Heat Transfer, Combustion Commons^™

Thermal Management With Supercritical Carbon Dioxide Under Extreme Applications, Devon Hardy

Doctoral Dissertations and Master's Theses

A unique challenge in thermal system design is minimizing the power required to operate cooling systems while maintaining effective heat removal. Traditional cooling systems utilize single-phase fluids where the heat transfer mechanisms are well understood. To meet a variety of cooling demands, a range of technologies are available, including microchannel forced convection, jet impingement, porous media, nanofluids, pin fin arrays, and film cooling, each offering distinct advantages and limitations. While the performance of single- or two-phase cooling systems are generally predictable, in extreme thermal environments, new cooling solutions are needed to improve overall system efficiency and reliability.

Supercritical fluids, particularly …

Experimental Investigation Of Heat Transfer To Tightly Packed Cylinder Arrays, Cameron M. Sexsmith

Doctoral Dissertations and Master's Theses

With the increased emphasis on the development of hybrid electric aircraft and other electric driven vehicles, the thermal demand on batteries is increasing. Unique to the aviation sector is the combined need of high battery thermal loads and a light-weight thermal management system. A proposed configuration is an array of batteries directly cooled with a dielectric coolant. The knowledge of heat transfer characteristics of battery cooling is becoming an ever pressing issue due to the need to optimize volume and mass in a safe manner. Tighter spacings between batteries provide higher pack densities, however, at the cost of increased cooling …

Development Of On-The-Fly Quasi-Steady State Approximation For Chemical Kinetics In Cfd, Abhinav Balamurugan

Doctoral Dissertations and Master's Theses

This study analyzes the feasibility of On-The-Fly Quasi-Steady-State Approximation (OTF-QSSA) application for solving chemical kinetics within Computational Fluid Dynamics (CFD) simulations, aiming to reduce the computational demand of detailed mechanisms. An algorithm that dynamically identifies and designates Quasi-Steady-State (QSS) species at specific grid locations and instances during the simulation was developed. With this information, our method pseudo-delays the advancement of concentrations for these QSS species—effectively setting their rate of concentration change to zero for a set number iteration before updating using the detailed mechanism and thereby omitting the computationally intensive processes typically required for their calculation during those skipped iteration. …

Benchmarking Of A Sco2 Heat Exchanger Flow Loop, David Velasco

Doctoral Dissertations and Master's Theses

Heat transfer of supercritical carbon dioxide (sCO2) was studied experimentally by commissioning a sCO2 flow loop featuring a horizontal tube-in-tube counterflow heat exchanger with a circular cross section. The main objective was to establish experimental heat transfer research capabilities for sCO2 at Embry-Riddle Aeronautical University’s (ERAU) Thermal Science Lab. sCO2 experiences a drastic change in thermophysical properties near its critical point that results in unique heat transfer characteristics. The high pressures at which sCO2 exists make the large gradients in thermophysical and transport properties difficult to study, experimentally and numerically. However, understanding the heat transfer characteristics and thermophysical behavior of …

Design And Characterization Of A High Pressure Flow Loop For Heat Transfer Experiments Of Supercritical Carbon Dioxide, Joseph Sauerbrun

Doctoral Dissertations and Master's Theses

Supercritical carbon dioxide (sCO2) sees heightened heat transfer characteristics near its critical point due to its drastically changing thermophysical properties. Conventional single phase heat transfer theory was not developed to capture this nonlinear variation in properties and cannot predict the heat transfer characteristics of sCO2 to a practical level useful for design. To delve deeper into the behavior near the critical point and shed light on this crucial phenomenon, a state-of-the-art closed flow loop was developed. This setup enabled convective heat transfer experiments of sCO2 under diverse boundary conditions and test section geometries. Key components of the loop include the …

The Influence Of Mixing Duct Length And Phase Of Flight On Wall Temperatures Of A Rocket Based Combined Cycle Engine In Ejector And Air-Augmented Modes, Jonathan Grow

Doctoral Dissertations and Master's Theses

Rocket Based Combined Cycle (RBCC) engines have been theorized as a possible means of powering launch vehicles and high-speed atmospheric vehicles. By incorporating aspects of both air-breathing and rocket propulsion, RBCC engines promise up to a 230 % increase in specific impulse over traditional chemical rocket propulsion by entraining a secondary flow of atmospheric air and mixing it with the exhaust of a rocket motor. Students within the Embry-Riddle Future Space Explorers and Developers Society (ERFSEDS) identified a
problem of excessive heating and structural failure of the mixing duct during launch and transonic flight of a student-built flight test vehicle. …

