An experimental study on flow boiling heat transfer of HFO1336mzz(Z) in microchannels-based polymeric heat sinks

Abstract

This paper presents the development, evaluation and comparison of the performances of two microchannels-based polymeric heat sinks, manufactured with pristine polyacetal (POM) and with a POM-matrix composite filled with a volumetric fraction of 10% of multi-walled carbon nanotubes (MWCNTs). The thermo-hydraulic performance of both heat sinks was evaluated during flow boiling of refrigerant HFO1336mzz(Z) in multi-microchannels, for effective footprint heat fluxes up to 21.2 kW/m2, mass velocities varying from 100 to 300 kg/m2s, saturation temperature of 31 °C and inlet subcooling of 1 °C. Average heat transfer coefficients and pressure drops up to 2640 W/m2K and 1.5 kPa were achieved, respectively. The increase of the heat transfer coefficient and pressure drop were verified with rising the heat flux for both heat sinks. Fixing the average vapor quality, the average heat transfer coefficient and pressure drop increase with increasing mass velocity. The composite heat sink presented higher pressure drop and average heat transfer coefficient, which is associated with the higher surface roughness and mainly to the higher thermal effusivity of the composite in comparison with the pristine polymer. The addition of 10% of MWCNTs implied on temperature reductions at the base of the heat sink up to 22 °C.