Master of Science (M.S.), University of Dayton, 2023, Aerospace Engineering

The main objective of this project is to investigate the performance of Phase Change Materials as the Heat Exchange media in a solar thermal propulsion system. The secondary objective is to visualize and develop the solar thermal propulsion system by running various ground tests using a solar simulator as power source. The project involves design, modelling and fabrication of a bench scale Solar Thermal Propulsion System that can be used to carry and deliver satellites to Moon or Mars' orbit from LEO. PCM's are essential for space travel since the solar energy needs to be stored for the spacecraft to successfully complete the interplanetary missions which consume time and fuel. Without the energy storage system, the spacecraft might need to use conventional fuel ignition systems, which cost money to manufacture and implement in the spacecraft. In this system, the energy from solar light is concentrated into a small cavity through a parabolic reflector and is used to heat the PCM, which in turn heats the propellant and directs it through the nozzle to provide thrust adequate to travel in space. The prototype of the system is first designed using a CAD software and later fabricated into a bench scale model. The model is then set up in the laboratory and connected to a high flux solar simulator. Computational simulations and some test runs of the physical model would be conducted to analyze the performance of PCM in this system

Committee: Rydge Mulford (Committee Chair); Andrew Schrader (Committee Member); Jamie Ervin (Committee Member) Subjects: Aerospace Engineering; Energy; Mechanical Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2019, Electrical and Computer Engineering

Electric power grids are currently undergoing a major transition from large centralized power stations to distributed generation in which small and flexible facilities produce power closer to where it is needed. This move towards a decentralized delivery of energy is driven by a combination of economic, technological and environmental factors. In recent years, the cost of renewable energy in the form wind turbines and solar PV has dropped dramatically due to advances in manufacturing and material science, leading to their rapid deployment across the US. To supplement the intermittent nature of wind and solar energy, there is a growing need for small, highly controllable sources such as natural gas turbines. With the fracking boom in the US, there is currently abundant natural gas to use for this purpose. The resulting proliferation of many small energy producers creates technical problems such as voltage and frequency control that can be addressed with battery storage, whose cost is also dropping. These factors are leading to a move away from large energy production facilities that require too much initial investment. Also, a distributed supply is more efficient and reliable. The threat of global climate change is creating pressure to increase the integration of distributed generation and information technology is now capable of managing a greater number of energy producers, utilizing a vast supply of information to predict supplies and demand and to determine optimal dispatching of energy. The move towards a higher percentage of renewable energy creates many interesting technical issues, many of which are due to the lack of control over the renewable resources. Energy dispatching between multiple sources, some controllable and some not, and multiple loads leads to a need for dispatching strategies that maximize the percentage of the load that is met with renewable energy. A growing aspect of this energy dispatch is a stream of information about energy demand, w (open full item for complete abstract)

Committee: Malcolm Daniels Dr. (Advisor) Subjects: Electrical Engineering; Energy; Mechanical Engineering

Master of Science (M.S.), University of Dayton, 2017, Renewable and Clean Energy

Photovoltaic-thermal (PVT) technology is a relatively new technology that comprises a photovoltaic (PV) panel coupled with a thermal collector to convert solar radiation into electricity and thermal energy simultaneously. Since cell temperature affects the electrical performance of PV panels, coupling a thermal collector with a PV panel contributes to extracting the heat from the latter to improve its performance. In order to ensure a sufficient temperature difference between the PV cells and the working fluid temperature entering the thermal collector, the circulated water has to reject the heat that has been removed from the PV cells into a relatively colder environment. Borehole thermal energy storage (BTES), which is located underground, often serves as this relatively colder environment due to the stability of underground temperatures, which are usually lower than the working cell temperature. Use of BTES is especially beneficial in summer, when the degradation in cells efficiency is highest. In this thesis, the electrical, thermal, and economic performances of a PVT system are evaluated for three types of buildings -- residential, small office, and secondary school -- in two different climates in the United States, one of which is hot and the other is cold. For each case, two different scenarios are considered. In the first, a PVT system is coupled with BTES, and a ground-coupled heat pump (GCHP) is in use. In the second, a PVT system is coupled with BTES and no GCHP is in use. Each scenarios' GCHP performance is assessed as well. Both the PVT collectors and GCHP performances are evaluated over short and long-term to study the effect of continued ground heat imbalance on both technologies.

