from agricultural wastes, as there are large quantities of agricultural wastes available in Malaysia. This paper outlines the experimental study on the pyrolysis of banana peel. The effects of pyrolysis temperatures on the yield of biochar from the banana peel were investigated. Banana peel was pyrolysed in a horizontal tubular reactor under inert atmosphere by varying the temperatures between 300 and 700 0C. With increasing temperature, the total biochar yield decreased with increased heating value. It was found that the pyrolysis temperature had major effect on the yield of biochar product. It also exerted major influence on the heating value and C,H and O composition. The obtained biochar ranged between 31.9 to 56.7 %wt, at different pyrolysis temperatures. The optimum biochar yield was obtained at 325 0C. Biochar yield obtained at optimum temperature was 47 % wt with a heating value of 25.9 MJ kg-1. The study has been performed in order to demonstrate that agricultural wastes like banana peel are also important source of solid fuel.

Keywords: agricultural Wastes, banana peel, biochar, pyrolysis

Procedia PDF Downloads 297