The novel, cost and energy-efficient synthesis of carbon nanotubes (CNTs) by radio-frequency (RF) induction thermal plasma is a promising process for large scale production of CNTs for industrial and commercial applications. Techniques and conditions for producing larger quantities of CNTs have mainly depended on trial-and-error empirical variations of several operating parameters. Therefore, a detailed kinetic mechanism for CNT production in numerical simulations of an RF plasma system is required for understanding the process and identifying the parameters that mainly influence nanotube production. Such a model could also be used to enhance and optimize the design of synthesis systems. In this work, a two-dimensional axisymmetric model was constructed for a RF processing system for the production of CNTs. The plasma field was solved using a computational fluid dynamics (CFD) Eulerian frame of reference. The interactions between the plasma and injected feed particles were considered using momentum, heat and mass transfer source terms in the plasma field governing equations. The trajectory and temperature history of the injected particles into the plasma were computed using a Lagrangian method. The effects of plasma gas composition and the raw material feed rate in the system on the plasma thermo-fluid fields were studied. It was found that when 100% He sheath gas was employed, compared to an Ar-He mixture, the evaporation rate of the injected feedstock particles in the plasma increased due to the higher thermal conductivity of the He gas. Based on the raw material feed rate analysis, a higher loading rate of feedstock reduces down the plasma temperature along the injection zone and increases the average evaporation time of the feedstock in the plasma. A chemistry model for the formation of CNTs from feedstock material was implemented into an in-house two-dimensional axisymmetric parallelized CFD code. 36 elementary chemical reactions representing the formation of CNTs were numerically solved in the computational domain parallelized for execution on 64 Central Processing Units (CPUs). It was shown that the reaction rates of key reactions could be adjusted within their uncertainty range to improve the predicted yield of CNTs to within the yield rate reported from the experiments.

The novel, cost and energy-efficient synthesis of carbon nanotubes (CNTs) by radio-frequency (RF) induction thermal plasma is a promising process for large scale production of CNTs for industrial and commercial applications. Techniques and conditions for producing larger quantities of CNTs have mainly depended on trial-and-error empirical variations of several operating parameters. Therefore, a detailed kinetic mechanism for CNT production in numerical simulations of an RF plasma system is required for understanding the process and identifying the parameters that mainly influence nanotube production. Such a model could also be used to enhance and optimize the design of synthesis systems. In this work, a two-dimensional axisymmetric model was constructed for a RF processing system for the production of CNTs. The plasma field was solved using a computational fluid dynamics (CFD) Eulerian frame of reference. The interactions between the plasma and injected feed particles were considered using momentum, heat and mass transfer source terms in the plasma field governing equations. The trajectory and temperature history of the injected particles into the plasma were computed using a Lagrangian method. The effects of plasma gas composition and the raw material feed rate in the system on the plasma thermo-fluid fields were studied. It was found that when 100% He sheath gas was employed, compared to an Ar-He mixture, the evaporation rate of the injected feedstock particles in the plasma increased due to the higher thermal conductivity of the He gas. Based on the raw material feed rate analysis, a higher loading rate of feedstock reduces down the plasma temperature along the injection zone and increases the average evaporation time of the feedstock in the plasma. A chemistry model for the formation of CNTs from feedstock material was implemented into an in-house two-dimensional axisymmetric parallelized CFD code. 36 elementary chemical reactions representing the formation of CNTs were numerically solved in the computational domain parallelized for execution on 64 Central Processing Units (CPUs). It was shown that the reaction rates of key reactions could be adjusted within their uncertainty range to improve the predicted yield of CNTs to within the yield rate reported from the experiments.

