Flow boiling heat transfer enhancement using a porous nanocoating in copper microchannels has been experimentally investigated. Results of the coated microchannel heat sink were compared to baseline results in a plain, CNC-milled copper microchannel heat sink at similar operating conditions, namely inlet pressure of 1 bar, mass flux of 200 kg/m^2^s and inlet subcooling of 10 K at wall heat fluxes between 25.0 kW/m^2^ to 164.2 kW/m^2^. Flow visualisation results and SEM surface analyses are presented. The coated surface was densely populated with defined cavities as small as 0.6 µm while shallow and larger cavities \~ 6 µm were found on the end-milled copper channels. Bubble generation frequency in the coated channels is significantly higher than in the plain channels due to the presence of more favourable nucleation sites on the coated surface. Flow pattern evolution occurred similarly in both test sections, namely bubbly to slug, churn and annular flow with increasing heat flux. Microchannel heat transfer is enhanced by up to 43.5 % at low wall heat flux where nucleate boiling mechanism is dominant. Heat transfer enhancement diminishes with further increase in heat flux to 13.2 % at the maximum wall heat flux.

Keywords: surface enhancement, nanocoating, heat transfer, flow boiling, microchannels


Flow Boiling Heat Transfer in Plain and Coated Microchannel Heat Sinks Using Hfe-7200

Division / Sponsors: 
Heat Transfer Division (HTD), Fluids Engineering Division (FED)

Heat Transfer Summer Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/HT/HT2020/volume/83709

18th International Conference on Nanochannels, Microchannels, and Minichannels
Paper Proceedings: https://asmedigitalcollection.asme.org/ICNMM/ICNMM2020/volume/83693

Fluids Engineering Division Summer Meeting
Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2020/volume/83716

HT-ICNMM2020 - Virtual Conference, SHTC - Virtual Conference, FEDSM2020 - Virtual Conference

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