This cryogenic heat transfer surface made of aluminum and an anodized aluminum oxide layer is capable of substantial heat transfer enhancement in all three boiling and quenching regimes. The surface layer features nanoscopic pores that effectively trap moisture to grant it substantial heat transfer enhancements. These enhancements can be applied effectively to a variety of engineering applications including power production, advance electronics, and cryogenic fluid systems. Cryogenic fluids are widely used in industrial applications, space explorations, and cryosurgery devices, and systems that use them require a "chilldown" process to adjust the system to low operating temperatures. Power production devices and advanced electronic systems rely on efficient heat transfer mechanisms to maintain an optimal temperature level to maximize power density for higher system efficiency. But as conventional convective heat transfer technologies reach their limits, researchers are looking for modern phase-change thermal energy transport mechanisms for solutions. Researchers at the University of Florida have developed a solution with this surface layer of anodized aluminum oxide nanopores that significantly enhances heat transfer.
Nanoporous aluminum oxide surface that enhances heat transfer efficiency to improve various industrial systems
The anodized aluminum oxide nanoporous texture of the surface layer creates a highly wettable and superhydrophilic property that drastically alters boiling and quenching properties. The pores are created by first electrically increasing the thickness of aluminum substrate, then using acid to create a pattern of nanopores on the aluminum surface. The nanoporous alumina substrates can be modified to have different pore sizes, distribution, and morphologies that in turn affect the heat exchange properties. For cryogenic applications, the nanoporous surface can shorten the chilldown time up to 20 percent, which can reduce cryogenic fluid consumption by nearly 30 percent and increase safely with reduced boil-off and venting points. This surface also significantly increases the Leidenfrost point, maintaining a higher level of heat transfer in a larger range of surface temperature.
