Building, testing, and post test analysis of durability heat pipe #6

ABSTRACT:
The Solar Thermal Program at Sandia supports work developing dish/Stirling systems to convert solar energy into electricity. Heat pipe technology is ideal for transferring the energy of concentrated sunlight from the parabolic dish concentrators to the Stirling engine heat tubes. Heat

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pipes can absorb the solar energy at non-uniform flux distributions and release this energy to the Stirling engine heater tubes at a very uniform flux distribution thus decoupling the design of the engine heater head from the solar absorber. The most important part of a heat pipe is the wick, which transports the sodium over the heated surface area. Bench scale heat pipes were designed and built to more economically, both in time and money, test different wicks and cleaning procedures. This report covers the building, testing, and post-test analysis of the sixth in a series of bench scale heat pipes. Durability heat pipe #6 was built and tested to determine the effects of a high temperature bakeout, 950°C, on wick corrosion during long-term operation. Previous tests showed high levels of corrosion with low temperature bakeouts (650-700°C). Durability heat pipe #5 had a high temperature bakeout and reflux cleaning and showed low levels of wick corrosion after long-term operation. After testing durability heat pipe #6 for 5,003 hours at an operating temperature of 750°C, it showed low levels of wick corrosion. This test shows a high temperature bakeout alone will significantly reduce wick corrosion without the need for costly and time consuming reflux cleaning.

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