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PhD Defense – Megan Watkins
March 12 @ 11:00 am - 1:00 pm
TITLE: A Heat Transfer Analysis of Vertical Dense Granular Flows
ADVISOR: Dr. Richard Gould
DATE & TIME: Monday, March 12, 2018 at 11 AM
LOCATION: EB3 – 3320
Particle-based heat transfer fluids for concentrated solar power (CSP) tower applications offer a unique advantage over traditional fluids, as they have the potential to reach very high operating temperatures. The present work studies the heat transfer behavior of dense granular flows through cylindrical tubes as a potential system configuration for CSP tower receivers. Experimental studies were conducted using a bench-scale apparatus to examine the heat transfer to such a flow configuration across a wide temperature range, as well as examine the effect of system parameters on the heat transfer to the flow. The experimental results corroborate the observations of other researchers; namely that the discrete nature of the flow limits the heat transfer from a tube wall to the flow due to an increased thermal resistance in the layer of particles adjacent to the heated wall. A two-layer model was developed to describe this heat transfer phenomenon. A correlation to approximate the increased thermal resistance adjacent to the wall was also developed, taking into consideration the variation with flow rate and system configuration. A simple radiation contribution was also incorporated into the model to predict the heat transfer to the flows at high operating temperatures. The model showed good agreement within experimental uncertainty across all systems tested. The results from all aspects of the work provide an understanding of the parameters controlling the heat transfer to a dense granular flow and pave the way for designing future dense flow systems.
Megan received her BS in Mechanical Engineering from the State University of New York at Binghamton in May 2013. After graduation, she came to NC State in pursuit of her PhD in Mechanical Engineering, where she was fortunate enough to find a research project focused on concentrated solar power technologies. She has grown fond of the thermal sciences during her time at NC State and hopes to continue to use her new background to continue working in the field of renewable energy technologies.