<p> The objective of the present research was to investigate the effects of rotating circular cylinders to control high intensity wind load. This research used computational fluid dynamics (CFD) to simulate high Reynolds number gust-like wind load condition for a transient duration of 12 seconds across a three-dimensional rectangular cylinder with dimension of 240x15x7 meters and aspect ratio (Breadth/Height) of 2.3. An array of 20 circular cylinders was positioned along the leading edges of the rectangular bridge cylinder. The research analyzed turbulent flow characteristics across the top and bottom deck surfaces and the development of wake region during two cases: 1) stationary cylinders and 2) rotated cylinders at 400 RPM or velocity ratio of &lambda; = 1.33. The Strouhal number flow characteristics of 0.08 and 0.17 for aspect ratio of 2 to 3 analyzed in this study were found to be in agreements with published literature.</p>

<p> Waste reduction and energy recovery have been an environmental focus. Many of these solutions involve the thermal degradation of waste, such as household garbage or organic waste. To help reduce the negative environmental impact associated with processes like incineration, methods have been developed to utilize the carbonaceous material and energy contained in waste. Wastewater treatment plants are responsible for collecting and cleaning billions of gallons of sewage and stormwater each year. The water collected goes through multiple cleaning stages before being discharged into surface water. Sewage sludge, commonly referred to as biosolids, are produced during the process. Biosolids are carbon rich particles that can be used as fertilizers. The city of Milwaukee dries its biosolids and sells them as a fertilizer called Milorganite^&reg;. </p><p> Pyrolysis is a thermochemical process which involves heating an organic material in an inert atmosphere to produce gases and a char residue. Applying pyrolysis to biosolids reduces the volume of waste to be landfilled and yields three products, including high-heating value light gases (py-gas) and a carbon rich porous char (biochar) that works well as a fertilizer, similar to dried biosolids. Pyrolysis of locally-produced dried biosolids will be studied in this thesis. </p><p> Thermogravimetric analysis (TGA) is an experimental technique used to study thermal decomposition reactions, such as pyrolysis, by measuring the mass of a sample as a function of temperature and time. In this study, non-isothermal TGA has been used to study the pyrolysis kinetics of Milorganite^&reg;. The kinetic parameters are essential for sizing reactors to optimize the pyrolysis process. Pyrolysis of dried biosolids is modeled as a combination of independent parallel reactions. Thermogravimetric (TG) and differential thermogravimetric (DTG) data were used with a nonlinear model-fitting method to determine the activation energy, pre-exponential factor, and fractional contribution for the five major pseudo-components found in the dried biosolid. In contrast with the few existing studies using model-fitting approaches for biosolid pyrolysis kinetics, this study first fits the kinetic parameters to TG data, then employs the results as initial guesses for a second fitting process to DTG data. This technique makes for a smoother convergence process in reducing the residual between fitted and experimental data. More importantly, this study performed the fitting process for a wide range of initial guesses and found that the solver converged to the same set of kinetic parameters for 95% of the initial guesses, inspiring confidence that the kinetic parameters correspond to a global, rather than a local, minimum.</p><p>

<p> Magnetic refrigeration is one of the alternative cooling technologies that is environmental friendly and has high theoretical coefficient of performance values. This thesis study focuses on magnetic field and heat transfer enhancement of a reciprocating-type magnetic refrigeration system. A set of NdFeB 52 MGOe permanent magnets were employed to form a Halbach magnet array. Gadolinium (Gd) was used as the magnetocaloric material. It was placed concentrically within the Halbach array aperture with the working fluid running through the gap in between the magnet assembly and Gd yielding annular flow. Three different annular flow geometries namely; circular, octagonal and hexagonal cross-sections were studied. Magnetization process was analyzed theoretically, numerically and experimentally for k = 4 configuration. Numerical analysis was done by Finite Element Method Magnetics (FEMM), theoretical analysis was conducted by a mathematical model, and experimental analysis was performed on a Halbach magnet array. Obtained magnetic field results were used to calculate corresponding entropy changes and heat flux values. These values were compared to numerical heat transfer results from ANSYS and a close agreement between results were observed.</p><p>

