Master of Science By Research
http://dl.lib.uom.lk/handle/123/743
2024-03-28T12:16:55ZDevelopment of a computational fluid dynamics model for pollutant dispersion in complex terrain
http://dl.lib.uom.lk/handle/123/21690
Development of a computational fluid dynamics model for pollutant dispersion in complex terrain
Sivakunalan I
This research investigated the issues of vehicular-emitted pollution in Kandy City, a
valley-like environment experiencing severe air pollution problems due to a higher
traffic volume, topographical aspect, and prevailing weather conditions. The COPERT
emission model was used to calculate the total emission rates of 𝑁𝑂
, 𝐶𝑂, and 𝑃𝑀 in
major road segments of the city. An OpenFOAM-based CFD model was developed to
predict dispersion characteristics over the complex terrain, considering physical phenomena
such as surface roughness, wind shear, Coriolis’s effect, surface heat flux,
buoyancy effect, and turbulence. The developed model was validated against experimental
results to investigate its sensitivity and efficiency, and it was found to show
good agreement.
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The developed CFD model was then applied to simulate the dispersion of vehiculargenerated
air pollutants in Kandy City, considering the region’s two main wind patterns
NE and SW, topography, and emission rates of major road segments. The model’s
concentration and dispersion pattern of pollutants were found to vary with urban topography
and wind pattern, with higher concentrations of pollutants observed in areas
with high traffic volume and severe traffic congestion, such as the central business district
and areas close to bus stands. The model was also used to investigate pollution
dispersion patterns in 27 locations at the pedestrian level, with good agreement found
between the model’s predicted concentrations of 𝑁𝑂
and experimental results.
Overall, this study highlights the significance of considering topography and me-
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teorological conditions when evaluating pollution dispersion mechanisms in urban environments.
The developed CFD model can be used as a promising tool for predicting
pollutant transport and wind flow in the built environment, aiding in proper urban
planning to reduce pollution accumulation in significant locations. This research
can contribute towards effective policies and interventions to mitigate the impacts of
vehicular-generated air pollution in valley cities.
2023-01-01T00:00:00ZAssessment of the feasibility of co-production of fucoxanthin, omega-3 fatty acids and bioethanol from marine microalgae
http://dl.lib.uom.lk/handle/123/18577
Assessment of the feasibility of co-production of fucoxanthin, omega-3 fatty acids and bioethanol from marine microalgae
Premarathne R G M M
The marine microalga Tisochrysis lutea is renowned for its ability to synthesize fucoxanthin and docosahexaenoic acid (DHA), which are nutritionally valuable high- value compounds. Although numerous studies in literature have assessed fucoxanthin and DHA production by T. lutea, very few have evaluated the feasibility of comprehensively utilizing biomass for co-production of these metabolites within the framework of biorefineries. To this end, the current study focused on the synthesis of fucoxanthin and DHA by cultivation of T. lutea under two different initial nitrate concentrations (1x: 882 μM, 3x: 2,646 μM) and three different illuminance levels (LL: 3,750 lux; ML: 7,500 lux; HL: 11,250 lux). The maximum fucoxanthin yield of 8.80 ± 0.30 mg/L (14.43 ± 0.52 mg/g) and DHA yield of 7.08 ± 0.02 mg/L (11.90 ± 0.14 mg/g) were achieved in the 3x HL culture at the end of 16 days of cultivation. Thereafter, a biphasic solvent extraction procedure using ethanol/n-hexane/water (10:9:1 v/v/v) was utilized for co-extraction of
97.96 ± 0.54% fucoxanthin and 74.11 ± 1.49% DHA from 3x HL biomass, and products were separated into two fractions. Fermentation of the residual biomass obtained from co- extraction resulted in a bioethanol yield of 48.49 ± 0.58 mg/g. Thus, results showcase the efficacy of the developed co-extraction procedure and the biorefinery potential of T. lutea.
2021-01-01T00:00:00ZInvestigation of the effect of preprocessing parameters on the efficacy of chlorophyll removal from mychonastes homospaera for biofuel production
http://dl.lib.uom.lk/handle/123/18511
Investigation of the effect of preprocessing parameters on the efficacy of chlorophyll removal from mychonastes homospaera for biofuel production
Kulasinghe KBYM
Microalgal lipids have become a potential candidate for biofuel production in recent years. High lipid accumulation and shorter doubling time enabling higher growth rate are foremost factors in microalgae to compete with first and second-generation biodiesel feedstocks. However, high levels of chlorophyll in feedstock limit its large-scale application. Chlorophyll makes oil more susceptible to photo-oxidation, decreases the storage stability, causes low-quality oil with a dull and dark color, and decreases the transesterification efficiency and combustion efficiency of biodiesel. This study aimed to develop a novel preprocessing method to identify the best solvent ratios, temperature, and reaction time for chlorophyll removal from the selected microalgae to synthesize high-quality biodiesel. Mychonastes homosphaera isolated from Beire Lake, Colombo, Sri Lanka with a doubling time, and the lipid accumulation of 2.89 d and 58 % (w/w) was selected for the study. The results indicated that the best solvent ratio (NaOH: ethanol), temperature, and reaction time were 7:3, 60 0C, and 90 min, respectively.
2021-01-01T00:00:00ZModelling the drying kinetics of microwave drying of coconut chips
http://dl.lib.uom.lk/handle/123/16940
Modelling the drying kinetics of microwave drying of coconut chips
Muhammed Aadhil MFH
Drying of coconut chips has been of interest for research due to the commercial value of coconut oil and desiccated coconut. More recently the industry has called for cost effective solutions for the drying unit operation of coconut chips used in the production of virgin coconut oil and desiccated coconut. This study was carried out to identify the parameters on which microwave assisted coconut drying kinetics were impacted and a mathematical model was developed to predict the microwave assisted drying behaviour of coconut chips. Drying time of coconut was found to depend on the microwave power and the mass loading when external parameters such as air velocity, air humidity, and shape factors of the coconut chips were kept constant. The drying behaviour was accurately predicted by several thin layer drying models and the Page model was selected due to its accuracy and simplicity. A new model was proposed to represent the parameters of the Page model as a function of microwave power. The proposed new model is given by, 𝑀𝑅=𝑒𝑥𝑝(𝑎.𝑒𝑥𝑝(𝑀𝑃).𝑡(𝑐.𝑃+0.6)) where, a = -0.07 min-1, M=37.29 Js-1 and c = 0.0007 sJ-1. Parameter t (time) needs to be substituted in minutes and P (power) in watts (W).
Moreover, the impact of mass loading was found to be effective only when the ratio of microwave power to mass loading (MPML) factor exceeded a value of about 3.7 Wg-1. Under this condition, the diffusivity per unit of microwave power was found as 1.31×10-11 m2s-1W-1. A sharp decrease in the drying rate was observed when the moisture content approached approximately 30 % (w/w dry basis), indicative of changing from the removal of free moisture to removal of bound moisture. The quality of the desiccated coconut and virgin coconut oil were analysed based on the standards stipulated by the Sri Lanka Standards Institute and Coconut Development Authority. A process development road map was proposed based on the drying kinetics, rehydration ratio, cooling time and maximum temperature to meet the quality requirements.
2020-01-01T00:00:00Z