Committee: Andrew Chiasson Ph.D. (Committee Chair); Youssef Raffoul Ph.D. (Committee Member); Robert Gilbert Ph.D. (Committee Member) Subjects: Energy; Engineering; Mechanical Engineering

Master of Sciences, Case Western Reserve University, 2022, Physics

The increasing adoption of renewable sources of electricity (i.e. wind and solar farms) is being driven by the demand for carbon neutral electricity production. Although zero carbon is emitted during electricity production, these renewable energy sources suffer from intermittency, which is a mismatch between the supply and demand of electricity of the grid. Renewable energy sources, such as wind and solar, produce their peak electricity at off-demand periods of the day. This strains the electrical grid as it risks over-generation in some locations as well as a need for quick ramping of the electrical load which is hard on electricity producing infrastructure. As a partial solution to intermittency, pumped storage hydropower (PSH) is the dominant form of grid-scale energy storage. PSH accounts for 95% of the U.S. grid-scale storage capacity, which amounts to 22.9 GW of capacity [1]. The EIA also estimates with all possible sites, the U.S. can double their PSH capacity [1]. However, much more than that is not feasible being constrained by the availability of locations suitable for PSH. As a result, other gridscale energy storage options are in development. The main options include batteries, thermal energy storage, compressed air energy storage (CAES) and flywheels. However, these storage options are plagued by high cost per kWh prices, location specificity (ex. PSH, CAES) and/or low energy density. With these concerns in mind, Cratus LLC is developing a molten salt thermal energy storage option known as ThermaBlox, which is location-independent, low-cost, and high-capacity (with the capability to scale). ThermaBlox will play a significant role in intermittency reduction while enabling increased adoption rates of renewable energy.

Committee: Edward Caner (Committee Chair); Dr. Benjamin Monreal (Committee Member); Dr. Robert Brown (Committee Member) Subjects: Chemical Engineering; Energy; Engineering; Entrepreneurship; Fluid Dynamics; Mathematics; Nanotechnology; Physics; Technology

Doctor of Philosophy (PhD), Ohio University, 2021, Chemical Engineering (Engineering and Technology)

Incorporation of potassium bifluoride (KF-HF) as an additive to lithium-halide electrolyte for thermal batteries was investigated. Results indicated that it is feasible to maintain a relatively high ionic conductivity at temperatures (250-300 C) lower than current thermal battery electrolytes (400-550 C). Mixtures of lithium fluoride and potassium bifluorides with the 40-60 wt.% provided the best ionic conductivity at 260 C. Ceramic felts are shown to be an effective alternative to widely used MgO. One of the major benefits of ceramic felts is their high porosity and low weight. LiSi/FeS2 thermal cells with YSZ and Al2O3 ceramic felt electrolyte/separators reported specific energy of 58.47 Wh kg-1 and 43.96 Wh kg-1. Pellet design pyrite (FeS2) cathodes for thermal batteries usually have low electronic conductivity. A new cathode design was developed using iron particles. By adding 11 wt.% Fe particles to the cathode the ohmic polarization was reduced by 17.5% while the available capacity was increased by 78% over the cell with traditional cathode pellet with no electrically conductive particle additives.

Committee: Gerardine Botte (Advisor); Valerie Young (Advisor) Subjects: Chemical Engineering; Energy; Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2020, Mechanical Engineering

This dissertation focusses mainly on loads determination, building informatics, and geothermal energy systems. The first chapter is Low-Energy Opportunity for Multi-Family Residences: A Simulation-Based Study of a Borehole Thermal Energy Storage System. In this chapter, we propose a district borehole thermal solar energy storage (BTES) system for both retrofit and new construction for a multi-family residence in the Midwestern United States, where the climate is moderately cold with very warm summers. Actual apartment interval power and water demand data was mined and used to estimate unit level hourly space and water heating demands, which was subsequently used to design a cost-optimal BTES system. Using a dynamic simulation model to predict the system performance over a 25-year period, a parametric study was conducted that varied the sizes of the BTES system and the solar collector array. A life-cycle cost analysis concluded that is it possible for an optimally-sized system to achieve an internal rate of return (IRR) of 11%, while reducing apartment-wide energy and carbon consumption by 46% The promise for district-scale adoption of BTES in multi-family residences is established, particularly for new buildings. In the second chapter (Alternate Approach to the Calculation of Thermal Response Factors for Vertical Borehole Ground Heat Exchanger Arrays Using an Incomplete Bessel Function), we presents another methodology for the calculation of dimensionless thermal response factors for vertical borehole ground heat exchanger (GHX) arrays, which is a concept introduced by Eskilson (1987). The presented method is based on a well-known solution to an analogous problem in the field of well hydraulics. This solution method, known mathematically as an incomplete Bessel function, and known in the field of well hydraulics as the `leaky aquifer function', describes the hydraulic head distribution in an aquifer with predominantly radial flow to a well combined with vertical (open full item for complete abstract)