Atmospheric Carbon Capture: A Review On Current Technologies And Analysis Of Energy Consumption For Various Direct Air Capture (Dac) Systems, Jennifer Perskin

Doctoral Dissertations and Master's Theses

Carbon dioxide (CO₂) capture is a crucial approach to reducing greenhouse gases in the atmosphere to directly combat climate change. Major components of the technology to desublimate CO₂ at cryogenic temperatures are mature and have the potential to be applied to build large Arctic/Antarctic direct-air CO₂ capture plants. Pressure swing adsorption another gas separation technique used in industry today that can be modified for atmospheric carbon capture. The discussion of energy consumption for cryogenic and combined direct air capture systems is explored in this study. The investigation of precompression of atmospheric air for a direct-air capture …

Thermal Boundary Condition Effects On Local Supercritical Co2 Heat Transfer Trends In Tubes, Nicholas C. Lopes

Doctoral Dissertations and Master's Theses

Supercritical carbon dioxide (sCO2) is a promising heat transfer fluid for the refrigeration and power generation industries due to its unique thermal properties and low environmental impact. To understand it as an alternative to traditional working fluids, the thermophysical and heat transfer phenomena of sCO2 are often studied using simplified geometries (tubes). Focus has been placed on investigating averaged heat transfer trends under an array of flow conditions with either a constant wall heat flux, constant wall temperature, or conjugate thermal boundary condition. Less emphasis has been placed on studying local sCO2 heat transfer developments. Tubular sCO2 numerical models that …

Experimental And Numerical Analysis Of A Commercial Phase Change Material Melting At Different Inclinations, Andrew Heiles

Doctoral Dissertations and Master's Theses

The study of various phase change materials (PCM), experimentally and numerically, have been completed over the past several years to address their feasibility and potential when used in latent heat thermal energy storage (LHTES) systems for a variety of potential applications. Previous studies have investigated changes into the type of PCM used in the system as well as the system configuration, ranging from boundary conditions to internal and external geometries and orientations of the system. The present study focused on conducting experiments at different inclination angles and isothermal wall temperatures with the organic PCM PureTemp37, and continued with a numerical …

Additive Manufacturing For Phase Change Thermal Energy Storage And Management, Thomas B. Freeman

Doctoral Dissertations and Master's Theses

Phase change materials can enhance the performance of energy systems by time shifting or reducing peak thermal loads. Certain electronic devices such as batteries, laser systems, or electric vehicle power electronics are highly transient and require pulse heat dissipation. Heat sinks, or thermal management devices made of a phase change material can absorb large heat spikes while maintaining a constant temperature. Additive manufacturing techniques hold tremendous potential to enable co-optimization of material properties and device geometry, while potentially reducing material waste and manufacturing time. Recently, a few efforts have emerged that employ additive manufacturing techniques to integrate a phase change …

Biomass Characterization And Insulation Optimization Studies, Hussein Awad Kurdi Saad

Doctoral Dissertations and Master's Theses

This study indicates how biomass materials can be effectively used as naturally sustainable alternatives to insulation materials. Barley grains and oak leaves, straw, and jute are collected, and crushed into powders/ chopped pieces. The physical characteristics are measured to characterize each powder. The biomass powder reinforced composites are manufactured in varying weight ratios. The density and thermal conductivity of composite materials are measured. The properties of composites compared to those of commercial insulation materials are found to be close to them. Furthermore, genetic algorithms (GA) can be used to achieve multi-objective optimization entailing maximizing insulation (minimizing heat transfer) and simultaneously …

Experimental And Numerical Investigation Of Lauric Acid Melting At Suboptimal Inclines, Casey J. Troxler

Doctoral Dissertations and Master's Theses

Validation experiments are the baseline for completing numerical studies for engineering design. Applications of the enthalpy-porosity model have expanded in research with the growth of new technologies such as metal additive manufacturing or the renewed interest in thermal energy storage for supplementing renewable energy. A simplified experiment examining the melting behavior of lauric acid from an isothermal surface has become a common case for validating the performance of numerical models. Several studies of this rectangular experiment have been repeatedly used as model validation in a variety of problem conditions.

