Papers by Sintayehu Mekuria Hailegiorgis
In this paper, unsteady flow of fractionalized Maxwell fluid over an inclined vertical plate is c... more In this paper, unsteady flow of fractionalized Maxwell fluid over an inclined vertical plate is considered by using thermo diffusion and slip effects. The flow model is solved using Constant proportional Caputo fractional derivative. Initially, the governing equations are made non-dimensional and then solved by Laplace transform. To see the impact of different flow parameters on the velocity, temperature and concentration, we have drawn some graphs. In addition, it is observed that magnetic field has decreasing effect on fluid motion whereas thermo-diffusion have increasing effect on fluid motion.
Biomass conversion and biorefinery, May 27, 2024
Journal of Molecular Liquids, 2018
Recently, magnetic nanoparticles have been considered to bacterial removal, due to monodisperse s... more Recently, magnetic nanoparticles have been considered to bacterial removal, due to monodisperse size, the ability of functionalization or modification. A novel amino-terminated poly (amidoamine) generation 5 (PAMAM-G5) functionalized Fe3O4/SiO2-GPTMS magnetic nanomaterial with a core-shell structure was developed. The nanocomposite was employed to determine antibacterial properties using paper disc diffusion, broth microdilution (Minimum Inhibitory Concentration -MIC and Minimum Bactericidal Concentration -MBC determination), adsorption, and surface plate count (Colony Forming Unit -CFU/ml) methods. The nanocomposite was characterized by FTIR, N2 adsorption/ desorption, Zeta potential, FE-SEM, TEM, EDX, DLS, XRD, TGA and VSM techniques. The impacts of different parameters including primary bacteria count, solution pH, reaction time and the nanocomposite dosage were studied. The nanocomposite cytotoxicity was investigated on AGS cell line by MTT assay. Nanocomposite was effective in preventing both bacterial strains growth. The MIC and MBC values for E. coli and S. aureus were determined 4 and 8 µg/ml and 16µg/ml for both strains respectively. Synthesized nanocomposite as antibacterial in an aqueous solution, was elimination effectiveness of 100 % for both selected bacteria in optimum condition (pH= 7, nanocomposite dosage = 16µg/ml, run time = 60 min, and initial bacteria count= 10 3 CFU/ml). FE-SEM analysis revealed morphological variations and the mechanism of killing and trapping the bacteria by nanocomposite. The nanocomposite cytotoxicity on the cell indicated the impact of exposure time and nanocomposite concentration. The reduction in cell viability in the concentration of 16µg/ml after 48 and 72 h treatment was shown to be 27.4 and 28.7%, respectively. The nanocomposite is able to reduce the E. coli and S. aureus count in drinking water, which meets the drinking water standards according to WHO guidelines.
Next materials, Apr 1, 2024
Journal of Nanomaterials, May 27, 2022
Lightweight materials play a vital role in many industries because of their weight reduction, cor... more Lightweight materials play a vital role in many industries because of their weight reduction, corrosion resistance, and formability. On the other hand, joining this alloy is a very tedious process for everyone in industries due to incompatibility in metallurgical properties. The thick intermetallic formation, porosity, and segregation of alloys in the weld are the possible causes during welding of dissimilar materials by the fusion welding process. Nowadays, these materials have been joined by solid-state welding friction stir welding. AA2024 and high carbon steel (HCS) were used for friction stir spot welding in this investigation. Tool rotational speed, plunge rate, plunge depth, and dwell time were the major influencing process parameters. Design of experiments and response surface methodology were used to optimize the process parameters to attain maximum lap shear strength of AA2024/HCS.
Article history: Received 17 April 2019 Received in revised form 3 July 2019 Accepted 11 Septembe... more Article history: Received 17 April 2019 Received in revised form 3 July 2019 Accepted 11 September 2019 Available online 28 October 2019 Unique physicochemical and barrier attributes of a biodegradable and sustainable polymer called poly (lactic acid) (PLA) is promising for various applications. Conversely, the issues related to the rigidity and fragility of this polymer that limits its wide usage needs to be inhibited. To surmount these shortcomings, various plasticizers have been incorporated into PLA to soften and make it useful for food packaging. In this research, tributyl citrate (TBC) was inserted as plasticizer into PLA matrix to modify its properties. The impact of varying TBC contents on the morphology, thermal and dynamic mechanical behaviour of PLA/TBC composites were evaluated. FESEM images of PLA composites revealed homogeneous fractured surfaces. The crystallinity of PLA/TBC composites was increased with the addition of plasticizer without altering its transparency. T...
