Metal-based microscale fin array structures are of interest for microscale heat transfer applications.
Previous work has shown the advantages of microscale structures with increased surface to volume ratio
in single-phase convective heat transfer applications, silicon-based structures are not optimal from the
perspective of heat transfer performance and mechanical integrity. Microscale compression molding was
used successfully to replicate one and two- dimensional (1D/2D), microscale features directly onto
surfaces of high thermal conductivity and high ductility metals, such as aluminum (Al) and copper (Cu).
Subsequent bonding of Al and Cu caps to open 1D microchannel arrays led to the formation of Al- and
Cu- based, enclosed, microchannel heat exchangers (MHEs). Such Al and Cu MHEs can be made with
low profile and high cooling capacity in the single-phase, forced flow, convective heat transfer regime.
Compression molding of metals at the microscale involves a mold insert containing a microscale surface
pattern inverse to the final desired pattern on the metal work piece. We have shown previously that roll
molding can be used to generate 1D microchannel arrays with large depths on sheet metal surfaces in a
parallel manner. Roll molding offers much increased fabrication throughput as compared to compression
molding. The potential of using roll molding to generate 1D/2D surface patterns on metal substrates and
the use of 1D/2D micro fin array structures for heat transfer applications provide motivation for the
present study. In addition to convective heat transfer in single-phase, forced liquid flow situations,
enhancing two-phase heat transfer efficiency using metals with microscale 1D/2D surface patterns is also
of interest for pool boiling environments, which have broad industrial processing applications including
power plants, refrigeration systems, and food production.
In our study:
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Microscale fin array structures were replicated onto surface of aluminum 1100 and aluminum
6061 alloy sheet though room-temperature instrumented roll molding with high throughput and
low cost.
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One-dimensional (1D) micro fin arrays were made though one-pass rolling, while twodimensional (2D) micro fin arrays were made by sequential 90˚ cross rolling with the same roller
sleeves.
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A series of pool boiling experiments on low profile Al micro fin arrays were performed within a
widely used commercial dielectric coolant.
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Results show roll molded Al micro fin arrays can increase heat flux at fixed surface temperature
as compared to un-patterned Al sheet.
Fig: (a) A schematic of roll molding for replicating straight,1D fin arrays on sheet metals. (b) An annotation of the
pool boiling experimental setup. Optical (c) and SEM (d) images of 1D micro fin arrays, along with the 2D micro
fin arrays produced via the same method (e-f). (g) Base area heat flux versus excess temperature for the three
sample types tested.