The first part of this study presents experimental data for the …

State-Of-The-Art Of Thermal Control Solutions To Establish A Modular, Multi-Orbit Capable Spacecraft Thermal Management System Design Methodology, Robert C. Consolo Jr

Doctoral Dissertations and Master's Theses

Today, the exploration and exploitation of space continues to become a more common occurrence. All types of spacecraft (S/C) utilize various types of thermal management solutions to mitigate the effects of thermal loading from the unforgiving vacuum of space. Without an appropriately designed thermal system, components on-board the S/C can experience failure or malfunction due to fluctuations in temperatures either beyond the designed operational parameters or unstable oscillating temperatures. The purpose of this study is to perform a comprehensive review of technologies available today that are being used for thermal management onboard S/C in addition to investigating the means to …

Numerical Simulation Of A Cryogenic Spray, Neel Kishorkumar Shah

Doctoral Dissertations and Master's Theses

Cryogenic sprays have many applications in modern engineering. Cooling of electronic equipment subject to high heat flows, surgical ablation of gastrointestinal mucosae or orbital maneuvering are a few examples of their versatility. However, the atomization of a cryogenic liquid is a complex process. During such an event, aerodynamic effects associated with secondary atomization are further affected by thermodynamic flashing. A better understanding of the characteristics of cryogenic sprays is then necessary to allow for improved design and optimization in applications. The overarching objective of this study is to document such characteristics. The numerical simulation was performed over cryogenic nitrogen spray …

Desalination For Sustainable Water Production With An Emphasis On Low Pressure Distillation, Jessica Vivian Savage

Doctoral Dissertations and Master's Theses

Freshwater resources depletion is a growing concern. This freshwater scarcity motivates research into seawater desalination as a means for alleviating the stresses on water demands. The primary methods of desalination include filtration and distillation. This paper explores the potential energy savings of vacuum distillation for seawater desalination to reduce the amount of energy needed to achieve phase change.

Depending on the vacuum boiler design, the vaporization mechanism may be boiling, evaporation, or cavitation. There is very little literature on cavitation that involves mass transfer, so cavitation is not developed here. This thesis focuses on standard models for boiling and evaporation …

Oscillatory Flow Mechanism For Enhanced Heat Transfer, Sultan Taher Raml

Doctoral Dissertations and Master's Theses

This research project is about the use of an oscillatory flow mechanism to enhance heat transfer. The idea behind this is to induce oscillation of the end wall of one of two connected chambers of a heat exchanger which effectively will induce oscillation of the boundary layer within the connecting duct. The main idea of this thesis came from using species separation studies before 40 years ago in hyperventilation technology to help patients under anesthesia in hospitals. There are many applications for this research such as removing heat from chemical reactors, electrical devices and other enclosed environments such as submarines, …

Inverse Volume-Of-Fluid Meshless Method For Efficient Non-Destructive Thermographic Evaluation, Hussein Awad Kurdi Saad

Doctoral Dissertations and Master's Theses

A novel computational tool based in the Localized Radial-basis Function (RBF) Collocation (LRC) Meshless method coupled with a Volume-of-Fluid (VoF) scheme capable of accurately and efficiently solving transient multi-dimensional heat conduction problems in composite and heterogeneous media is formulated and implemented. While the LRC Meshless method lends its inherent advantages of spectral convergence and ease of automation, the VoF scheme allows to effectively and efficiently simulate the location, size, and shape of cavities, voids, inclusions, defects, or de-attachments in the conducting media without the need to regenerate point distributions, boundaries, or interpolation matrices. To this end, the Inverse Geometric problem …

Investigation Of Shroud Geometry To Passively Improve Heat Transfer In A Solar Thermal Storage Tank, Matthew Keene Zemler

Doctoral Dissertations and Master's Theses

A shroud and baffle configuration is used to passively increase heat transfer in a thermal store. The shroud and baffle are used to create a vena contracta near the surface of the heat exchanger, which will speed up the flow locally and thereby increasing heat transfer. The goal of this study is to investigate the geometry of the shroud in optimizing heat transfer by locally increasing the velocity near the surface of the heat exchanger. Two-dimensional transient simulations are conducted. The immersed heat exchanger is modeled as an isothermal cylinder, which is situated at the top of a solar thermal …