The adhesion of solid wax ink droplets to porous polyethylene and Teflon substrates was studied experimentally. Wax droplets with a diameter of 3 mm and an initial temperature of 110°C were dropped onto test surfaces. As the mean pore diameter increases, the spreading reduces. Increasing the impact velocity maximizes the wetted area of the splat. The detachment force increased with droplet impact velocity. An analytical model was proposed to predict the force attaching the wax splat to the surface. The model comprises summation of two components: An adhesive component, calculated by multiplying the contact area between the splat and substrate by the strength of adhesion; and a cohesive component, calculated by multiplying the area of the pores into which wax penetrates by the ultimate tensile strength of wax. Predictions from the model agreed reasonably well with measurements.

The adhesion of solid wax ink droplets to porous polyethylene and Teflon substrates was studied experimentally. Wax droplets with a diameter of 3 mm and an initial temperature of 110°C were dropped onto test surfaces. As the mean pore diameter increases, the spreading reduces. Increasing the impact velocity maximizes the wetted area of the splat. The detachment force increased with droplet impact velocity. An analytical model was proposed to predict the force attaching the wax splat to the surface. The model comprises summation of two components: An adhesive component, calculated by multiplying the contact area between the splat and substrate by the strength of adhesion; and a cohesive component, calculated by multiplying the area of the pores into which wax penetrates by the ultimate tensile strength of wax. Predictions from the model agreed reasonably well with measurements.

The influence of periodic excitation from synthetic jet actuators, SJA, on boundary layer separation and reattachment over a NACA 0025 airfoil at a low Reynolds number is studied. All experiments reported are performed in a low-turbulence recirculating wind tunnel at a Reynolds number of 100000 and angle of attack of α=5◦. Mounted below the surface of the airfoil, the SJA consists of four 32.8 mm diameter piezoelectric ceramic diaphragms positioned in a single row. Flow visualization results show a reattachment of the boundary layer and a significant reduction in wake structure. Velocity profiles downstream of the trailing edge and the results show a drastic reduction in wake size as excitation is introduced. A spectral analysis was conducted in the wake region and showed the presence of vortex shedding at a frequency of 22 Hz. When excitation was applied at 935 Hz and 250 Vp−p, the shedding frequency shifted to 50Hz.

The influence of periodic excitation from synthetic jet actuators, SJA, on boundary layer separation and reattachment over a NACA 0025 airfoil at a low Reynolds number is studied. All experiments reported are performed in a low-turbulence recirculating wind tunnel at a Reynolds number of 100000 and angle of attack of α=5◦. Mounted below the surface of the airfoil, the SJA consists of four 32.8 mm diameter piezoelectric ceramic diaphragms positioned in a single row. Flow visualization results show a reattachment of the boundary layer and a significant reduction in wake structure. Velocity profiles downstream of the trailing edge and the results show a drastic reduction in wake size as excitation is introduced. A spectral analysis was conducted in the wake region and showed the presence of vortex shedding at a frequency of 22 Hz. When excitation was applied at 935 Hz and 250 Vp−p, the shedding frequency shifted to 50Hz.

Tissue engineering has emerged as a promising approach to repair, replace or regenerate damaged tissues using tissue constructs created in vitro. The standard procedure of the strategy to create a functional tissue is to seed cells on a 3-D biodegradable and biocompatible scaffold, to grow them under precisely controlled culture conditions provided by a bioreactor system, and to deliver the matured construct into the patient’s body to induce and direct the growth of the new and healthy tissue. In this thesis, a novel bioreactor system is designed and developed, which can provide uniaxial cyclic stretch to the tissue patch during culture process. The biostretch apparatus employs non-contact electromagnetic force to cyclically stretch a cell-seeded three-dimensional scaffold. The non-contact driving force and the specially designed mount allow researchers to use standard Petri dishes and commercially available CO2 incubators to culture an engineered tissue patch with precisely controlled strain. The device greatly simplifies the procedure to deliver mechanical stimulation during engineering a tissue patch. Since the applied mechanical stimulus is generated by a magnetic force, the engineered tissue construct is not only affected by a mechanical force, but also exposed to a magnetic field. Thus, the effects of the time-varying magnetic field during the culture process are investigated. The flux density of the field is modeled by COMSOL, and verified by a Gaussmeter. In addition, one side effect of using electromagnets, that of a temperature increase, is also investigated. The biomedical experiment results show that neither a weak low frequency magnetic field (0.1T, 1Hz) nor an increase of 1℃ in temperature has a significant effect on the cell culture. The performance of the designed apparatus is verified by the biomedical experiments from the aspects of cell proliferation and reorganization. Moreover, the mechanical parameters (strain distribution, strain rate, and stretch force) provided by the apparatus have also been quantitatively investigated.

