In this article, an experimental investigation is performed to measure the boiling heat transfer coefficient of water flow in a microchannel with a hydraulic diameter of 500 mu m. Experimental tests are conducted with heat fluxes ranging from 100 to 400 kW/m(2), vapor quality from 0 to 0.2, and mass fluxes of 200, 400, and 600 kg/m(2)s. Also, this study has modified the liquid Froude number to present a flow pattern transition toward an annular flow. Experimental results show that the flow boiling heat transfer coefficient is not dependent on mass flux and vapor quality but on heat flux to a certain degree. The measured heat transfer coefficient is compared with a few available correlations proposed for macroscales, and it is found that previous correlations have overestimated the flow boiling heat transfer coefficient for the test conditions considered in this work. This article proposes a new correlation model regarding the boiling heat transfer coefficient in mini-and microchannels using boiling number, Reynolds number, and modified Froude number.