Doctor of Philosophy (Ph.D.), University of Dayton, 2018, Mechanical Engineering

This research presents engineering models that simulate steady-state and transient operations of air-cooled condensing units and an automatic commercial ice making machines ACIM, respectively. The models use easily-obtainable inputs and strategies that promote quick computations. Packaged, air-cooled condensing units include a compressor, condensing coil, tubing, and fans, fastened to a base or installed within an enclosure. A steady-state standard condensing unit system simulation model is assembled from conventional, physics-based component equations. Specifically, a four-section, lumped-parameter approach is used to represent the condenser, while well-established equations model compressor mass flow and power. To increase capacity and efficiency, enhanced condensing units include an economizer loop, configured in either upstream or downstream extraction schemes. The economizer loop uses an injection valve, brazed-plate heat exchanger (BPHE) and scroll compressor adapted for vapor injection. An artificial neural network is used to simulate the performance of the BPHE, as physics-based equations provided insufficient accuracy. The capacity and power results from the condensing unit model are generally within 5% when compared to the experimental data. A transient ice machine model calculates time-varying changes in the system properties and aggregates performance results as a function of machine capacity and environmental conditions. Rapid "what if" analyses can be readily completed, enabling engineers to quickly evaluate the impact of a variety of system design options, including the size of the air-cooled heat exchanger, finned surfaces, air flow rate, ambient air and inlet water temperatures, compressor capacity and/or efficiency for freeze and harvest modes, refrigerants, suction/liquid line heat exchanger and thermal expansion valve properties. Simulation results from the ACIM model were compared with the experimental data of a fully instrumented, standar (open full item for complete abstract)

Committee: David Myszka (Advisor); Kevin Hallinan (Committee Member); Andrew Chiasson (Committee Member); Rajan Rajendran (Committee Member) Subjects: Computer Engineering; Condensation; Conservation; Design; Endocrinology; Energy; Engineering; Environmental Economics; Environmental Education; Environmental Engineering; Environmental Science; Mechanical Engineering

Master of Science, The Ohio State University, 2011, Mechanical Engineering

A zero-dimensional fluid and thermodynamic model of an engine, cooling system, and exhaust system was developed in order to simulate the operation of an advanced thermal management system. The model was calibrated with experimental data where available. The thermal management system modeled in this work employed waste heat recovery to reduce engine, coolant, and lubricating fluid warm-up times and fuel consumption following a cold-start. The model was used to develop a control strategy for two valves in the exhaust system which control the flow of exhaust through an exhaust-to-coolant heat exchanger. The objective of the controller was to minimize coolant warm-up time without violating any of the system constraints. A model-based open-loop controller was developed that was able to reduce warm-up time by nearly 35% on the FTP city drive cycle while respecting the limitations of the system.

Committee: Marcello Canova Dr. (Advisor); Giorgio Rizzoni Dr. (Committee Member); Timothy Scott Dr. (Committee Member) Subjects: Automotive Engineering

Doctor of Philosophy, University of Akron, 2016, Mechanical Engineering

Waste heat energy harvesting has been one of the techniques used to reduce emission of CO2 and improve efficiency of power generation, oil mining and different industrial processes. Nearly 90% of waste heat is considered low-grade (< 230OC) and is unsuitable for traditional waste heat recovery techniques. Thus, a non-continuous SMA Energy Harvesting prototype (EHP) to convert low-grade heat into electricity is presented in this research. We first demonstrate the feasibility of EHP using non-continuous shape memory alloy actuators (SMA) to convert waste heat energy to electricity. Both linear and spring shaped SMA wires made of NiTi alloy have been used to evaluate the energy harvesting capability of EHP. The experimental results proved that the EHP can generate oscillatory shaft rotation. The EHP test where the generator was connected to the main shaft through gear-box provided nearly 10V and 2.5rads shaft rotation in 0.3s. It was also found that the helical spring SMA actuator energy conversion factor was higher than that of the linear SMA actuator. Next, energy storage on both super-capacitors and micro-capacitors by the EHP with the helical spring SMA wire was explored. Using full-wave rectifier circuit, the average steady state energy stored across 6F capacitor per 2.5s of operation was 7.4mJ that is greater by factors of 4, 2 2 from the stored energy across 1.4mF, 2.2mF & 3.3mF capacitors, respectively. The SMA cyclic heating and cooling experiment was developed to evaluate the relationship between SMA stress and SMA temperature, and to validate the hysteretic behavior of SMA actuator upon thermal loading. Sigmoidal-Weibull 4 parameter model was obtained as the best curve fitted model to the experimental SMA stress-temperature data. The test results also disclosed the hysteretic characteristic of SMA wires induced by cyclic thermal loading This confirmed the functionality of presented energy harvesting device using SMA actuators. Then, Heat trans (open full item for complete abstract)