Committee: Kevin P Hallinan Professor (Committee Chair); Andrew D. Chiasson Professor (Committee Member); Robert J. Brecha Professor (Committee Member); Robert B. Gilbert Professor (Committee Member) Subjects: Mechanical Engineering

MS, University of Cincinnati, 2008, Engineering : Mechanical Engineering

Sensible charging of cold and hot water thermal energy storage tanks has been studied experimentally and theoretically using a heat exchanger equipped with multiple thermoelectric (TE) modules. The primary objective was to design a simple, but effective, modular Peltier heat pump system component to provide chilled or hot water for domestic use at the appliance level; and when arranged in multiple unit combinations, a system that can potentially satisfy small home cooling and heating requirements. Moreover, when the TEs are directly energized using solar PV panels, the system provides a renewable, pollution free and off-the-grid solution to supplement home energy needs. The present work focuses on the (1) design, (2) testing and (3) theoretical modeling of a thermoelectric heat exchanger component that consists of two water channels machined from two aluminum plates with an array of three or five thermoelectric modules placed in between to transiently cool and/or heat the water in the thermal energy storage tank. The water passing over either the cold or hot side of the TE modules is recirculated to charge the cold or hot thermal storage tank, respectively. The temperatures in the prototype Peltier heat exchanger test component and thermal energy water storage tank were measured during both cold tank charging and hot tank charging operation. In addition, a mathematical model was developed and numerically solved to predict the charging of cold and hot water tanks using thermoelectric modules heat exchanger device. Equations are developed for the heat pumped by the TE module as a function of the temperature difference across it for the appropriate values of the heat sink temperatures. These equations, along with those for the three lumps, are then finite differenced with a stable time step, so that a smooth variation of temperatures could be obtained. The temperature history of the tank water, thus obtained as a function of time using a three-lumped parameter model i (open full item for complete abstract)

Committee: Michael Kazmierczak (Committee Chair); Sang Young Son (Committee Member); Ronald Huston (Committee Member); Rupak Banerjee (Committee Member) Subjects: Mechanical Engineering

Master of Science (M.S.), University of Dayton, 2011, Chemical Engineering

The specific energy storage capacities of phase change materials (PCMs) increase with temperature, leading to a lack of thermal management (TM) systems capable of handling high heat fluxes in the temperature range from 20°C to 100°C. State of the art PCMs in this temperature range are usually paraffin waxes with energy densities on the order of a few hundred kJ/kg or ice slurries with energy densities of the same magnitude. However, for applications where system weight and size are limited, it is necessary to improve this energy density by at least an order of magnitude. The compound ammonium carbamate (AC), [NH4 ][H2NCOO], is a solid formed from the reaction of ammonia and carbon dioxide which endothermically decomposes back to ammonia and carbon dioxide in the temperature range of 20°C to 100°C with an enthalpy of decomposition of 2,010 kJ/kg. Various methods to use this material for TM of low-grade, high-flux heat have been evaluated including: bare powder, thermally conductive carbon foams, thermally conductive metal foams, hydrocarbon based slurries, and a slurry in ethylene glycol or propylene glycol. A slurry in glycol is a promising system medium for enhancing heat and mass transfer for TM. Small-scale system level characterizations of AC in glycol have been performed and results indicate that AC is indeed a promising material for TM of low-grade heat. It has been shown that pressures on the order of 200 torr will achieve rapid decomposition and thermal powers of over 300 W at 60°C have been found, demonstrating the capability of AC.

