Phase change material emulsions (PCMEs) are mixture of fine phase change material (PCM) particles and water. PCM particles are dispersed in the water by the action of a surfactant. PCMEs have high thermal energy storage density due to latent heat of fusion of PCM particles, and fluidity. Therefore, they are expected to be used as thermal energy storage and transport media. In order to use PCMEs as storage and transport media for thermal energy, it is important to know their heat transfer characteristics. In this study, heat transfer characteristics of PCMEs were investigated experimentally and numerically. In particular, the heat transfer characteristics of PCMEs flowing in a circular tube and being heated under constant heat flux condition were investigated. An alkane-type PCM, n-hexadecane, was used as PCM. When PCMEs flow without melting of PCM particles, noticeable heat transfer enhancement effect was not confirmed. On the other hand, when PCMEs flow with melting of PCM particles, significant heat transfer enhancement was confirmed. This is attributed to the increase of apparent specific heat of PCMEs due to melting of PCM particles. Moreover, the heat transfer enhancement effect was more significant when PCMEs flow in a horizontal circular tube. The heat transfer coefficient of PCMEs flowing in a circular tube was shown to be higher at the bottom of circular tube and was lower at the top of the tube. This phenomenon might be attributed to the secondary convection caused by density change due to melting of PCM particles. However, the secondary convection could not be observed experimentally because PCMEs are milky white fluid. Therefore, velocity profile of PCMEs was investigated numerically. In the calculation, dispersed PCM particles and dispersant were not treated separately, and PCMEs was treated as a single-phase fluid. The density change and discharge of latent heat of fusion associated with melting of PCM particles was considered as changes in the physical properties of PCMEs. The Nusselt number of PCME obtained from the calculation was in good agreement with the Nusselt number obtained from the experiments, indicating that the heat transfer of PCME can be well reproduced by treating the density change and discharge of latent heat of fusion associated with the melting of PCM as changes in the physical properties of PCME.