Now showing items 21-40 of 506

    • Developing a combined intake and exhaust vent for heat recovery ventilation in cold climates

      Bickford, Riley Joseph; Marsik, Tom; Peterson, Rorik; Dekenberger, David (2022-08)
      Heat recovery ventilation systems have become increasingly popular in modern residential buildings, particularly in cold climates. This has led to the research and development of supporting technologies, such as combined intake/exhaust vents. Conventionally, the intake and exhaust airflows of a heat recovery ventilation system use separate vents and penetrations in a building's envelope; combined intake/exhaust vents package these airflows together and use only one penetration. This simplifies heat recovery ventilation system installation and can lead to higher operating efficiencies; the implications are reduced up-front and operating costs as well as broadened access to heat recovery ventilation. Unfortunately, in cold climates, existing combined intake/exhaust vent designs are susceptible to frost accumulation, a mode of failure. The aim of this work was to develop a combined intake/exhaust vent more suitable for cold climate use: the Arctic Dual Hood. The design was developed in iterations informed by experimentation. These experiments included climate chamber evaluations and field performance comparisons. This design process produced a functional prototype with favorable frost mitigation characteristics compared to an existing combined intake/exhaust vent design, as determined through the field performance comparisons. Additionally, this prototype observed the constraints and met the performance requirements imposed by the American Society of Heating, Refrigeration, and Air-Conditioning Engineer's Standard 62.2: Ventilation and Acceptable Indoor Air Quality in Residential Buildings.
    • Optimization and forecasting algorithms for converter dominated distribution networks using blockchain and AI

      Shah, Chinmay; Wies, Richard W.; Al-Badri, Maher; Huang, Daisy; Cicilio, Phylicia (2022-05)
      Integration of power electronic converter-based distributed energy resources (DERs) in electric power distribution networks is growing exponentially with the recent interest in reducing carbon emissions from fossil fuel-based generation. As the contribution of renewable energy sources in the DER mix continues to increase, so does the incorporation of battery energy storage systems and other controllable loads to compensate for the high variability and uncertainty in the generation from renewable DERs and grid demand. Strategies for increasing the contribution of renewable energy sources and using reserves to accommodate for variations and uncertainty in generation and load include distributed optimal power flow (OPF) methods and improved forecasting. This work proposes a co-optimization of power flow and flexibility reserves, executed on a private blockchain for security, solved using a parameterized deterministic method based on semi-distributed architecture and alternating direction method of multipliers (ADMM) based distributed architecture that addresses uncertainty and enhances the flexibility of the distribution network. However, ADMM guarantees convergence only for strictly convex problems and hence a relax-and-fix heuristic algorithm is proposed in co-ordination with ADMM to solve the OPF problem, which is non-convex in nature. Also, an accurate short-term load forecasting algorithm is essential to reduce the uncertainty in the dispatch results using the OPF algorithm. In this work, a short-term residential load forecasting algorithm is proposed using a two-stage stacked long short-term memory network-based recurrent neural network and Hampel filter to address this issue. All the proposed algorithms are tested using different case studies. Results demonstrate that the proposed algorithms reduce the impact of uncertainty in the distribution network, automate scheduling flexibility reserve and minimize its cost, reduce the OPF execution time using a distributed architecture, and produce residential load forecast with a significantly lower prediction error.
    • Experimental investigation of nonthermal enhanced oil recovery techniques for improving oil recovery on Alaska North Slope