Committee: Kevin Myers D.Sc., P.E. (Committee Chair); Douglas Dudis Ph.D. (Advisor); Robert Wilkens Ph.D., P.E. (Committee Member) Subjects: Chemical Engineering

PhD, University of Cincinnati, 2023, Engineering and Applied Science: Mechanical Engineering

Storage technologies play a significant role in managing temporal fluctuations in energy supply and demand, which is key to transition towards a renewable and sustainable energy infrastructure. Thermal energy storage (TES) systems, in particular, have different applications across numerous industries to improve thermal management, reliability and reduce operation cost. This study focuses on investigating its novel use in enhancing the performance of an air-cooled condenser in thermal power plants. Despite numerous investigations, the large-scale adoption of Phase Change Material (PCM) based TES Systems (which are relatively compact and cost-effective) has been limited due to frequent reports of low PCM reliability, poor TES performance and the lack of relevant experimental data in the literature. This dissertation aims to address such issues to develop and test novel TES designs for high performance and reliability. To select the PCM to be used in the TES, in Chapter 2, the salt hydrate PCM- lithium nitrate trihydrate (Tsf= 30°C, hsf= 274 kJ/kg)- is identified and evaluated by subjecting it to extended thermal cycling to ascertain its long-term performance. Additionally, the material compatibility of the PCM with metals is also evaluated. The results suggest negligible loss of capacity and subcooling indicating the superior performance of the PCM with self-seeding compared to the traditional methods where nucleating agents are used. Additionally, the low thermal conductivity of PCM has typically limited the heat transfer performance in a TES. While a large section of the literature addresses the issue by designing high thermal conductivity PCM composites, the current study looks at a simpler alternative by reducing the length scale of the PCM encasement, thereby avoiding limitations and complications associated with the former method. Experimental and numerical work was carried out to identify the optimal l (open full item for complete abstract)

Committee: Raj Manglik Ph.D. (Committee Chair); Milind Jog Ph.D. (Committee Member); Kishan Bellur Ph.D. (Committee Member); Je-Hyeong Bahk Ph.D. (Committee Member) Subjects: Engineering

Master of Science in Engineering, Youngstown State University, 2023, Department of Electrical and Computer Engineering

Lithium-ion batteries have revolutionized our everyday lives by laying the foundation for a wireless, interconnected and fossil-fuel-free society. Additionally, the demand for Li-ion batteries has seen a dramatic increase, as the automotive industry shifts up a gear in its transition to electric vehicles. To optimize the power and energy that can be delivered by a battery, it is necessary to predict the behavior of the cell under different loading conditions. However, electrochemical cells are complicated energy storage systems with nonlinear voltage dynamics. There is a need for accurate dynamic modeling of the battery system to predict behavior over time when discharging. The study conducted in this work develops an intuitive model for electrochemical cells based on a mechanical analogy. The mechanical analogy is based on a three degree of freedom spring-mass-damper system which is decomposed into modal coordinates that represent the overall discharge as well as the mass transport and the double layer effect of the electrochemical cell. The dynamic system is used to estimate the cells terminal voltage, open-circuit voltage and the mass transfer and boundary layer effects. The modal parameters are determined by minimizing the error between the experimental and simulated time responses. Also, these estimated parameters are coupled with a thermal model to predict the temperature profiles of the lithium-ion batteries. To capture the dynamic voltage and temperature responses, hybrid pulse power characterization (HPPC) tests are conducted with added thermocouples to measure temperature. The coupled model estimated the voltage and temperature responses at various discharge rates within 2.15% and 0.40% standard deviation of the error. Additionally, to validate the functionality of the developed dynamic battery model in a real system, a battery pack is constructed and integrated with a brushless DC motor (BLDC) and a load. Moreover, because of the unique pole ori (open full item for complete abstract)

Committee: Kyosung Choo PhD (Advisor); Frank Li PhD (Committee Member); Alexander Pesch PhD (Committee Member) Subjects: Electrical Engineering; Energy; Engineering; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2022, Chemistry

