Chemical Kinetic and High Fidelity Modeling of Transesterification

The modeling and simulation of transesterification require an understanding of the chemical reactions that take place inside the reactor. The development of reaction mechanism of the multiple step triglyceride, triglycerides and mono-glycerides and their reversal reaction is beyond the interest of chemical or mechanical engineers, whose main interests are to assess the conversion overall and to establish performance process metrics. This chapter undertakes the transesterification conversion by firstly establishing and formulating the overall process kinetics as far as the rate constant and activation energy. Secondly, use the obtained kinetic values to carry out high fidelity reactive flow of the multiple species which are co-present inside the reactor and otherwise complex to capture experimentally. Following these two steps, this work provides qualitative and quantitative information on the concentration of the reactants, intermediates and the overall yield. This two-step-approach can also be utilized as reactor design tool and gaining in-depth insight on reaction progress and species distribution. Experimental results, high-fidelity numerical results, and parametric sensitivity studies will be introduced and discussed

Comparison of energy storage options and detrmination of suitable technique for solar power systems

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.The efficiency and cost of renewable solar and wind power systems using intermittent resources could significantly be improved by developing low cost, high efficiency and more sustainable energy storage systems. A comparison study between energy storage options is presented in this paper. The energy storage options include: (1) electro chemical storage: lead acid, Li-ions, Nickel-Cadmium, Nickel metal hydride, Sodium Sulfur, and vanadium flow batteries; (2) electro-magnetic energy storage: super capacitors and super conducting magnetic energy storage; (3) hydrogen storage: onboard systems and utility scale; (4) mechanical storage: compressed air, flywheel, pumped hydro, spring (composite and metal), and (5) thermal energy storage. The resource intensities and operational parameters of the energy storage options are compared in this study. The main objective is to review the various types of storage techniques and their characteristics and to determine the most appropriate technique for solar and wind energy applications: energy storage system with suitable discharge time, lowest resource intensities, best operation performance and lowest cost. Based on the results obtained in this study, super capacitors, super conducting magnetic, and flywheel energy storage systems could be a good option for solar and wind applications: they offer fast discharging/charging times, greater performance (high specific power, high cycle efficiency, high cycle life and they) and are very attractive with respect to the operating costs.dc201

A Unified Approach for Taxonomy-based Technology Forecasting

For decision makers and researchers working in a technical domain, understanding the state of their area of interest is of the highest importance. For this reason, we consider in this chapter, a novel framework for Web-based technology forecasting using bibliometrics (i.e. the analysis of information from trends and patterns of scientific publications). The proposed framework consists of a few conceptual stages based on a data acquisition process from bibliographic online repositories: extraction of domainrelevant keywords, the generation of taxonomy of the research field of interests and the development of early growth indicators which helps to find interesting technologies in their first phase of development. To provide a concrete application domain for developing and testing our tools, we conducted a case study in the field of renewable energy and in particular one of its subfields: Waste-to-Energy (W2E). The results on this particular research domain confirm the benefit of our approach

New correlations for the average Nusselt number in squealer turbine blade tip

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Numerical simulations of the flow field and heat transfer of squealer blade tip are performed in this study. The effects of the Reynolds number, the clearance gap to width ratios (C/W = 5% -15%) and the cavity depth to width ratios (D/W = 10%-50%) on fluid flow and heat transfer characteristics are obtained. The temperature and velocity distributions inside the cavity, the local heat transfer coefficients, and the average Nusselt numbers for the pressure and suction sides of the turbine blade tip are determined. This paper presents the results of the effects of Reynolds number, clearance gap and width ratios on the Nusslet number for the pressure and suction sides of squealer turbine blade tip. The results show a good agreement with the experimental data obtained by Metzger and Bunker. New correlations for the average Nusselt numbers for turbine blade tip pressure and suction sides are presented.cf201

Numerical simulation of internal channel cooling via jet impingement in fluent and its sensitivity study