Committee: Erik Engeberg Dr. (Advisor); Celal Batur Dr. (Committee Co-Chair); D. Dane Quinn Dr. (Committee Member); Hariharan Subramaniya I Dr. (Committee Member); Alper Buldum Dr. (Committee Member) Subjects: Automotive Engineering; Energy; Engineering; Materials Science; Mechanical Engineering; Mechanics

Master of Sciences, Case Western Reserve University, 2011, Materials Science and Engineering

A brazing method is developed for high efficiency microchannel heat plate heat exchangers for waste heat recovery. Prototype elements for these heat exchangers are fabricated by laser machining 316 stainless steel, and bonding with AMS 4777 brazing alloy. Specifications require that the heat exchangers withstand in excess of 5000psi of fluid pressure, tested with a high pressure water system that was developed for this project. Due to the costly nature of the pressure test, a model is developed to correlate braze performance in the heat exchanger with data from inexpensive mechanical tensile and peel tests. The model predicts that the maximum peel load per specimen width will be 342lbs/in and a maximum pressure of 7200psi in the heat exchanger. The highest value from the experiments is 330lbs/in for peel load and 6467psi in the pressure test, 97% and 90% of their respective theoretical values.

Committee: David Schwam PhD (Advisor); John Lewandowski PhD (Committee Member); Gerhard Welsch PhD (Committee Member) Subjects: Energy; Materials Science; Mechanical Engineering

Doctor of Philosophy (PhD), Ohio University, 2023, Mechanical and Systems Engineering (Engineering and Technology)

The science of organic Rankine cycle (ORC) waste heat recovery is advanced through a demonstration system including a scroll expander-generator, zeotropic mixture working fluid, low approach temperature counterflow heat exchangers, and regenerative-turbine liquid pump. A warm-water cooled information and communication technology high performance computing rack consuming 30kW electricity is the focus system. Viability of ultra-low waste heat recovery is improved by maximizing electricity production and minimizing both heat transfer inefficiencies and parasitic losses. Peak scroll expander isentropic efficiency exceeds 60% but falls precipitously in off-design conditions. The selected working fluid complies with environmental, health, and safety requirements and exhibits optimum thermal performance but built environment use rules of A2L fluids are in process of being formalized. Liquid pump limitations create space challenges for heat rejection to ambient equipment. The ORC is a net consumer of electricity but can significantly improve power usage effectiveness (PUE). However, TH to TL difference with typical maximum CPU temperature and maximum data center ambient temperature create a flow instability regime in the expander. Year-round ORC operation is thus precluded.

Committee: Greg Kremer (Committee Chair) Subjects: Experiments; Mechanical Engineering

MS, University of Cincinnati, 2022, Engineering and Applied Science: Electrical Engineering

Solar Thermoelectric (TE) uses thermoelectric modules to absorb radiative energy given off by the sun and convert it into electricity. While its main competition, photovoltaic panels boast an efficiency of around 20%, solar TE panel can only muster around 5-7 % efficiency. This reason along with high material and manufacturing cost has been the cause as to why solar TE has not been extensively explored as an alternative solar energy harvester so far. However, due to the increasing effects of global warming, alternative sources of harnessing energy such as solar TE have been more closely researched. In the past decades, scientists have synthesized new TE materials that have shown great promise in increasing efficiency and power output, surpassing even the properties of Bismuth Telluride-based alloys, which have been widely used for low-temperature TE applications due to having one of the best efficiencies and power output available in the temperature range. This new materials discovery promises a great new technological innovation for the field of thermoelectric for years to come, but there are not many tools currently available that can simulate the effect of harnessing solar radiation using these materials. The Concentrating Solar Thermoelectric Generator Tool developed in the work takes advantage of the ever-developing world of thermoelectric materials by inputting users' newly developed or already known thermoelectric properties into the simulation. By using the users' own data, a power output and efficiency can be presented with varying independent variables: the cross-sectional area and thickness of the TE element, solar concentration, and fractional coverage while also taken into consideration the optical parameters and emissivity of the grey surfaces and heat transfer, amongst other data for an ideal optimization of solar TE design. This tool is intended to bridge the gap between the theoretical and experimental by introducing a way that scientists (open full item for complete abstract)

