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An examination of various methods for mass flow rate measurements was undertaken to evaluate their applicability for measuring refrigerant R-134a two-phase mass flow in refrigeration and air-conditioning equipment. An experimental apparatus was constructed to generate the required two-phase flow conditions. A turbine and a venturi flowmeter were used together with either a capacitance transducer or a gamma densitometer to determine the two-phase mass flow rate. The time-averaged void fraction was measured using a capacitance transducer and a gamma densitometer. Their measurements were in good agreement. Hence, for mass flow rate measurements, the capacitance transducer was used as the void fraction meter because of its ease of operation. A number of models were used to combine the output of either the turbine flowmeter or the venturi flowmeter, with the void fraction measurement to estimate the mass flow rate. It was found that, within the range of experimental data tested in the present work, the venturi flowmeter, in conjunction with Chisholm's model, provided the best agreement with the experimental results. / Thesis / Master of Engineering (MEngr)

A growing industry demand for smart pressure sensors that can be quickly calibrated to compensate for sensor drift, nonlinearity effects, and hysteresis without the need for expensive equipment has led to the development of a self-calibrating pressure sensor. Pressure sensor inaccuracies are often resolved with sensor calibration, which typically requires the use of laboratory equipment that can produce a known, standard pressure to actuate the sensor. The developed MEMS-based, self-calibrating pressure sensor is a piezoresistive-type sensor with a sensing element made from a silicon on insulator (SOI) wafer using deep reactive-ion etching to create a hollow reference cavity. Using a micro-heater to heat the small, air-filled reference cavity of the sensing element, a standard pressure is generated to actuate the sensor's pressure-sensitive membrane, creating a self-calibration effect. Previous work focused on modeling and improving the thermal performance of the sensor identified potential solutions to extend the sensor's calibration and operating range without increasing the micro-heater's power consumption. This report focuses on using a water liquid-to-vapor phase change inside the sensor's reference cavity to increase the sensor's effective range and response time without increasing power demands. A combination of Ansys Fluent CFD modeling and benchtop experiments were used to guide the development of the two-phase, self-calibrating pressure sensor. A two-phase benchtop testing rig was built to demonstrate the anticipated effects of a liquid-to-vapor phase change in a closed domain and to provide experimental data to anchor CFD models. Due to the complexity of modeling a phase-change within a closed domain with Ansys Fluent R21.1, the CFD modeling was performed in two stages. First, the two-phase benchtop rig was modeled, and validated using benchtop test data to verify the Volume of Fluid multiphase model setup in Ansys Fluent. Then, a 2D Ansys Fluent model of the self-calibrating pressure sensor's reference cavity using the validated multiphase model was made, demonstrating the potential temperature, pressure, and density gradients inside the reference cavity at steady state. Using the guidance from the benchtop testing and CFD modeling, a prototype two-phase, self-calibrating pressure sensor was fabricated with a water volume fraction of at least 0.1 in the reference cavity. Testing the prototype two-phase sensor showed that the addition of a water liquid-to-vapor phase change inside the sensor's reference cavity can nearly triple the sensor's effective range of operation and self-calibration without increasing the power consumption of the cavity micro-heater. / Master of Science / Highly sensitive pressure sensors are essential to many modern engineering applications. For a pressure sensor to be accurate and functional, it must be properly calibrated with a known, standard pressure range that overlaps with the sensor's intended operating range. Mechanical wear, material aging, and thermal effects all reduce a pressure sensor's accuracy over time, requiring recalibration which often involves expensive equipment and long downtimes. To eliminate the need for additional equipment and the removal of the pressure sensor from its use-site for calibration, the authors have developed a pressure sensor capable of self-calibration. The self-calibrating sensor uses a MEMS sensing element with an integrated micro-actuator in the form of a small heating element to create the standard pressure range necessary for calibration. Previous work focused on modeling the thermal performance of the sensor identified potential solutions to extend the sensor's calibration and operating range without increasing the micro-heater's power consumption. This report focuses on using a water liquid-to-vapor phase change inside the sensor's reference cavity to increase the sensor's effective range and response time without increasing power demands. To help guide the development of the two-phase, self-calibrating sensor, a benchtop testing rig and CFD model were used to examine the effects of heating a liquid inside of a closed domain. A 2D CFD model of the sensor's reference cavity was also used to provide insight into the expected temperature and pressure gradients inside the sensing element after heating with the micro-actuator. Using the guidance from the CFD models, a prototype two-phase, self-calibrating pressure sensor was fabricated. Testing the prototype two-phase sensor showed that the addition of a water liquid-to-vapor phase change inside the sensor's reference cavity can nearly triple the sensor's effective range of operation and self-calibration without increasing the power consumption of the cavity micro-heater.

