Convective heat transfer characteristics of microencapsulated phase change material slurries (MPCSs) flowing in a circular tube under constant heat flux are studied and a feasible heat transfer model is presented. The heat transfer coefficient of MPCS and the wall temperature of the circular tube are simulated. The simulation results agree qualitatively with the experimental results. The effects of Stefan (Ste) number, mass concentration, phase change temperature range, and Reynolds (Re) number on heat transfer characteristics are discussed. The results indicate that the Ste-number and mass fraction are the most important parameters influencing heat transfer properties compared to the phase change temperature range and Re-number which less affect these characteristics.