<p> Better understanding of phase change phenomena can be obtained through local measurements of the heat transfer process, which cannot be attained by traditional thermocouple point measurements. Infrared (IR) technology, which has been used by many researchers in the past, cannot be used under certain circumstances due to spectral transparency issues present in some materials. In the current study, the optical properties of fluorescing materials are proposed as a novel tool for heat transfer measurements. Two fluorescing materials were examined within the framework of the current dissertation: Namely Quantum dots and Ruthenium based temperature sensitive paint, which tend to fluoresce upon excitation by blue or Ultraviolet (UV) light. The light intensity emitted by those fluorescing materials tends to drop with temperature, which can be utilized to obtain the surface temperature distribution at a pixel resolution, for a given monochromic camera. Advantages of the fluorescing materials include feasibility, applicability to various surface geometries, and the ability to resolve submicron features. The main objective behind the current research work was to develop and assess the optical measurement technique of fluorescing materials, where phase change heat transfer applications, including ethanol drop evaporation and pool boiling, were used to quantify the advantages and limitations of the current temperature measurement technique. Furthermore, a thermofluid study was conducted in order to examine the mechanism of rapid vapor patch formation near critical heat flux (CHF) conditions. Results from the current research work show a correlation between the fluid velocity gradient near the wall and surface heat flux, where both tend to follow similar trend with surface super heat. Thus, it&rsquo;s believed that the incomplete wetting of previous vapor patches near CHF is associated with restricted capillary motion near the surface, where the wetting liquid fails to reach the dry areas with the increased bubble generation activity, due to the local heating caused by the mushroom bubble ebullition.</p><p>

<p> An experimental effort has been completed in which water injection was investigated as a means of enabling increases in engine output and high load efficiency. Water was injected into the intake port of a direct fuel injected, 4-cylinder, boosted engine with dual independent variable valve timing. The water was shown to increase volumetric efficiency and decrease the onset of knock which in turn enable more optimal combustion phasing. Both of these affects resulted increases in load of up to 5.5% at the same manifold pressure as the baseline case. The advancement of combustion phasing, combined with elimination of fuel enrichment resulted in an increase in full load thermal efficiency of up to 35%. Analysis is provided around these affects, as well as the phase transformation of water throughout the engine cycle.</p><p>

<p> In-cylinder heat transfer is one of the most critical physical behaviors which has a direct influence on engine out emission and thermal efficiency for IC engine. In-cylinder wall temperature has to be precisely controlled to achieve high efficiency and low emission. However, this cannot be done without knowing gas-to-wall heat flux. This study reports on the development of a technique suitable for engine in-cylinder surface temperature measurement, as the traditional method is &ldquo;hard to reach.&rdquo; A laser induced phosphorescence technique was used to study in-cylinder wall temperature effects on engine out unburned hydrocarbons during the engine transitional period (warm up). A linear correlation was found between the cylinder wall surface temperature and the unburned hydrocarbons at mediate and high charge densities. At low charge density, no clear correlation was observed because of miss-fire events. A new auto background correction infrared (IR) diagnostic was developed to measure the instantaneous in-cylinder surface temperature at 0.1 CAD resolution. A numerical mechanism was designed to suppress relatively low-frequency background noise and provide an accurate in-cylinder surface temperature measurements with an error of less than 1.4% inside the IC engine. In addition, a proposed optical coating reduced time delay errors by 50% compared to more conventional thermocouple techniques. A new cycle-averaged <span style="text-decoration:overline">Re_s</span> number was developed for an IC engine to capture the characteristics of engine flow. Comparison and scaling between different engine flow parameters are available by matching the averaged <span style="text-decoration:overline">Re_s</span> number. From experimental results, the engine flow motion was classified as intermittently turbulent, and it is different from the original fully developed turbulent assumption, which has previously been used in almost all engine simulations. The intermittent turbulence could have a great impact on engine heat transfer because of the transitional turbulence effect. Engine 3D CFD model further proves the existence of transitional turbulence flow. A new multi zone heat transfer model is proposed for IC engines only. The model includes pressure work effects and improved heat transfer prediction compared to the standard Law of the wall model.</p><p>

<p> In the interest of studying the propagation of shock waves, this work sets out to design, construct, and characterize a pneumatic accelerator that performs high-velocity flyer plate impact tests. A single stage gas gun with a dual diaphragm breach allows for a non-volatile, reliable experimental testing platform for shock phenomena. This remotely operated gas gun utilizes compressed nitrogen to launch projectiles down a 14 foot long, 2 inch diameter bore barrel, which subsequently impacts a target material of interest. A dual diaphragm firing mechanism allows the 4.5 liter breech to reach a total pressure differential of 10ksi before accelerating projectiles to velocities as high as 1,000 m/s (1570-2240 mph). The projectile&rsquo;s velocity is measured using a series of break pin circuits. The target response can be measured with Photon Doppler Velocimetry (PDV) and/or stress gauge system. A vacuum system eliminates the need for pressure relief in front of the projectile, while additionally allowing the system to remain closed over the entire firing cycle. Characterization of the system will allow for projectile speed to be estimated prior to launching based on initial breach pressure.</p><p>