Covalent organic frameworks (COFs) are an emerging class of crystalline porous organic polymers composed of light elements (C, H, N, O, and B) connected through strong covalent bonds. The design and syntheses of COFs primarily relies on the principles of dynamic covalent chemistry in conjunction with non-covalent interactions. COF structures are often accessed via the utilization of reversible bond-forming reactions under reaction conditions that promote this reversibility to achieve porous, ordered materials that can be characterized as having high surface areas, permanent porosities, low densities, and high chemical and thermal stabilities. One of the prominent advantages of COFs is their modular nature. Through reticular chemistry, careful structure design, and choice of building units can allow for the fabrication of materials suited for specific applications. These principles have been employed to tune the stability, crystallinity, and properties of different materials.COFs also possess a high degree of π-conjugation and are insoluble in most common organic solvents. These attractive assets have made COFs of great interest in a range of applications and fields including chemical sensing, energy storage, catalysis, and gas capture and storage. This research will focus on the design of COFs for use as organic anode materials in potassium ion batteries as well as the investigation of their thermal conductivities. There is currently growing interest in the development of organic electrode materials for energy storage devices due to their sustainability and low costs. Currently, the industry standard anode material is graphite, a material that has yet to reach its theoretical potential. In efforts to synthesize a layered material with properties similar to the carbon allotrope, graphyne, two alkynyl-containing COFs were investigated as potential organic anode materials in potassium ion batteries; TAEB-COF and DBA-COF 3. After 300 cycles at a current density of (open full item for complete abstract)

Committee: Psaras McGrier (Advisor); Jovica Badjic (Committee Member); Jon Parquette (Committee Member) Subjects: Chemistry

MS, University of Cincinnati, 2021, Engineering and Applied Science: Mechanical Engineering

In effort to both save operating expenses and be environmentally friendly, thermal energy storage provides a means for companies to handle daytime HVAC requirements while using off-peak (nighttime) electrical power. This paper sets out to compare three of the most common techniques used for thermal energy storage, by comparing both the analytical modeling of their energy storage and actual experimental data for their energy storage, using the same exact test apparatus for each of the techniques. The results of this experiment show that using normal HVAC temperatures, sensible water chilled to its maximum value after only about two hours, while PCM would take nearly six hours to achieve “linkage,” or solidified material merging between the helix coils. Ice building, done with -7° coolant, took 4.5 hours to achieve linkage. Initial heat transfer was proportional to the difference between initial tank temperature and the coolant temperature, and went asymptotically towards zero for sensible as the temperature of the tank and coolant reach equilibrium. For ice, the heat transfer rate was always more than twice that of PCM during latent storage, which is attributed to the difference between coolant temperatures and freezing points for the respective materials. Sensible water cooldown would require 232.8% of the tank volume to store the same energy relative to the environment compared to ice building, and 126.3% of the tank volume compared to phase change material. This is to be weighed with the benefit of using existing HVAC condensing units to chill the water, and the fact that water itself is inexpensive. The high latent heat of freezing for water meant it held more energy than both the water sensible cooldown and PCM freezing, but with the downside of requiring medium temperature condenser units in order to be efficient (instead of the high temperature units used in typical HVAC). After 4.5 hours, PCM would surpass the energy stored in the same volume as water sensi (open full item for complete abstract)

Committee: Michael Kazmierczak Ph.D. (Committee Chair); Ahmed Elgafy Ph.D. (Committee Member); Sang Young Son Ph.D. (Committee Member) Subjects: Mechanical Engineering

MS, University of Cincinnati, 2021, Engineering and Applied Science: Mechanical Engineering

Electric power plants generally operate on the Rankine cycle where the steam from the turbine exhaust is cooled and condensed. A significant amount of water is used as the coolant for the condensation process, and it becomes a challenge where water resources are scarce. Use of air-cooled condensers can help solve the problem. However, the air-cooled condensers can be less efficient in the hottest months of the year and this issue must be addressed to increase their adoption in power plants. One method to overcome this second law limitation is to use an air pre-cooler coupled with a phase change material (PCM) based thermal energy storage (TES) to cool the air supplied to the air-cooled condenser during peak day time temperatures. The TES is recharged at night when ambient air temperature drops below the PCM freezing temperature. In the present study, a computational model is developed to simulate the working of a TES unit coupled with an air pre-cooler using an Eulerian approach. The model was developed using MATLAB and the numerical results are validated against the available experimental data. The energy storage capacities of the two units considered in the study are 100 kJ and 1 MJ. The hot fluid entering the TES unit enables the PCM to undergo melting (extraction). The heat absorbed from the fluid is stored in the PCM and is released during the daytime when the air temperatures are high. The flow direction is switched based on certain conditions and the cold fluid is passed through the opposite direction in the TES unit. This enables the PCM to freeze (charging) and be ready for the next cycle. A parametric study involving the effect of changing PCM melt temperatures and mass flow rates has been carried out for the system. Results show that the PCM melting temperature significantly affects the performance of the TES. A change in the mass flow rate of the heat transfer fluid between the air pre-cooler and the TES can change the melt fraction of the PCM. The comb (open full item for complete abstract)

