Current Search: melting (x)
-
-
Title
-
DESIGN AND EXPERIMENTAL STUDY OF AN INTEGRATED VAPOR CHAMBER THERMAL ENERGY STORAGE SYSTEM.
-
Creator
-
Kota, Krishna, CHOW, LOUIS, University of Central Florida
-
Abstract / Description
-
Future defense, aerospace and automotive technologies involve electronic systems that release high pulsed waste heat like during high power microwave and laser diode applications in tactical and combat aircraft, and electrical and electronic systems in hybrid electric vehicles, which will require the development of an efficient thermal management system. A key design issue is the need for fast charging so as not to overheat the key components. The goal of this work is to study the fabrication...
Show moreFuture defense, aerospace and automotive technologies involve electronic systems that release high pulsed waste heat like during high power microwave and laser diode applications in tactical and combat aircraft, and electrical and electronic systems in hybrid electric vehicles, which will require the development of an efficient thermal management system. A key design issue is the need for fast charging so as not to overheat the key components. The goal of this work is to study the fabrication and technology implementation feasibility of a novel high energy storage, high heat flux passive heat sink. Key focus is to verify by theory and experiments, the practicability of using phase change materials as a temporary storage of waste heat for heat sink applications. The reason for storing the high heat fluxes temporarily is to be able to reject the heat at the average level when the heat source is off. Accordingly, a concept of a dual latent heat sink intended for moderate to low thermal duty cycle electronic heat sink applications is presented. This heat sink design combines the features of a vapor chamber with rapid thermal energy storage employing graphite foam inside the heat storage facility along with phase change materials and is attractive owing to its passive operation unlike some of the current thermal management techniques for cooling of electronics employing forced air circulation or external heat exchangers. In addition to the concept, end-application dependent criteria to select an optimized design for this dual latent heat sink are presented. A thermal resistance concept based design tool/model has been developed to analyze and optimize the design for experiments. The model showed that it is possible to have a dual latent heat sink design capable of handling 7 MJ of thermal load at a heat flux of 500 W/cm2 (over an area of 100 cm2) with a volume of 0.072 m3 and weighing about 57.5 kg. It was also found that with such high heat flux absorption capability, the proposed conceptual design could have a vapor-to-condenser temperature difference of less than 10 0C with a volume storage density of 97 MJ/m3 and a mass storage density of 0.122 MJ/kg. The effectiveness of this heat sink depends on the rapidness of the heat storage facility in the design during the pulse heat generation period of the duty cycle. Heat storage in this heat sink involves transient simultaneous laminar film condensation of vapor and melting of an encapsulated phase change material in graphite foam. Therefore, this conjugate heat transfer problem including the wall inertia effect is numerically analyzed and the effectiveness of the heat storage mechanism of the heat sink is verified. An effective heat capacity formulation is employed for modeling the phase change problem and is solved using finite element method. The results of the developed model showed that the concept is effective in preventing undue temperature rise of the heat source. Experiments are performed to investigate the fabrication and implementation feasibility and heat transfer performance for validating the objectives of the design i.e., to show that the VCTES heat sink is practicable and using PCM helps in arresting the vapor temperature rise in the heat sink. For this purpose, a prototype version of the VCTES heat sink is fabricated and tested for thermal performance. The volume foot-print of the vapor chamber is about 6"X5"X2.5". A custom fabricated thermal energy storage setup is incorporated inside this vapor chamber. A heat flux of 40 W/cm2 is applied at the source as a pulse and convection cooling is used on the condenser surface. Experiments are done with and without using PCM in the thermal energy storage setup. It is found that using PCM as a second latent system in the setup helps in lowering the undue temperature rise of the heat sink system. It is also found that the thermal resistance between the vapor chamber and the thermal energy storage setup, the pool boiling resistance at the heat source in the vapor chamber, the condenser resistance during heat discharging were key parameters that affect the thermal performance. Some suggestions for future improvements in the design to ease its implementation and enhance the heat transfer of this novel heat sink are also presented.
Show less
-
Date Issued
-
2008
-
Identifier
-
CFE0002332, ucf:47802
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0002332
-
-
Title
-
Characterization of SLM-Manufactured Turbine Blade Microfeatures from Superalloy Powders.
-
Creator
-
Ealy, Brandon, Kapat, Jayanta, Ahmed, Kareem, Vasu Sumathi, Subith, University of Central Florida
-
Abstract / Description
-
The limits of gas turbine technology are heavily influenced by materials and manufacturing capabilities. Inconel remains the material of choice for most hot gas path (HGP) components in gas turbines, however recent increases in turbine inlet temperature (TIT) are associated with the development of advanced convective cooling methods and ceramic thermal barrier coatings. Increasing cycle efficiency and cycle specific work are the primary drivers for increasing TIT. Lately, incremental...