      Cheng, Yaoze; Zhang, Yin; Dandekar, Abhijit; Ahmadi, Mohabbat; Li, Xiaoli (2022-05)
      Exploitation of viscous and heavy oils on Alaska North Slope (ANS) requires nonthermal enhanced oil recovery (EOR) techniques. Currently, three nonthermal EOR methods, including solvent injection, low salinity water (LSW) flooding, and low salinity polymer (LSP) injection, have been proved to be useful on ANS. ANS viscous and heavy oils can be developed effectively by combining those three nonthermal EOR techniques. In this dissertation, lab experiments have been conducted to investigate the potential of the proposed hybrid nonthermal EOR techniques, including HSW (high salinity water)-LSW-softened LSW flooding, HSW-LSW-LSP flooding, CO₂-enriched LHS (light hydrocarbon solvent)-alternating-LSW flooding, LHS-alternating-LSW flooding, CO₂-enriched LHS (light hydrocarbon solvent)-alternating-LSP flooding, and LHS-alternating-LSP flooding, to improve ANS viscous oil recovery. Besides, the effect of essential clay minerals, including sodium-based montmorillonite (Na-Mt), calcium-based montmorillonite (Ca-Mt), illite, and kaolinite, on LSW flooding has been examined. In addition, the CO₂ influence on solvent-alternating-LSP flooding in enhancing ANS viscous oil recovery has been investigated. Furthermore, the blockage issue during CO₂-enriched LHS-alternating-LSP flooding has been investigated, and its solution has been proposed and analyzed. The EOR potential of the proposed hybrid EOR techniques has been evaluated by conducting coreflooding experiments. Additionally, relative permeability, swelling property, zeta potential, interfacial tension (IFT), and pressure-volume-temperature (PVT) tests have been conducted to reveal the EOR mechanisms of the proposed hybrid EOR techniques. Moreover, water ion analysis of DI-water/natural-sand and DI-water/natural-sand/CO₂ systems has been carried out to reveal the complex reaction between CO₂, sand, and LSP solution. It was found that, compared to conventional waterflooding, all the proposed hybrid EOR techniques could result in better oil recovery potential. It was noticed that the presence of CO₂ in LHS could be more beneficial to the solvent-alternating-LSW/LSP flooding processes during the 1st cycle due to the greater effectiveness of oil viscosity reduction. In particular, severe blockage issue occurred when conducting CO₂-enriched LHS-alternating-LSP flooding using sand pack due to the polymer precipitation. Additionally, the calculated water relative permeabilities are much lower than the typical values, implying more complex interactions between the reservoir rock, heavy oil, and injected water. Moreover, comparing to HSW, LSW could further swell Na-Mt significantly, which may benefit LSW flooding by improving sweep efficiency since in-situ swelling of Na-Mt has the potential to block the higher permeable water-flooded zone and divert the injected brine to lower permeable and unswept area. Comparing to Na-Mt, LSW couldn't swell Ca-Mt and illite further, whereas kaolinite was incapable of swelling in both HSW and LSW. Furthermore, about 60 mole% of solvent could be dissolved into the ANS viscous oil at target reservoir condition, resulting in oil swelling and viscosity reduction effects, which provided better microscopic displacement efficiency. Although the presence of CO₂ in LHS had a negative impact on the oil swelling effect, the influence on the oil viscosity reduction was positive. In addition, reducing the salinity of water could generate more negative zeta potential values on the surface of clay minerals and sand, making it more water wet. Besides, IFT of oil/LSW system is higher than that of oil/HSW system, indicating that IFT reduction is not an EOR mechanism of LSW flooding in our proposed hybrid EOR techniques. Additionally, after introducing CO₂ to the DIwater/natural-sand system, the concentration of multivalent cations was increased, which may be responsible for the polymer precipitation. The blockage issue could be solved by injecting LSW as a spacer between CO₂-enriched LHS injection and LSP injection.
    • Study on emulsification/demulsification behavior and mechanism of produced liquid from polymer flooding on Alaska North Slope

      Chang, Hongli; Zhang, Yin; Dandekar, Abhijit; Trainor, Tom; Guerard, Jennifer (2022-05)
      Heavy oil reservoirs on Alaska North Slope (ANS) are unconsolidated and contain abundant clay minerals, where the first-ever field pilot is currently implemented to validate the use of polymer floods for heavy oil enhanced oil recovery (EOR). The polymer molecules and/or fine clay particles carried with the produced liquid could potentially affect the oil/water separation, which is one of the major concerns for field operators. This dissertation aims to investigate the emulsification behavior of produced liquid, understand the emulsifying mechanism, and seek an adaptive and cost-effective method to treat the produced liquid from polymer flooding. Emulsions were prepared by mechanically mixing the actual heavy oil and the produced water from the pilot site, of which the stability was investigated by bottle test method or multiple light scattering method. Drop size distribution and interfacial properties were measured via microscope and pendant drop technique to probe the stability mechanism further. Results showed that oil-continuous or water-continuous emulsion could be generated depending on the water cut, clay types, clay concentration, and polymer concentration. In the crude oil/water system, the increasing water cut triggered the phase inversion of oil-continuous emulsion to water-continuous emulsion, resulting in faster separation and lower emulsion stability. Whereas, clay particles, no matter added to the oil or water phase, resulted in an unfavorable phase inversion from the loose watercontinuous emulsion to the tight oil-continuous emulsion as clay concentration increased. For all four types of clay except Ca-montmorillonite, clay particles added to water led to an earlier phase inversion and higher emulsion stability than that added to the oil. The dual function of polymer on emulsion stability was observed. On the one hand, both sheared and unsheared polymer tended to convert the oil-continuous emulsion formed in either crude oil/water system or complex crude oil/water/clay particle system to the water-continuous emulsion, acting as a weak demulsifier to accelerate the oil/water separation. On the other hand, the addition of polymer to the watercontinuous emulsion could result in enhanced emulsion stability, which is primarily attributed to the increased viscosity of the continuous phase and the decreased drop size of the dispersed oil phase. Particularly, the sheared polymer had a weaker ability to stabilize the o/w emulsion than the unsheared polymer due to the lower viscosity of the sheared polymer solution resulting from the breakdown of the polymer macromolecules. As for the chemical demulsification tests, the performance of demulsifiers showed a complex dependency upon the water cut, the shearing intensity, demulsifier type and dosage, and the polymer concentration. A compound emulsion breaker, E12+E18, exhibited the most satisfactory demulsification performance despite the varied test conditions. For severe water-continuous emulsions that might require a multi-fold dosage of demulsifier, a less expensive electrolyte, KCl, was proposed to be used in combination with demulsifier E12+E18 to improve the demulsification performance. In the proposed demulsifier formula, the effectiveness of the commercial demulsifier relied on its destructive effect on the interfacial film, while the efficacy of KCl was mainly dependent on its viscosity reduction effect on the continuous phase. This dissertation illustrates that intermediate layer elimination and water clarification are the major challenges for produced liquid treatment from polymer flooding. It also provides practical and theoretical guidance in advance for the demulsification strategy of the produced liquid from the ongoing first-ever polymer flooding pilot on ANS.
    • Understanding permafrost dynamics and geohazards with a terrain-cryofacies approach

