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Title: A Comparison of Coolant Options for Brayton Power Conversion Heat Rejection Systems

Abstract

This paper describes potential heat rejection design concepts for Brayton power conversion systems. Brayton conversion systems are currently under study by NASA for Nuclear Electric Propulsion (NEP) and surface power applications. The Brayton Heat Rejection Subsystem (HRS) must dissipate waste heat generated by the power conversion system due to inefficiencies in the thermal-to-electric conversion process. Sodium potassium (NaK) and H2O are two coolant working fluids that have been investigated in the design of a pumped loop and heat pipe space HRS. In general NaK systems are high temperature (300 to 1000 K) low pressure systems, and H2O systems are low temperature (300 to 600 K) high pressure systems. NaK is an alkali metal with health and safety hazards that require special handling procedures. On the other hand, H2O is a common fluid, with no health hazards and no special handling procedures. This paper compares NaK and H2O for the HRS pumped loop coolant working fluid. A detailed excel analytical model, HRS{sub O}pt, was developed to evaluate the various HRS design parameters. It is capable of analyzing NaK or H2O coolant, parallel or series flow configurations, and numerous combinations of other key parameters (heat pipe spacing, diameter and radial flux, radiatormore » facesheet thickness, fluid duct system pressure drop, system rejected power, etc.) of the HRS. This paper compares NaK against water for the HRS coolant working fluid with respect to the relative mass, performance, design and implementation issues between the two fluids.« less

Authors:
 [1];  [2]
  1. Thermal Energy Conversion Branch, Analex Corporation, 21000 Brookpark Rd., Cleveland, OH, 44135 (United States)
  2. Thermal Energy Conversion Branch, NASA Glenn Research Center, 21000 Brookpark Rd., Cleveland, OH, 44135 (United States)
Publication Date:
OSTI Identifier:
20798010
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 813; Journal Issue: 1; Conference: 10. conference on thermophysics applications in microgravity; 23. symposium on space nuclear power and propulsion; 4. conference on human/robotic technology and the national vision for space exploration; 4. symposium on space colonization; 3. symposium on new frontiers and future concepts, Albuquerque, NM (United States), 12-16 Feb 2006; Other Information: DOI: 10.1063/1.2169249; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BRAYTON CYCLE POWER SYSTEMS; COMPARATIVE EVALUATIONS; COOLANT LOOPS; COOLANTS; COOLING; DESIGN; HEALTH HAZARDS; POTASSIUM; POTASSIUM ALLOYS; POWER GENERATION; PRESSURE DROP; PROPULSION; RADIATORS; SODIUM; SODIUM ALLOYS; SURFACES; THERMOELECTRIC CONVERSION; WASTE HEAT; WORKING FLUIDS

Citation Formats

Siamidis, John, and Mason, Lee. A Comparison of Coolant Options for Brayton Power Conversion Heat Rejection Systems. United States: N. p., 2006. Web. doi:10.1063/1.2169249.
Siamidis, John, & Mason, Lee. A Comparison of Coolant Options for Brayton Power Conversion Heat Rejection Systems. United States. doi:10.1063/1.2169249.
Siamidis, John, and Mason, Lee. Fri . "A Comparison of Coolant Options for Brayton Power Conversion Heat Rejection Systems". United States. doi:10.1063/1.2169249.
@article{osti_20798010,
title = {A Comparison of Coolant Options for Brayton Power Conversion Heat Rejection Systems},
author = {Siamidis, John and Mason, Lee},
abstractNote = {This paper describes potential heat rejection design concepts for Brayton power conversion systems. Brayton conversion systems are currently under study by NASA for Nuclear Electric Propulsion (NEP) and surface power applications. The Brayton Heat Rejection Subsystem (HRS) must dissipate waste heat generated by the power conversion system due to inefficiencies in the thermal-to-electric conversion process. Sodium potassium (NaK) and H2O are two coolant working fluids that have been investigated in the design of a pumped loop and heat pipe space HRS. In general NaK systems are high temperature (300 to 1000 K) low pressure systems, and H2O systems are low temperature (300 to 600 K) high pressure systems. NaK is an alkali metal with health and safety hazards that require special handling procedures. On the other hand, H2O is a common fluid, with no health hazards and no special handling procedures. This paper compares NaK and H2O for the HRS pumped loop coolant working fluid. A detailed excel analytical model, HRS{sub O}pt, was developed to evaluate the various HRS design parameters. It is capable of analyzing NaK or H2O coolant, parallel or series flow configurations, and numerous combinations of other key parameters (heat pipe spacing, diameter and radial flux, radiator facesheet thickness, fluid duct system pressure drop, system rejected power, etc.) of the HRS. This paper compares NaK against water for the HRS coolant working fluid with respect to the relative mass, performance, design and implementation issues between the two fluids.},
doi = {10.1063/1.2169249},
journal = {AIP Conference Proceedings},
number = 1,
volume = 813,
place = {United States},
year = {Fri Jan 20 00:00:00 EST 2006},
month = {Fri Jan 20 00:00:00 EST 2006}
}
  • Among the many solar-powered energy-conversion systems, a recuperated closed Brayton cycle (CBC) is the most promising one. Several investigated aspects are discussed in the present study: the first assessment of a reference 25 kW system, simulation studies related to various operating conditions and heat-rejection studies related to the transfer of the Brayton cycle waste heat to the radiating area. In addition, particular attention is paid to the significance of the reduction of system mass required for the radiation of waste heat from a closed Brayton cycle to space. Conceptually, the radiator area can be reduced by rejecting the heat frommore » a radiator at a higher temperature level than that of the waste heat of CBC, operating a kind of heat pump by using a fraction of the generated power. The optimum radiator to waste heat on the order greater than 5, the total radiator area is reduced remarkably. The required mass addition by the inclusion of the heat pump is estimated.« less
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