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Thermal State-of-Charge in Solar Heat ReceiversA theoretical framework is developed to determine the so-called thermal state-of-charge (SOC) in solar heat receivers employing encapsulated phase change materials (PCMS) that undergo cyclic melting and freezing. The present problem is relevant to space solar dynamic power systems that would typically operate in low-Earth-orbit (LEO). The solar heat receiver is integrated into a closed-cycle Brayton engine that produces electric power during sunlight and eclipse periods of the orbit cycle. The concepts of available power and virtual source temperature, both on a finite-time basis, are used as the basis for determining the SOC. Analytic expressions for the available power crossing the aperture plane of the receiver, available power stored in the receiver, and available power delivered to the working fluid are derived, all of which are related to the SOC through measurable parameters. Lower and upper bounds on the SOC are proposed in order to delineate absolute limiting cases for a range of input parameters (orbital, geometric, etc.). SOC characterization is also performed in the subcooled, two-phase, and superheat regimes. Finally, a previously-developed physical and numerical model of the solar heat receiver component of NASA Lewis Research Center's Ground Test Demonstration (GTD) system is used in order to predict the SOC as a function of measurable parameters.
Document ID
19980174902
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Hall, Carsie A., Jr. (Howard Univ. Washington, DC United States)
Glakpe, Emmanuel K. (Howard Univ. Washington, DC United States)
Cannon, Joseph N. (Howard Univ. Washington, DC United States)
Kerslake, Thomas W. (NASA Lewis Research Center Cleveland, OH United States)
Date Acquired
September 6, 2013
Publication Date
June 1, 1998
Subject Category
Spacecraft Propulsion And Power
Report/Patent Number
AIAA Paper 98-0000
NASA/TM-1998-207920
NAS 1.15:207920
E-11203
Meeting Information
Meeting: Aerospace Sciences Meeting and Exhibit
Location: Reno, NV
Country: United States
Start Date: January 12, 1998
End Date: January 15, 1998
Sponsors: American Inst. of Aeronautics and Astronautics
Funding Number(s)
PROJECT: RTOP 547-10-41
CONTRACT_GRANT: NAG3-1907
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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