Emulsions are mixtures of two materials that do not normally mix together, and these are used widely in many industrial fields. Oil-in-water (O/W) emulsions contain many small oil particles in water. We studied the flow and heat transfer characteristics of the O/W emulsion experimentally by measuring the pressure drop and heat transfer coefficient of the emulsion in a microchannel, because the particles may affect the emulsion's characteristics. A silicone oil-in-water emulsion was prepared by varying the volume fraction of the dispersed oil, amount of surfactant, and kinetic viscosity of the oil. The O/W emulsion in microchannel parallel flow can be treated as a Newtonian fluid. The derived apparent viscosity of the emulsion is dependent on the relative particle size to flow, oil volume fraction, and oil kinematic viscosity. The emulsion heat transfer in the microchannel is enhanced for a large relative particle size. The range in which the emulsion can be treated as single phase flow was revealed. (C) 2017 Elsevier Ltd. All rights reserved.