      Stephani, Eva; Shur, Yuri; Doré, Guy; Darrow, Margaret; Kanevskiy, Mikhail (2021-12)
      The Arctic and its permafrost terrain are inherently dynamic, complex, and sensitive environments. Understanding the past and current changes occurring in these systems is key in predicting future variations, including the response of permafrost to climate change, and to terrain modifications resulting from natural processes or anthropogenic activities. This study contributes to advance our understanding of permafrost dynamics in varying permafrost environments of northern Alaska and northwestern Canada using a terrain-cryofacies approach. This unique approach helps to increase our understanding of permafrost dynamics from the site-specific scale to over extended areas by recognizing linkages between terrain and subsurface properties, and by identifying similar terrain units in remote sensing analysis. In the Colville River Delta (Alaska), our terrain-cryofacies study integrated data from 79 boreholes with a remote sensing analysis to evaluate the temporal changes in the Nigliq channel positions from 1948 to 2013 and the related permafrost dynamics. Most land cover changes occurred as land exposition (64%), whereas about 36% of the total changes were classified as eroded. The erosion of the older terrain units from the floodplain toposequence, such as the inactive-floodplain cover deposits, implied ground loss volumes of about one-fifth of soil solids and four-fifths of ground ice. Along this channel, we also identified the typical configuration and properties of taliks and cryopegs, as well as subsequent epigenetic permafrost growth. We found that the active channel was underlain by closed taliks, rather than through taliks and thus did not penetrate the entire layer of permafrost connecting supra- and sub-permafrost groundwater. A cryopeg connected to the active channel talik was identified from borehole data in the adjacent terrain units that developed following channel migration. We estimated the likelihood of encountering such taliks and cryopegs over extended areas. The terrain-cryofacies approach was also applied to understand permafrost dynamics of hillslope thermokarst located in multiple ecoregions of northern Alaska and northwestern Canada, including areas affected by interactions with infrastructure. Six features were studied through the combination of field-based and remote sensing methods, whereas 150 others were assessed solely by remote sensing. Studies along a pipeline indicated that embankment construction led to an increase in the active layer thickness, reaching the underlying ice-rich intermediate layer, and causing thaw settlement. This formed a thermokarst-ditch that facilitated channelization of cross-drainage water, and thermal erosion of the ice-rich permafrost that became affected by thermal denudation and caused a retrogressive thaw slump (RTS). The RTS later selfstabilized mainly due to the lateral discontinuity of massive ice (i.e., ice wedge) and the low-relief terrain. We suggested approaches to develop adaptation strategies for infrastructure at risk of RTS based on: these findings and conditions that favor or limit RTS growth by local feedbacks; considering the interaction patterns that we identified between RTS and infrastructure; and the main destabilization processes that we highlighted by terrain units. Further research is necessary, however, and must include testing potential mitigation techniques at multiple sites with monitoring programs to assess the variability in performance with respect to site-specific conditions.
    • Landslides in the Fairbanks North Star Borough, Alaska: inventory map and Tanana 440 landslide assessment