Show moreThe limits of gas turbine technology are heavily influenced by materials and manufacturing capabilities. Inconel remains the material of choice for most hot gas path (HGP) components in gas turbines, however recent increases in turbine inlet temperature (TIT) are associated with the development of advanced convective cooling methods and ceramic thermal barrier coatings. Increasing cycle efficiency and cycle specific work are the primary drivers for increasing TIT. Lately, incremental performance gains responsible for increasing the allowable TIT have been made mainly through innovations in cooling technology, specifically convective cooling schemes. An emerging manufacturing technology may further facilitate the increase of allowable maximum TIT, thereby impacting cycle efficiencies. Laser Additive Manufacturing (LAM) is a promising manufacturing technology that uses lasers to selectively melt powders of metal in a layer-by-layer process to directly manufacture components, paving the way to produce designs that are not possible with conventional casting methods. This study investigates manufacturing qualities seen in LAM methods and its ability to successfully produce complex microfeatures in a mock turbine blade leading edge. Various cooling features are incorporated in design, consisting of internal impingement cooling, internal lattice structures, and external showerhead cooling. The internal structure is designed as a lattice of intersecting cylinders in order to mimic that of a porous material. Through a non-destructive approach, the presented design is analyzed against the departure of the design by utilizing X-ray computed tomography (CT). Employing this non-destructive testing (NDT) method, a more thorough analysis of the quality of manufacture is established by revealing the internal structures of the porous region and internal impingement array. Variance distribution between the design and manufactured test article are carried out for both internal impingement and external transpiration hole diameters from CT data. Flow testing is performed to characterize the uniformity of porous regions and flow behavior across the entire article for various pressure ratios. Discharge coefficients of internal impingement arrays and porous structures are quantified. A numerical model of fluid flow through the exact CAD geometry is analyzed over the range of experimental flowrates. By comparison of experimental and numerical data, performance discrepancies associated with manufacturing quality are observed. Simplifying assumptions to the domain are evaluated to compare predictions of CFD using the exact geometry. This study yields quantitative data on the build quality of the LAM process, providing more insight as to whether it is a viable option for manufacture of micro-features in current turbine blade production.
Show less
-
Date Issued
-
2016
-
Identifier
-
CFE0006452, ucf:51428
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0006452
-
-
Title
-
Methodological Improvements in the mRNA Profiling Assays for Incorporation into DNA Casework Workflows.
-
Creator
-
Volk, Paris, Ballantyne, John, Gerasimova, Yulia, Baudelet, Matthieu, University of Central Florida
-
Abstract / Description
-
Currently, DNA profiling is the gold standard to identify an individual. However, determining body fluid origin is important in criminal investigations, offering additional information surrounding the circumstances of a crime. However, crime labs can only definitively identify blood and semen and presumptively saliva using techniques that consume time and sample and do not simultaneously identify all forensically relevant body fluids. This causes many crime labs to want to bypass body fluid...
Show moreCurrently, DNA profiling is the gold standard to identify an individual. However, determining body fluid origin is important in criminal investigations, offering additional information surrounding the circumstances of a crime. However, crime labs can only definitively identify blood and semen and presumptively saliva using techniques that consume time and sample and do not simultaneously identify all forensically relevant body fluids. This causes many crime labs to want to bypass body fluid identification altogether. Therefore, advances into more definitive molecular-based body fluid methods are necessary. One such technique is mRNA profiling because it provides a highly sensitive and specific approach to definitively identifying all relevant body fluids in parallel. Although advancements have been made, improvements to mRNA profiling methodologies still need to be researched such as 1) possible mRNA recovery from established DNA workflows and 2) possible integration of mRNA profiling into an upfront male DNA screening assay for triaging sexual-assault evidence likely to contain male DNA and reduce/eliminate a significant bottleneck in the standard DNA workflow of microscopic sperm identification. This study was designed to address these two issues by evaluating a novel way to recover RNA, for body fluid identification, from the waste fractions of a PrepFiler(TM) DNA extraction, and from the DNA extracts directly. Next, this study aimed to provide a relatively quick molecular-based approach for screening sexual-assault evidence. It involves extraction of RNA using the Dynabeads(TM) mRNA DIRECT(TM) Kit, while saving the extraction waste fractions for downstream male-DNA quantitation and STR profiling. The RNA is then used in a rapid and sensitive 1-step combined reverse transcription-HRM assay to positively detect the presence of sperm. Both non-conventional co-extraction methods successfully addressed current body fluid identification challenges and allowed for easy integration into existing workflows when single sourced, mixture and mock casework samples were analyzed.
