Pool boiling performance of 3D-printed reentrant microchannels structures

This study developed reentrant microchannels structures (RMS) by the Selective Laser Melting (SLM) technique for pool boiling enhancement. The 3D-printed reentrant microchannels structures were of parallel Omega-shaped reentrant channels with rough wall surfaces, which were built of bronze powder. Pool boiling tests of the RMS were conducted in deionized water in both saturated and subcooled boiling conditions with two liquid subcoolings of 15 degrees C and 30 degrees C. The pool boiling enhancement was explored by the comparison of a solid plain surface as benchmark. It was found that the reentrant microchannels structures reduced the wall superheat for onset of nucleation boiling (ONB) considerably, and generally present a 10% to 330% enhancement in boiling heat transfer coefficients over the plain surface in subcooled boiling conditions. The enhancement can be attributed to that the reentrant microchannels structures contributed to significant increase in active nucleation sites, enlarged surface area for heat exchange, and more liquid replenishment for surface rewetting. The boiling heat transfer coefficients of RMS generally exhibited a rapid decline at small heat fluxes region, then maintained to be more or less stable or increased slightly at moderate to high heat flux regions, and lastly decreased slightly at high heat flux region. The boiling heat transfer of RMS can be enhanced remarkably in the subcooled boiling tests. (C) 2020 Elsevier Ltd. All rights reserved.