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Impinging jets against surface provide effective heat transfer in various industrial applications. It includes vast applications such as gas turbine cooling, rocket launcher cooling, heat treatment, cooling of electronic components, heating of optical surfaces for defogging, cooling of turbine components, cooling of critical machinery structures, and many other industrial processes. In this work, the numerical analysis of various heat transfer configurations of jet impingement on a semi-circular surface was studied. These heat transfer configurations were compared on the basis of effective heat transfer by achieving higher Nusselt number as convection is becoming the dominant phenomenon. The internal channel, on which analysis is performed, is a curved surface with a uniform heat flux. The numerical result obtained is favorably comparable with the experiment results. Furthermore, sensitivity study for various materials, configuration (geometry) and conditions was carried out to gain more insight on the underlining physics of the flow. Finally, the favorable application of inner cooling to turbine blade is numerically demonstrated.dc201

Hydrogen production from coal gasification using solar energy : Thermodynamic equilibrium modelling and exergy analysis

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.In this study the merits of hydrogen production using solar energy are discussed. The primary focus of the paper is to perform thermodynamics analysis of coal gasification via solar energy. Initially the chemical properties of coal are determined using proximate analysis, ultimate analysis and calorimeter. Using the coal properties a thermodynamics model bases on equilibrium constant approach is developed. The model is tested against the experimental data and further exergetic and cold gas efficiency is calculated. The effect of temperature and moisture contents is studied which shows that efficiency as high as 70% can be achieved with hydrogen yield of around 57% by volume. The model is further used to explore the potential of solar energy along with the partial combustion of coal. The result shows a sharp decline in the CO2 emission, while 43% increase in the yield of Hydrogen is calculated.dc201

Numerical Simulation of Tower Rotor Interaction for Downwind Wind Turbine

Downwind wind turbines have lower upwind rotor misalignment, and thus lower turning moment and self-steered advantage over the upwind configuration. In this paper, numerical simulation to the downwind turbine is conducted to investigate the interaction between the tower and the blade during the intrinsic passage of the rotor in the wake of the tower. The moving rotor has been accounted for via ALE formulation of the incompressible, unsteady, turbulent Navier-Stokes equations. The localized CP, CL, and CD are computed and compared to undisturbed flow evaluated by Panel method. The time history of the CP, aerodynamic forces (CL and CD), as well as moments were evaluated for three cross-sectional tower; asymmetrical airfoil (NACA0012) having four times the rotor's chord length, and two circular cross-sections having four and two chords lengths of the rotor's chord. 5%, 17%, and 57% reductions of the aerodynamic lift forces during the blade passage in the wake of the symmetrical airfoil tower, small circular cross-section tower and large circular cross-section tower were observed, respectively. The pronounced reduction, however, is confined to a short time/distance of three rotor chords. A net forward impulsive force is also observed on the tower due to the high speed rotor motion

Techno-economic analysis of the co-gasification of sewage sludge and petroleum coke

In this study, the co-gasification of sewage sludge and petroleum coke is assessed with equilibrium and numerical modeling. The gasification process of these binary wastes provides a potential pathway for waste management and environmental sustainability. First, the thermodynamic equilibrium approach is used to calculate the maximum cold gasification efficiency (CGE) at different mixture ratios in an attempt to narrow down and focus on the appropriate composition of the two kinds of feedstock within the entrained flow gasifier. Furthermore, a parametric study is conducted to show the gasification metrics, i.e., CGE and feedstock conversion, and the syngas composition at different gasification conditions. The equilibrium model is based on eight unknowns in the gasification product, namely, H2, CO, CO2, H2O, CH4, O2, Csolid, and the temperature, under variable O2 and H2O molar ratios. Using three elemental mass balances, four equilibrium (Csolid) constant relations, and energy balance, the mathematical model is developed. The model incorporates the solid unburnt carbon in the product species. The temperature of gasification is determined through an iterative process. Using the result of the equilibrium model, a high-fidelity reactive flow model that accounts for the reactor geometry and the devolatilization kinetics is developed. This model accounts for an extended set of reactions covering the char combustion, water and gas shifts, Boudouard and devolatilization. Finally, economic analysis is carried out to assess the conditions when such a process can be deemed to be profitable. The result of the model shows that the maximum CGE is achieved when all the solid carbon is converted into carbon monoxide with nearly all hydrogen present in the feedstock converted into hydrogen gas. The maximum conversion was attained with sewage sludge and petroleum coke ratio of 1 at 1,200°C. The mole fraction of the syngas species obtained is XH2 = 0.4227 and XCO = 0.5774 and a small fraction of XCH4 = 0.0123. Moreover, the cold gasification efficiency (CGE) measures 87.02% for the H2 and CO syngas species and reached 91.11% for the three species, including CH4. The gasification of the sewage sludge and petroleum coke at 50:50 is economically viable at temperatures higher than 950°C. A peak net gain of 0.16 $/kg of fuel blend was achieved at 1,250°C. At temperatures lower than 950°C, net losses were realized. This could be associated with less product gas yield, which is not significant enough to counteract the input costs. For instance, the net losses were −0.03 and −0.17$/kg of feedstock at 950 and 800°C, respectively