      Schwarber, Jaimy A.; Darrow, Margaret; Kidanu, Shishay; Daanen, Ronald (2021-12)
      Landslides are geologic hazards that threaten human life, property, and infrastructure. Effective threat mitigation requires knowledge of where past landslides occurred. Until now, no published landslide inventory maps existed for any part of Alaska. Here we present an overview of our landslide mapping within parts of the Fairbanks North Star Borough (FNSB), Alaska and a thorough investigation and assessment of the Tanana 440 (T440) landslide. We mapped 1,679 landslides, and field-verified 51 landslides within the FNSB. These landslides vary in age, movement type, and material. Most are prehistoric, but we did observe some historic and active landslides. Observed slope failures include flows in soil, translational and rotational slides in bedrock, and complex features that combine multiple types of movement. Potential landslide triggers may include thawing permafrost, increased pore water pressure conditions, seismic events, and river erosion. The landslide inventory map, the first of its kind for Alaska, directly benefits the Borough, the State, and the general public, as it can be used by public agencies to make informed land management decisions and to incorporate landslides within multiple-disaster scenarios. Additionally, the map serves as the foundation for future landslide analysis within the FNSB. We also present results of in-depth mapping, subsurface exploration, soil engineering properties, and slope stability analysis of the T440 landslide. Based on analysis of stratigraphy, soil testing, and geomorphology, we determined the T440 landslide is a flow slide in loess that occurred during the late Pleistocene to mid-Holocene. Our modeling results suggest that thawing permafrost and/or seismic loading were possible triggers for the T440 landslide. We also present the first comprehensive direct shear testing of non-plastic silt with variation in moisture content, as well as the first comparison of direct shear and field vane shear measurements of silt. These results can be used for engineering design purposes for Interior Alaska silt for any gravimetric water content over 5%.
    • Theory, design, and development of an open-source 3D printed peristaltic pump for microfluidics applications

      MacEachern, Joshua M.; Chen, Cheng-fu; Peterson, Rorik; Huang, Daisy; Laughlin, Bernard (2022-05)
      Microfluidics research is a constantly evolving and developing field of research in the biological, chemical, and medical sciences. To perform microfluidic analyses, various types of pump designs have been developed or optimized. These pumps are generally capable of pumping flow in the range of 0.1-100s of microliters (µL) per minute, with the goal of pumping fluid with an extremely consistent flow rate. These pumps include, but are not limited to, peristaltic, syringe, membrane, and lobe pumps. Both commercial and open-source designs have been developed to meet the needs of continued research. Commercial designs are very expensive, but offer limited flexibility to tailor the usage for custom assays. Open-source designs that have been presented may lack support, or may be designed to use fabrication technologies that are less commonly available than conventional desktop 3D printing. Due to this, many laboratories may be limited in their microfluidic research work due to either availability of commercial pumps, or usability of open-source pump designs. This work presents two iterations of a novel design for a 3D-printable microfluidic peristaltic pump. The pumps developed herein have been tested to demonstrate consistent performance operating over long-term periods of up to ten days continuously. These pumps have been tested to demonstrate capability of delivering aqueous flow as slow as flow ranges of 10s of µL/min. These pumps are capable of maintaining an outlet pressure of up to 220 kilopascals (kPa). In a tube of 1 mm inner diameter, this pressure would drive a flow rate of 10 µL/min through tubing up to 6.6 meters long. Finally, this design has been optimized to improve the user experience and make these peristaltic pumps both easy to maintain and easy to operate by a non-technical user.
    • Technical and economic evaluation of the first ever polymer flood field pilot to enhance the recovery of heavy oils on Alaska's North Slope via machine assisted reservoir simulation

      Keith, Cody D.; Zhang, Yin; Ahmadi, Mohabbat; Dandekar, Abhijit (2022-05)
      Polymer flooding has become globally established as a potential enhanced oil recovery method for heavy oils. To determine whether this technology may be useful in developing the substantial heavy oil resources on the Alaska North Slope, a polymer flood field pilot commenced at the Milne Point Unit in August 2018. This study seeks to evaluate the results of the field pilot on a technical and economic basis. A reservoir simulation model is constructed and calibrated to predict the oil recovery performance of the pilot through machine-assisted reservoir simulation techniques. To replicate the early water breakthrough observed during waterflooding, transmissibility contrasts are introduced into the simulation model, forcing viscous fingering effects. In the ensuing polymer flood, these transmissibility contrasts are reduced to replicate the restoration of injection conformance during polymer flooding. Transmissibility contrasts are later reinstated to replicate fracture overextension interpreted in one of the producing wells. The calibrated simulation models produced at each stage of the history matching process are used to forecast oil recovery. These forecasts are used as input for economic analysis, incremental to waterflooding expectations. The simulation forecasts indicate that polymer flooding significantly increases the heavy oil production for this field pilot compared to waterflooding alone, yielding attractive project economics. However, meaningful variations between simulation scenarios demonstrate that a simulation model is only valid for prediction if flow behavior in the reservoir remains consistent with that observed during the history matched period. Critically, this means that a simulation model calibrated for waterflooding may not fully capture the technical and economic benefits of an enhanced oil recovery process such as polymer flooding. Subsequently, the simulation model and economic model are used in conjunction to conduct a sensitivity analysis for polymer flood design parameters, from which recommendations are provided for both the continued operation of the current field pilot and future polymer flood designs. The results demonstrate that a higher polymer concentration can be injected due to the development of fractures in the reservoir. The throughput rate should remain high without exceeding operating constraints. A calculated point-forward polymer utilization parameter demonstrates the decreasing efficiency of the polymer flood at later times in the pattern life. Future projects will benefit from starting polymer injection earlier in the pattern life. A pattern with tighter horizontal well spacing will observe a greater incremental benefit from polymer flooding.
    • Application of probabilistic decline curve analysis to unconventional reservoirs

