Sodium reflux pool-boiler solar receiver on-sun test results

Technical Report · Mon Jun 01 00:00:00 EDT 1992

DOI:https://doi.org/10.2172/7239599· OSTI ID:7239599

Andraka, C E; Moreno, J B; Diver, R B; Moss, T A ^[1]

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1. Oak Ridge National Lab., TN (United States)

The efficient operation of a Stirling engine requires the application of a high heat flux to the relatively small area occupied by the heater head tubes. Previous attempts to couple solar energy to Stirling engines generally involved directly illuminating the heater head tubes with concentrated sunlight. In this study, operation of a 75-kW{sub t} sodium reflux pool-boiler solar receiver has been demonstrated and its performance characterized on Sandia's nominal 75-kW{sub t} parabolic-dish concentrator, using a cold-water gas-gap calorimeter to simulate Stirling engine operation. The pool boiler (and more generally liquid-metal reflux receivers) supplies heat to the engine in the form of latent heat released from condensation of the metal vapor on the heater head tubes. The advantages of the pool boiler include uniform tube temperature, leading to longer life and higher temperature available to the engine, and decoupling of the design of the solar absorber from the engine heater head. The two-phase system allows high input thermal flux, reducing the receiver size and losses, therefore improving system efficiency. The receiver thermal efficiency was about 90% when operated at full power and 800{degree}C. Stable sodium boiling was promoted by the addition of 35 equally spaced artificial cavities in the wetted absorber surface. High incipient boiling superheats following cloud transients were suppressed passively by the addition of small amounts of xenon gas to the receiver volume. Stable boiling without excessive incipient boiling superheats was observed under all operating conditions. The receiver developed a leak during performance evaluation, terminating the testing after accumulating about 50 hours on sun. The receiver design is reported here along with test results including transient operations, steady-state performance evaluation, operation at various temperatures, infrared thermography, x-ray studies of the boiling behavior, and a postmortem analysis.

• Research Organization: Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 7239599
• Report Number(s): SAND-89-2773; ON: DE92018932
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
CENTRAL RECEIVERS
STIRLING ENGINES
PERFORMANCE TESTING
LATENT HEAT STORAGE
PARABOLIC DISH COLLECTORS
SODIUM
SOLAR HEAT ENGINES
SOLAR THERMAL CONVERSION
ALKALI METALS
CONCENTRATING COLLECTORS
CONVERSION
ELEMENTS
ENERGY CONVERSION
ENERGY STORAGE
ENGINES
EQUIPMENT
HEAT ENGINES
HEAT STORAGE
METALS
PARABOLIC COLLECTORS
SOLAR COLLECTORS
SOLAR ENERGY CONVERSION
SOLAR EQUIPMENT
SOLAR RECEIVERS
STORAGE
TESTING
CSP
Concentrating Solar Power
140702* - Solar Thermal Power Systems- Central Receiver