Influences Affecting Parental Acceptance of Rotavirus Vaccine

A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine.Objective: To evaluate factors contributing to the rotavirus vaccine parental hesitancy. We hypothesize that the greatest cause of hesitancy is the fear of intussusception. Identifying hesitancy factors will enable physicians to address concerns and help parents make informed decisions regarding the vaccine. Study Design: A comprehensive search was done for key words on PubMed and OvidSP. MeSH terms were combined and filters were utilized to find relevant primary articles. Articles were screened based on titles, abstracts, conclusions, and full texts. Last search was completed on August 25, 2016. Three additional articles were found through other resources and searching references. A total of 32 articles supported the background and 4 articles supported the analysis. Results: This Systematic Review identified key barriers that are still causing parental rotavirus vaccine hesitancy: fear of side effects, cost of rotavirus vaccine, vaccine not included in free public programs, not protecting against all diarrhea, given in three doses, child receiving enough vaccines, vaccine is not useful, not wanting to administer a live vaccine, newness of the vaccine, narrow window of age for the vaccine, immunity achieved from acquiring the virus itself, needing to evaluate data, producing a stronger mutated virus, preventing through holistic approaches, and a perceived lack of disease threat. Conclusion: Identifying hesitancy factors enables advancements in parental acceptance of the rotavirus vaccine through increasing parental awareness of disease burden, removing rotavirus vaccine age limits, and educating parents on vaccine myths. Limitations include a narrow number of databases used and filtering for English-only articles.This item is part of the College of Medicine - Phoenix Scholarly Projects 2020 collection. For more information, contact the Phoenix Biomedical Campus Library at [email protected]

Kinetic Study on Thermal Degradation of Crosslinked Polyethylene Cable Waste

Abstract Kinetic study of the pyrolysis of waste plastic is crucial in the design of an efficient and predictable thermochemical conversion system amidst the huge amount of plastic waste being rejected daily. Here, the chemical kinetics of cross-linked polyethylene under pyrolysis condition is conducted. The thermal degradation of the cross-linked LDPE/Si-XLPE was investigated under two different conditions: dynamic and isothermal heating. Moreover, two popular models of Kissinger and Flynn–Wall–Ozawa were used to infer the activation energy and pre-exponential constant during the dynamic heating at different heating rates. The isothermal conditions were tested at four different temperatures and reaction times based on the Arrhenius kinetic parameters. Thermo-gravimetric results showed the main region of weight loss occurs between 450 and 480 °C which corresponds to the highest conversion rate. The computed activation energies were 290.26 kJ/mole and 287.56 kJ/mole for Kissinger and Flynn–Wall–Ozawa models, respectively. The dynamic heating produced slightly different values than the one obtained from isothermal heating. This is because the kinetic parameters are highly dependent on the reaction time. These results suggest that Si-XLPE, which is commonly used in the cable industry, follows a similar behavior to the LDPE. This was demonstrated by the detailed analysis of the composition, melting point, thermal stability and thermal degradation