      Egbe, Uchenna C.; Awoleke, Obadare; Goddard, Scott; Ahmadi, Mohabbat (2022-05)
      This work presents the various probabilistic methodology for forecasting petroleum production in shale reservoirs. Two statistical methods are investigated, Bayesian and frequentist, combined with various decline curve deterministic models. A robust analysis of well-completion properties and how they affect the production forecast is carried out. Lastly, a look into the uncertainties introduced by the statistical methods and the decline curve models are investigated to discover any correlation and plays that otherwise would not be apparent. We investigated two Bayesian methods - Absolute Bayesian Computation (ABC) and GIBBS sampler - and two frequentist methods - Conventional Bootstrap (BS) and Modified Bootstrap (MBS). We combined these statistical methods with five empirical models - Arps, Duong, Power Law Model (PLE), Logistic Growth Model (LGA), and Stretched Exponential Decline Model (SEPD) - and an analytical Jacobi 2 theta model. This allowed us to make a robust comparison of all these approaches on various unconventional plays across the United States, including Permian, Marcellus, Eagle Ford, Haynesville, Barnett, and Bakken shale, to get detailed insight on how to forecast production with minimal prediction errors effectively. Analysis was carried out on a total of 1800 wells with varying production history data lengths ranging from 12 to 60 months on a 12-month increment and a total production length of 96 months. We developed a novel approach for developing and integrating informative model parameter priors into the Bayesian statistical methods. Previous work assumed a uniform distribution for model parameter priors, which was inaccurate and negatively impacted forecasting performance. Our results show the significant superior performance of the Bayesian methods, most notably at early hindcast size (12 to 24 months production history). Furthermore, we discovered that production history length was the most critical factor in production forecasting that leveled the performance of all probabilistic methods regardless of the decline curve model or statistical methodology implemented. The novelty of this work relies on the development of informative priors for the Bayesian methodologies and the robust combination of statistical methods and model combination studied on a wide variety of shale plays. In addition, the whole methodology was automated in a programming language and can be easily reproduced and used to make production forecasts accurately.
    • An analysis of turbulent effects on hydrokinetic power generation

      Browning, Emily A.; Kasper, Jeremy; Hung, Daisy; Peterson, Rorik (2022-05)
      The effects of turbulence on power generation from a Current Energy Converter (CEC) are not fully understood. This thesis investigates the correlation between a vertical axis CEC's power output and the water velocity in the frequency and time domains. Chapter 2 shows the correlation between velocity and electrical power in frequency space. This correlation gives insight into the size of eddies that influence the CEC's power output. The results of this correlation analysis show that eddies of diameter around 0.8m have a noticeable impact on the power generation. Calculating the observed average integral length scale, the range of eddy diameters around the CEC are 0.52m-5.8m. Since 0.8m is in this observed range it suggests that the turbulence may influence the CEC's power output. Chapter 3 analyzes the relationship between the turbulence velocity cubed and electrical power through the correlation of the two data sets. The correlation was carried out by first separating out the four velocity components derived from cubing the sum of the turbulence and average velocities. The commonly used ratio of the turbulence kinetic energy to total kinetic energy does not include these cross terms nor are these cross terms typically included in the calculation of power derived from the turbulence velocity. The turbulence velocity cubed has a correlation of -0.007 with the CEC power output indicating that the turbulence has a small, negative impact on the CEC power output.
    • History matching and prediction of a polymer flood pilot in heavy oil reservoir on Alaska North Slope