Committee: Milind Jog Ph.D. (Committee Chair); Raj Manglik Ph.D. (Committee Member); David Thompson Ph.D. (Committee Member) Subjects: Mechanical Engineering

MS, University of Cincinnati, 2019, Engineering and Applied Science: Mechanical Engineering

One of the major steps taken against global warming is to reduce the dependency of fossil fuels that forms 78.9% of the primary energy consumed [1]. This effort is pushed forward primarily by designing more efficient systems and tapping in to renewable sources of power. Thermal energy storage (TES) systems provide numerous solutions for such challenges. Some of them include providing optimum temperature for system operation from chips in computers to condensers in thermal power-plants. TES also help to capture and store intermitted supply of solar energy for later use such as in concentrated solar power plants and district heating applications. It also has applications in HVAC, aviation and process industries [2]. With the increase in demand for such solutions the market for TES systems and Phase Change Materials is expect to double by 2023. This research explores salt hydrate based phase-change materials (PCM) that can store this heat. These salts are screened and promising ones are characterized based on their thermal properties and cycling stability. After screening several salt hydrate based PCM in the melting range of 25-35°C, Lithium Nitrate Trihydrate and Calcium Chloride Hexahydrate was chosen because of their relatively stable behavior. Firstly, the phase change temperature and the latent heat capacity was measured using the Lumped Capacitance T-History method. Following which a mDSC was used to measure the specific heat. Additionally, the density of the liquid and solid phase was also determined using Archimedes' Principle. After the initial characterization, the effects of nucleating agents on Lithium Nitrate Trihydrate (LNT) and Calcium Chloride Hexahydrate (CCH) was studied. CCH was doped with a known nucleating agent - SrCl2- which reduced subcooling to <4°C and thermal capacity to 167kJ/kg from 187kJ/kg. In the case of LNT a novel nucleating agent was discovered by conducting crystallographic using lattice mismatch technique. The new nucleating ag (open full item for complete abstract)

Committee: Raj Manglik Ph.D. (Committee Chair); Milind Jog Ph.D. (Committee Member); Navin Kumar Ph.D. (Committee Member) Subjects: Energy

MS, University of Cincinnati, 2016, Engineering and Applied Science: Mechanical Engineering

The University of Cincinnati utilizes large scale stratified thermal energy storage (TES) tanks in its water cooling system. The goal of this study is to investigate the potential benefits of an affordable, easily manufactured and installed system incorporating phase change materials (PCM) to augment the thermal capacity of these pre-existing stratified tanks. A 187-gallon laboratory TES tank has been constructed and installed into the chilled water system at the University of Cincinnati's east power plant. A rack made of PVC with cylindrical copper tubes full of PCM placed along its height was set in the center of the laboratory TES tank to test the effects of augmenting the University's TES tanks with PCM. The laboratory TES tank was tested first without the PCM (sensible thermal storage) in order to gather reference data, and then was tested with the cylinders of PCM (sensible and latent thermal storage) augmenting thermal capacity. Separate charge and discharge half-cycle tests were run with flow rates between 0 and 2.5 GPM, and then continuing half-cycle tests were run with a controlled flow rate of 2.5 GPM. Charge time, discharge time, thermocline thickness, storage capacity, half figure of merit (FOM), and system efficiency were calculated for each test and used to draw conclusions on tank performance. It was found that the use of PCM in the laboratory stratified TES tank increased the thermal storage capacity of the tank by approximately 10% while thermocline thickness remained nearly the same, and system efficiency slightly increased.

Committee: Michael Kazmierczak Ph.D. (Committee Chair); Ahmed Elgafy Ph.D. (Committee Member); Milind Jog Ph.D. (Committee Member) Subjects: Engineering

Master of Science (MS), Ohio University, 2014, Mechanical Engineering (Engineering and Technology)

The goal of this study is to evaluate thermally conductive graphite foams for use in thermal energy storage (TES) devices. A phase change material (PCM) can absorb heat during melting and release it during solidification. Most PCM have very low thermal conductivity values, which leads to slow melting rates. Therefore, a thermally conductive enhancer (TCE) is needed to melt the PCM at a faster rate. Graphite foams can be used as a TCE due to their high overall surface area, relatively low weight, and their ability to be manufactured with high thermal conductivity. This thesis examines the melt behavior of the PCM when infiltrated into graphite foam. The heat exchanger coupon used in this study is made of two blocks of foam separated by a parting plate. Two different materials are investigated as the parting plate: stainless steel and aluminum. Two different methods of bonding the foam to the parting plate are evaluated; they are bonding by epoxy, and a brazing method. The melting time of the PCM with different bonding methods are compared to the case when the foam coupons are not bonded to the parting plate. The experimental results indicate that the heat transfer rate is significantly influenced by the bonding method as well the thermal mass associated with the bonding material.

