Addressing fundamental challenges in liquid-vapor interface transport modeling for space applications
|Dates:||24 January 2023|
|Times:||15:00 - 16:00|
|What is it:||Webinar|
|Organiser:||Department of Mechanical, Aerospace and Civil Engineering|
|Who is it for:||University staff, External researchers, General public|
|Speaker:||Dr. Kishan Bellur|
Abstract of the lecture
Prediction and control of evaporation/condensation of cryogenic propellants is one of the key factors limiting long-term space missions. A clear understanding of propellant phase change is lacking as evidenced by the inconsistency in values of the accommodation coefficients. These coefficients are fundamental interfacial transport parameters that denote the fraction of vapor molecules that reflect off the liquid-vapor interface. Even for a common fluid such as water, prior measurements have spanned 3 orders of magnitude and until now, there was no published data for cryogenic fluids. Phase change experiments were conducted in the BT-2 Neutron Imaging Facility at the National Institute of Standards and Technology (NIST). These resulted in the first ever published images of controlled phase change in liquid H2 and CH4. Using a combination of neutron imaging, CFD modeling and multi-scale evaporation modeling, a unique value of the accommodation coefficient is determined for each experimental dataset. These are first ever reported values of accommodation coefficients for H2 and CH4. The results show a remarkable agreement with transition state theory predictions. If the local variation in thermophysics is accounted for, the coefficient becomes a well-behaved property that is fluid independent and invariant to changes in both container geometry and material. To further explore whether the coefficient varies between evaporation and condensation the Constrained Vapor Bubble (CVB) dataset from ISS experiments is analyzed and discussed.
Dr. Kishan Bellur
Role: Assistant Professor
Organisation: University of Cincinnati
Biography: Dr. Bellur is currently currently an assistant professor in Mechanical and Materials Engineering at University of Cincinnati. I recieved a BS in Mechanical Engineering from Milwaukee School of Engineering in 2013. I then briefly worked as a hydraulics engineer at The Raymond Corp. in Greene, NY. It only took me a few months to realize grad school is where I belonged. I graduated with an MS in 2016 and a PhD in August 2018, both from Michigan Technological University.
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