      Wang, Xindan; Zhang, Yin; Dandekar, Abhijit; Khataniar, Santanu (2021-12)
      The first-ever polymer flood pilot to enhance heavy oil recovery on Alaska North Slope is ongoing. After more than 3 years of polymer injection, significant benefit has been observed from the decrease in water cut from 65% to less than 15% in the project producers. The primary objective of this study is to develop a robust history-matched reservoir simulation model capable of predicting future polymer flood performance. In this work, the reservoir simulation model has been developed based on the geological model and available reservoir and fluid data. In particular, four high transmissibility strips were introduced to connect the injector-producer well pairs, simulating short-circuiting flow behavior that can be explained by viscous fingering and reproducing the water cut history. The strip transmissibilities were manually tuned to improve the history matching results during the waterflooding and polymer flooding periods, respectively. It has been found that higher strip transmissibilities match the sharp water cut increase very well in the waterflooding period. Then the strip transmissibilities need to be reduced with time to match the significant water cut reduction. The viscous fingering effect in the reservoir during waterflooding and the restoration of injection conformance during polymer flooding have been effectively represented. Based on the validated simulation model, numerical simulation tests have been conducted to investigate the oil recovery performance under different development strategies, with consideration for sensitivity to polymer parameter uncertainties. The oil recovery factor with polymer flooding can reach about 39% in 30 years, twice as much as forecasted with continued waterflooding. Besides, the updated reservoir model has been successfully employed to forecast polymer utilization, a valuable parameter to evaluate the pilot test's economic efficiency. All the investigated development strategies indicate polymer utilization lower than 3.5 lbs/bbl in 30 years, which is less than that of the same polymer used in a polymer pilot in Argentina.
    • Conceptual design of two tiltrotor aircraft for urban air mobility

      Radotich, Michael T.; Peterson, Rorik; Chen, Cheng-fu; Hatfield, Michael (2021-12)
      There has been an abundance of new and novel aircraft designs created for Urban Air Mobility (UAM) in recent years. The National Aeronautics and Space Administration (NASA) contributes to the research and development of this industry in part by applying its aircraft design tools to create conceptual designs of UAM reference vehicles. The vehicles are intended to quantify the tradeoffs and performance capabilities necessary for VTOL (vertical takeoff and landing) aircraft in the UAM design space. The reference vehicles represent a variety of configurations that seek to encompass many of the design characteristics suitable for UAM. This thesis focuses on the conceptual design process of two new NASA reference vehicles. Both aircraft are configured as conventional tiltrotors, but one is powered by turboshaft engines, and one is fully electric. The sizing and performance of the two aircraft are discussed, as well as how the performance and characteristics compare to a selection of other NASA reference vehicles. It is found that the tiltrotor configuration is capable of reaching speeds 43% to 51% faster than the other turboshaft designs, and 63% to 106% faster than the other electric designs. The increased speed leads to a 24% to 42% decrease in overall mission time. With this speed increase comes moderate tradeoffs in areas including weight and installed power.
    • Application of vortex tubes in an underground mine ventilation system

      Dumakor-Dupey, Nelson K.; Arya, Sampurna N.; Ghosh, Tathagata; Chen, Gang (2021-12)
      A major challenge for deep underground mines in tropical regions is high-temperature climate conditions at a working face. The high-temperature conditions can cause discomfort to people working underground and lead to health and safety issues. In some instances, airflow from primary ventilation and central refrigeration systems is not adequate to reduce the ambient temperature below a permissible limit at remotely located working faces. In some mines, mobile cooling systems are used in conjunction with an existing central cooling system. However, mining companies are often skeptical about implementing the combined cooling system due to its high operating costs involved with refrigeration infrastructure. This research examines the potential of a low-cost, maintenance-free vortex tube spot cooling system that operates on compressed air and can work with or without a central cooling system. Using an underground metal mine in Ghana as a case study, the impact of a vortex tube cooling system at a working face was evaluated using the computational fluid dynamics (CFD) technique. An integrated CFD model of vortex tube, ventilation duct, and development heading was developed. The airflow was simulated within the CFD model with a varying number of vortex tubes and locations. The simulation result shows that the mine can achieve a decent temperature drop from 28°C (82.4°F) to 24°C (75.2°F) with 20 vortex tubes at the working face.
    • Carbon dioxide enhanced oil recovery and sequestration in the Orion Oil Field in the North Slope region of Alaska