Show less
-
Date Issued
-
2019
-
Identifier
-
CFE0007551, ucf:52627
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0007551
-
-
Title
-
Adiabatic Film Cooling Effectiveness of a Transpiration-Cooled Leading Edge Fabricated by Laser Additive Manufacturing.
-
Creator
-
Calderon, Luisana, Kapat, Jayanta, Raghavan, Seetha, Mingareev, Ilya, University of Central Florida
-
Abstract / Description
-
Laser additive manufacturing (LAM) is an emerging technology capable of fabricating complex geometries not possibly made by investment casting methods for gas turbine applications. LAM techniques consist of building parts in a layer-by-layer process by selectively melting metal powders. In the present study, a mock leading edge segment of a turbine blade fabricated by LAM of Inconel 718 powders is investigated. For this particular design, the traditional showerhead film cooling holes have...
Show moreLaser additive manufacturing (LAM) is an emerging technology capable of fabricating complex geometries not possibly made by investment casting methods for gas turbine applications. LAM techniques consist of building parts in a layer-by-layer process by selectively melting metal powders. In the present study, a mock leading edge segment of a turbine blade fabricated by LAM of Inconel 718 powders is investigated. For this particular design, the traditional showerhead film cooling holes have been replaced by two strips containing engineered-porous regions with the purpose of simulating the effect of transpiration cooling. Transpiration cooling has been considered a promising external convective cooling method capable of providing a more uniform film and higher adiabatic film cooling effectiveness than conventional discrete film cooling. In addition, many studies have shown that this technique can yield high firing temperatures with much less coolant consumption than discrete film cooling. In this current study, adiabatic film cooling effectiveness is investigated by means of mass transfer using pressure sensitive paint (PSP). The experiments are conducted for blowing ratios ranging between M = 0.03 and M = 0.28 for a nominal density ratio of 1.5. The density ratio is obtained by using air as the mainstream flow and CO2 as the secondary flow (or coolant source). Results indicate higher coverage and film cooling effectiveness when increasing blowing ratio at the expense of higher pressure drop. In addition, the experimental results are compared to numerical analyses performed using steady state Reynolds Average Navier Stokes (RANS) simulations.
Show less
-
Date Issued
-
2018
-
Identifier
-
CFE0007315, ucf:52117
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0007315
-
-
Title
-
Characterization of Anisotropic Mechanical Performance of As-Built Additively Manufactured Metals.
-
Creator
-
Siddiqui, Sanna, Gordon, Ali, Raghavan, Seetha, Bai, Yuanli, Sohn, Yongho, University of Central Florida
-
Abstract / Description
-
Additive manufacturing (AM) technologies use a 3D Computer Aided Design (CAD) model to develop a component through a deposition and fusion layer process, allowing for rapid design and geometric flexibility of metal components, for use in the aerospace, energy and biomedical industries. Challenges exist with additive manufacturing that limits its replacement of conventional manufacturing techniques, most especially a comprehensive understanding of the anisotropic behavior of these materials...
Show moreAdditive manufacturing (AM) technologies use a 3D Computer Aided Design (CAD) model to develop a component through a deposition and fusion layer process, allowing for rapid design and geometric flexibility of metal components, for use in the aerospace, energy and biomedical industries. Challenges exist with additive manufacturing that limits its replacement of conventional manufacturing techniques, most especially a comprehensive understanding of the anisotropic behavior of these materials and how it is reflected in observed tensile, torsional and fatigue mechanical responses. As such, there is a need to understand how the build orientation of as-built additively manufactured metals, affects mechanical performance (e.g. monotonic and cyclic behavior, cyclically hardening/softening behavior, plasticity effects on fatigue life etc.); and to use constitutive modeling to both support experimental findings, and provide approximations of expected behavior (e.g. failure surfaces, monotonic and cyclic response, correlations between tensile and fatigue properties), for orientations and experiments not tested, due to the expensive cost associated with AM. A comprehensive framework has been developed to characterize the anisotropic behavior of as-built additively manufactured metals (i.e. Stainless Steel GP1 (SS GP1), similar in chemical composition to Stainless Steel 17-4PH), through a series of mechanical testing, microscopic evaluation and constitutive modeling, which were used to identify a reduced specimen size for characterizing these materials. An analysis of the torsional response of additively manufactured Inconel 718 has been performed to assess the impact of build orientation and as-built conditions on the shearing behavior of this material. Experimental results from DMLS SS GP1 and AM Inconel 718 from literature were used to constitutively model the material responses of these additively manufactured metals. Overall, this framework has been designed to serve as standard, from which build orientation selection can be used to meet specific desired industry requirements.
Show less
-
Date Issued
-
2018
-
Identifier
-
CFE0007097, ucf:52883
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0007097