Bench-scale screening tests for a boiling sodium-potassium alloy solar receiver

by Albuquerque Sandia National Laboratories, NM

Technical Report, 1993

Barcode

CSP Unique ID 190708405

Status

Electronic Resource

Call number

**Click on MARC view for more information on this report.**

Publication

SAND Report: SAND92-2253, June 1993.

Language

Library's review

ABSTRACT:
Bench-scale tests were carried out in support of the design of a second-generation 75-kWt reflux pool-boiler solar receiver. The receiver will be made from Haynes Alloy 230 and will contain the sodium-potassium alloy NaK-78. The bench-scale tests used quartz-lamp-heated boilers to screen
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candidate boiling-stabilization materials and methods at temperatures up to 7500C. Candidates that provided stable boiling were tested for hot-restart behavior. Poor stability was obtained with single l/4-inch diameter patches of powdered metal hot-press-sintered onto the wetted side of the heat input area. Laser-drilled and electric- discharge-machined cavities in the heated surface also performed poorly. Small additions of xenon, and heated-surface tilt out of the vertical dramatically improved poor boiling stability; additions of helium or oxygen did not. The most stable boiling was obtained when the entire heat-input area was covered by a powdered-metal coating. The effect of heated-area size was assessed for one coating: at low incident fluxes, when even this coating performed poorly, increasing the heated-area size markedly improved boiling stability. Good hot restart behavior was not observed with any candidate, although results were significantly better with added xenon in a boiler shortened from 3 to 2 feet. In addition to the screening tests, flash radiography imaging of metal-vapor bubbles during boiling was attempted. Contrary to the Cole- Rohsenow correlation, our bubble-size estimates did not vary with pressure; instead they were constant consistent with the only other alkali metal measurements, but about 1/2 their size.
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