      Dogah, Banabas D.; Ahmadi, Mohabbat; Atashbari, Vahid; Awoleke, Obadare (2021-12)
      Carbon dioxide flooding in viscous oil systems has been proven to improve oil recovery and store CO₂ in several geologic basins worldwide. With global energy steadily transitioning towards decarbonization, CO₂-EOR and Sequestration can reduce the carbon footprint from crude oil production. Although well accepted globally, the potential of improved oil recovery and CO₂ storage capacity has not been extensively studied in Alaska. Since the CO₂ injection process involves phase transition, reservoir simulation becomes more complex. It requires reliable techniques to estimate the ultimate recovery factor, oil production rate, and CO₂ storage volumes precisely. This study focuses on carbon dioxide enhanced oil recovery (CO₂-EOR) and storage in the Orion satellite field of Alaska, its ability to reduce greenhouse gases, and the technical and economic feasibility of a CO₂ flooding project. In this study, the Peng-Robinson equation of state is tuned to model fluid behavior from the respective sands accurately. Core flooding results from the Orion Oil Pool in the Schrader Bluff Formation provided the basis for developing relative permeability curves for the various layers in the geological model. The geological model was then coupled with the developed fluid model and introduced into a compositional simulator capable of handling the heterogeneous complexity to simulate CO₂ injection. Simulations suggested that the CO₂ gas injection is partially miscible in the Orion reservoir at pressures close to the average initial reservoir pressure. Consequently, CO₂ mixes with oil in the reservoir, reduces oil viscosity, increases oil mobility, and improves oil recovery. Different simulation scenarios were considered and compared, including the effects of fluid injection mixtures on oil recovery, well trajectory effects, and production bottom hole pressure effects on oil recovery. A considerable volume of injected CO₂ is expected to be sequestered in the reservoir, for which economic analysis is conducted for tax credit purposes. The results show that 40% Enriched CO₂ injection achieved the highest oil recovery, which highlights the importance of selecting the appropriate injector and producer well trajectory. This work provides insights into the optimum CO₂ gas flooding controlling parameters for incremental oil production through sensitivity analysis. The study's novelty is further expanded by quantifying the potential of CO₂ sequestration in each layer of the Orion oil field.
    • Determination of minimum miscibility pressure using vanishing interfacial tension in support of Alaska North Slope heavy oil development

      Tathed, Vinit Santosh; Dandekar, Abhijit Y.; Patil, Shirish L.; Khataniar, Santanu (2008-12)
      "Developing Alaskan heavy oils resources has become necessary as, the production from light oil fields in Alaska's North Slope (ANS) is on the decline. Due to the extremely viscous nature of these heavy oils, they are hard to produce by natural pressure. Miscible gas injection Enhanced Oil Recovery (EOR) can be one of the methods for production of these heavy oils. Minimum miscibility pressure (MMP) is an important optimization parameter for EOR processes involving CO₂ or hydrocarbon gas injection. The MMP for a gas-oil system is directly related to the interfacial tension between the injected gas and the reservoir crude oil. In this study, a new technique called Vanishing Interfacial Tension (VIT) was used to measure MMP at reservoir conditions. Experiments were conducted using various gas-oil systems to determine the MMP. The experimental results were modeled using the Peng-Robinson Equation-of-State (EOS) with a commercial simulator (CMG). The Peng-Robinson EOS was tuned with experimental data to predict the MMP accurately. This study has demonstrated the accuracy of the VIT technique in predicting MMP by pendant drop method experiments and simulations using CMG software."--Leaf iii
    • An engineering study to investigate the methane hydrate resource potential associated with the Barrow gas fields in Alaska

      Singh, Praveen Kumar; Dandekar, Abhijit Y.; Patil, Shirish L.; Panda, Manmath N.; Stokes, Peter J.; Khataniar, Santanu; Walsh, Thomas P. (2008-12)
      "Previous studies on the Barrow Gas Fields (BGF) in Alaska have suggested that accumulations of natural gas hydrates could exist within these reservoirs. In consideration of future energy challenges, and the potential of gas hydrates in meeting them, a comprehensive engineering study was undertaken to investigate the BGF for hydrates, and to recommend an optimal plan for future field development. The methane hydrate resource potential of the BGF, viz. the East Barrow (EB), South Barrow (SB), and Walakpa (WAL) gas pools, was analyzed by developing gas hydrate stability models. Material balance studies were performed on the EB gas field to understand the reservoir drive mechanisms. Gas-water relative permeability experiments were conducted on a hydrate-saturated consolidated core sample, by maintaining the EB reservoir conditions, to model two-phase fluid flow behavior. Finally, field-scale dynamic reservoir simulation models were developed for the EB and WAL gas fields. Production history data were matched, reservoir drive mechanisms were confirmed, free gas and hydrate resources were quantified, hydrate dissociation patterns were examined, optimum locations for drilling infill wells were identified, and future production scenarios were simulated. Findings from this work indicate that BGF are associated with hydrates that are constantly recharging the gas reservoir by dissociation"--Leaf iii
    • Measurement of rheological and thermal properties and the freeze-thaw characteristics of nanofluids