In recent years two-phase catalysis has been established as a new field of catalyzed processes and has achieved industrial-scale importance in olefin hydroformylation. Two-phase reactions have a number of advantages, for example, ease of separation of catalyst and product, catalysts can be tailored to the particular problem, use of special properties and effects of water as a solvent, and low environmental impact. For higher olefins (* C6), the reaction suffers low activity due to low water solubility of higher olefins. Tricesium analog of TPPTS, m,m,m-trisulfonated triphenylphosphine, was synthesized and fully characterized. Two-phase olefin hydroformylation with Rh(acac)(CO)2 was investigated. The results indicated that both activity and selectivity (linear to branch aldehyde ratio) are similar to Rh/TPPTS system. The salt effect showed that increase the solution ionic strength will increase the selectivity and decrease the activity in the olefin hydroformylation with TPPTS. A new surface active phosphine, trisulfonated tris-m-(3henylpropyl)phenylphosphine, was synthesized and fully characterized. The results of biphasic olefin hydroformylation were consistent with aggregation of the ligand. The two phase 1-octene hydroformylation results showed that with only 3 methylene groups, there is no difference between the para and meta position of C3 group. A new chelating diphosphine, tetrasulfonated 2,2'-bis{di[p-(3 phenylpropyl)phenyl]phosphinomethyl}-1,1'-biphenyl,was prepared and fully characterized. Its application in two-phase hydroformylation of olefin showed enhanced activity and selectivity compared to the non-chelated phosphine analog. Finally, homogeneous asymmetric hydrogenation was carried out in the presence of a chiral surfactant in an attempt to affect asymmetric induction. The catalytic results showed that at a surfactant/Rh ratio of 25, the asymmetric hydrogenation of AACA-Me (a-Acetamidocinnamic Acid Methyl Ester) in methanol has no effect on asymmetric induction with the introduction of this chiral surfactant. / Master of Science

Tobacco has long been considered as a host to produce large quantities of high-valued recombinant proteins. However, dealing with large quantities of biomass with a dilute concentration of product is a challenge for down-stream processing. Aqueous two-phase extraction (ATPE) has been used in purifying proteins from various sources. It is a protein-friendly process and can be scaled up easily. ATPE was studied for its applicability to recombinant protein purification from tobacco using egg white lysozyme as the model protein. Separate experiments with polyethyleneglycol(PEG)/salt/tobacco extract, and PEG/salt/lysozyme were carried out to determine the partition behavior of tobacco protein and lysozyme, respectively. Two level fractional factorial designs were used to study the effects of factors such as PEG molecular weight, PEG concentration, the concentration of phase forming salt, sodium chloride concentration, and pH on protein partitioning. The results showed that PEG/sodium sulfate system was most suitable for lysozyme purification. Detailed experiments were conducted by spiking lysozyme into the tobacco extract. The conditions with highest selectivity of lysozyme over native tobacco protein were determined using a response surface design. The purification factor was further improved by decreasing the phase ratio along the tie line corresponding to the phase compositions with the highest selectivity. Under selected conditions the lysozyme yield was predicted to be 87% with a purification factor of 4 and concentration factor of 14. The binodial curve and tie line corresponding to the optimal condition for lysozyme recovery for the PEG 3400/sodium sulfate system were developed. The selectivity at the optimal condition was experimentally determined to be 47 with a lysozyme yield of 79.6 % with a purification factor of 10 and a concentration factor of 20. From this study, ATPE was shown to be suitable for initial protein recovery and partial purification from transgenic tobacco. / Master of Science

The surface active phosphine ((C6H4))C3H6((C6H4)S03 N+)3,1, aggregates in aqueous solution to form micelles. Light scattering experiments were used to determine the hydrodynamic radius of the aggregates. Fluorescence, conductivity, and surface tension experiments were used to measure the critical micelle concentration of these aggregates. Fluorescence experiments, using a quencher and probe analysis, show the number of particles per aggregate. Nuclear Magnetic Resonance (NMR) shows that these micelles are able to incorporate olefin within the hydrophobic region and are acting as phase transfer agents. / Master of Science

An experimental investigation was performed to study the details of flow in the tip clearance gap of a linear turbine blade cascade. The cascade was designed and built to be geometrically similar to the earlier VPI&SU cascade; however, the new cascade also had a tip gap (2.1 percent of blade height) and two endwall boundary layer bleeds upstream of the blade row. The boundary layer bleeds were designed to reduce secondary flow other than the tip gap leakage flow in the cascade, and they performed well. The cascade flow had an exit Reynolds number based on the axial chord of 4.5 x 10⁵. Static pressure measurements were made on the blades and on the endwall with particular attention given to the tip gap. Also, flow visualizations on the endwall and on the suction surface of the middle blade were performed. From the pressure measurements, a minimum static pressure coefficient of -6.85 (based on the freestream velocity head) was obtained along the bottom of the blade, near the tip gap inlet. Avena contracta was evident, also in the tip gap entrance region, and a contraction coefficient of 0.61 was calculated from measured data. Mixing occurred after the vena contracta with the static pressure across the tip gap exit being fairly uniform. The flow visualizations showed a separation and reattachment on the endwall under the blade and a tip gap leakage vortex in the passage. Models of the tip gap flow, based on potential flow theory and potential flow theory with mixing were discussed and developed. Potential flow theory accurately models the unloading along the pressure surface of the blade, and the endwall static pressure distribution of the tip gap, up to the vena contracta. It also predicts a contraction coefficient of 0.61. The combined potential flow and mixing model accounts for the pressure rise in the tip gap due to mixing. It predicts a minimum static pressure coefficient under the blade of -6.81, which agrees well with measured data. / M.S.

