Experimental study on heat transfer to a liquid water film in a microchannel was performed. The liquid film was introduced into a nitrogen stream through a 350 mu m circular hole upstream of a 1 mm x 1 mm heater in a 220 mu m deep and 1.5 mm wide rectangular microchannel. Average heat transfer coefficient was obtained for different gas and liquid flow rates and results were compared to single-phase flow. Significant improvement in heat transfer performance was observed with no appreciable change in pressure drop. Experimental data combined with a heat transfer analysis was used to infer the mechanisms controlling the heat transfer process. (c) 2013 Elsevier Ltd. All rights reserved.