      Sahoo, Bhaskar C. (2008-12)
      "This research investigates the rheological and thermal properties and the freeze-thaw characteristics of nanofluids. Nanofluids are dispersions of nano-scale particles (<100 nm) in a base fluid such as water, ethylene glycol, propylene glycol or a mixture of more than one fluid. In cold regions, a mixture of 60% ethylene glycol in water by mass (60:40 EG/W) is normally used as the heat transfer fluid due to its low freezing point. Rheological properties of aluminum oxide nanofluid in the 60:40 EG/W base fluid were investigated and new correlations, expressing viscosity as a function of temperature and particle concentration, were developed. Results from the specific heat experiments on zinc oxide nanofluid in the 60:40 EG/W were compared with available correlations and a new model was developed. The thermal conductivity of silicon dioxide nanofluid in a 60:40 EG/W was measured and compared with existing models, considering the Brownian motion of nanoparticles. A new correlation, expressing thermal conductivity as a function of particle concentration, size, base fluid properties and temperature, was proposed by improving an existing model. Freeze-thaw characteristics of copper oxide nanoparticle dispersions in water were studied for a single freeze-thaw cycle. The freezing rate, agglomeration of nanoparticles and the effect on the freezing point of nanofluid were examined"--Leaf iii
    • Comparative and sensitivity study of the effects of flow parameters on pressure drop in vertical tubing

      Elekwachi, George Kaetochi; Chukwu, Godwin; Patil, Shirish; Khataniar, Santanu; Dandekar, Abhijit (2008-12)
      "Two-phase gas-liquid flow occurs in vertical pipes during the production of reservoir fluids. The two most common flow patterns that are observed during oil production are the Bubble and Slug flows. Determination of pressure drop in two-phase flow is more complicated than single-phase flow because two fluids with different densities flow in the tubing at different velocities. Using two multiphase correlations (Hagedorn and Brown, and Duns and Ros), the effect of fluid properties variation at different flow conditions on pressure drop were studied. Fluid data developed with correlations and West Sak fluid data were used for the analysis. Plots showing the relationship between pressure drop and different fluid properties were made. From the analysis, it was concluded that oil density, oil viscosity and oil flow rate are the three factors that influence pressure drop in vertical pipes the most. The Hagedorn and Brown correlation was shown to be able to compute pressure drop for high-viscosity oil"--Leaf iii
    • Modeling discharge using HBV in the Imnavait Basin, North Slope, Alaska

      Trochim, Erin Dawn (2009-12)
      "The Arctic fresh water hydrological cycle is dominated by the melting of the seasonal snow cover and scattered precipitation events during the summer months. Predicting and characterizing potential hydrological response is an important component for engineering infrastructure for the appropriate climatic conditions. A semi-distributed Swedish conceptual model, HBV, has been applied to the Imnavait basin, located in the headwaters of the Kuparuk River on the North Slope of Alaska, to examine runoff during spring and summer months. The methodology began by analyzing the long-term climatic records of the Imnavait basin from 1986 to present. Initial calibration work was completed in both spring and summer periods using the Monte Carlo technique; one set from each period was selected and used in the complete version of HBV. The model was recalibrated from 1988 to 2002 and then validated against the 2003 to 2008 time frame. The overall model performance was adequate for engineering purposes, with the best results when the input precipitation was accurate in terms of timing and magnitude. Differences between observed and modeled results included the impact of snow-damming and evaporation during the spring, while convective storms and melting of basal ice in the active layer distorted the summer period"--Leaf iii
    • Heat transfer performance of nanofluids in facility heating applications

      Strandberg, Roy T. (2009-12)
      "Nanofluids are a class of fluids comprised of a base fluid with nanoparticles in a colloidal suspension. These fluids have been shown to exhibit substantially higher thermal conductivity than their corresponding base fluids. Investigation is required to determine if this property may be exploited for the purpose of improving the performance of systems employing liquid heat transfer. Detailed analyses of CuO/60% ethylene glycol and Al₂O₃/60% ethylene glycol nanofluids' heat transfer properties were conducted to determine if they provide a net benefit in commercial facility heating systems. The analyses employed previously developed correlations for nanofluid thermophysical, fluid dynamic and heat transfer properties. Computational models were also developed to characterize the performance of hydronic finned tube heaters and air heating coils with nanofluids, and to compare the nanofluids' performance with that of their base fluids. Several aspects of heat transfer performance were analyzed including heating output, frictional pressure loss, and associated pumping power. These data are analyzed to determine if the selected nanofluids can improve heating output, reduce required liquid pumping power or reduce the size of heating equipment. The analyses predict that the nanofluids examined exhibit superior heat transfer performance to that of the base fluids under certain conditions"--Leaf iii