Nucleation and Atmospheric Aerosols, 2017
In this study, the solubility of carbon dioxide (CO2) in the aqueous solution of piperazine (PZ) ... more In this study, the solubility of carbon dioxide (CO2) in the aqueous solution of piperazine (PZ) activated Nmethyldiethanolamine (MDEA) was investigated. In the aqueous solution the concentrations of the Nmethyldiethanolamine (MDEA) and piperazine (PZ) were kept constant at 30 wt. % and 3 wt. %, respectively. The solubility experiments were carried out between the temperatures ranges of 303.15 to 333.15 K. The pressure range was selected as 2-50 bar for solubility of carbon dioxide in the aqueous solution. The solubility of the CO2 is reported in terms of CO2 loading capacity of the solvent. The loading capacity of the solvent is the ratio between the numbers of moles of CO2 absorbed to the numbers of moles of solvent used. The experimental data showed that the CO2 loading increased with increase in CO2 partial pressure, while it decreased with increase in system's temperature. It was also observed from the experimental data that the higher pressure favors the absorption process while the increased temperature hinders the absorption process of CO2 capture. The loading capacity of the investigated solvent was compared with the loading capacity of the solvents reported in the literature. The investigated solvent showed better solubility in terms of loading capacity.
Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, 2020
Coffee is one of Indonesia's main commodity which competes in international market. However, Indo... more Coffee is one of Indonesia's main commodity which competes in international market. However, Indonesia's coffee production still faces some problems. One of the main problems is for the drying process. Moisture contents of coffee need to be reduced to 12%. All this time, most coffee producers use conventional method by using heat source from sunlight. However, uncertain weathers become one of the factors which slows down the drying process. Therefore, the purpose of this research is to find and utilize an alternative energy to solve the drying process problem. One of energy sources which is possible to be used for those criteria is geothermal energy especially with low enthalpy that usually is used for daily activities such as bathing, cooking, and warming houses. In this research, Heat Pipe Heat Exchanger (HPHE) which consists of 42 straight heat pipes with staggered configuration is used for utilizing geothermal energy. The heat pipe has a length of 700 mm OD 10 mm with filling ratio of 50% and added by 181 pcs of aluminum with dimension size of 76 x 345 x 0.105 mm as a fin. Geothermal fluid is simulated by water that heated by 9000 watt heater. Temperature of hot water with range of 50, 60, and 70˚C and air speed of 0.2, 0.4, 0.6 m/s are variations for the experiment. The result shows that the highest effectiveness of HPHE is 78.8% with the temperature of 70˚C and 0.2 m/s air speed while the lowest effectiveness is 68.8% with the temperature of 50˚C and 0.6 m/s air speed. Other than that, the drying process with the temperature of 70˚C and 0.6 m/s air speed is the fastest while the slowest is at 50˚C and air speed of 0.2 m/s. This result proves that increasing the temperature and air speed lead to the less time needed for the drying process.
Bioresource Technology Reports
Nano-Structures & Nano-Objects
Advances in Materials Science and Engineering
Silica has shown numerous applications in different fields such as environmental, biomedical, agr... more Silica has shown numerous applications in different fields such as environmental, biomedical, agriculture, and even in chemical processing. However, due to high energy-intensive and cost-effective issues, researchers show interest to replace the conventional methods with biobased environmentally-friendly techniques for biosilica production from renewable biomass sources. Generally, silica is found to be available in amorphous and crystalline structures. For commercial purposes, silica is produced from alkyl orthosilicates ore that consists of polyethlydiorthosilicate, tetraethyl ortothosilicate, and tetramethyl orthosilicate. Another form of silica, silica gel, is produced from the selected resources of biomass, such as palm tree, wheat straw, maize leaves, teff straw, sugarcane bagasse, rice husk, rice straw, sugarcane leaf, oat husk, bamboo leaf, and corn cob. The production of biobased silica gel from agricultural residues is found to be a sustainable which receives a significant...
Journal of Thermal Analysis and Calorimetry
Biomass energy is becoming the most promising renewable energy source as it can be used in variou... more Biomass energy is becoming the most promising renewable energy source as it can be used in various energy forms. One such use is the co-firing of pelletized biomass burnt with coal to minimize the impact of coal as an industrial energy source. In the present work, the effects of mixed torrefied pellet biomasses co-firing with coal were investigated. Corncob and khat stem were used as agriculture residues. The torrefied pellet of corncob and khat stem was co-fired with coal at temperatures of 766, 800, 850, 900, and 935 °C and residence times of 20, 60, 120, 180, and 220 s with pellet-to-coal ratios of 0.2, 0.25, 0.3, 0.4, and 0.45 g/g. The optimum parameters were investigated using central composite design (CCD) of response surface methodology. The combustion efficiency was profoundly enhanced in the range of 84.32-94.97% as the mixed torrefied pellet fraction increased from 20 to 30%. Statistical response surface optimizer exhibited that at a combustion temperature of 855 °C, a residence time of 177 s, and a torrefied pellet ratio of 0.33 g/g, the highest combustion efficiency of 93.22% was obtained. This study would be useful for proper design and operation of solid bio-fuel/coal co-firing combustion in the cement industries.
