Open Access. Powered by Scholars. Published by Universities.®
- Institution
Articles 1 - 6 of 6
Full-Text Articles in Engineering
Numerical Simulation Of A Cryogenic Spray, Neel Kishorkumar Shah
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 …
A New Technique To Determine Accommodation Coefficients Of Cryogenic Propellants, Kishan Bellur
A New Technique To Determine Accommodation Coefficients Of Cryogenic Propellants, Kishan Bellur
Dissertations, Master's Theses and Master's Reports
The control of propellant boil-off is essential in long-term space missions. However, a clear understanding of cryogenic propellant phase change and the values of accommodation coefficients are lacking. To that effect, a new method to determine accommodation coefficients using a combination of neutron imaging, thin film evaporation modeling and CFD modeling has been established. Phase change experiments were conducted in the BT-2 Neutron Imaging Facility at the National Institute of Standards and Technology (NIST) by introducing cryogenic vapor (H2 and CH4) at a set pressure into Al6061 and SS316L test cells placed inside a 70mm cryostat. Condensation is achieved by …
Development Of An Evaporation Sub-Model And Simulation Of Multiple Droplet Impingement In Volume Of Fluid Method, Sathya Prasad Potham
Development Of An Evaporation Sub-Model And Simulation Of Multiple Droplet Impingement In Volume Of Fluid Method, Sathya Prasad Potham
Dissertations, Master's Theses and Master's Reports
Droplet collision and impingement on a substrate are widely observed phenomenon in many applications like spray injection of Internal Combustion Engines. Existing Lagrangian models do not provide a comprehensive picture of the outcome of these events and may involve model constants requiring experimental data for validation. Physics based models like Volume of Fluid (VOF) method involve no parametric tuning and are more accurate. The aim of this thesis is to extend the basic VOF method with an evaporation sub-model including an additional vapor phase and implement this model in an open source Computational Fluid Dynamics (CFD) software, OpenFOAM. The new …
An Assessment Of The Validity Of The Kinetic Model For Liquid-Vapor Phase Change By Examining Cryogenic Propellants, Kishan Bellur
An Assessment Of The Validity Of The Kinetic Model For Liquid-Vapor Phase Change By Examining Cryogenic Propellants, Kishan Bellur
Dissertations, Master's Theses and Master's Reports
Evaporation is ubiquitous in nature and occurs even in a microgravity space envi- ronment. Long term space missions require storage of cryogenic propellents and an accurate prediction of phase change rates. Kinetic theory has been used to model and predict evaporation rates for over a century but the reported values of accommodation coefficients are highly inconsistent and no accurate data is available for cryogens. The proposed study involves a combined experimental and computational approach to ex- tract the accommodation coefficients. Neutron imaging is used as the visualization technique due to the difference in attenuation between the cryogen and the metallic …
Evaluation Of Two-Phase Evaporation Pressure Drop Correlations For Low Refrigerant Mass Flux., Anna Fenko
Evaluation Of Two-Phase Evaporation Pressure Drop Correlations For Low Refrigerant Mass Flux., Anna Fenko
Electronic Theses and Dissertations
This study was conducted to evaluate three currently popular two-phase pressure drop models for extremely low velocity refrigerant flow through smooth circular evaporators in household refrigeration systems. Experimental data was taken at mass fluxes under 70 kg/m2s for two refrigerants, R134A and R600A, internal diameters of aluminum evaporators ranging from 0.186 to 0.317 inches, U-bend internal radii ranging from 0.342 to 0.750 inches in horizontal and vertical orientations of evaporators. The geometry of the samples closely resembled a commonly used serpentine shape with multiple U-bends experiencing both, up- and down-flow of the refrigerant. Two empirical models, Müller-Steinhagen & …
Evaporative Techniques For Stormwater Runoff Alleviation, Allison M. Arnold
Evaporative Techniques For Stormwater Runoff Alleviation, Allison M. Arnold
Graduate Theses, Dissertations, and Problem Reports
Current climate changes have led to a projected steady increase in rainfall over the next several decades, notably in the Greater Pittsburgh Area. Even without this predicted increase the urbanization of many regions has altered local natural environments, which in the past stored, shed and evaporated this runoff water effectively, maintaining balance within the water table. These added rainfall forecasts, combined with America’s growing trend to develop and expand the urbanization of our natural earth, has resulted in a growing surplus of stormwater runoff water affecting these cities and their suburbs, leaving many sanitation departments unable to meet the heightened …