Tissue engineering has emerged as a promising approach to repair, replace or regenerate damaged tissues using tissue constructs created in vitro. The standard procedure of the strategy to create a functional tissue is to seed cells on a 3-D biodegradable and biocompatible scaffold, to grow them under precisely controlled culture conditions provided by a bioreactor system, and to deliver the matured construct into the patient’s body to induce and direct the growth of the new and healthy tissue. In this thesis, a novel bioreactor system is designed and developed, which can provide uniaxial cyclic stretch to the tissue patch during culture process. The biostretch apparatus employs non-contact electromagnetic force to cyclically stretch a cell-seeded three-dimensional scaffold. The non-contact driving force and the specially designed mount allow researchers to use standard Petri dishes and commercially available CO2 incubators to culture an engineered tissue patch with precisely controlled strain. The device greatly simplifies the procedure to deliver mechanical stimulation during engineering a tissue patch. Since the applied mechanical stimulus is generated by a magnetic force, the engineered tissue construct is not only affected by a mechanical force, but also exposed to a magnetic field. Thus, the effects of the time-varying magnetic field during the culture process are investigated. The flux density of the field is modeled by COMSOL, and verified by a Gaussmeter. In addition, one side effect of using electromagnets, that of a temperature increase, is also investigated. The biomedical experiment results show that neither a weak low frequency magnetic field (0.1T, 1Hz) nor an increase of 1℃ in temperature has a significant effect on the cell culture. The performance of the designed apparatus is verified by the biomedical experiments from the aspects of cell proliferation and reorganization. Moreover, the mechanical parameters (strain distribution, strain rate, and stretch force) provided by the apparatus have also been quantitatively investigated.

Thermal spray coating processes have been employed in the current study to deposit well-adhered, dense skins onto the surfaces of open-cell metal foams. The result is a channel that consists of a metal foam core and a thermal sprayed skin wall that can be used as a compact heat-exchanger by directing the coolant flow through the foam. To study the feasibility of the metallic foam heat-exchangers, hydraulic and heat-transfer characteristics were investigated experimentally. The local wall and fluid temperature distribution and the pressure drop along the length of the heat exchanger were measured for different coolant flow velocities. The Dupuit-Forchheimer modification is employed with the experimental results to determine flow characteristics. To measure the heat transfer performance, a length average Nusselt number is derived from a volumetric heat transfer coefficient based on the local wall and fluid temperatures. Heat transfer was shown to have increased nearly 7 times compared to that of a channel without a foam core.

Thermal spray coating processes have been employed in the current study to deposit well-adhered, dense skins onto the surfaces of open-cell metal foams. The result is a channel that consists of a metal foam core and a thermal sprayed skin wall that can be used as a compact heat-exchanger by directing the coolant flow through the foam. To study the feasibility of the metallic foam heat-exchangers, hydraulic and heat-transfer characteristics were investigated experimentally. The local wall and fluid temperature distribution and the pressure drop along the length of the heat exchanger were measured for different coolant flow velocities. The Dupuit-Forchheimer modification is employed with the experimental results to determine flow characteristics. To measure the heat transfer performance, a length average Nusselt number is derived from a volumetric heat transfer coefficient based on the local wall and fluid temperatures. Heat transfer was shown to have increased nearly 7 times compared to that of a channel without a foam core.