Offshore wind energy technology is maturing in Europe and is poised to make a significant contribution to the U.S. energy production portfolio. Building on the knowledge the wind industry has gained to date, this dissertation investigates the influences of different site conditions on offshore wind farm micrositing—the layout of individual turbines within the boundaries of a wind farm. For offshore wind farms, these conditions include, among others, the wind and wave climates, water depths, and soil conditions at the site. An analysis tool has been developed that is capable of estimating the cost of energy (COE) from offshore wind farms. For this analysis, the COE has been divided into several modeled components: major costs (e.g. turbines, electrical interconnection, maintenance, etc.), energy production, and energy losses. By treating these component models as functions of site-dependent parameters, the analysis tool can investigate the influence of these parameters on the COE. Some parameters result in simultaneous increases of both energy and cost. In these cases, the analysis tool was used to determine the value of the parameter that yielded the lowest COE and, thus, the best balance of cost and energy. The models have been validated and generally compare favorably with existing offshore wind farm data. The analysis technique was then paired with optimization algorithms to form a tool with which to design offshore wind farm layouts for which the COE was minimized. Greedy heuristic and genetic optimization algorithms have been tuned and implemented. The use of these two algorithms in series has been shown to produce the best, most consistent solutions. The influences of site conditions on the COE have been studied further by applying the analysis and optimization tools to the initial design of a small offshore wind farm near the town of Hull, Massachusetts. The results of an initial full-site analysis and optimization were used to constrain the boundaries of the farm. A more thorough optimization highlighted the features of the area that would result in a minimized COE. The results showed reasonable layout designs and COE estimates that are consistent with existing offshore wind farms.

The concept of seasonal heat storage is based on storing sensible heat during the season of low heat demand to be used during the cold season, when the need for heating is higher. Combining this concept with solar thermal energy collection produces what is known as: Central Solar Heating Plant with Seasonal Storage (CSHPSS). Thermal energy is stored by injecting heat into the ground by circulating hot water through a matrix of U-tubes inserted 10 to 30 meters deep into the soil. While the CSHPSS technology is becoming increasingly attractive the heat transfer process of seasonal storage remains complex and only very few modeling tools are available. In an effort to properly design a CSHPSS system for the University of Massachusetts at Amherst, several comprehensive design and performance analyses were conducted. Thus, a complete and detailed CSHPSS system model using TRNSYS is presented in this dissertation. The U-tube seasonal storage is modeled based on a validated ground heat storage module, DST. The storage performance given by this model was compared with a finite element model and experimental results. The simulations yielded positive comparisons and a procedure for modeling U-tube storage system was established. The CSHPSS model developed in this work features a unique control strategy that operates on a seasonal basis. This control strategy is based on four modes of operation and is found to contribute to the simulation stability. This strategy can also provide greater solar contribution to the load as opposed to the conventional ON/OFF controllers. The heat collected by solar collectors is transferred to a storage or a building side through a shell and tube heat exchanger. A heat exchanger model that takes into account variations in the heat transfer coefficient and effectiveness caused by variable flow rates is developed to provide a realistic heat exchanger performance. A thermal analysis of the seasonal storage and the heat exchanger was performed from the first and second law analysis viewpoints. Meaningful interpretations of the heat transfer process in the CSHPSS system can be made from these analyses. Finally, recommendations for improving CSHPSS simulations and performance are discussed.

This research develops superior approaches to the traditional site assessment process, as well as novel strategies that offer a distinct advantage over the traditional process. Two major contributions are presented: new analysis approaches for site assessment, and new technical approaches to wind resource monitoring. Two new analysis approaches for wind energy site assessment are developed. The first is a method for site assessment uncertainty analysis. Analytical expressions for the sensitivity factors of the Weibull parameters are developed, which yield exact values for any combination of wind resource, power curve, and energy losses. This enables better determination of the uncertainty in the annual energy production estimate. The second approach is a decision making strategy to determine whether or not to stop measuring the wind resource at any point in the process. In contrast, in the standard approach, the wind resource is almost always measured for a full year, which can be inefficient in many cases. The results show that this approach is just as accurate as measuring for a year, but saves significant time and money. Two new technical approaches for measuring the wind resource are developed. The first measures multiple sites in a year using one ground-based device, which is brought back and forth between sites, resulting in two discontinuous measured data sets, each distributed over the year. The accuracy and uncertainty of the predictions of the wind resource are equivalent to those using a full year of measured data. The second new technical approach can improve shear extrapolation. It relies on short-term data from a ground-based device at a site where a met tower is installed for a year. The short-term data are used to correct the year-long shear parameter. The results show substantial improvements in the accuracy and uncertainty of shear predictions. These new analysis approaches and technical monitoring strategies are unified into a comprehensive "Streamlined Site Assessment Methodology." It provides a flexible, unified approach for executing the site assessment process in which the specific priorities and constraints of the project dictate the resulting approach. This methodology can drastically alter and improve site assessment.