Condensation flow patterns and heat transfer in horizontal microchannels

•Experimental study of HFE-710 condensing in a small rectangular channel of 0.57mm hydraulic diameter.•Local heat transfer coefficient increases with increasing mass flux and decreases with decreasing vapour quality.•The interfacial shear stress is the dominant regime at this scale and with this particular fluid.•The main flow regime is annular flow.•Comparisons with existing flow pattern maps and heat transfer correlations were performed.