Heat pipes are heat transfer device that do not need externa l power; as a result, they are used ... more Heat pipes are heat transfer device that do not need externa l power; as a result, they are used in various thermal systems. Enhancing the performance of heat transfer device is a continues effort. Thus, this study investigates the effect of copper nanofluid on the thermal performance of cylindrical heat pipe (HP) that has screen mesh wick for heat transfer applications. The copper HP consists of 350 mm length and 12.7 mm outside diameter. To investigate its thermal performance mathematical model is developed. Demineralized water based 20 nm copper n anofluids with 0 to 4% particle concentrations were considered in the study. Simulation was done at 100 W heat input and results showed that when the particle concentra tion increases the evaporator wall temperature drops. At 4% particle concentration nanofluid the HP thermal resistance reduced by 17.5% compared to when the HP uses demineralized water. Furthermore, for a given particle concentration as the heat input increases the tempe...
International Journal of Chemical Engineering
This study was focused on the synthesis of activated carbon from a waste tire and the enhancement... more This study was focused on the synthesis of activated carbon from a waste tire and the enhancement of its specific area by a demineralization technique that can be used for the removal of methylene blue dye (MB). Maximum MB removal (89.41%) was attained at an impregnation ratio value of 0. A maximum yield (42.65%) was found at 48 h. Waste tire-based activated carbon (WTAC)'s ability to remove MB was increased by large values up to an impregnation time of 24 h. WTAC has a maximum MB removal of 90.13% at 4 M of KOH. The sample had a surface area of 53 m2/g. This sample was demineralized by using NaOH and H2SO4 in a 1 : 1 ratio, and the surface area was enhanced to 257 m2/g. In the demineralization process, a massive decrement of metals from the waste was seen; for each metal, namely, Zn2+, Al3+, Ca2+, and Mg2+, 43.79%, 32.45%, 27.95%, and 6.843% reductions were achieved, respectively. After this process, the maximum removal of MB was found at 1.2 g adsorbent dosage, 120 min, pH 8, ...
Naphtha and kerosene are mixed with Iraqi heavy crude oil at different concentrations rounded bet... more Naphtha and kerosene are mixed with Iraqi heavy crude oil at different concentrations rounded between (3-12) wt.%, in order to reduce viscosity to enhance its followability. This research investigated drag reduction (%Dr) in heavy oil mixtures at different flow rates (2 to 10 m 3 /hr) in temperature range 20-50°C. The experimental results proved that Naphtha offered 40% reduction in pressure drop. The Power law model was adopted in this study to empirically correlate fiction factor (f) and the percentage of drag reduction (%Dr) from experimental data for Reynolds number range (534-14695) and the concentration range from 3 to 12 wt.%.
The present research work investigated the removal efficiency of acid-activated bentonite blended... more The present research work investigated the removal efficiency of acid-activated bentonite blended with a sugarcane bagasse ash (SCBA) adsorbent for the removal of reactive red 198 (RR198) from a synthetic dye solution. The effect of the adsorption parameters of bentonite on SCBA blending ratio, dye solution pH, adsorption contact, adsorbent dosage, and initial dye concentration was investigated, and the parameters were optimized for maximum RR198 removal from the synthetic dye solution. At an optimum condition of 1:1 bentonite to the SCBA blending ratio, a solution pH of 2, 3.7 g/L of adsorbent dosage, and 15 mg/L of initial dye concentration 150 min of adsorption time, the properties of adsorbents such as adsorbent specific surface area, crystalline phase structure, functional groups, and surface morphologies of the adsorbents were investigated. At optimum conditions, 97% RR198 removal efficiency of the adsorbent was achieved. In order to determine adsorption kinetics and isotherm models, different adsorption models were employed. It was observed that the adsorption of the RR198 dye into the acid-activated bentonite blended with the SCBA adsorbent was represented well by the Langmuir isotherm model and the adsorption kinetics order was found to be the pseudo-second order.
Heat pipes are heat transfer device that do not need external power; as a result, they are used i... more Heat pipes are heat transfer device that do not need external power; as a result, they are used in various thermal systems. Enhancing the performance of heat transfer device is a continues effort. Thus, this study investigates the effect of copper nanofluid on the thermal performance of cylindrical heat pipe (HP) that has screen mesh wick for heat transfer applications. The copper HP consists of 350 mm length and 12.7 mm outside diameter. To investigate its thermal performance mathematical model is developed. Demineralized water based 20 nm copper nanofluids with 0 to 4% particle concentrations were considered in the study. Simulation was done at 100 W heat input and results showed that when the particle concentration increases the evaporator wall temperature drops. At 4% particle concentration nanofluid the HP thermal resistance reduced by 17.5% compared to when the HP uses demineralized water. Furthermore, for a given particle concentration as the heat input increases the temperature change between the evaporator and the condenser increases. The outcome of the investigation can be input to the design of solar heat exchangers that use HPs filled with nanofluids.
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Papers by Sintayehu Mekuria Hailegiorgis