Heat transfer characteristics of microencapsulated phase change material (MPCM) slurry flow in a circular horizontal tube are presented in this paper. Phase change due to the melting is investigated for water-based slurries using microencapsulated 1-bromohexadecane (C16H33Br) with a mass concentrations varying from 0 to 27.6%. The local heat transfer coefficients varied significantly along the test section when PCM particles were melting. The average Nusselt numbers were calculated based on the local heat transfer data and found to be significantly higher than those for single-phase fluid flow. Two new heat transfer correlations, one used for the slurry under laminar condition (0 < Re < 2000) and another used for the slurry under slightly turbulent condition (2200 < Re < 3500), were proposed for predicting the heat transfer behaviors of MPCM slurry in a circular tube. (C) 2008 American Institute of Chemical Engineers.