Bubble columns and airlift reactors were modeled numerically to better understand the hydrodynamics and analyze the mixing characteristics for each configuration. An Eulerian-Eulerian approach was used to model air as the dispersed phase within a continuous phase of water using the commercial software FLUENT. The Schiller-Naumann drag model was employed along with virtual mass and the standard k-e turbulence model. The equations were discretized using the QUICK scheme and solved with the SIMPLE coupling algorithm. The flow regimes of a bubble column were investigated by varying the column diameter and the inlet gas velocity using two-dimensional simulations. The typical characteristics of a homogeneous, slug, and heterogeneous flow were shown by examining gas holdup. The flow field predicted using two-dimensional simulations of the airlift reactor showed a regular oscillation of the gas flow due to recirculation from the downcomer and connectors, whereas the bubble column oscillations were random and resulted in gas flow through the center of the column. The profiles of gas holdup, gas velocity, and liquid velocity showed that the airlift reactor flow was asymmetric and the bubble column flow was symmetric about the vertical axis of the column. The average gas holdup in a 10.2 cm diameter bubble column was calculated and the results for the two-dimensional simulation of varying inlet gas velocities were similar to published experimental results. The average gas holdup in the airlift reactor for the three-dimensional simulations compared well with the experiments, and the two-dimensional simulations underpredicted the average gas holdup. / Master of Science

In the emergence of switched reluctance motors to the commercial market, two-phase motors have received relatively little attention. Higher power and industrial applications have focused on the use of three and occasionally four phase machines, while low cost applications demanding only modest performance have largely been the domain of single phase machines. By contrast, while two phase systems have been the subject of occasional studies, they have not been widely applied. Two phase systems represent a compromise between the higher cost but higher performance three phase machines, and the lower cost but lower performance single phase systems. They do not suffer from the same magnitude of peak to peak torque ripple that single phase machines experience due to their wide zero torque arcs. Yet two phase systems keep a relatively low component count in their power-converter designs. The primary drawback to two phase motors is the difficulty of torque production at startup speeds. Although sizably reduced from single phase machines, the zero torque regions in two phase machines can still result in rotor lock unless steps are taken to circumvent them. These steps can include measures such as: placement of permanent magnets or other means to ensure the rotor is positioned outside of these zero torque regions when at rest, mechanically spinning the motor before energizing the phase windings on startup, shaping of the rotor or stator poles to extend the positive torque regions of each phase, or use of the machines mutual inductance with both phases energized to produce enough torque to initiate motion. This project is intended to develop a variable speed controller for a 4:6 two-phase switched reluctance motor. The motor is to operate in all four quadrants, and is to demonstrate self starting capability. The controller is also supposed to produce signals needed to operate the motor with multiple converter designs. Two different converter designs will be built and tested with the converter. One makes use of a single switch and two diodes per phase, the other has one switch and one diode per phase plus a common switch and common diode shared by all phases. There are many possible applications of the system being developed in this project. Any application needing four quadrant operation while still being constrained by low cost requirements would be ideal. Some examples include washing machines, power tools, and low power industrial applications. / Master of Science

Hydrothermal processes at oceanic spreading centers are largely influenced by changing magmatic heat input. I use the FISHES code to investigate the evolution of surface temperature and salinity as a function of time-varying heat flux at the base of a two-phase, vapor-brine hydrothermal system. I consider a two-dimensional rectangular box that is 1.5 km deep and 4 km long with homogeneous permeability. Impermeable, insulated conditions are imposed on the left and right hand boundaries. To simulate time-varying heat flux from a sub-axial magma chamber of 500 m long half-width, I consider a variety of basal boundary conditions: (1) a constant heat flux with an value of 130 W/m2; (2) a sinusoidal heat flux with a period of 6 years and an amplitude ranging between 100 and 50 W/m2; (3) step, random, and exponential heat fluxes ranging between 200 and 15 W/m2; and (4) an analytical function of temporally decaying heat flux resulting from a simulated cooling, crystallizing magmatic sill. As a result of the investigation I find: (1) changes in bottom temperature and salinity closely follow the temporal variations in magmatic heat inputs; (2) the surface temperature response is severely damped and high frequency variations in heat flow are not detected; (3) in regions where phase separation of vapor and brine occurs, surface salinity variations may be recorded in response to changing conditions at depth, but these are smaller in amplitude. / Master of Science