Engineering: Hot tin proof

A ceramic mechanical pump that can continuously circulate liquid tin at temperatures of up to 1,673 kelvin (1,400 degrees Celsius) is reported in a paper published in this week’s Nature. At extremely high temperatures a molten metal could become a medium for the efficient storage and transport of energy. However, the manipulation of liquid metals at extreme temperatures has proven challenging for many applications.

Virtually every energy-conversion process creates heat as a product or byproduct, making it one of the most abundant forms of energy. Thermal energy, which is fundamental to power generation and many industrial processes, is most valuable at high temperatures. Although liquid metals can be highly effective heat-transfer fluids, high-temperature liquid-metal pumping has been severely limited by the corrosion of pump materials. Even in cases where high-temperature fluids are effectively used (such as gas turbines and rocket engines), the pumps are kept in a relatively cold portion of the system.

Asegun Henry and colleagues show how, through careful engineering, usually brittle ceramics can be used to construct the mechanical and sealing components of a molten metal pump that is capable of continuous operation at temperatures up to a record 1,673 kelvin. The authors’ approach focused on two critical challenges: overcoming the use of breakable ceramics in rotating machinery, and demonstrating the ability to seal liquid tin above 1,300 kelvin. Their prototype pump system, consisting of a reservoir, visual flow meter, necessary piping and joints, was successfully tested for 72 hours, during which it pumped molten tin at an average of 1,473 kelvin (and up to 1,673 kelvin) without failure. This new system for effective heat transfer and storage using liquid in record temperature ranges will enable innovations in thermal energy storage, electric power production, and chemical or materials processing.

doi: 10.1038/nature24054

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