Committee: Je-Hyeong Bahk Ph.D. (Committee Member); Tao Li Ph.D. (Committee Member); Marc Cahay Ph.D. (Committee Member); Chong Ahn Ph.D. (Committee Member) Subjects: Materials Science

MARCH, University of Cincinnati, 2020, Design, Architecture, Art and Planning: Architecture

About 4.5 billion people across the world accessed the Internet in 2019. Every second, 63,000 searches occur on Google, over 8,600 tweets are sent, and roughly 940 photos are uploaded to Instagram. As we move toward a digital age, our economy and society continue to shift towards increased digital information management. This digital information is stored in data centers which have become ever present – they are found in nearly every sector of the economy – and are essential to the function of communication, business, academics, and governmental systems. These facilities can range from small, closet-sized rooms to massive warehouses full of thousands of servers. While we continue to embrace the digital world, the majority of us do not consider the physical ramifications data centers have. They are high-energy consuming typologies and collectively account for approximately 2% of the total electricity usage in the United States. As our country's appetite for data continues to grow, so does the demand for data centers. So, to what degree can architecture further develop the sustainability of data centers? Data centers produce heat, and a lot of it, which creates an opportunity to recapture that energy and use it to power the local communities they inhabit. Through architecture, their environmental impacts can be mitigated by transforming these high-energy consuming typologies into energy-producing resources. And how can architecture change the way we interact with these typologies? By incorporating new programs with the data, it will create a hub of technology and community spaces that reintroduce a human touch back into the otherwise mechanical and digitalized data center. As we continue to create more data, the demand for storage increases and it's time to talk about the physicality of “the cloud” and the impact it has on the communities it inhabits.

Committee: Elizabeth Riorden M.Arch. (Committee Chair); Michael McInturf M.Arch. (Committee Member) Subjects: Architecture

Master of Science, The Ohio State University, 2017, Mechanical Engineering

As fuel efficiency and emissions requirements continue to rise, auto manufacturers are continuously striving to adopt new technologies to help reach these goals. With methods such as turbocharging, direct fuel injection, variable valve actuation, and engine stop-start now common in mass production vehicles, the next step forward could be in waste heat recovery. In most vehicles today, more than 60 percent of fuel energy is lost to waste heat in the cooling system and exhaust. The higher temperature heat energy in the exhaust can be recovered using an Organic Rankine Cycle (ORC). Past research on ORC's focused on creating highly detailed models for performance prediction or controlling extremely simple models. Neither of these options are ideal for use in operating a real system. The detailed model is too slow and the controls based on the simple model are not accurate enough to predict what the real system will do. This thesis takes a highly detailed model and uses model order reduction to create a reduced order model which retains most of the prediction accuracy of the full model but is now smaller and faster. This new reduced model has been used with feedforward and feedback controls, but it also has the potential to be used in advanced model based controls such as model predictive control (MPC).

Committee: Marcello Canova Ph.D. (Advisor); Giorgio Rizzoni Ph.D. (Committee Member) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 2014, Mechanical Engineering

Organic Rankine Cycles are used for Waste Heat Recovery from low temperature heat sources. In an Internal Combustion Engine, roughly one-third of the fuel energy is sent out through the exhaust. ORC's were investigated for fuel efficiency improvements for heavy duty trucks in the 70's during the oil crisis. ORC's have once again gained interest with the current energy scenario and advances in technology. A recuperated ORC with R245fa as refrigerant is modeled in this thesis using the commercial 1-D simulation software GT-SUITE. The ORC is designed to extract energy from the exhaust of a gasoline powered light duty vehicle. Control inputs for the ORC are pump speed, expander speed and exhaust gas bypass valve position. The exhaust gas is not a steady source of heat, with varying temperature and mass flow rate depending on the operation of the vehicle. To maintain the ORC at a pre-determined operating state, feed-forward maps will be created. Exergy destruction is proposed to be used as a parameter that limits the control effort within reasonable limits. A second law analysis will be performed to identify points of exergy destruction and the ORC will be optimized using a Multi-Objective Particle Swarm Optimization algorithm to generate a Pareto front of net power output and exergy destruction in the system for a single exhaust condition that will allow the decision maker to choose a suitable state for the ORC. The Pareto front will be constructed for other off-design exhaust conditions and the trends will be observed between multiple exhaust gas conditions.

Committee: Marcello Canova PhD (Advisor); Shawn Midlam-Mohler PhD (Committee Member) Subjects: Automotive Engineering