In an attempt to analyze the effect of red blood cells on heat transfer, a two-phase flow heat transfer model of flowing blood was proposed in this paper. In this model, blood is treated as a two-phase fluid composed of red blood cells as the particle phase and plasma as the carrier fluid. The micro-particle dynamics, including aggregation, deformation, mutual collisions of red blood cells and relative movement of red blood cells to plasma, are considered by some equations or simplified methods. The velocity field, temperature field, fluid viscosity and volume fraction of red blood cells in a two-phase blood flow can be calculated using this model. To verify the accuracy of the simulation results of the model, the velocity distribution and heat transfer efficiency calculated by this model were compared with available experimental data from the literature. Good agreement was obtained between these data; thus, this model can accurately simulate the blood flow and heat transfer in a vessel. Then, the model was used to analyze how the micro-particle red blood cells affect the heat transfer of blood, and red blood cells were found to enhance heat transfer efficiency of blood. The viscosity properties of blood, the solid pressure and the lateral movement of red blood cells are the important determinants of this enhancement. The influence of red blood cells on the heat transfer efficiency of pulsatile blood flow was also calculated using this model. (C) 2017 Elsevier Ltd. All rights reserved.