SUBJECT: Ph.D. Proposal Presentation
BY: Adrienne Little
TIME: Wednesday, July 10, 2013, 9:00 a.m.
PLACE: Love Building, 210
TITLE: Two-Phase Flow in Ejectors for Refrigeration Technology
COMMITTEE: Dr. Srinivas Garimella, Chair (ME)
Dr. Lawrence Jacobs (CE)
Dr. Caroline Genzale (ME)
Dr. Yann Bartosiewicz (ME)
Dr. Sheldon Jeter (ME)


In an attempt to reduce the dependence on fossil fuels, a variety of research initiatives have focused on developing alternative fuel sources and on increasing the efficiency of conventional sources. One such approach is to use waste heat recovery to reclaim energy that is typically lost in the form of dissipative heat. An example of such reclamation is waste heat recovery systems that take low temperature heat and deliver cooling in space-conditioning applications. In this proposed work, the ejector refrigeration waste heat recovery system will be studied from the system to component to sub-component level, with a specific focus on the ejector pump device. The ejector is a passive device used to compress refrigerants in waste heat driven heat pumps without the use of high grade electricity or wear-prone complex moving parts. With such ejectors, the electrical input for the overall system can be reduced or eliminated entirely under certain conditions, allowing for a cooling system that can operate in off-grid, mobile, or remote applications. The performance of this system, measured typically as a coefficient of performance, is primarily dependent on the performance of the ejector pump. The proposed work will study ejector performance experimentally using two different techniques. First, a stand-alone large-scale air-water ejector is used to obtain preliminary visual and global performance data, providing a comparison for basic CFD simulation work to analyze the details of internal flow phenomena including oblique shock/expansion formation. Using this visualization technique, flow of refrigerant in a small-scale ejector in a refrigeration system operating under realistic conditions will be investigated. These data will be compared with the results from basic two-phase CFD models. It is expected that integrated visual, CFD, and analytical data will provide insights into flow structure and location of condensation regions. Potential improvement in ejector performance that has been reported in the literature due to improved momentum transfer characteristics through condensation of flow inside the ejector will also be investigated. These studies will provide guidance on the specific ejector inlet conditions conducive to improved performance at both the ejector component and the system levels, and how ejector design can be augmented to better take advantage of the yet unknown effects of flow condensation on ejector performance and resulting cooling system COP.