Flow boiling characteristics in plain and porous coated microchannel heat sinks

•Bubbly, slug, churn and annular flow observed in plain and coated microchannels.•Transition from bubbly to slug flow occurs earlier in coated microchannels.•Heat transfer enhancement observed in coated microchannels.•Two-phase pressure drop increases with the coating but additional pumping power is small.•Porous coating is an effective way to enhance heat transfer in microchannels.