Committee: Khairul Alam (Advisor); David Bayless (Committee Member); John Cotton (Committee Member); Tatiana Savin (Committee Member) Subjects: Mechanical Engineering

MS, University of Cincinnati, 2014, Engineering and Applied Science: Mechanical Engineering

This thesis describes a novel system that is being developed that utilizes latent thermal energy storage (LTES) to shift residential heating and cooling loads, between 2-4 hr. time periods, away from the electrical power grid (during the utilities' peak demand period) for the main purpose of residential demand-side-management. More and more utilities are now offering residential time-of-day rates (and load interrupt programs) to help improve their load factor as a means to curtail the building of new power generating stations, and will only increase in time with greater implementation and the enabling use of smart meters. TES is ideally suited to capitalize on this fact and stands ready in this proposed new system; running the HVAC equipment during the time of excess system capacity and storing the “hot or cold energy created” in the PCM for later use during the peak system demand period will improve the system's load. This thesis describes the proposed system and the equipment layout along with its operating strategy. In addition to being modular in design and thus allowing for all different size homes, another major key feature of the proposed system is that it is of the “plug-in” type which utilizes the current cooling and heating hardware of the existing home, and as such, is equally applicable to new home construction or retrofits. This thesis also presents the economics of the system and potential benefits to the home owner, more specifically, simple calculations are given showing the estimated monthly operating cost savings when using this TES system with residential time-of-day (TD) rates, over that of the home operating without TES and running on the standard residential service (RS) rate structure. This thesis document provides the detailed mathematical formulation for the solution of planar moving boundary problems using enhanced enthalpy method with given fixed temperature and insulated boundary conditions. The solution methodology and results, obt (open full item for complete abstract)

Committee: Michael Kazmierczak Ph.D. (Committee Chair); Ahmed Elgafy Ph.D. (Committee Member); Frank Gerner Ph.D. (Committee Member) Subjects: Mechanics

MS, University of Cincinnati, 2004, Engineering : Mechanical Engineering

Substantial thermal performance improvement in ice-on-tube TES (thermal energy storage) systems is possible by making use of porous copper mesh as a HCED (Heat Conducting Enhancement Device). HCEDs are inexpensive heat transfer augmentation devices that will result in faster rate of ice growth and larger final steady state ice build volume by reducing the controlling thermal conduction resistance of the ice layer. This will improve the competitiveness of external ice-on-tube systems as compared to other TES systems such as dynamic ice harvesters and static internal melt systems. In this study the degree of ice growth enhancement is predicted theoretically, by performing simplified calculations, and is then validated in the laboratory through carefully controlled experiments. This study shows ice volume increase between 50-90% is possible.

Committee: Dr. Michael Kazmierczak (Advisor) Subjects: Engineering, Mechanical

Master of Science (M.S.), University of Dayton, 2011, Aerospace Engineering

A thermal energy storage device that uses pentaglycerine as a phase change material was developed. This solid-state phase change material was embedded in a carbon foam thermal conduction enhancer. This device and others identically constructed but using a paraffin phase change material were tested by imposing different input fluxes, 2.3 or 6.0 W/cm2 on one end, while the opposite end was either insulated or actively cooled with an output flux that varied from 3.1 to 5.4 W/cm2. The resulting temperature distributions within the devices were recorded at five locations; this information was used to determine the specific energy storage capacity, heating rate and the cycling performance of each device. It was found that the pentaglycerine/foam combination is capable of a specific storage capacity of 67 J/g; it demonstrated a storage capacity 174% of the paraffin/foam device, by eliminating the volume change and leakage problems associated with solid-liquid phase change materials.

Committee: Jamie S. Ervin PhD (Advisor); Steven Zabarnick PhD (Committee Member); Paul J. Kreitzer PhD (Committee Member) Subjects: Aerospace Engineering; Aerospace Materials; Engineering; Materials Science