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Performance Expectations of Closed-Brayton-Cycle Heat Exchangers in 100-kWe Nuclear Space Power SystemsPerformance expectations of closed-Brayton-cycle heat exchangers to be used in 100-k We nuclear space power systems were forecast. Proposed cycle state points for a system supporting a mission to three of Jupiter's moons required effectiveness values for the heat-source exchanger, recuperator and rejection exchanger (gas cooler) of 0.98, 0.95, and 0.97, respectively. Performance parameters such as number of thermal units (Ntu), equivalent thermal conductance (UA), and entropy generation numbers (Ns) varied from 11 to 19, 23 to 39 kW/K, and 0.019 to 0.023 for some standard heat exchanger configurations. Pressure-loss contributions to entropy generation were significant; the largest frictional contribution was 114% of the heat transfer irreversibility. Using conventional recuperator designs, the 0.95 effectiveness proved difficult to achieve without exceeding other performance targets; a metallic, plate-fin counterflow solution called for 15% more mass and 33% higher pressure-loss than the target values. Two types of gas-coolers showed promise. Single-pass counterflow and multipass cross-counterflow arrangements both met the 0.97 effectiveness requirement. Potential reliability-related advantages of the cross-counterflow design were noted. Cycle modifications, enhanced heat transfer techniques and incorporation of advanced materials were suggested options to reduce system development risk. Carbon-carbon sheeting or foam proved an attractive option to improve overall performance.
Document ID
20040112040
Acquisition Source
Glenn Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Barrett, Michael J.
(NASA Glenn Research Center Cleveland, OH, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2003
Subject Category
Spacecraft Propulsion And Power
Report/Patent Number
AIAA Paper 2003-5956
Meeting Information
Meeting: 1st International Energy Conversion Engineering Conference (IECEC)
Location: Portsmouth, VA
Country: United States
Start Date: August 17, 2003
End Date: August 21, 2003
Sponsors: American Inst. of Aeronautics and Astronautics
Funding Number(s)
WBS: WBS 973-80-10
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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